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

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

Script detects and exposes your local web servers on localhost and your local network. 2019-05-26

I hate telephones. Some rational reasons: lack of authentication, no spam filtering, forced synchronous communication. But also just a visceral fear. 2017-11-08

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

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

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 pastime. 2019-01-20

Try setting the root font-size to calc(1rem + 0.25vw) instead of using media queries with fixed breakpoints. 2024-03-12

Comparing the genome sequences of the Wuhan coronavirus and a bat coronavirus using diff and NCBI BLAST reveals an 89% similarity. 2020-02-09

foo.bar, foo.bar(), or foo.bar = baz - what do they mean? A deep dive into prototypical inheritance and getters/setters. 2020-11-01

Trick Android to display an SMS as coming from any contact. Convincing phishing vuln, but still unpatched. 2020-08-06

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

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

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

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. 2019-02-16

OpenSSL’s inadequate documentation, confusing key formats, and deprecated interfaces make it difficult to use, despite its importance. 2017-12-02

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

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

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

2024-04-12

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

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

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

Summarizing my blog posts using Claude Haiku. The benefits of providing business context. The benefits of iterating. 2024-03-26

Often, content is self-labelling. Removing its label can make the content more scannable. Programmers often over-label. 2024-03-20

Including uncaught errors, unhandled promise rejections, image load failures, Content Security Policy violations, and console.error calls. 2024-03-14

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

Try setting the root font-size to calc(1rem + 0.25vw) instead of using media queries with fixed breakpoints. 2024-03-12

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

“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

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

A workshop to show the importance of estimation, and teach self-calibration using facts about your company. 2023-09-13

2023-09-04

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

Lean is used to define and prove the commutativity of addition on natural numbers. 2023-06-14

2022-12-14

2022-11-02

2022-10-17

2022-10-13

2022-09-10

2022-09-08

2022-07-15

2022-02-24

2022-02-09

2022-01-17

Exporting a TensorFlow model, converting it to the TensorFlow.js format, and running it in the browser with interactive input. 2021-03-09

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

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

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

To replace a GIF with an HTML <video> element in 2021, use a long list of attributes disable unwanted browser behaviors. 2021-01-19

A demo of real-time microphone volume measurement using the Web Audio API’s AnalyserNode. 2021-01-18

Screen recording accidentally encoded superwhite/superblack due to obsolete yuv420p(tv) color space; rescaling fixes it. 2021-01-13

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

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

Homogeneous coordinates enable a matrix to translate points. I show a six-line JS library. 2020-11-28

A 5-line matrix library, and how to derive it without rote memorization. 2020-11-27

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

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

foo.bar, foo.bar(), or foo.bar = baz - what do they mean? A deep dive into prototypical inheritance and getters/setters. 2020-11-01

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

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

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

Async iterators use the Symbol.asyncIterator method to define the iteration protocol. 2020-10-19

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

Babel is a JavaScript compiler that transforms JavaScript code. Here I use its API programmatically. 2020-10-16

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

An Electron instance is basically a Chromium instance. It just has some Node.js integration. 2020-10-14

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

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

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

Involves downloading the model manifest file and associated binary weight files, to avoid downloading large models every application launch. 2020-10-07

Creating a “floating head” effect using WebGL and the BodyPix machine learning model to segment the face from a webcam feed. 2020-10-06

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

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

“Simplified CommonJS wrapping” feature is a hacky attempt to support synchronous require calls by using regexes. It’s gross. 2020-10-03

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

Publishing an npm package @jameshfisher/numsyslib with a stringifyRoman function that converts a number to a Roman numeral. 2020-10-01

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

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

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

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

Source maps map generated JavaScript to original source files, allowing debugging of the original code in the browser’s dev tools. 2020-09-26

JavaScript modules enable better dependency management and scoping. A guide for developers like me who still use <script> tags everywhere. 2020-09-25

A WebGL shader that uses BodyPix segmentation to set the alpha channel. 2020-09-24

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

The CSS resize property allows any element to be resized, not just <textarea>! But there are some gotchas. 2020-09-22

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

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

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

BodyPix is a TensorFlow model for person segmentation. A demo of BodyPix in the browser. 2020-08-16

WebGL alpha-transparency may appear wrong because of premultiplied alpha. Fix it by setting premultipliedAlpha: false when creating the WebGL context. 2020-08-12

A green screen implementation in the browser using WebGL and chroma key. Includes a live demo. 2020-08-11

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

A green screen implementation in the browser using WebGL and chroma key. Includes a live demo. 2020-08-09

Trick Android to display an SMS as coming from any contact. Convincing phishing vuln, but still unpatched. 2020-08-06

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

Use AVCaptureDeviceDiscoverySession instead of the deprecated AVCaptureDevice.devices(for:) to discover video capture devices. 2020-07-31

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

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

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. Display a helpful error message instead of crashing. 2020-04-24

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

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

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

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

A WebGPU-powered simulation of the Rule 110 cellular automaton, rendering a dynamic image on a canvas. 2020-03-02

I write an ArrayBuffer to a canvas by interpreting the buffer as pixel data and using ImageData to provide the dimensions. 2020-03-01

Blurring sensitive information in images may not effectively protect privacy, as the original content can often be recovered using deblurring techniques. 2020-02-29

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

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

An interactive simulation showing how disease characteristics and human behavior can significantly impact the spread of an epidemic. 2020-02-15

Comparing the genome sequences of the Wuhan coronavirus and a bat coronavirus using diff and NCBI BLAST reveals an 89% similarity. 2020-02-09

An algorithm in Haskell using a breadth-first search to find the reachable set of nodes. 2020-01-24

An O(n) algorithm to check if a binary tree is balanced, by passing up the height from recursive calls. 2020-01-23

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

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

A Haskell solution to the classic Towers of Hanoi problem. 2020-01-20

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

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

The head of the list is the top of the stack. 2020-01-17

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

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

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

A C function to partition a linked list around a value x, running in optimal time and space. 2020-01-13

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

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

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

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

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

A C function to replacing spaces with "%20" in-place, by iterating from the end, preserving true string length. 2020-01-07

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

An in-place string reversal function in C, starting by swapping the first and last characters, then iterating towards the middle. 2020-01-05

A recursive algorithm to determine if a string has all unique characters, with an analysis of its time complexity. 2020-01-04

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

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

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

A pixel art game developed over Christmas, with code on GitHub and development on Glitch. 2019-12-28

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

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

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

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

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

Script detects and exposes your local web servers on localhost and your local network. 2019-05-26

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

JavaScript’s function* defines a generator function, which can be used to generate and consume data. 2019-05-17

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

Formulas to calculate stopping distances for different speeds, using thinking and braking distances, instead of memorizing a table. 2019-05-15

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

Demo of the user’s webcam in a <video> element, using the navigator.mediaDevices.getUserMedia() API. 2019-05-06

A plugin to create tag pages on a Jekyll blog, and a minimal layout for those tag pages. 2019-05-05

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

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

I create a native Node.js addon called addon in C++ using node-gyp. The addon exports a hello() function. 2019-04-20

Installing Electron, creating an HTML web page, and writing the main entry point script to load the page. 2019-04-19

Cycling tour of France’s Loire Valley, visiting chateaux, wineries, and medieval attractions over 5 days, from Tours to Nantes. 2019-04-09

Matched betting exploits differences in odds between betting exchanges to guarantee a profit, by betting on both sides of a proposition. 2019-04-02

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

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

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

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

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

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. 2019-02-16

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

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

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 pastime. 2019-01-20

Jekyll build breaks due to Bundler 2 incompatibility. Fixed by removing Bundler 1 version from Gemfile.lock. 2019-01-09

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

Use nc (netcat) to create a web server that returns custom HTTP responses. 2018-12-31

I use a custom blogpost command to quickly create new blog post files with the current date and post title. 2018-12-30

I demonstrate animating a cat walk cycle on an HTML canvas using a sprite sheet image and the drawImage method. 2018-12-29

A pixel art animation of a “walk cycle”, created using GIMP, for use in a retro game. 2018-12-28

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

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

The Morris approximate counter is incremented probabilistically. 2018-12-17

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

2018-11-15

How to use the undocumented Strava Route Builder API to get routes between two points, including a JavaScript example. 2018-10-13

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

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

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

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

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

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

2018-09-13

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

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

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

Discover your strengths, work styles, and values through feedback analysis. Align your career and relationships with your unique characteristics. 2018-04-01

/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 temporary files. 2018-03-31

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

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

Creating and using an SSH certificate authority, an alternative to the default “trust on first use” model. 2018-03-16

A lambda calculus interpreter in Haskell, using de Bruijn indexing and lazy evaluation, with simple integer literals added. 2018-03-15

An x86-64 program that writes to stdout and exits. 2018-03-10

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

An interpreter for an imperative language in Haskell, featuring integers, operators, global variables, control flow, and I/O primitives. 2018-03-06

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

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

Linux uses exponential backoff to retry dropped TCP connections, with a configurable retry limit. 2018-02-27

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

tcpdump captures network traffic. Capture and analysis of a TCP connection, including the 3-way handshake and message exchange. 2018-02-23

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

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

Replacing printf with write, and finally directly using the syscall function with inline assembly. 2018-02-19

Struggling with mundane diary entries, I implement random writing prompts to reinvigorate the process. 2018-02-17

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

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

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

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

A C implementation of run-length encoding, a compression scheme that works well on inputs with consecutive repeated characters. 2018-02-08

ping uses ICMP, or “Internet Control Message Protocol”, to send “echo request” packets and receive “echo reply” packets. 2018-02-07

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

nscd, a local DNS resolver within glibc, is non-standard. Instead, use a local DNS server like named or dnscache. 2018-02-05

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

tcpdump captures and displays network traffic. An example inspecting DNS requests and responses. 2018-02-01

2018-01-23

A compiler that converts a text file containing hex codes and comments into a binary output file. 2018-01-21

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

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

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

A stream cipher in Go that generates an infinite keystream from a shared key using SHA-256. 2018-01-01

osquery allows querying a UNIX system using SQL. 2017-12-11

An open addressing hash table implementation in C, which resolves collisions by finding alternative buckets for elements using linear probing. 2017-12-10

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

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

Inline quizzes make reading more engaging by requiring readers to participate in the content. 2017-12-07

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

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

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

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

OpenSSL’s inadequate documentation, confusing key formats, and deprecated interfaces make it difficult to use, despite its importance. 2017-12-02

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

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

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

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

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

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

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

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

Replaced static image on this site with a looped video. Experimenting with subtle motion to mimic images at first glance. 2017-11-12

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. 2017-11-11

Added a header to the blog with a photo that links to the homepage, as people expect a header for navigation. 2017-11-10

Composer’s autoloader uses PSR-4 to map namespaces to directories, allowing you to load classes without explicit require statements. 2017-11-09

I hate telephones. Some rational reasons: lack of authentication, no spam filtering, forced synchronous communication. But also just a visceral fear. 2017-11-08

Implementing a Promise API in JavaScript, including handling asynchronous callbacks, promise chaining, and automatically wrapping non-promise values. 2017-11-07

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

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

Added Open Graph meta tags to improve how blog posts appear when auto-posted to Facebook. 2017-11-04

Generating ECDH keys and deriving a shared AES key. 2017-11-03

Generating a key, encrypting and decrypting text, and explaining the implementation. 2017-11-02

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

The Web Cryptography API provides low-level crypto primitives in JavaScript, including hashing strings using SHA-256. 2017-10-30

Setting up guest writers on a Jekyll blog. Marking authors in the metadata. Storing author information in a YAML file. 2017-10-29

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

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

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

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 ciphertext to the group. 2017-10-25

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

Implements a 1024x1024 grid of Conway’s Game of Life using WebGL fragment shaders. 2017-10-23

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

Rendering an animated 3D cube in WebGL using a vertex shader, face color uniforms, and matrix transformations for rotating the cube. 2017-10-21

Generating dynamic normal-mapped ripple effects using WebGL, with the mouse position controlling the light source. 2017-10-20

GLSL varying allows vertex shader outputs to be passed to fragment shaders. A WebGL demo with colors interpolated between vertices. 2017-10-19

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

Combining two textures in a WebGL fragment shader, using texture units and uniform locations to access the textures. 2017-10-17

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

Random slopes are interpolated to create a smooth, wiggly line. More realistic noise is achieved by combining multiple octaves. 2017-10-15

A program to create a cyan window on macOS using C and the GLFW library. 2017-10-14

A WebAssembly program that prints 42 to the console, demonstrating the structure and usage of WebAssembly. 2017-10-13

Contrasting diffuse and specular shading models in WebGL, with live demos showing matte vs. shiny surface renderings. 2017-10-12

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

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

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

WebGL has several spaces that need to be properly managed to display content correctly. 2017-10-08

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

Using WebGL to load an image and swap its RGB channels with a fragment shader. 2017-10-06

A WebGL fragment shader that animates a pulsating colored square by updating a time-based uniform in the shader. 2017-10-05

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

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

A demo WebGL fragment shader that draws concentric circles, with a live editor to experiment with the shader code. 2017-10-02

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

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

Lack of a standard Unicode feed icon despite its widespread use. I plan to submit a proposal for its inclusion. 2017-09-28

A WebGL demo that creates a green square in a canvas element, showing the difference between 2D canvas and WebGL contexts. 2017-09-27

How to create an IndexedDB database, add an object store, and read/write data. 2017-09-26

Compiling a C program with debugging flags, then using lldb to set breakpoints, step through the code, and observe output. 2017-09-25

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

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

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

Browser generates keys, shares public key; server encrypts data with it; browser decrypts push payload. 2017-09-21

notificationclick service worker event lets the web app open a webpage via clients.openWindow. 2017-09-20

Web applications can “subscribe” for notifications via PushSubscription endpoint, but there’s poor interoperability between different browsers’ push services. 2017-09-19

2017-09-19

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

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

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

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

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

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

Deprecated new Notification() replaced with ServiceWorkerRegistration.showNotification(). 2017-09-12

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

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

Bitcoin could fail due to theoretical inferiority, lack of practicality, bans, critical bugs, centralized control, or technological collapse. 2017-09-09

Using a service worker to monitor the sitemap and display updates via browser notifications. 2017-09-08

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

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

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

Guidelines for writing compelling yet substantively questionable essays, focused on rhetorical techniques over truth. 2017-09-04

Internal workshop on Laravel+Pusher. Structured approach with checkpoints helped keep everyone on track. 2017-09-03

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

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 cryptocurrencies. 2017-09-01

Permanent blog pages are now generated from tagged blog posts, providing automatic updates, separate URLs, and chronological ordering. 2017-08-31

Use CSS padding-top and position properties to create a full-width iframe with fixed 16:9 aspect ratio. 2017-08-30

Old Bitcoin wallet on a sketchy 2012 laptop. Block database corrupted but wallet.dat found. 2017-08-29

An updated calendar-based homepage, highlighting gaps in posting. 2017-08-29

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

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

Static linking in C involves compiling a library and main program separately, then linking the object files together into an executable. 2017-08-26

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

Dynamically load and unload shared libraries using dlopen, dlsym, and dlclose. 2017-08-24

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

Using otool to see dynamic library dependencies, and nm to see function symbols. 2017-08-22

#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

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

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

stdatomic provides atomic operations like atomic_fetch_add to ensure thread-safe access to shared variables. 2017-08-18

2017-08-17

Embedly respects Open Graph og:image meta tag for thumbnail selection. Adding it to vidr.io enables Reddit thumbnail. 2017-08-16

> is redundant; < alone suffices for all comparisons. I prefer it because it aligns with the number line. 2017-08-15

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

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

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

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

<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

Moved GitHub Pages blog to Netlify, using custom domain, HTTPS, and redirects from the old site. 2017-08-08

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

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

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

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

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

A malloc/free implementation that maps allocations directly to mmap/munmap, with the allocation size stored before the returned pointer. 2017-08-02

dtruss allows tracing system calls on macOS. It shows the syscall, arguments, return value, and errno. 2017-08-01

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

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

Spoke with Will about the Go garbage collector at GoWayFest in Minsk, Belarus. Orderly city. Software engineering scene surprisingly big. 2017-07-25

Presented “Go garbage collector” talk at GoWayFest in Minsk, met fellow Gophers, and did some tourism around Belarus and Ukraine. 2017-07-21

A talk about the Fisher Tree, a data structure, with slides and code. 2017-07-05

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

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

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

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

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

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

CIColorKernel is a type of CIKernel optimized for pixel-wise image transformations, with input as pixel samples instead of image samplers. 2017-05-03

A Swift CLI program that applies a Core Image kernel to image files, allowing operations like averaging two images. 2017-05-02

A CIKernel in Swift can have multiple inputs, including image samplers and other data types. Example: an alpha-compositing kernel. 2017-04-30

A macOS app that displays a webcam preview in a floating panel, using the AVFoundation framework. 2017-04-29

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

Using a CIFilter using a GLSL kernel to swap the red and green components of an image. 2017-04-27

Using CIFilter to apply a sepia tone filter to an NSImage and save the result to a file. 2017-04-26

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

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

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

Run Swift scripts from the command line using swift hello.swift, or compile them to an executable with swiftc hello.swift. 2017-04-20

A program that squares an array of floats on the GPU, using the OpenCL API on macOS. 2017-04-19

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

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

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

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

Generate ECC private key with openssl ecparam, extract public key from it using openssl ec, derive shared secret using openssl pkeyutl. 2017-04-14

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

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

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

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

A screencast about go tool trace, a profiling tool for Go applications. 2017-04-06

rxi/vec provides dynamic arrays in C, including push, pop, and iteration, without the need to manage array resizing and length. 2017-04-06

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

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

A screencast about go tool trace, a profiling tool for Go applications. 2017-04-03

A strategy for growing a product by starting with an extremely specific target market and gradually expanding to broader markets. 2017-04-02

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

A “Replay with sound” button to control a muted video, implemented using the YouTube Iframe API. 2017-03-30

Prevent annoying video autoplay on mobile by detecting mobile devices and serving a manual play button instead. 2017-03-29

Using CSS media queries to re-word navbar elements based on screen width. 2017-03-28

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

An analysis of the Framer.com promo video, highlighting its engaging music, timed animations, and succinct text slides. 2017-03-25

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

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

Using openssl genrsa, openssl rsa, openssl rsautl -sign, and openssl rsautl -verify. 2017-03-22

Generating RSA keys, extracting the public key, encrypting with the public key, and decrypting with the private key. 2017-03-21

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

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

The @NSApplicationMain annotation in Swift is a macro that calls NSApplicationMain(...) to set up the Cocoa application’s UI event loop. 2017-03-18

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 delegate. 2017-03-17

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

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

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

Use the openssl s_client command to fetch a server’s SSL certificate chain, including the root certificate. 2017-03-11

Generate random bytes with openssl rand, which uses a PRNG seeded with entropy from ~/.rnd. 2017-03-10

Discussed Go’s real-time garbage collector at an internal conference, after presenting the same talk at The Realtime Guild. 2017-03-10

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

Xcode uses “teams” to manage developer identities, and revoking a certificate on one device may require regenerating provisioning profiles. 2017-03-03

To submit a macOS app build to iTunes Connect, archive the app in Xcode, enable App Sandbox, then upload the build. 2017-03-02

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

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

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

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

Install ebe assembler with a one-liner, but be wary of the SourceForge installation script. 2017-03-01

1) Enroll in the Apple Developer Program. Create an “App Record” in iTunes Connect. Upload the app. Submit it for review. 2017-03-01

A TCP server that uses pthread to serve multiple clients concurrently, with an “echo” server for each connection. 2017-02-28

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

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

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

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

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

A program in C that prints the individual bits of various data types, showing how they are represented in memory. 2017-02-23

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

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

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

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

lsof lists open system resources, including pipes, sockets, and yes, files. It shows their type, owner, and location. 2017-02-20

Generate Intel and AT&T assembly with clang, demonstrating the difference in syntax between the two styles. 2017-02-19

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

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

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

A talk given with Will Sewell. Overview of Go’s concurrent garbage collector. 2017-02-15

Use the dup system call to duplicate a file descriptor in C, allowing two references to the same underlying pipe. 2017-02-15

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

French preposition examples for common spatial relationships like behind, in front of, next to, under, on, above, in, and between. 2017-02-13

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

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

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

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

Reassessing daily routine - shifting sleep, work, and commute times to wake up earlier, improve sleep quality, and align with daylight hours. 2017-02-08

GeoDNS uses geo-IP to locate clients and connect them to the nearest server, reducing latency. 2017-02-08

To call a program from C, use `fork` then `execve`. There is no more direct way! 2017-02-07

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

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

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

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

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

Compiling with the -S flag generates assembly. 2017-02-03

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

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

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

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

A multiplayer web-based version of the cooperative game Spaceteam, using Pusher for real-time communication between players. 2017-01-30

Processes can communicate via files, pipes, signals, sockets, message queues, semaphores, and shared memory. 2017-01-29

To write to a file, open the file, mmap the file descriptor, then write to memory. 2017-01-28

Use mmap to map a file into memory, then read and write the memory directly. 2017-01-27

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

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

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

To subtract in binary, we use carry bits and two’s complement representation. 2017-01-24

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

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

“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

The UINT64_C macro appends the ULL suffix to a 64-bit unsigned integer literal, converting it to the appropriate type. 2017-01-20

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

Electric charge is the number of electrons minus the number of protons in an object. 2017-01-18

The RTCDataChannel API lets us configure the delivery guarantees, including the ordered, maxPacketLifeTime, and maxRetransmits properties. 2017-01-17

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

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

C signal handlers reuse the same call stack as normal functions, but can optionally use a special signal stack instead. 2017-01-14

sigaction says what to do when a signal is received. signal is a simplified interface to sigaction. 2017-01-13

Executing do_something() N times in C using a while loop and post-decrement operator. 2017-01-12

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

signal returns the old signal handler pointer for given signal number. 2017-01-10

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

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

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

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

Using unique error codes with linkable documentation improves error reporting. Provide a central error page URL with each error message. 2017-01-05

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

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

Efficient packing of game player data into 16 bits using bitwise operations on a uint16_t type. 2017-01-02

IP packets travel at ~20% the speed of light, with most time spent in routers rather than on the wire. 2017-01-01

The structure and contents of a DNS request datagram, including the header, question section, and how to represent it in C. 2016-12-31

GCC’s ‘statement expressions’ allow inserting statements into expression positions. Behavior is unspecified. 2016-12-30

Redis uses length-prefixed strings with pointers into the middle of the allocation, allowing C-string operations on the string data. 2016-12-28

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

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

C array literals can use explicit indexes. The array length is determined by the largest explicit index. 2016-12-25

perror in C prints a human-readable description of the last error that occurred, as stored in the global errno variable. 2016-12-24

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

Useful to show how C represents various data types. 2016-12-22

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

A C program that creates an HTTP server that responds with “Hello, world!” to every request. 2016-12-20

The syscalls needed for a simple UDP echo server are socket, bind, recvfrom, sendto, and close. 2016-12-19

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

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

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

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

A minimal TCP server in C uses the socket, bind, listen, accept, recv, send, and close syscalls to manage connections. 2016-12-14

errno lets you access error codes from system calls. It’s a global int. 2016-12-13

static functions in C are only callable within the translation unit they are defined in, not across the whole program. 2016-12-12

Use i & (n-1) to compute i % n, when n is a power of two. This avoids the modulo operation. 2016-12-10

Macros in C can define token replacements or function-like replacements. 2016-12-09

Arrays in C can “decay” to pointers, but are not inherently pointers. The size of an array is lost during decay. 2016-12-08

Automatic variables in a Makefile, like $@ for the target and $^ for the dependencies, reduce repetition in rules. 2016-12-07

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

Set the C compiler in Makefile using predefined variable $(CC), which defaults to cc and can be redefined. 2016-12-05

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

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

const is a type qualifier in C that makes a variable unassignable, except during initialization. 2016-12-02

C99 introduced the stdbool.h header, providing bool, true, and false for boolean values, building on the _Bool type. 2016-12-01

realloc resizes an allocated memory block, copying contents if necessary. 2016-12-01

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

Computing a pointer to unowned memory invokes undefined behavior, even without dereferencing! 2016-11-30

Use concatenated string literals with newline characters to define multi-line string literals in C. 2016-11-30

C string literals can contain comment-like characters, which are treated as literal text, not as comments. 2016-11-30

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

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

size_t is used to represent the size of objects in memory. It is commonly used for array indexing. 2016-11-29

Use uintptr_t to count objects in C, as it can represent the largest possible pointer value. 2016-11-29

static in C can modify variable declarations inside and outside a function body, and function parameters. 2016-11-28

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

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

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 behavior. 2016-11-27

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

Avoid using ambiguous pronouns like “it” in technical writing. Refer to specific referents explicitly to improve clarity. 2016-11-25

A convention for expressing complex C types using typedef and a “reverse Polish notation” syntax to improve readability. 2016-11-24

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

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

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

Comparing meal replacement options Huel and Joylent, I choose Joylent’s vegan version. 2016-11-20

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

To get more screen real-estate, go to System Preferences > Displays, and select “More Space” . 2016-11-18

An .xcworkspace file is a directory that contains a workspace configuration for Xcode projects. 2016-11-17

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

A UDP server that listens for packets and prints the received messages. A UDP client that sends “hello” to the server. 2016-11-17

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

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

I try Vim. I give up after discovering that the cursor cannot sit at the end of a line. 2016-11-16

Serialize JSON in Swift with JSONSerialization.data(withJSONObject:options:). 2016-11-16

Daily blogging pledge; punishment for failure TBD. 2016-11-16

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 incorrectly collected. 2016-11-16

Hired a cleaning service that takes a third of the hourly rate. 2016-11-16

Limiting CSS to 128 bytes prevents bloat and distractions, allowing focus on content. 2016-11-15

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 set, allowing the white set to be cleared. 2016-11-11

2016-08-10

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. 2016-05-12

2015-01-28

2015-01-26

2014-10-25

2014-10-23

2014-10-11

2014-10-06

2014-10-04

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

2014-09-19

2014-09-14

2014-09-13

2014-08-25

Prolog as a better alternative to “semantic triples” and SPARQL. 2014-08-24

2014-08-21

2014-08-19

2014-08-15

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 names, homepages, and inline help. 2014-08-13

2014-08-10

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

The difference between estimates and deadlines, and why conflating the two can cause problems in project management. 2014-07-27

2014-07-27

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

2014-05-10

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. 2014-05-04

A JS function to decide the Halting Problem will always have a logical contradiction. 2013-12-24

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

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

Flip a biased coin twice to get an unbiased outcome. Use HT and TH as the outcomes, ignoring HH and TT. 2013-11-16

2012-10-30

2012-04-16

2012-04-15

2012-04-12

2012-04-08

A visual programming language inspired by Haskell. 2012-02-27

2010-02-10

2010-01-25

2010-01-19

2010-01-19

2010-01-17

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 heresies, creating a precedent for condemning Galileo. 2008-02-15

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

An ode to the Tetra Pak carton. 2007-05-23

Humanism, the Reformation, centralized administration, the decline of feudalism, and the rise of national identity. 2007-03-10

Natural magic and scientific method share commonalities, but only scientific method distinguished correlation from causation. The Scientific Revolution arose from internal technological developments, the link between knowledge and political power, and the destruction of absolute truth from the Renaissance and Reformation. 2007-02-09

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, from the events of 1789. 2006-12-11