Tags
#php
#kotlin
#bash
#go
#sql
#rust
#typescript
#html
#java
#python
#files
#utils
#strings
#http
#concurrency
#async
#json
#arrays
#security
#types
#crypto
#database
#dates
#format
Kotlin
Coroutine Cancellation
Cancellation is cooperative — your coroutine must check via `ensureActive()`, `yield()`, or any other suspending call. CPU-busy loops without a suspend point are NOT cancellable.
@admin
PHP
Validate IP Address (v4 + v6)
Distinguish IPv4 from IPv6, optionally reject private/reserved/loopback ranges. Useful for hardening server-side fetchers against SSRF.
Go
Fan-Out / Fan-In
Distribute work across N workers (fan-out), then merge their results back into one channel (fan-in). Used when you can't process items strictly in order but want to retain output as one stream.
Go
Channels — Basics
Channels are typed pipes between goroutines. Unbuffered = synchronous handoff; buffered = up to N values queued. Close a channel to signal "no more values" — receivers see ok=false.
Kotlin
zip and zipWithIndex
`zip` pairs elements positionally; the result is the length of the shorter list. `withIndex()` gives you `(index, value)` pairs without the manual `forEachIndexed`.
PHP
cURL Multipart File Upload
Upload one or more files via multipart/form-data using cURL's CURLFile abstraction. No manual boundary or body construction needed.
Kotlin
Coroutine Testing with runTest
`runTest { }` from kotlinx-coroutines-test gives you a virtual time scheduler — `delay(1000)` finishes instantly while preserving ordering. No more flaky 1-second test sleeps.
Kotlin
Channel — Coroutine Communication
A `Channel<T>` is a coroutine-safe queue — producer side sends, consumer side receives. Bounded buffer applies backpressure. Use Flow when broadcasting; use Channel for hand-off between coroutines.
Kotlin
withContext — Switching Dispatchers
`withContext(dispatcher)` suspends the calling coroutine, runs the block on the given dispatcher, returns the result. Use `Dispatchers.IO` for blocking I/O, `Default` for CPU work, `Main` for UI updates.
Bash
HMAC-SHA256 with openssl
Sign a payload with a shared secret for webhook verification (Stripe, GitHub, etc.). openssl reads the input from stdin or -in.
TypeScript
Typed Fetch Wrapper
A thin fetch wrapper that returns parsed JSON typed as `T`, throws on non-2xx, and accepts an AbortSignal. Single source of truth for "how this app talks to APIs."
Go
Functional Options Pattern
Replace giant config structs with a variadic list of `Option` functions. Lets you add optional parameters later without breaking existing callers. The standard Go API design for constructors.
Go
Struct Embedding (Composition over Inheritance)
Go has no inheritance. Embed a type to "promote" its fields and methods as if they were on the outer type. Same effect as inheritance for most purposes, but explicit.
PHP
Memoize a Function's Result
Cache the result of an expensive pure function by its arguments. Returns a closure with the same call signature that only invokes the inner function once per unique argument set.
SQL
date_trunc — Bucket Times into Hours/Days/Weeks
`date_trunc('day', ts)` rounds a timestamp down to the start of the day. Use for time-series GROUP BYs — daily/weekly/hourly buckets without messy arithmetic.
Kotlin
repeat, also lateinit and isInitialized
`repeat(n) { i -> ... }` for N-times loops where you don't care about index naming. `lateinit var` lets you declare a non-null var without initializing it — common for DI / framework injection.
TypeScript
Promisify a Callback Function
Convert a Node-style `(err, result)` callback API into a Promise-returning function. Type-safe via generics — the inferred Promise resolves to the original callback's result type.