The Curious Engineer

All blogs / Software / engineering practice

Jim Fisher’s blog

jameshfisher.com

Software / engineering practiceJavaScript / TypeScriptGraphicsMath

’15’20’25
Posts
539 from 27 Feb 2012 to 18 Nov 2025
Posting
now and then (1 in the last year)
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personal blog
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2025 3

  1. The migration SQL should go in the table
  2. A job queue in two lines of JS
  3. Sticky snap: a better snapping algorithm

2024 10

  1. `window.ai` hello world
  2. Interactive Turing patterns in WebGPU
  3. WebGPU hello world in 2024
  4. What is Monte Carlo integration?
  5. How to escape JavaScript for a script tag
  6. On that flickering blur in Chrome
  7. What is the Metropolis algorithm?
  8. Blogroll
  9. Speaking
  10. How do I call a program in C, setting up standard pipes? A C function to create a new process, set up its standard input/output/error pipes, and return a struct containing the process ID and pipe file descriptors. 2017-02-17

2023 5

  1. Granddad died today Granddad died. The unspoken practice of death-by-dehydration in the NHS. The Liverpool Care Pathway. Assisted dying in the UK. The importance of planning in end-of-life care. 2017-05-19
  2. The Three Ts of Time, Thought and Typing: measuring cost on the web Businesses often tout “free” services, but the real costs come in terms of time, thought, and typing required from users. Reducing these “Three Ts” is key to improving sign-up flows and increasing conversions. 2017-10-26
  3. Project C-43: the lost origins of asymmetric crypto Bob invents asymmetric cryptography by playing loud white noise to obscure Alice’s message, which he can cancel out but an eavesdropper cannot. This idea, published in 1944 by Walter Koenig Jr., is the forgotten origin of asymmetric crypto. 2019-02
  4. The hacker hype cycle I got started with simple web development, but because enamored with increasingly esoteric programming concepts, leading to a “trough of hipster technologies” before returning to more productive work. 2019-03-23
  5. Time is running out to catch COVID-19 Simulation shows it’s rational to deliberately infect yourself with COVID-19 early on to get treatment, but after healthcare capacity is exceeded, it’s better to avoid infection. Includes interactive parameters and visualizations. 2020-03-14

2022 10

  1. A probabilistic pub quiz for nerds A “true or false” quiz where you respond with your confidence level, and the optimal strategy is to report your true belief. 2020-04-26
  2. Smear phishing: a new Android vulnerability Trick Android to display an SMS as coming from any contact. Convincing phishing vuln, but still unpatched. 2020-08-06
  3. What does the dot do in JavaScript? foo.bar, foo.bar(), or foo.bar = baz - what do they mean? A deep dive into prototypical inheritance and getters/setters. 2020-11-01
  4. Diffing coronaviruses Comparing the genome sequences of the Wuhan coronavirus and a bat coronavirus using diff and NCBI BLAST reveals an 89% similarity. 2020-02-09
  5. Shape typing in Python 2024-04-12
  6. The sorry state of OpenSSL usability OpenSSL’s inadequate documentation, confusing key formats, and deprecated interfaces make it difficult to use, despite its importance. 2017-12-02
  7. A formula for responsive font-size Try setting the root font-size to calc(1rem + 0.25vw) instead of using media queries with fixed breakpoints. 2024-03-12
  8. My parents are Flat-Earthers For decades, my parents have been working up to Flat-Earther beliefs. From Egyptology to Jehovah’s Witnesses to theories that human built the Moon billions of years in the future. Surprisingly, it doesn’t affect their successful lives very much. For me, it’s a fun family
  9. How Hacker News stays interesting Hacker News buried my post on conspiracy theories in my family due to overheated discussion, not censorship. Moderation keeps the site focused on interesting technical content. 2019-01-26
  10. Your syntax highlighter is wrong Syntax highlighters make value judgments about code. Most highlighters judge that comments are cruft, and try to hide them. Most diff viewers judge that code deletions are bad. 2014-05-11

2021 7

  1. I hate telephones I hate telephones. Some rational reasons: lack of authentication, no spam filtering, forced synchronous communication. But also just a visceral fear. 2017-11-08
  2. I can see your local web servers Script detects and exposes your local web servers on localhost and your local network. 2019-05-26
  3. The dots do matter: how to scam a Gmail user Gmail’s “dots don’t matter” feature lets scammers create an account on, say, Netflix, with your email address but different dots. Results in convincing phishing emails. 2018-04-07
  4. The inception bar: a new phishing method A new phishing technique that displays a fake URL bar in Chrome for mobile. A key innovation is the “scroll jail” that traps the user in a fake browser. 2019-04-27
  5. ‘A liberal revolution that was blown off course’. Is this an adequate description of what happened in France? The French Revolution, far from being a “liberal revolution”, was defined by violence from the start, with the Terror and subsequent instability being a logical continuation, not a deviation
  6. In what ways might natural magic be seen to have contributed to the emergence of modern scientific method? Natural magic and scientific method share commonalities, but only scientific method distinguished correlation from causation. The Scientific Revolution arose from internal technological develop
  7. What were the principal factors governing state formation in the early modern period? Humanism, the Reformation, centralized administration, the decline of feudalism, and the rise of national identity. 2007-03-10

2020 80

  1. Tetra Pak: Faithful Friend, Silent Hero, and Protector of All Things Good An ode to the Tetra Pak carton. 2007-05-23
  2. Do not ask if I had a good holiday A disastrous start to a holiday in Turkey, involving a naked midnight run, injured toes, heat exhaustion, and a serious bacterial infection, leading to an unpleasant but unforgettable trip. 2007-07-27
  3. To what extent did the trial of Giordano Bruno set a precedent for that of Galileo? The trials of Giordano Bruno and Galileo were connected, not because Bruno was a proto-Galileo, but because the Inquisition associated Galileo’s Copernicanism with Bruno’s condemned Hermeticism and theological heresi
  4. A proposal for visual pure functional programming A visual programming language inspired by Haskell. 2012-02-27
  5. Visualizing world population 2012-10-30
  6. Un-biasing a biased coin Flip a biased coin twice to get an unbiased outcome. Use HT and TH as the outcomes, ignoring HH and TT. 2013-11-16
  7. Where is the Firefox application shortcut? Firefox still lacks a built-in feature to create application shortcuts, unlike Chrome, despite the rise of web apps over the past decade. 2013-11-19
  8. TODO DAG A task management system using a directed acyclic graph (DAG) to represent task dependencies and priorities, allowing for more nuanced organization than a flat to-do list. 2013-12-19
  9. A proof that the Halting problem is undecidable, using JavaScript and examples A JS function to decide the Halting Problem will always have a logical contradiction. 2013-12-24
  10. On the absence of energy and time in the virtual world of applications, or, the misconception of the “distraction-free” mode Physical books and board games require energy and time to access, which creates a sense of focus. Virtual applications lack these constraints, leading to constant distraction.
  11. Why can’t I see my phone screen in sunlight? Phone screens have low contrast in sunlight because the reflected sunlight overpowers the screen’s own light output, reducing the effective contrast ratio. 2014-08-09
  12. Documentation black holes: things we write that don’t get read Documentation often ends up in black holes - internal documents, issue trackers, test cases, conversations, commit messages, and wikis - where it goes unread. Focus on writing documentation that people will actually read, like product na
  13. A semantic wiki in Prolog Prolog as a better alternative to “semantic triples” and SPARQL. 2014-08-24
  14. Nix by example, Part 1: The Nix expression language Nix is a functional programming language used for package management. We see the Nix expression language, including strings, primitives, operators, functions, let expressions, and conditionals. 2014-09-28
  15. Low latency, large working set, and GHC’s garbage collector: pick two of three Large working sets and low latency are incompatible with GHC’s stop-the-world garbage collector, which optimizes for throughput instead of latency. The collector’s pause times scale linearly with working set size. 2016-05
  16. How does tricolor garbage collection work? Golang’s garbage collector uses a “tricolor” algorithm, dividing heap objects into black, white, and grey sets. The algorithm can run concurrently with the program, and the “tricolor” invariant ensures no pointers go directly from the black set to the white
  17. 128 byte of CSS is enough Limiting CSS to 128 bytes prevents bloat and distractions, allowing focus on content. 2016-11-15
  18. Should I get a cleaner? Hired a cleaning service that takes a third of the hourly rate. 2016-11-16
  19. A summary of ‘On-the-Fly Garbage Collection: An Exercise in Cooperation’ A concurrent garbage collection algorithm that keeps synchronization constraints between the mutator and collector processes as weak as possible. It uses node markings (white, grey, black) to ensure reachable objects are not in
  20. Post every day Daily blogging pledge; punishment for failure TBD. 2016-11-16
  21. How do I serialize JSON in Swift? Serialize JSON in Swift with JSONSerialization.data(withJSONObject:options:). 2016-11-16
  22. Learning vim (a short adventure) I try Vim. I give up after discovering that the cursor cannot sit at the end of a line. 2016-11-16
  23. Summary of ‘Zero to One’, Chapter 1: the challenge of the future Progress comes from either copying or creating. Global progress since 1971 has been copying via globalization, except for computing. Startups create, not copy, because small groups, not large, can think anew. 2016-11-17
  24. How do I replace target/action with callbacks in Swift? Use a CallbackWrapper object to associate a closure with an NSControl, setting the target and action properties to enable callback-based event handling. 2016-11-17
  25. How do I write a UDP server in Go? A UDP server that listens for packets and prints the received messages. A UDP client that sends “hello” to the server. 2016-11-17
  26. What is an .xcodeproj file? The .xcodeproj “file” is actually a directory that contains a project.pbxproj file, which is a text file that stores the settings of an Xcode project, including information about the files, build configurations, targets, and dependencies. 2016-11-17
  27. What is an .xcworkspace file? An .xcworkspace file is a directory that contains a workspace configuration for Xcode projects. 2016-11-17
  28. How do I change the resolution on macOS? To get more screen real-estate, go to System Preferences > Displays, and select “More Space” . 2016-11-18
  29. What is symmetric cryptography? Symmetric cryptography uses a shared secret key for both encryption and authentication, providing confidentiality and integrity. We look at the API, HMAC, and Authenticated Encryption. 2016-11-19
  30. Should I buy Huel or Joylent? Comparing meal replacement options Huel and Joylent, I choose Joylent’s vegan version. 2016-11-20
  31. How does a stream cipher work? A stream cipher works like a one-time pad, but uses a pseudorandom “keystream” from a PRNG seeded by a secret key and nonce, preventing attacks based on pad disclosure or reuse. 2016-11-21
  32. How do varargs work in C? Variadic functions in C use the ... syntax to accept an arbitrary number of arguments. The stdarg.h library provides va_start, va_arg, and va_end to access the arguments. 2016-11-23
  33. How is the stack laid out in C? The stack layout in C includes function arguments, return address, and local variables. Addresses decrease as you go through the arguments, and the stack grows downward with each function call. 2016-11-24
  34. A C typedef convention for complex types A convention for expressing complex C types using typedef and a “reverse Polish notation” syntax to improve readability. 2016-11-24
  35. Don’t use the word ‘it’ Avoid using ambiguous pronouns like “it” in technical writing. Refer to specific referents explicitly to improve clarity. 2016-11-25
  36. Bike front derailleur The front derailleur (Shimano FD-2203) is incompatible with the triple crankset, causing shifting issues. A compatible front derailleur like Shimano FD-5603 may be needed to resolve the problem. 2016-11-27
  37. What is K&R style function definition in C? The “K&R-style” function definition in C uses an initializer list to declare parameters, unlike the more common parameter type list. This old-style definition has significant semantic differences and should be avoided due to its potential for undefined beh
  38. What is void in C? void in C has multiple meanings: as a return type to indicate no return value, as a parameter type to indicate no parameters, and as a pointer type to indicate a pointer to an unknown type. 2016-11-27
  39. What does void mean as a function parameter in C? void in a C function parameter list means the function takes no arguments, whereas an empty list allows for an unspecified number of arguments. 2016-11-27
  40. What is static in C? static in C can modify variable declarations inside and outside a function body, and function parameters. 2016-11-28
  41. What type should I use to count objects in C? Use uintptr_t to count objects in C, as it can represent the largest possible pointer value. 2016-11-29
  42. What is size_t for? How do I iterate over an object in C? size_t is used to represent the size of objects in memory. It is commonly used for array indexing. 2016-11-29
  43. How do I find out which preprocessor my C compiler uses? To find out which preprocessor your C compiler uses, run the compiler with the -print-prog-name=cpp flag, which shows the path to the preprocessor subprogram it calls. 2016-11-29
  44. What do array subscripts mean in C? C array subscripts are defined as pointer arithmetic, where a[b] means *(a+b). This means a[b] is the same as b[a]! 2016-11-30
  45. Can I put comments in string literals in C? C string literals can contain comment-like characters, which are treated as literal text, not as comments. 2016-11-30
  46. How do I write a multi-line string literal in C? Use concatenated string literals with newline characters to define multi-line string literals in C. 2016-11-30
  47. Does C allow pointer arithmetic? Computing a pointer to unowned memory invokes undefined behavior, even without dereferencing! 2016-11-30
  48. Where is the C programming language defined? C is defined in several places, including “The C Programming Language” by Kernighan and Ritchie, and a series of ISO C standards (C89, C99, C11). 2016-11-30
  49. What is realloc in C? realloc resizes an allocated memory block, copying contents if necessary. 2016-12-01
  50. Does C have booleans? C99 introduced the stdbool.h header, providing bool, true, and false for boolean values, building on the _Bool type. 2016-12-01
  51. What does const mean in C? const is a type qualifier in C that makes a variable unassignable, except during initialization. 2016-12-02
  52. What does the restrict keyword mean in C? The restrict keyword in C is a type qualifier that indicates a pointer parameter points to an object not accessed through any other pointer in the function’s scope. This allows the compiler to make optimizations. 2016-12-03
  53. What is FILE in C? A FILE is a C data type that represents an open file. It contains metadata about the file, such as its file descriptor and buffers. 2016-12-04
  54. How do I set the C compiler in a Makefile? Set the C compiler in Makefile using predefined variable $(CC), which defaults to cc and can be redefined. 2016-12-05
  55. What is a ‘binary-safe’ string? C strings use null-terminated byte arrays, which cannot represent arbitrary binary data. Binary-safe strings explicitly store the length, allowing them to represent any sequence of bytes. 2016-12-06
  56. What are automatic variables (dollar variables) in a Makefile? Automatic variables in a Makefile, like $@ for the target and $^ for the dependencies, reduce repetition in rules. 2016-12-07
  57. What is ‘array decaying’ in C? Arrays in C can “decay” to pointers, but are not inherently pointers. The size of an array is lost during decay. 2016-12-08
  58. What are ‘macro functions’ in C? Macros in C can define token replacements or function-like replacements. 2016-12-09
  59. How can I do modulo with a bitmask in C? Use i & (n-1) to compute i % n, when n is a power of two. This avoids the modulo operation. 2016-12-10
  60. What are static functions in C? static functions in C are only callable within the translation unit they are defined in, not across the whole program. 2016-12-12
  61. What is errno in C? errno lets you access error codes from system calls. It’s a global int. 2016-12-13
  62. What syscalls does a TCP server need? A minimal TCP server in C uses the socket, bind, listen, accept, recv, send, and close syscalls to manage connections. 2016-12-14
  63. What is a “file descriptor”, really? File descriptors should be called “resource descriptors”. They represent various system resources, not just regular files. The operations you can perform depend on the specific resource. 2016-12-15
  64. How to write a TCP server with the select syscall The select syscall allows a process to sleep and wake up when a file descriptor is ready for reading, writing, or has an exceptional condition. This enables a TCP server to handle multiple clients concurrently. 2016-12-16
  65. What is fdset in C? fdset in C is a data structure that represents a set of file descriptors. The FD_SET, FD_CLR, FD_ISSET, and FD_ZERO macros are used to manipulate and inspect these sets. 2016-12-17
  66. How to write a TCP server with the kqueue API Kqueue is a more efficient alternative to select for managing multiple TCP connections, providing a publish-subscribe model for tracking events in the kernel. 2016-12-18
  67. What syscalls does a UDP server need? The syscalls needed for a simple UDP echo server are socket, bind, recvfrom, sendto, and close. 2016-12-19
  68. How to write a ‘hello world’ HTTP server in C A C program that creates an HTTP server that responds with “Hello, world!” to every request. 2016-12-20
  69. What is htons in C? htons and htonl convert values between host and network byte order, where network order is big-endian. ntohl and ntohs are the inverse functions. 2016-12-21
  70. How do I print bytes in C? Useful to show how C represents various data types. 2016-12-22
  71. What are ‘protocol numbers’ in IP? An IP packet contains a ‘protocol number’ that identifies the protocol (e.g. TCP, UDP) running over IP. The kernel uses this to determine how to handle the packet. 2016-12-23
  72. What is perror in C? perror in C prints a human-readable description of the last error that occurred, as stored in the global errno variable. 2016-12-24
  73. How to write an array literal in C (with explicit indexes) C array literals can use explicit indexes. The array length is determined by the largest explicit index. 2016-12-25
  74. How do I measure program execution time in C? How do I use the times function? Use the times() system call in C to measure the CPU time used by a process, distinguishing between time charged to the process itself and time charged to the kernel on its behalf. 2016-12-26
  75. How do I put an array in a struct in C? C allows a single array field of incomplete type (char []) at the end of a struct definition. The size of the struct is determined by the size of the fixed fields, and the dynamic-sized array is allocated separately. 2016-12-27
  76. Pointer to middle of allocation, part 1 Redis uses length-prefixed strings with pointers into the middle of the allocation, allowing C-string operations on the string data. 2016-12-28
  77. What are ‘statement expressions’ in GCC? GCC’s ‘statement expressions’ allow inserting statements into expression positions. Behavior is unspecified. 2016-12-30
  78. What do DNS datagrams look like? The structure and contents of a DNS request datagram, including the header, question section, and how to represent it in C. 2016-12-31
  79. How fast does an IP packet travel? IP packets travel at ~20% the speed of light, with most time spent in routers rather than on the wire. 2017-01-01
  80. How do I pack bits in C? (An answer using masks) Efficient packing of game player data into 16 bits using bitwise operations on a uint16_t type. 2017-01-02

2019 33

  1. What is a union in C? A union in C allows one variable to hold different data types, where the storage is shared. The size of a union is at least the size of its largest member. Fields in a union have the same byte offset. 2017-01-03
  2. What are ‘bitfields’ in C? Bitfields in C allow compact bit packing in structs, avoiding manual bitwise operations for greater safety and clarity, at the cost of some language complexity. 2017-01-04
  3. Error URLs (addressable errors) Using unique error codes with linkable documentation improves error reporting. Provide a central error page URL with each error message. 2017-01-05
  4. What is the Ivy Lee method? 1) At end of day, list 6 tasks for tomorrow, ranked; 2) Next day, work through the list in order; 3) Discard the old list before making a new one. 2017-01-06
  5. How does the USB power wire work? The four wires in a USB cable are power (black, red) and data (white, green). One can power devices by connecting the ground and +5V wires, ignoring the data wires. 2017-01-07
  6. How does differential signaling work in USB? USB uses “differential signaling” where the sender transmits two signals, D+ and D-, and the receiver interprets the difference D+ - D-. This cancels out electromagnetic interference that affects both wires equally. 2017-01-08
  7. What are ‘signals’ in C? Signals in C are software interrupts that allow programs to respond to events. The signal.h header provides functions to register signal handlers and send signals. 2017-01-09
  8. What does the C signal function return? signal returns the old signal handler pointer for given signal number. 2017-01-10
  9. How do I unregister a signal handler in C? To unregister a signal handler in C, use signal(signum, SIG_DFL) to reset the disposition to the default, or signal(signum, SIG_IGN) to set the disposition to ignore the signal. 2017-01-11
  10. Doing something n times in C with while and decrement Executing do_something() N times in C using a while loop and post-decrement operator. 2017-01-12
  11. What is sigaction in C? sigaction says what to do when a signal is received. signal is a simplified interface to sigaction. 2017-01-13
  12. How do C signals interact with the stack? C signal handlers reuse the same call stack as normal functions, but can optionally use a special signal stack instead. 2017-01-14
  13. What is STUN? STUN is a protocol that allows clients to discover their public IP address and port, enabling peer-to-peer connections in WebRTC. 2017-01-15
  14. How to write a ‘hello world’ serverless WebRTC app Including setting up the RTCPeerConnection, creating a data channel, handling ICE candidates, and generating an offer to be shared with the remote peer. The signaling channel is copy-paste! 2017-01-16
  15. How does reliability work in RTCDataChannel? The RTCDataChannel API lets us configure the delivery guarantees, including the ordered, maxPacketLifeTime, and maxRetransmits properties. 2017-01-17
  16. What is electric charge? Electric charge is the number of electrons minus the number of protons in an object. 2017-01-18
  17. What is electric current? Electric current measures the change in electric charge across a boundary, like a wire. It is measured in amperes (coulombs per second) and reflects the net movement of electrons and protons from one side of the boundary to the other. 2017-01-19
  18. What is the UINT64_C macro in C? The UINT64_C macro appends the ULL suffix to a 64-bit unsigned integer literal, converting it to the appropriate type. 2017-01-20
  19. What are lvalue and rvalue in C? “lvalue” either means “expression which can be placed on the left-hand side of the assignment operator”, or means “expression which has a memory address”. “rvalue” is defined as “all other expressions”. 2017-01-21
  20. What is the difference between C constants and C literals? Literals are lvalues with addresses, while constants are rvalues without addresses. In C, only string literals are literals; other “literals” like numbers and characters are constants. 2017-01-22
  21. What is the type of a constant in C? Integers in C are int by default, while suffixes like L and U denote long and unsigned types. Floats are double without a suffix. 2017-01-23
  22. How to subtract in binary To subtract in binary, we use carry bits and two’s complement representation. 2017-01-24
  23. Quickly checking for a zero byte in C using bitwise operations How to check if a 64-bit word contains a zero byte. A step-by-step example and a proof of correctness. 2017-01-24
  24. What is Coulomb’s law? Coulomb’s law describes the force between charged particles, which is proportional to the product of their charges and inversely proportional to the square of the distance between them. 2017-01-25
  25. What is mmap in C? mmap is a system call in C that allows programs to manipulate underlying hardware resources, such as physical memory or files, using ordinary memory manipulation. 2017-01-26
  26. How can I read a file with mmap in C? Use mmap to map a file into memory, then read and write the memory directly. 2017-01-27
  27. How can I write a file with mmap in C? To write to a file, open the file, mmap the file descriptor, then write to memory. 2017-01-28
  28. In what ways can processes communicate? Processes can communicate via files, pipes, signals, sockets, message queues, semaphores, and shared memory. 2017-01-29
  29. Cloning Spaceteam A multiplayer web-based version of the cooperative game Spaceteam, using Pusher for real-time communication between players. 2017-01-30
  30. How do I read man pages? The man command is used to access the UNIX manual pages, which are organized into numbered sections. man searches a predefined path to find the relevant manual page. 2017-01-30
  31. What system calls does macOS have? All system calls on macOS 10.12, categorized by the functionality they provide, such as process management, file operations, memory management, etc. 2017-01-31
  32. Monthly review: 2017-01 Reviewing January 2017 - covered networking, C/UNIX, WebRTC, and electronics. Plans to learn fundamentals of circuits, C compilation, UNIX process management, and WebRTC protocols. 2017-02-01
  33. How do I access environment variables in C? Access environment variables in C by using the global environ variable, which points to an array of string pointers representing the environment. 2017-02-02

2018 53

  1. How do I generate assembly from a C file? Compiling with the -S flag generates assembly. 2017-02-03
  2. What are the stages of C compilation? C compilation involves 6 stages: preprocessing, parsing, AST generation, LLVM IR production, assembly generation, and linking to produce the final executable or shared library. 2017-02-04
  3. WebRTC - low barrier to entry, low barrier to exit? WebRTC has many challenges - browser API inconsistencies, protocol ambiguities, infrastructure requirements, and lack of built-in “business logic”. Not as easy as it seemed at first. 2017-02-04
  4. FOSDEM: The Challenges and Secrets of the Realtime World Realtime apps use protocols like HTTP streaming, long polling, WebSocket to enable live updates. Scaling pub/sub requires distributed servers and routing clients to the closest server. 2017-02-04
  5. How do I use execve in C? execve replaces the current process with a new one. It takes a path, an argument array, and an environment array. The process never returns unless execve fails. 2017-02-05
  6. How do I use fork in C? fork duplicates the current process. It returns 0 in the child process. In the parent process, it returns the child’s new process id. 2017-02-06
  7. How do I call a program from C? To call a program from C, use `fork` then `execve`. There is no more direct way! 2017-02-07
  8. How does GeoDNS work? GeoDNS uses geo-IP to locate clients and connect them to the nearest server, reducing latency. 2017-02-08
  9. How can I wake up earlier? Reassessing daily routine - shifting sleep, work, and commute times to wake up earlier, improve sleep quality, and align with daylight hours. 2017-02-08
  10. How to wake up earlier To wake up earlier, set a physical alarm in a location away from the bed, and schedule early meetings to create firm deadlines for your day. 2017-02-09
  11. What is the happened-before relation? The happened-before relation models time in distributed systems, where events at different locations may not have a total order. It defines time using causality. 2017-02-10
  12. Are processes and messages different? Processes and messages can be unified - processes are just very slow messages, and message passing can be seen as splitting and fusing atoms. 2017-02-11
  13. What are Lamport timestamps? Lamport timestamps measure time and causality in distributed systems. Timestamps are assigned to events, with the property that if event A happened-before event B, then A’s timestamp is less than B’s. 2017-02-12
  14. French preposition examples French preposition examples for common spatial relationships like behind, in front of, next to, under, on, above, in, and between. 2017-02-13
  15. UNIX as a SQL database UNIX represents various system components, like processes, file descriptors, and memory, using in-memory data structures that can be modeled as relational database tables. 2017-02-14
  16. How do I duplicate a file descriptor in C? Use the dup system call to duplicate a file descriptor in C, allowing two references to the same underlying pipe. 2017-02-15
  17. Golang’s realtime garbage collector, at The Realtime Guild A talk given with Will Sewell. Overview of Go’s concurrent garbage collector. 2017-02-15
  18. How do I close a file descriptor in C? To close a file descriptor in C, use the close system call. Multiple descriptors can reference the same underlying file or pipe. The pipe is only closed when all references are closed. 2017-02-16
  19. What are setjmp and longjmp in C? setjmp and longjmp in C bypass normal function call and return flow, allowing a function to return to a previously saved state. setjmp saves the current execution context, and longjmp restores it. 2017-02-18
  20. How to generate Intel and AT&T assembly with clang Generate Intel and AT&T assembly with clang, demonstrating the difference in syntax between the two styles. 2017-02-19
  21. What is lsof? lsof lists open system resources, including pipes, sockets, and yes, files. It shows their type, owner, and location. 2017-02-20
  22. How to write an assembly ‘hello world’ on macOS A “Hello, world!” program in x86-64 assembly for macOS, using the NASM assembler and system calls for writing to stdout and exiting. 2017-02-20
  23. What is a a FIFO, or “named pipe”? What is mkfifo in C? A FIFO is a special file that allows inter-process communication. The mkfifo system call creates a FIFO, enabling processes to read from and write to it. 2017-02-21
  24. Don’t use the word ‘simply’ Avoid using the word “simply” as it can come across as insulting to the reader by implying the task is easy or the reader is stupid. Instead, rephrase to be more objective and avoid comparatives like “simply” or “just.” 2017-02-22
  25. What is ssize_t in C? ssize_t is a signed version of size_t, used to represent return values from system calls that may need to indicate error with -1. 2017-02-22
  26. How do I print bits in C? A program in C that prints the individual bits of various data types, showing how they are represented in memory. 2017-02-23
  27. What is mode_t in C? mode_t is a bitfield type in C that represents file permissions, including read, write, and execute permissions for the owner, group, and other classes. It provides symbolic constants to set and check these permissions. 2017-02-24
  28. Should I go paperless? Going paperless by scanning, shredding, and storing documents digitally in Google Drive can solve issues with physical clutter and document management, while carefully considering the tradeoffs of legal weight, fidelity, sentiment, independence, and privacy. 2017-02-25
  29. How to write a TCP server using the fork syscall A TCP server that uses the fork system call to create a new child process for each accepted connection, allowing it to handle multiple clients concurrently. 2017-02-25
  30. What is UTF-8? UTF-8 is a character encoding that can represent the entire Unicode character set. It’s variable-length, self-synchronizing, and an extension of ASCII. 2017-02-26
  31. What are the domain and type arguments to the socket system call? The domain and type arguments to socket() describe the protocol family and socket type, respectively. The protocol argument specifies the actual protocol to use, which may be inferred from the domain and type. 2017-02-27
  32. How to write a TCP server with the pthread API A TCP server that uses pthread to serve multiple clients concurrently, with an “echo” server for each connection. 2017-02-28
  33. What is the Apple Store release process? 1) Enroll in the Apple Developer Program. Create an “App Record” in iTunes Connect. Upload the app. Submit it for review. 2017-03-01
  34. Installing and running ebe Install ebe assembler with a one-liner, but be wary of the SourceForge installation script. 2017-03-01
  35. Monthly review: 2017-02 Focused on learning C, UNIX, and networking fundamentals. To avoid becoming a neckbeard, I’ll keep my projects grounded in real-world applications. March will be dedicated to Vidrio. 2017-03-01
  36. Justifying posts A technique to improve blogging focus by including a justification for each post, referring back to monthly targets. Allows room for off-the-wall posts. 2017-03-01
  37. Redis Pub/Sub under the hood Examines Redis’s source code to understand how it tracks subscriptions, handles disconnections, and implements pattern subscriptions, highlighting potential pitfalls and attack vectors. 2017-03-01
  38. How do I create the AppIcon for my app? To fix misconfigured App Icons, create properly-sized PNG files and update the Contents.json file to reference the correct image files. 2017-03-01
  39. How to submit an app build to iTunes Connect To submit a macOS app build to iTunes Connect, archive the app in Xcode, enable App Sandbox, then upload the build. 2017-03-02
  40. How to add a developer account to XCode Xcode uses “teams” to manage developer identities, and revoking a certificate on one device may require regenerating provisioning profiles. 2017-03-03
  41. How do I encrypt text with openssl? Encrypt and decrypt text using the openssl enc command with a password and AES-256 cipher. The encrypted text is base64-encoded. 2017-03-09
  42. Golang’s realtime garbage collector at Not On The High Street Conference Discussed Go’s real-time garbage collector at an internal conference, after presenting the same talk at The Realtime Guild. 2017-03-10
  43. How do I generate random bytes with openssl? Generate random bytes with openssl rand, which uses a PRNG seeded with entropy from ~/.rnd. 2017-03-10
  44. How do I fetch a server’s SSL certificate using openssl? Use the openssl s_client command to fetch a server’s SSL certificate chain, including the root certificate. 2017-03-11
  45. How do I hash a password with openssl? The openssl passwd command hashes passwords using the outdated crypt algorithm, with truncation to 8 characters - a poor choice for secure password hashing. 2017-03-12
  46. How do I create a message digest using openssl? Create message digests using the openssl dgst command, specifying the hash algorithm (e.g. -sha512) and optionally signing with a shared password using -hmac. 2017-03-13
  47. Don’t say ‘it will take five minutes’ Avoid claiming unrealistic time estimates like “5 minutes” for product onboarding or tutorials. Realistic estimates like “a couple hours” are more honest and set appropriate expectations. 2017-03-14
  48. How to make a Cocoa application without a .xib file To create a Cocoa app without a .xib file, remove the NSMainNibFile key from the Info.plist, and replace the @NSApplicationMain annotation on your AppDelegate class with a custom main.swift file that manually sets up the application and its delegat
  49. What is Swift’s @NSApplicationMain annotation? The @NSApplicationMain annotation in Swift is a macro that calls NSApplicationMain(...) to set up the Cocoa application’s UI event loop. 2017-03-18
  50. What is NSApplication? How is it instantiated? What is NSApp? NSApplication is the core of a Cocoa application. It is typically instantiated via NSApplicationMain or by calling NSApplication.shared(). NSApp is a global variable that holds the singleton instance of NSApplication. 2017-03-19
  51. How is MainMenu.xib found in Cocoa? NSApplicationMain loads the MainMenu.xib file to create the application’s main menu and window. It first looks for the NSMainNibFile key in the Info.plist file, and if not found, it falls back to the first nib/xib file in the main bundle. 2017-03-20
  52. How do I do public-key encryption with openssl? Generating RSA keys, extracting the public key, encrypting with the public key, and decrypting with the private key. 2017-03-21
  53. How do I do public-key signatures with openssl? Using openssl genrsa, openssl rsa, openssl rsautl -sign, and openssl rsautl -verify. 2017-03-22

2017 245

  1. How to get your point across with spaced repetition Repetition is key for effective communication. Spaced repetition throughout the text, not just in the intro and conclusion, helps readers remember the main point. 2017-03-23
  2. Your password is the private key. So what is the public key? Asymmetric cryptography uses public and private keys. The private key can be derived from a password using a secure PRNG, avoiding the need to store the private key. 2017-03-24
  3. Study of framer.com promo video An analysis of the Framer.com promo video, highlighting its engaging music, timed animations, and succinct text slides. 2017-03-25
  4. How to use keycastr Keycastr is a tool that displays your keystrokes on the screen during screencasts, but has some issues like not displaying over maximized windows, fixed positioning, and using obscure key symbols. 2017-03-27
  5. Varying navbar for mobile and desktop Using CSS media queries to re-word navbar elements based on screen width. 2017-03-28
  6. How to prevent autoplay on mobile Prevent annoying video autoplay on mobile by detecting mobile devices and serving a manual play button instead. 2017-03-29
  7. Replay with sound A “Replay with sound” button to control a muted video, implemented using the YouTube Iframe API. 2017-03-30
  8. Monthly review: 2017-03 Completed Vidrio release in March, but fell short on other goals. Focused heavily on Vidrio development and marketing, rather than technical learning. Plans to continue Vidrio work and study OpenSSL, iptables, NAT, OAuth, and payment systems in April. 2017-04-01
  9. What is ‘sequencing markets’? A strategy for growing a product by starting with an extremely specific target market and gradually expanding to broader markets. 2017-04-02
  10. How to run go tool trace A screencast about go tool trace, a profiling tool for Go applications. 2017-04-03
  11. What is the viewport meta tag? How can I display my website on mobile? Mobile browsers magically scale pages to fit mobile screens. Setting width=device-width disables this, but it requires the website to be designed for small screens. 2017-04-04
  12. How do I set a socket to be non-blocking? To set a socket as non-blocking, use fcntl to mark it with the O_NONBLOCK flag. This allows the socket to fail gracefully instead of blocking when no data is available. 2017-04-05
  13. rxi/vec - a simple C vector library rxi/vec provides dynamic arrays in C, including push, pop, and iteration, without the need to manage array resizing and length. 2017-04-06
  14. What is go tool trace? A screencast about go tool trace, a profiling tool for Go applications. 2017-04-06
  15. Multiplexing by looping over nonblocking sockets A TCP server that multiplexes multiple clients without select by looping over non-blocking sockets, maintaining a shared counter of total bytes received. 2017-04-07
  16. How to implement a ‘free trial’ for macOS apps Implementing a ‘free trial’ for macOS apps involves a license-generation system on a server and a license-verification system in the app, plus storing the license data in the app’s preferences file. 2017-04-08
  17. Product key server as a service I want a service to manage product keys for software monetization, including key generation, signing, distribution, and verification, with optional machine or user licensing restrictions. 2017-04-09
  18. Playing with Stripe Investigating Stripe as a payment processor for Vidrio. Trying out the client-side and server-side integration, creating a simple Go server to handle the Stripe token and charge the user. 2017-04-10
  19. How can I do elliptic curve crypto with OpenSSL? Generate ECC private key with openssl ecparam, extract public key from it using openssl ec, derive shared secret using openssl pkeyutl. 2017-04-14
  20. How to create a public-key infrastructure I demonstrate creating a public-private key pair, distributing the public key, and using a trusted third party (CA) to vouch for the public key. 2017-04-15
  21. What is a business? What is a company? Businesses can take different legal forms, such as companies, sole traders, and partnerships. Companies are unique in that they are considered “legal persons” with their own finances and liabilities, distinct from their directors and shareholders. 2017-04-16
  22. What company information is public? What’s on Companies House? Companies House is the UK company register. It provides public information about registered companies, including their registration details, officers, business activities, and financial statements. 2017-04-17
  23. How to write a TCP chat server in 55 lines of Golang A TCP chat server in Go, where each client message is broadcast to all other connected clients. Uses the net package and goroutines to manage multiple connections. 2017-04-18
  24. How to write an OpenCL ‘hello world’ on macOS A program that squares an array of floats on the GPU, using the OpenCL API on macOS. 2017-04-19
  25. How to run Swift from the CLI Run Swift scripts from the command line using swift hello.swift, or compile them to an executable with swiftc hello.swift. 2017-04-20
  26. What is a .app? A .app is a macOS application bundle, a directory structure containing the executable and supporting files. The .app directory contains the real program binary, but cannot be directly executed. 2017-04-21
  27. What is the simplest neural network? One neuron A neural network with one neuron that classifies binary-encoded natural numbers. We can decide whether the number is even, or whether it’s greater/less than 5. 2017-04-22
  28. How to write ‘hello world’ in TensorFlow Two ways to calculate the cost per gram of chocolate: one without machine learning, and another using TensorFlow to learns a linear model. 2017-04-23
  29. How to apply a CIFilter to an image in Swift Using CIFilter to apply a sepia tone filter to an NSImage and save the result to a file. 2017-04-26
  30. How to make a custom CIFilter in Swift Using a CIFilter using a GLSL kernel to swap the red and green components of an image. 2017-04-27
  31. What are samples in a Core Image kernel? Kernels in Core Image operate on output pixels, using samplerCoord to find corresponding input pixels. sample then retrieves the color of the input pixel. Kernel can apply transformations by modifying the samplerCoord expression. 2017-04-28
  32. How to write a webcam app in Swift on macOS A macOS app that displays a webcam preview in a floating panel, using the AVFoundation framework. 2017-04-29
  33. How to pass multiple inputs to a CIKernel A CIKernel in Swift can have multiple inputs, including image samplers and other data types. Example: an alpha-compositing kernel. 2017-04-30
  34. How to make a Core Image kernel program running on the CLI A Swift CLI program that applies a Core Image kernel to image files, allowing operations like averaging two images. 2017-05-02
  35. What is CIColorKernel? CIColorKernel is a type of CIKernel optimized for pixel-wise image transformations, with input as pixel samples instead of image samplers. 2017-05-03
  36. What is the clear program? The clear program clears the terminal screen using the escape sequence \033c, where \033 is the ASCII code for “escape” and 'c' is the command to clear the screen. 2017-05-06
  37. Don’t trust cat! cat can hide malicious content behind terminal control sequences, so you should not trust its visual output. Use less or hexdump to inspect files instead. 2017-05-07
  38. Defining the sine function as an oscillator The sine function can be defined as the oscillation of an object on a spring, which can be simulated with a simple iterative function. This provides an intuitive definition of sine beyond the standard trig-based one. 2017-06-04
  39. Long calendar A long-term personal calendar that captures life goals, plans, and trajectories rather than daily schedules. Focuses on broad life stages and scenarios rather than precise event planning. 2017-06-06
  40. Pattern jokes via WordNet/NLTK A chatbot that generates “pattern jokes” by replacing a word in a phrase with a related word from the same category, using WordNet and NLTK. 2017-06-25
  41. The Fisher Tree at The Realtime Guild A talk about the Fisher Tree, a data structure, with slides and code. 2017-07-05
  42. Golang’s realtime garbage collector at GoWayFest, Minsk Presented “Go garbage collector” talk at GoWayFest in Minsk, met fellow Gophers, and did some tourism around Belarus and Ukraine. 2017-07-21
  43. Notes from Minsk Spoke with Will about the Go garbage collector at GoWayFest in Minsk, Belarus. Orderly city. Software engineering scene surprisingly big. 2017-07-25
  44. Are concurrent fwrites atomic? No! Concurrent fwrites are not atomic and can lead to interleaving of characters, invoking undefined behavior. POSIX does not specify behavior of concurrent writes to a file, so applications should use concurrency control. 2017-07-29
  45. How to cut out the CA middleman Eliminate Certificate Authorities by storing the public key for a domain directly in the DNS, allowing browsers to verify the identity of a server without relying on a third-party CA. 2017-07-30
  46. How to watch system calls with dtruss dtruss allows tracing system calls on macOS. It shows the syscall, arguments, return value, and errno. 2017-08-01
  47. How to implement malloc/free A malloc/free implementation that maps allocations directly to mmap/munmap, with the allocation size stored before the returned pointer. 2017-08-02
  48. How can I do DNS lookup in Go? Using the Go "net" package to look up IP addresses for a given domain name, using either the C stdlib or a pure Go DNS resolver. 2017-08-03
  49. How to write a DNS server in Go A DNS server in Go that responds to A queries for a hardcoded set of domain-to-IP mappings, using the miekg/dns package. 2017-08-04
  50. How to let your users sign in with Google, from scratch Implemented Google Sign-In for a web app, handling the authentication flow and verifying ID tokens to authorize access to a private diary feature. 2017-08-05
  51. Instance DNS in multi-tenant services Pusher could use runtime DNS lookup to identify the cluster for each app instance, instead of hardcoding the cluster. This allows more flexibility, and easier changes, at the cost of some lookup overhead. 2017-08-06
  52. This site is now on jameshfisher.com Moved blog from jameshfisher.github.io to jameshfisher.com, with CNAME setup and GitHub custom domain settings. Switching to Netlify for HTTPS hosting. 2017-08-07
  53. How to move your GitHub pages blog to Netlify Moved GitHub Pages blog to Netlify, using custom domain, HTTPS, and redirects from the old site. 2017-08-08
  54. What is the rel=canonical tag? <link rel="canonical" href="..."/> specifies the preferred URL of a page duplicated across domains. Search engines use this to determine which page to recommend. 2017-08-09
  55. How to trace a DNS lookup Tracing a DNS lookup for ws-mt1.pusher.com using dig +trace reveals the iterative process of resolving the domain name, starting from the root name servers and following referrals to the top-level domain and authoritative name servers. 2017-08-10
  56. How do peer-to-peer programs discover each other? Peer-to-peer programs use centralized discovery mechanisms like BitTorrent trackers and Bitcoin DNS seeds to find peers, as a purely decentralized approach would require an impractical brute-force search. 2017-08-11
  57. How to build a .dmg to distribute MacOS apps Package a macOS app for distribution outside the Mac App Store by archiving it in Xcode, exporting it with a Developer ID signature, then creating a .dmg disk image. 2017-08-12
  58. How to distribute a MacOS .dmg Distributing Vidrio outside the Mac App Store with a signed .app in a .dmg, and creating custom download badges to comply with Apple’s guidelines. 2017-08-13
  59. Greater-than is redundant > is redundant; < alone suffices for all comparisons. I prefer it because it aligns with the number line. 2017-08-15
  60. How do Reddit thumbnails work? Embedly respects Open Graph og:image meta tag for thumbnail selection. Adding it to vidr.io enables Reddit thumbnail. 2017-08-16
  61. Golang’s realtime garbage collector at GolangUK 2017-08-17
  62. What is stdatomic in C? stdatomic provides atomic operations like atomic_fetch_add to ensure thread-safe access to shared variables. 2017-08-18
  63. Does C have generics? C’s _Generic is not true generics. It requires manual implementation of concrete type cases, unlike generics that automatically generate code for any type. 2017-08-19
  64. What is an authoritative DNS server? What is a recursive DNS server? Authoritative DNS servers provide definitive responses for their domains, while recursive DNS servers consult other servers to serve responses, caching results to reduce load on authorities. 2017-08-20
  65. What is C include? #include in C does not import functionality, but rather inserts the preprocessed text of the included file. The actual implementation of the included functions, like fprintf, is provided through linking. 2017-08-21
  66. How to inspect Mach-O files Using otool to see dynamic library dependencies, and nm to see function symbols. 2017-08-22
  67. Sentence wrap Sentence-wrap is a text-wrapping approach that inserts newlines between sentences. Diffs are easier to read, and sentences more apparent. Reminiscent of poetry. 2017-08-23
  68. How to make plugins with dlopen Dynamically load and unload shared libraries using dlopen, dlsym, and dlclose. 2017-08-24
  69. What system calls does dlopen use? The dlopen API uses open, mmap, close, and munmap to load a shared object file into memory, without requiring any special syscalls. 2017-08-25
  70. What is extern in C? extern declares a variable without defining it, allowing the linker to find the definition elsewhere. This is useful when a variable is declared in one file but defined in another. 2017-08-27
  71. What is static linking in C? Static linking in C involves compiling a library and main program separately, then linking the object files together into an executable. 2017-08-26
  72. What is an extern function in C? In C, function declarations are implicitly extern, meaning they have external linkage. The static keyword can be used to give a function internal linkage instead. 2017-08-28
  73. A calendar view for this blog An updated calendar-based homepage, highlighting gaps in posting. 2017-08-29
  74. Securing my Bitcoin Old Bitcoin wallet on a sketchy 2012 laptop. Block database corrupted but wallet.dat found. 2017-08-29
  75. How do I make a full-width iframe with fixed aspect ratio? Use CSS padding-top and position properties to create a full-width iframe with fixed 16:9 aspect ratio. 2017-08-30
  76. Post-driven permanent blog pages Permanent blog pages are now generated from tagged blog posts, providing automatic updates, separate URLs, and chronological ordering. 2017-08-31
  77. August review After a long blogging hiatus, I’m back. I’ve been giving conference/meetup talks, and have moved my blog to a permanent home at jameshfisher.com. In August, I wrote about C and DNS, and did marketing work on Vidrio. For September, I’m focusing on understanding and investing in cryptocu
  78. What makes a good blog post title? 5 steps to going VIRAL! To write a viral blog post title, use a question format, focus on a single topic, and employ clickbait tactics to pique readers’ curiosity. 2017-09-02
  79. Running a Laravel+Pusher workshop at work Internal workshop on Laravel+Pusher. Structured approach with checkpoints helped keep everyone on track. 2017-09-03
  80. How to write an essay Guidelines for writing compelling yet substantively questionable essays, focused on rhetorical techniques over truth. 2017-09-04
  81. Worst interview Disastrous interview experience. Unable to enter building. Was this a test to weed out the idiots? Ran away and never came back. 2017-09-05
  82. Array vs. dictionary pagination Paginate an API with either array indexing (?page_number=) or dictionary indexing (?first_word=). Array indexing suffers from shifting page boundaries, but is easier to parallelize. Dictionary indexing requires ordering, but handles dynamic ordering better. 2017-09-06
  83. What is the web Notification API? The web Notification API allows web apps to display system-level notifications, requiring user permission. It has two key parts: requesting permission and creating notifications. 2017-09-07
  84. Publication notifications for static sites Using a service worker to monitor the sitemap and display updates via browser notifications. 2017-09-08
  85. How could Bitcoin fail? Bitcoin could fail due to theoretical inferiority, lack of practicality, bans, critical bugs, centralized control, or technological collapse. 2017-09-09
  86. What are service workers? Service workers are scripts that run outside the browser context, allowing web apps to perform tasks like caching, network requests, and offline functionality. 2017-09-10
  87. Service worker hello world A service worker that responds to a “ping” message with “pong”, and a client-side script that registers the service worker and sends it the “ping” message. 2017-09-11
  88. new Notification(...) is deprecated Deprecated new Notification() replaced with ServiceWorkerRegistration.showNotification(). 2017-09-12
  89. What is the web Background Sync API? The Background Sync API lets service workers execute tasks even when the client page is not active. It queues jobs that run as sync events, which can trigger desktop notifications. 2017-09-13
  90. What is a Web App Manifest? A web app manifest is a JSON file that provides metadata about a web app, such as its name, icons, and display mode, enabling features like adding it to a homescreen. 2017-09-14
  91. Why are there 21 million bitcoins? The 21 million bitcoins limit was chosen to ensure the smallest unit, the satoshi, would have a reasonable value if Bitcoin were the world’s exclusive currency. 2017-09-15
  92. Hello world in Rust I install Rust, create a “Hello World” program, and compare it to the equivalent C program. The Rust binary has additional dependencies beyond the standard C library. 2017-09-17
  93. Coping with depression Depression involves negative cycles of repression, guilt, and reclusiveness. Coping strategies include getting out, making healthy meals, reading, and talking about it. 2017-09-16
  94. ICFP: Ode on a Random Urn An efficient way to represent and sample from a discrete probability distribution, using a balanced binary tree data structure called the “urn”. 2017-09-18
  95. What is the web Push API? Web applications can “subscribe” for notifications via PushSubscription endpoint, but there’s poor interoperability between different browsers’ push services. 2017-09-19
  96. Web Notification API onclick notificationclick service worker event lets the web app open a webpage via clients.openWindow. 2017-09-20
  97. How can I encrypt data in the Web Push API? Browser generates keys, shares public key; server encrypts data with it; browser decrypts push payload. 2017-09-21
  98. Adding an RSS feed to a Jekyll blog Adding an RSS feed to a Jekyll blog using the jekyll-feed gem, configuring _config.yml, and adding links to the HTML template. 2017-09-22
  99. How can I store things on the browser? Browsers offer various storage options, including cookies, localStorage, sessionStorage, IndexedDB, CacheStorage, WebSQL, and AppCache, each with its own tradeoffs in terms of use case, persistence, and support. 2017-09-23
  100. LocalStorage hello world LocalStorage allows web apps to store key-value pairs locally in the browser, with storage scoped to the origin. Comes with a free demo. 2017-09-24
  101. lldb hello world Compiling a C program with debugging flags, then using lldb to set breakpoints, step through the code, and observe output. 2017-09-25
  102. IndexedDB hello world How to create an IndexedDB database, add an object store, and read/write data. 2017-09-26
  103. WebGL hello world A WebGL demo that creates a green square in a canvas element, showing the difference between 2D canvas and WebGL contexts. 2017-09-27
  104. Where is the Unicode feed icon? Lack of a standard Unicode feed icon despite its widespread use. I plan to submit a proposal for its inclusion. 2017-09-28
  105. Unicode is only for plaintext The Unicode Consortium rejected proposals for encoding a “external link sign” character, citing that it is not “an element of plain text”. This precedent makes it unlikely that a proposal for a Unicode feed icon would be approved. 2017-09-29
  106. Drawing a triangle with WebGL A WebGL example that draws a cyan triangle on a pink canvas by creating shaders, a program, a vertex buffer, and rendering using gl.drawArrays(). 2017-09-30
  107. WebGL fragment shader A demo WebGL fragment shader that draws concentric circles, with a live editor to experiment with the shader code. 2017-10-02
  108. WebGL shader uniforms Shader uniforms in WebGL are global variables that allow passing data from the JavaScript application to the shader. A demo shows how to update a uniform representing the mouse position and use it to generate a dynamic pattern. 2017-10-03
  109. Textures in WebGL shaders A WebGL demo that creates a 2x2 checkerboard texture, uploads it to the graphics driver, and samples from it in the fragment shader to display a blurred checkerboard pattern. 2017-10-04
  110. WebGL fragment shader animation A WebGL fragment shader that animates a pulsating colored square by updating a time-based uniform in the shader. 2017-10-05
  111. How to load an image in WebGL Using WebGL to load an image and swap its RGB channels with a fragment shader. 2017-10-06
  112. Drawing a clock face with WebGL A WebGL clock face with moving hands that updates every second, using a vertex shader to convert polar coordinates to 3D positions. 2017-10-07
  113. WebGL canvas size vs. CSS size vs. viewport vs. clipspace vs. world space WebGL has several spaces that need to be properly managed to display content correctly. 2017-10-08
  114. WebGL clipspace point visualization A WebGL visualization of a point in 4D homogeneous clip space. Explore the effects of the x, y, z, and w components. 2017-10-09
  115. WebGL matrix visualization A WebGL-powered matrix visualization tool that lets you interactively edit a 4x4 transformation matrix and see the effects on a 3D cube render. 2017-10-10
  116. WebGL Lambertian shading Interactive WebGL demo that shows Lambertian shading, with a fragment shader that calculates lighting based on a normal map and mouse position. 2017-10-11
  117. WebGL shading: diffuse vs. specular Contrasting diffuse and specular shading models in WebGL, with live demos showing matte vs. shiny surface renderings. 2017-10-12
  118. WebAssembly hello world A WebAssembly program that prints 42 to the console, demonstrating the structure and usage of WebAssembly. 2017-10-13
  119. macOS OpenGL hello world using GLFW A program to create a cyan window on macOS using C and the GLFW library. 2017-10-14
  120. One-dimensional Perlin noise Random slopes are interpolated to create a smooth, wiggly line. More realistic noise is achieved by combining multiple octaves. 2017-10-15
  121. WebGL shaders with color WebGL shaders that respond to mouse movement, using normal maps and color maps to simulate diffuse and specular lighting on a rockface texture. 2017-10-16
  122. Multiple textures in WebGL Combining two textures in a WebGL fragment shader, using texture units and uniform locations to access the textures. 2017-10-17
  123. Generating a normal map in WebGL Generates a normal map of a cone in WebGL dynamically, without needing to load a static file. Using a rotation matrix and color conversion functions to create the normal map. 2017-10-18
  124. GLSL varying variables GLSL varying allows vertex shader outputs to be passed to fragment shaders. A WebGL demo with colors interpolated between vertices. 2017-10-19
  125. Generated normal-mapped ripples Generating dynamic normal-mapped ripple effects using WebGL, with the mouse position controlling the light source. 2017-10-20
  126. Drawing a cube in WebGL Rendering an animated 3D cube in WebGL using a vertex shader, face color uniforms, and matrix transformations for rotating the cube. 2017-10-21
  127. Game of Life implemented with a fragment shader A Conway’s Game of Life simulation implemented using WebGL fragment shaders, with rendering to texture and a Gosper Glider Gun initial state. 2017-10-22
  128. Giant Game of Life Implements a 1024x1024 grid of Conway’s Game of Life using WebGL fragment shaders. 2017-10-23
  129. Web Push API in Firefox Differences between the Web Push API in Google Chrome and Firefox. Firefox uses the Mozilla Push Service, enabling push notifications without Google’s GCM/FCM. 2017-10-24
  130. Group chat with end-to-end encryption Group chat with end-to-end encryption can use “client-side fan-out” where the sender encrypts the message separately for each recipient, or “server-side fan-out” where the sender encrypts the message once using a shared secret, then the server distributes the ci
  131. Forward secrecy with hash ratchets A “hash ratchet” ensures that a compromise of the current key does not allow decryption of past messages. Each message’s encryption key is derived from the previous key using a hash function. 2017-10-27
  132. WebGL shading: both diffuse and specular A WebGL shader that combines diffuse and specular lighting, allowing the user to adjust the relative contribution of each using keyboard controls. Guest post by Luís Fonseca. 2017-10-28
  133. Guest writers Setting up guest writers on a Jekyll blog. Marking authors in the metadata. Storing author information in a YAML file. 2017-10-29
  134. Hashing a string with the Web Cryptography API The Web Cryptography API provides low-level crypto primitives in JavaScript, including hashing strings using SHA-256. 2017-10-30
  135. Signing a string with HMAC using the Web Crypto API A web page that allows you to sign a string using the HMAC algorithm with SHA-256, implemented using the Web Crypto API. 2017-10-31
  136. Symmetric encryption with the Web Cryptography API Generating a key, encrypting and decrypting text, and explaining the implementation. 2017-11-02
  137. Asymmetric encryption with the Web Cryptography API Generating ECDH keys and deriving a shared AES key. 2017-11-03
  138. Adding Open Graph meta tags to jameshfisher.com Added Open Graph meta tags to improve how blog posts appear when auto-posted to Facebook. 2017-11-04
  139. What are promises in JavaScript? Promises in JavaScript represent future values. They provide a way to handle asynchronous operations, allowing chaining of callbacks. Promises can be fulfilled or rejected, with callbacks handling each case. 2017-11-05
  140. How do I release a PHP Composer package? To release a PHP Composer package, create a GitHub repo, add a composer.json file, submit the package to Packagist.org, and tag a stable version. Then Composer users can require your package. 2017-11-06
  141. A JavaScript Promises implementation Implementing a Promise API in JavaScript, including handling asynchronous callbacks, promise chaining, and automatically wrapping non-promise values. 2017-11-07
  142. How PHP and Composer find your code Composer’s autoloader uses PSR-4 to map namespaces to directories, allowing you to load classes without explicit require statements. 2017-11-09
  143. Adding a blog header Added a header to the blog with a photo that links to the homepage, as people expect a header for navigation. 2017-11-10
  144. SaaS price models: cost-based pricing vs. value-based pricing Cost-based pricing sets prices to cover costs plus profit, while value-based pricing sets prices based on customer willingness to pay. The optimal SaaS pricing model uses value-based inputs like user count that approximate customer value.
  145. Moving pictures Replaced static image on this site with a looped video. Experimenting with subtle motion to mimic images at first glance. 2017-11-12
  146. What is Swift’s @NSApplicationMain annotation? The @NSApplicationMain annotation in Swift automatically sets up the application’s entry point, including creating the NSApplication instance and assigning the AppDelegate class. 2017-11-13
  147. Diff views as instructions A proposal to use “diff views” in technical writing to clearly differentiate code under discussion from contextual information, similar to the format of version control diffs. 2017-11-23
  148. Adding blog tags I start using tags to categorize blog posts, enabling audience-specific features like subreddit auto-posting, customizable RSS feeds, and push notifications. 2017-11-24
  149. DNS resolution procedure DNS resolution is a recursive procedure involving different record types like A, CNAME, and NS. Resolving a domain name can require multiple DNS queries to different nameservers. 2017-11-25
  150. Nativité, a pastoral Christmas game A Christmas game where sisters compete to move their toy sheep closer to the Christ Child by doing good deeds, played out in real-time through a web app with an admin interface for the parents. 2017-11-26
  151. UNIX free: used does not mean what you think it means The used metric in free -m includes memory used for caching, not just application memory. The true memory usage is lower, calculated as used minus buffers/cache. 2017-11-29
  152. Diff views in GitHub-Flavored Markdown GitHub-Flavored Markdown supports “diff views” with + and - prefixes. While it loses syntax highlighting, it’s a quick and easy way to show changes. 2017-11-27
  153. What is ASN.1? ASN.1 is a data format used to encode structured data like RSA private keys and certificate signing requests. Using openssl asn1parse to reveal its structure. 2017-11-30
  154. An encrypted diary using OpenSSL Generate a master keypair. Encrypting each diary entry with a one-time shared secret. Encrypt the shared secret with the public key. Decrypt entries using the private key and the shared secret. 2017-12-03
  155. How less works: the terminal’s alternative buffer less uses the terminal’s “alternate screen” feature to clear the screen and display the contents of a file, and then restores the previous screen when exiting. 2017-12-04
  156. Nativité 2017: creating a Facebook Messenger bot Creating a Facebook Messenger bot for a Christmas game ‘Nativité’, switching from expensive SMS notifications. The bot is hosted on Heroku and Netlify, with Pusher for real-time updates. 2017-12-05
  157. Linking to external posts from Jekyll Using an external_url property for linking to external blog posts from a website built with Jekyll, allowing a comprehensive directory of all posts regardless of platform. 2017-12-06
  158. Inline quizzes Inline quizzes make reading more engaging by requiring readers to participate in the content. 2017-12-07
  159. What is modular arithmetic? Modular arithmetic involves operations like addition, subtraction, multiplication, and exponentiation that “wrap around” a fixed modulus. This is useful for cryptography like RSA. 2017-12-08
  160. What is a TTY? Terminals in Unix are files in the filesystem, identified by names like /dev/ttys008. Processes have standard input, output, and error streams that can be connected to terminals. The terminal a process is attached to can be inspected and manipulated. 2017-12-09
  161. What is open addressing? An open addressing hash table implementation in C, which resolves collisions by finding alternative buckets for elements using linear probing. 2017-12-10
  162. osquery: UNIX as a SQL database osquery allows querying a UNIX system using SQL. 2017-12-11
  163. Making a stream cipher A stream cipher in Go that generates an infinite keystream from a shared key using SHA-256. 2018-01-01
  164. How to hash multiple values Methods for hashing multiple values, including hash-then-XOR, concat-then-hash, and serialize-then-hash. The only method that’s collision-resistant is serialize-then-hash! 2018-01-09
  165. What is a random oracle? A random oracle is an idealized model of a hash function, where each call queries a global server that returns a true random value. This models important properties of real-world hash functions like collision resistance. 2018-01-10
  166. Bootstrapping a C compiler I propose BootstrapCC, a project to build a C compiler from a tiny handwritten program, avoiding the trust problem in Thompson’s “Reflections on Trusting Trust”. 2018-01-11
  167. A hex compiler in C A compiler that converts a text file containing hex codes and comments into a binary output file. 2018-01-21
  168. Don’t say “simply”, at Write The Docs London 2018-01-23
  169. What is tcpdump? tcpdump captures and displays network traffic. An example inspecting DNS requests and responses. 2018-02-01
  170. What does getaddrinfo do? getaddrinfo ostensibly does DNS lookups. Sounds simple, but it uses more than 100 system calls! Let’s trace the crazy path of address lookup on Linux. 2018-02-03
  171. Don’t use nscd nscd, a local DNS resolver within glibc, is non-standard. Instead, use a local DNS server like named or dnscache. 2018-02-05
  172. What is DHCP? DHCP dynamically assigns IP addresses to hosts, using a client-server protocol over UDP. It involves a sequence of DORA (Discover, Offer, Request, Acknowledge) messages to obtain and configure a network lease. 2018-02-06
  173. How does ping work? ping uses ICMP, or “Internet Control Message Protocol”, to send “echo request” packets and receive “echo reply” packets. 2018-02-07
  174. How does reverse DNS lookup work? Reverse DNS lookup maps an IP address to a domain name by querying PTR records. The mapping is not always consistent with the forward DNS lookup. 2018-02-09
  175. Run-length encoding in C A C implementation of run-length encoding, a compression scheme that works well on inputs with consecutive repeated characters. 2018-02-08
  176. What is a subnet? Subnets divide the IP address space hierarchically using bitstring prefixes. We check if an IP address is in a subnet using C. 2018-02-10
  177. How does an IP address get translated to a MAC address? IP addresses are mapped to MAC addresses using the Address Resolution Protocol (ARP). The OS maintains an ARP cache to store these mappings. 2018-02-11
  178. What is the routing table in Linux? When a packet arrives, Linux determines which network interface should handle it. It uses the first rule in the routing table that matches the destination address. Surprisingly, all 127.0.0.0/8 addresses go to the loopback interface. 2018-02-12
  179. What are TCP sequence numbers? TCP uses sequence numbers to map unordered IP packets to an ordered byte stream. The sequence number field is 32 bits, but wraps around to 0 after reaching the max value. The sender chooses a random “initial sequence number” during the connection handshake. 2018-02-24
  180. Running tcpdump on a TCP connection tcpdump captures network traffic. Capture and analysis of a TCP connection, including the 3-way handshake and message exchange. 2018-02-23
  181. How does swapping stdin and stderr work? The magic shell string 3>&2 2>&1 1>&3- swaps stdout and stderr. It does with the dup2 system call to swap file descriptors. 2018-02-22
  182. Hello world in C inline assembly A C program that writes “hello, world!” to the console using inline assembly instead of standard library functions, demonstrating direct system call invocation. 2018-02-20
  183. How to make a system call in C Replacing printf with write, and finally directly using the syscall function with inline assembly. 2018-02-19
  184. Diary writing prompts Struggling with mundane diary entries, I implement random writing prompts to reinvigorate the process. 2018-02-17
  185. What does Linux do with a lost TCP connection? Linux uses exponential backoff to retry dropped TCP connections, with a configurable retry limit. 2018-02-27
  186. How does network address translation work? NAT allows multiple devices in a local network to share a single public IP address. Routers modify IP and port information in network packets, and manage a translation table. 2018-03-02
  187. Creating a UDP connection with netcat nc can create UDP connections. UDP connections are established when the first data packet is sent, and terminated when the server becomes unreachable. ICMP messages notify the client of an unreachable server. 2018-03-04
  188. Writing a parser in Haskell I write a parser for JimScript, an imperative programming language, in Haskell. The parser goes through three stages: tokenization, nesting, and parsing. 2018-03-09
  189. An interpreter in Haskell An interpreter for an imperative language in Haskell, featuring integers, operators, global variables, control flow, and I/O primitives. 2018-03-06
  190. Hello world in Linux x86-64 assembly An x86-64 program that writes to stdout and exits. 2018-03-10
  191. A lambda calculus interpreter in Haskell A lambda calculus interpreter in Haskell, using de Bruijn indexing and lazy evaluation, with simple integer literals added. 2018-03-15
  192. What is HTTP keep-alive? What is HTTP request pipelining? HTTP keep-alive allows reusing the same TCP connection for multiple requests, avoiding the overhead of opening a new connection. HTTP request pipelining sends multiple requests without waiting for their responses. 2018-03-27
  193. How to create an SSH certificate authority Creating and using an SSH certificate authority, an alternative to the default “trust on first use” model. 2018-03-16
  194. Rounding up to the next power of two in C An efficient algorithm to round up to the next power of two in C, using bitwise operations and compiler intrinsics for constant-time performance. 2018-03-30
  195. A summary of Managing Oneself by Peter Drucker Discover your strengths, work styles, and values through feedback analysis. Align your career and relationships with your unique characteristics. 2018-04-01
  196. What are /dev/stdout and /dev/stdin? What are they useful for? /dev/stdin, /dev/stdout, and /dev/stderr are special files in the /dev directory that represent the standard input, output, and error streams of a process. They can be used to connect processes in a shell pipeline without creating tempor
  197. How is the Redis sorted set implemented? Redis sorted sets are implemented using a hash table for efficient key-value lookups and a skip list for efficient score-based ordering. I show a Haskell implementation that uses a forward map for keys and a reverse map for scores. 2018-04-22
  198. Month of Jack Robinson Jack Robinson is an instant messaging app where your message is shared as you type, with no “submit” button, reducing finger-to-eye delay compared to traditional chat apps. 2018-07-29
  199. Don’t say ‘simply’, at Write the Docs 2018, Prague 2018-09-13
  200. Summary of ‘Zero to One’, Chapter 3: All happy companies are different Profitable companies are monopolies, not competitors. Competition drives down prices but also wages and quality. Monopolies are not permanent, as new markets and products can create new monopolies. 2018-09-15
  201. Summary of ‘Zero to One’, Chapter 2: party like it’s 1999 The dot-com bubble showed that conventional wisdom is often wrong. Lessons learned, like being “lean” and avoiding new markets, prevent bold visions and are the opposite of what companies like Google and PayPal needed. 2018-09-14
  202. Summary of ‘Zero to One’, Chapter 4: The ideology of competition Competition is often destructive and distracting. Wise companies either diverge into new space or merge into a monopoly, rather than imitate each other through competition. 2018-09-16
  203. Summary of ‘Zero to One’, Chapter 5: Last mover advantage To build a lasting monopoly, focus on proprietary technology, network effects, economies of scale, and branding. Start small, sequence your markets, and aim to be the last mover in your industry. 2018-09-17
  204. Summary of ‘Zero to One’, Chapter 6: You are not a lottery ticket The USA believes in the future is unpredictable but will get better. A false contradiction. Success is not random, as evidenced by serial entrepreneurs who have founded multiple billion-dollar businesses. 2018-09-19
  205. Summary of ‘Zero to One’, Chapter 7: Follow the money The power law distribution is key in venture capital, companies, and careers. Focus on finding and growing the few with vast potential, rather than trying to fix failures. 2018-09-23
  206. Strava route builder API How to use the undocumented Strava Route Builder API to get routes between two points, including a JavaScript example. 2018-10-13
  207. How to count at scale at Redis Day London 2018 2018-11-15
  208. How does a Morris approximate counter work? The Morris approximate counter is incremented probabilistically. 2018-12-17
  209. What is the API for Google Ngram Viewer? The Google Ngram Viewer API is undocumented, but can be accessed by replacing the graph in the URL with json. This returns a JSON response with the frequency of the searched phrase over time. 2018-11-25
  210. A history of time in 40,000 pixels A visualization of how frequently different years are referenced in writing over time, showing patterns in how the past and future are viewed. 2018-12-18
  211. What is document.cookie? Cookies are client-side storage that get sent with every HTTP request. A cookie is scoped to a domain suffix, a path prefix, and a time range. The API is old and weird. 2018-12-22
  212. A cat walk cycle A pixel art animation of a “walk cycle”, created using GIMP, for use in a retro game. 2018-12-28
  213. How to make a webserver with netcat (nc) Use nc (netcat) to create a web server that returns custom HTTP responses. 2018-12-31
  214. How I start Jekyll blog posts I use a custom blogpost command to quickly create new blog post files with the current date and post title. 2018-12-30
  215. How to draw sprites on an HTML canvas I demonstrate animating a cat walk cycle on an HTML canvas using a sprite sheet image and the drawImage method. 2018-12-29
  216. How to run Redis Sentinel Redis Sentinel provides high availability for Redis. We start a Redis master, then three Redis Sentinel instances. They discover each other, then we trigger a failover. 2019-01-08
  217. How to fix ‘Activating bundler (< 2) failed’ error in your jekyll build Jekyll build breaks due to Bundler 2 incompatibility. Fixed by removing Bundler 1 version from Gemfile.lock. 2019-01-09
  218. Summary of ‘Zero to One’, Chapter 8: Secrets Valuable businesses are built on secrets - things that are hard but still doable. Look for secrets by thinking contrarily and exploring outside the mainstream. When you find a secret, share it only with the people you need to. 2019-01-27
  219. Why can’t I set the font size of a visited link? CSS visited link styles are limited for security reasons, as they could reveal a user’s browsing history. Color can be changed, but getComputedStyle will lie about it. 2019-03-08
  220. Probability notation for odds Different notations for betting odds, including fractional, decimal, and probability. Probability notation is shown to be the most transparent, revealing the bookmaker’s expected positive gain. 2019-03-30
  221. What is a betting exchange? Betting exchanges like Betfair allow users to act as bookmakers, offering bets at their own chosen odds. This contrasts with traditional bookmakers who set the odds. 2019-03-31
  222. What is a prediction market? Prediction markets allow people to bet on the outcome of future events, with the traded share prices reflecting the market’s probability estimate for those events. 2019-04-01
  223. Vélos, vins et vassaux dans la Loire Cycling tour of France’s Loire Valley, visiting chateaux, wineries, and medieval attractions over 5 days, from Tours to Nantes. 2019-04-09
  224. What is matched betting? Matched betting exploits differences in odds between betting exchanges to guarantee a profit, by betting on both sides of a proposition. 2019-04-02
  225. Electron hello world Installing Electron, creating an HTML web page, and writing the main entry point script to load the page. 2019-04-19
  226. Node.js addon hello world I create a native Node.js addon called addon in C++ using node-gyp. The addon exports a hello() function. 2019-04-20
  227. Does Redis Pub/Sub work with master-slave replication? Redis Pub/Sub works with master-slave replication, allowing messages published on the master to be replicated to the slave and received by subscribed clients on the slave. 2019-05-04
  228. How can I add tags to a Jekyll blog? A plugin to create tag pages on a Jekyll blog, and a minimal layout for those tag pages. 2019-05-05
  229. Browser webcam hello world Demo of the user’s webcam in a <video> element, using the navigator.mediaDevices.getUserMedia() API. 2019-05-06
  230. How do JavaScript iterators work? JavaScript iterators are objects that implement a specific protocol, providing a way to iterate over a sequence of values. The for...of loop is syntactic sugar for manually creating and using an iterator. 2019-05-10
  231. How to remember stopping distances for the Highway Code Formulas to calculate stopping distances for different speeds, using thinking and braking distances, instead of memorizing a table. 2019-05-15
  232. What are symbols in JavaScript? Symbols are a new fundamental data type in JavaScript, introduced in 2015. They are used to create unique object property keys that won’t clash with other properties. 2019-05-16
  233. What is function* in JavaScript? JavaScript’s function* defines a generator function, which can be used to generate and consume data. 2019-05-17
  234. JavaScript generators are also consumers! Generators in JavaScript can act as both producers and consumers of data. An example Metric generator batches and sends data using the yield keyword. 2019-05-18
  235. What is a McCulloch-Pitts neuron? A mathematical model where the neuron is a function that takes binary inputs and produces a binary output based on a threshold. The model can implement basic logic gates like AND and OR, but not more complex functions like XOR. 2019-05-27
  236. What is simulated annealing? Simulated annealing is a variation of trial-and-error optimization that generates mutations of the current best guess, and gradually reduces the magnitude of the mutations over time, similar to how metals cool. 2019-05-28
  237. How to name a product with reduplication Product names often use reduplication, like “Tic Tac” or “Fit Bit”, to mimic the babbling sounds of babies. This creates a sense of familiarity and simplicity. 2019-10-06
  238. Summary of ‘Zero to One’, Chapter 9: Foundations Startups must get the foundations right from the start. Choose co-founders carefully, keep the board small, hire full-time employees, and compensate with equity over high salaries, even for the CEO. 2019-10-07
  239. What are CSS variables? CSS variables, also called custom properties, allow defining and using dynamic values in CSS. They cascade and inherit like other CSS properties, with the var() function used to reference them. 2019-12-21
  240. Les Aventures De Toupac - a pixel art game A pixel art game developed over Christmas, with code on GitHub and development on Glitch. 2019-12-28
  241. What are CSS percentages? CSS percentages have varying meanings depending on the property. They can refer to the containing block’s width/height, the element’s own font size, or other specific measurements. 2019-12-29
  242. Browsing my genome Exploring my 23andMe genome data - a text file of single nucleotide polymorphisms, not a full DNA sequence, requiring a reference genome to interpret. 2019-12-30
  243. How does Glitch refresh my app? Glitch’s “Show in a new window” feature uses the window.open API to open a new window, and then manipulates the contents of that window by updating its location property when the source code is edited. 2020-01-01
  244. Determine if a string has all unique characters A recursive algorithm to determine if a string has all unique characters, with an analysis of its time complexity. 2020-01-04
  245. How to reverse a string in C An in-place string reversal function in C, starting by swapping the first and last characters, then iterating towards the middle. 2020-01-05

2016 61

  1. Determine whether one string is a permutation of the other A C function to determine if one string is a permutation of another, using a character distribution representation for optimal time and space complexity. 2020-01-06
  2. How to percent-encode strings in-place A C function to replacing spaces with "%20" in-place, by iterating from the end, preserving true string length. 2020-01-07
  3. Run-length encoding in C Compresses a string by replacing consecutive repeated characters with the character and its count. The solution requires two passes to first calculate the length of the compressed string, then generate it. 2020-01-08
  4. How to rotate a square matrix in-place An in-place algorithm to rotate a square matrix by 90 degrees. The key is to rotate 4 corresponding points using a formula, applying this to all points in the top-left corner. 2020-01-09
  5. How to remove duplicates from an unsorted linked list To remove duplicates from an unsorted linked list with no extra memory, use a nested loop to check each node against all others, removing duplicates as you go. Time complexity is O(n^2). 2020-01-10
  6. How to find kth last node of a linked list Use the “runner” technique with two pointers - one leading by k nodes - to find the kth last element of a singly linked list without knowing the list length in advance. 2020-01-11
  7. How to delete a node from the middle of a linked list To delete a node from the middle of a linked list, copy the value and next pointer of the next node to the current node, then free the next node. 2020-01-12
  8. How to partition a linked list A C function to partition a linked list around a value x, running in optimal time and space. 2020-01-13
  9. How to reverse a linked list Reverse a linked list by treating it as a stack, popping elements and pushing them onto a new list. An implementation in C without a separate stack. 2020-01-14
  10. How to find the middle of a linked list A trick to find the middle of a linked list by using two pointers, slow and fast, where fast moves twice as fast as slow. 2020-01-15
  11. How to check whether a linked list is a palindrome Find the middle node of the linked list using the “runner” trick. Reverse the first half, then compare the nodes pairwise from the middle outwards. Restore the list to its original state before returning. 2020-01-16
  12. Implementing a stack using a linked list The head of the list is the top of the stack. 2020-01-17
  13. Implementing a queue using a linked list The head is the front of the queue, allowing efficient dequeue. The tail is the back of the list. To enqueue efficiently, we keep a reference to the tail. 2020-01-18
  14. A stack with minimum element A stack with a min operation that runs in O(1) time. Store the current minimum alongside each element, or use run-length encoding to compress the stack of minimums. 2020-01-19
  15. Towers of Hanoi in Haskell A Haskell solution to the classic Towers of Hanoi problem. 2020-01-20
  16. Implementing a queue using two stacks Implement a queue using two stacks, with one stack for the back of the queue and one for the front. Reverse the back stack onto the front stack when dequeuing to maintain the queue order. 2020-01-21
  17. How to sort a stack using one additional stack We can model “infinite tape” using two stacks. Then we can navigate the list in both directions. This lets us bubble-sort the list in O(n^2) time. 2020-01-22
  18. How to check if a binary tree is balanced An O(n) algorithm to check if a binary tree is balanced, by passing up the height from recursive calls. 2020-01-23
  19. Is there a route between these two nodes in this directed graph? An algorithm in Haskell using a breadth-first search to find the reachable set of nodes. 2020-01-24
  20. Simulating epidemics An interactive simulation showing how disease characteristics and human behavior can significantly impact the spread of an epidemic. 2020-02-15
  21. Why does this RNA virus look like DNA? RNA genomes of viruses like COVID-19 are often sequenced as complementary DNA (cDNA) for practical reasons, though the actual genome is made of RNA with uracil instead of thymine. 2020-02-16
  22. Simulating epidemics with WebGL A spatial SIR model for simulating epidemics, implemented using WebGL fragment shaders. Tracks susceptible, infected, and recovered populations in a 2D grid. 2020-02-23
  23. When in doubt, don’t blur it out Blurring sensitive information in images may not effectively protect privacy, as the original content can often be recovered using deblurring techniques. 2020-02-29
  24. How to write an ArrayBuffer to a canvas I write an ArrayBuffer to a canvas by interpreting the buffer as pixel data and using ImageData to provide the dimensions. 2020-03-01
  25. Rule 110 in WebGPU A WebGPU-powered simulation of the Rule 110 cellular automaton, rendering a dynamic image on a canvas. 2020-03-02
  26. Game of Life in WebGPU Implementing Conway’s Game of Life in WebGPU, a 2D cellular automaton simulation. Uses compute shaders to update the game state and render the cells. 2020-03-03
  27. Simulating epidemics in WebGPU Simulating an epidemic in WebGPU using a direct index into an array of cells, avoiding the issues encountered with the previous WebGL implementation that used a texture. 2020-03-12
  28. How to record a canvas to video Using the MediaRecorder API to record a canvas element as a WebM video file, allowing the user to download the recorded video. 2020-03-13
  29. What is the order of NSWindow levels? The order of NSWindow levels is defined by the CGWindowLevelKey constants, with lower numerical values being behind higher ones. The NSWindow.Level enum provides a more limited set of semantic level names, with some levels overlapping. 2020-08-03
  30. devices(for:) was deprecated in macOS 10.15: Use AVCaptureDeviceDiscoverySession instead Use AVCaptureDeviceDiscoverySession instead of the deprecated AVCaptureDevice.devices(for:) to discover video capture devices. 2020-07-31
  31. Why is the contentRect of my NSWindow ignored? Calling setFrameAutosaveName on an NSWindow causes its size and position to be saved to user defaults, overriding the contentRect passed to the constructor. To avoid this, do not call setFrameAutosaveName. 2020-07-10
  32. How to resolve “the app shows no response upon launch” in App Review To resolve “the app shows no response upon launch” in App Review, identify and handle potential sources of fatal errors, such as uncaught exceptions, force-unwrapping nil values, unsafe downcasts, and out-of-bounds array access. Di
  33. How to implement green screen in WebGL An green screen implementation in the browser using WebGL and a chroma key shader. Includes a demo that replaces sufficiently green pixels with magenta. 2020-08-10
  34. How to implement green screen in the browser A green screen implementation in the browser using WebGL and chroma key. Includes a live demo. 2020-08-09
  35. Production-ready green screen in the browser A green screen implementation in the browser using WebGL and chroma key. Includes a live demo. 2020-08-11
  36. Step-away background removal A step-away background removal technique using WebGL, which compares both chrominance and luminance differences between the webcam feed and a captured background image to create a transparent mask. 2020-09-20
  37. Edge detection with Sobel filters A WebGL fragment shader that implements the Sobel filter, a method for detecting edges in an image. A demo processes your webcam video stream. 2020-08-31
  38. BodyPix hello world BodyPix is a TensorFlow model for person segmentation. A demo of BodyPix in the browser. 2020-08-16
  39. Why does my WebGL alpha-transparency look wrong? WebGL alpha-transparency may appear wrong because of premultiplied alpha. Fix it by setting premultipliedAlpha: false when creating the WebGL context. 2020-08-12
  40. BlazeFace hello world A demo that uses the BlazeFace model from TensorFlow.js to detect faces in a webcam stream, and draws the detected landmarks on the video. 2020-09-21
  41. Running BodyPix on a video stream Applying the BodyPix machine learning model to a video stream for real-time person segmentation, with separate render and segmentation loops to optimize performance. 2020-09-23
  42. Resizable boxes in pure CSS! The CSS resize property allows any element to be resized, not just <textarea>! But there are some gotchas. 2020-09-22
  43. Using BodyPix segmentation in a WebGL shader A WebGL shader that uses BodyPix segmentation to set the alpha channel. 2020-09-24
  44. JavaScript modules for grumpy developers from 2005 JavaScript modules enable better dependency management and scoping. A guide for developers like me who still use <script> tags everywhere. 2020-09-25
  45. What are JavaScript source maps? Source maps map generated JavaScript to original source files, allowing debugging of the original code in the browser’s dev tools. 2020-09-26
  46. What does the require function do in Node.js? The require function in Node.js loads modules, either local files or external packages. I show the algorithm that searches node_modules directories and package.json files. 2020-09-27
  47. JavaScript live bindings are just concatenation ES modules are just concatenated source files, with some error checking and variable renaming. Live bindings are an illusion - they’re just ordinary variables at the top-level scope. 2020-09-28
  48. What are AMD modules? Fetch your sick bag “Simplified CommonJS wrapping” feature is a hacky attempt to support synchronous require calls by using regexes. It’s gross. 2020-10-03
  49. Executables in npm? NPM packages can contain executables, not just Node.js modules. NPM provides features to help distribute and run these executables, such as the bin field in package.json and the npm run-script command. 2020-10-02
  50. How to publish an npm package Publishing an npm package @jameshfisher/numsyslib with a stringifyRoman function that converts a number to a Roman numeral. 2020-10-01
  51. What is npm? NPM is Node.js’s package system, allowing installation of arbitrary stuff, not just Node.js modules. Packages are folders, tarballs, URLs, or version identifiers published to the NPM registry. 2020-09-30
  52. How do ECMAScript modules work in Node.js? ECMAScript modules and CommonJS modules in Node.js are interoperable. Node.js looks at file extensions and package.json fields to determine the module type. ECMAScript modules can only use import, while CommonJS modules can only use require. 2020-09-29
  53. Head tracking with BlazeFace A method for calculating a bounding circle around a head, using facial landmarks from BlazeFace. Plus a live demo that you can run on your own face. 2020-10-11
  54. How to self-host a TensorFlow.js model Involves downloading the model manifest file and associated binary weight files, to avoid downloading large models every application launch. 2020-10-07
  55. How to make a floating head Creating a “floating head” effect using WebGL and the BodyPix machine learning model to segment the face from a webcam feed. 2020-10-06
  56. How does the Node.js REPL display previews? Node.js REPL uses the inspector module to safely evaluate expressions as you type, using V8’s evaluation with throwOnSideEffect: true to avoid executing harmful code. 2020-10-05
  57. What are UMD modules? One final module system to rule them all (except ES modules which are a different thing) UMD modules are a way to write JavaScript code that can be used in any module system (e.g. CommonJS, AMD, or as a global variable). 2020-10-04
  58. A head in a box with BlazeFace A method for calculating a bounding circle around a head, using facial landmarks from BlazeFace. Plus a live demo that you can run on your own face. 2020-10-12
  59. WebRTC group chat hello world A WebRTC-based group chat application that uses Ably’s publish-subscribe system for signaling. Clients connect directly via peer-to-peer data channels, with Ably facilitating the initial connection. 2020-10-13
  60. The Electron process architecture is the Chromium process architecture An Electron instance is basically a Chromium instance. It just has some Node.js integration. 2020-10-14
  61. How does require work in Electron? require in Electron works like Node.js, allowing you to load modules, but each Renderer process has its own isolated module state. Relative module resolution depends on whether you use loadFile or loadURL. 2020-10-15

2015 2

  1. Babel JS from the ground up Babel is a JavaScript compiler that transforms JavaScript code. Here I use its API programmatically. 2020-10-16
  2. MediaRecorder hello world The MediaStream Recording API converts a MediaStream to a Blob of compressed video and audio. A demo where you can record a 5-second clip. 2020-10-17

2014 21

  1. How do JavaScript async iterators work? Async iterators use the Symbol.asyncIterator method to define the iteration protocol. 2020-10-19
  2. Use varyings for texture2D coordinates! Using a varying to pass the texture coordinates to the fragment shader avoids the need to perform divisions in the fragment shader, improving performance. 2020-10-21
  3. Why is my WebGL texture upside-down? WebGL’s texImage2D function expects pixels in bottom-to-top order, while browsers provide them top-to-bottom. UNPACK_FLIP_Y_WEBGL fixes this behavior. 2020-10-22
  4. The many sizes of a video element A playground to explore the various widths and heights of a <video> element, as reported by different browser APIs, when displaying a webcam stream with dynamically adjustable constraints. 2020-10-23
  5. How do JavaScript prototypes work? JavaScript has two different “prototype” concepts: an own property with the string key “prototype”, and a parent slot. Don’t confuse the two! 2020-11-02
  6. How do classes work in JavaScript? JavaScript class syntax is just syntactic sugar over the traditional prototype-based inheritance. Deconstructing a simple class reveals the underlying constructor functions, prototype assignment, and use of super to call the superclass’s constructor. 2020-11-03
  7. A matrix library in 5 lines of code A 5-line matrix library, and how to derive it without rote memorization. 2020-11-27
  8. Homogeneous coordinates in 2D, from scratch Homogeneous coordinates enable a matrix to translate points. I show a six-line JS library. 2020-11-28
  9. Homogeneous coordinates in 3D I implement homogeneous coordinates in 3D, including rotation, scaling, translation, and projection matrices, and use them to create an animated 3D house scene. 2020-11-29
  10. NPM addon package hello world How to create an NPM addon package from C++ code using the node-gyp tool and a binding.gyp file, with a JavaScript wrapper module for a more idiomatic API. 2020-12-07
  11. MP4 can encode superwhite and superblack, thanks to analog TV Screen recording accidentally encoded superwhite/superblack due to obsolete yuv420p(tv) color space; rescaling fixes it. 2021-01-13
  12. Measuring audio volume in JavaScript A demo of real-time microphone volume measurement using the Web Audio API’s AnalyserNode. 2021-01-18
  13. How to replace GIF with HTML video in 2021 To replace a GIF with an HTML <video> element in 2021, use a long list of attributes disable unwanted browser behaviors. 2021-01-19
  14. How to run a pre-trained model in TensorFlow.js Load the model, convert the input to a tensor, preprocess the tensor to match the model’s expected format, run inference with .predict(), and decode the prediction tensor. 2021-02-15
  15. What is a Single-Shot Multibox Detector? A neural network architecture that can output bounding boxes. It uses a fixed set of “anchor points” and predicts offsets and sizes for each anchor. 2021-02-16
  16. TensorFlow 2 ‘hello world’ A TensorFlow 2 program that learns the cost per gram of chocolate by training a linear model on example chocolate bar weights and prices. 2021-02-17
  17. Proving 1+1=2 and other advanced theorems Lean is used to define and prove the commutativity of addition on natural numbers. 2023-06-14
  18. How to export a model for TensorFlow.js Exporting a TensorFlow model, converting it to the TensorFlow.js format, and running it in the browser with interactive input. 2021-03-09
  19. Build norms, not features A primary feature of a collaborative product is its social norms. I look at LessWrong, a forum product, and show how it builds its social norms. 2023-08-28
  20. Let’s get calibrated! A workshop A workshop to show the importance of estimation, and teach self-calibration using facts about your company. 2023-09-13
  21. The golden rule of PR reviews The “golden rule” of code reviews is to approve improvements. Approve pull requests that fix bugs, even if the implementation isn’t ideal. 2023-10-07

2013 3

  1. How does HotJar record your screen? “Session replay” tools record user interactions by capturing DOM changes, external resources, and viewport state, using efficient techniques like the MutationObserver API. 2024-03-09
  2. Setting font-size based on viewing distance Estimating viewing distance from screen size to set optimal font-size, but other factors like user mobility, long-sightedness, and short-sightedness complicate the ideal font-size calculation. 2024-03-11
  3. How do errors in a web page reach the dev console? Errors in JavaScript cause an ErrorEvent on window. Preventing the default action blocks console output. Resource errors follow the capture-bubble event model. 2024-03-13

2012 6

  1. How can I capture all crashes in a web page? Including uncaught errors, unhandled promise rejections, image load failures, Content Security Policy violations, and console.error calls. 2024-03-14
  2. It might not need a label Often, content is self-labelling. Removing its label can make the content more scannable. Programmers often over-label. 2024-03-20
  3. Auto-summarizing my blog posts Summarizing my blog posts using Claude Haiku. The benefits of providing business context. The benefits of iterating. 2024-03-26
  4. Tell the LLM the business context Tell LLM why its task is needed and how the output will be used. You’ll get better results, but programmers often don’t do this because it’s anti-modular. 2024-03-30
  5. What is numerical differentiation? Differentiation asks: how does tweaking the inputs change the output? Numerical differentiation is a simple, general way to do this. But it’s not very accurate, and it’s inefficient when there are many inputs. 2024-04-01
  6. Automatic differentiation with dual numbers Differentiation asks: how does tweaking the inputs change the output? To accurately differentiate an arbitrary function, perhaps the simplest way is using “dual numbers”. 2024-04-02