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timruffles / finalizer.go
Last active January 17, 2025 14:03
golang - demonstrates the risk of using runtime.SetFinalizer to 'manage' C memory. Since C heap is invisible to Go GC, without sufficient Go memory pressure the finalizers won't run, and your process can hog a lot of memory. Suggestion: add a manual Close() method to your CGO bindings, so your library users can get predictable memory use.
package main
import "C"
import (
"fmt"
"runtime"
"sync"
"syscall"
"unsafe"
)
@timruffles
timruffles / error_from_panic.go
Created December 18, 2024 15:43
FromPanicValue - returns an error with the best possible stack-trace from the value obtained from calling recover() within a defer
package error
import pkgerrors "github.com/pkg/errors"
// FromPanicValue returns an error with the best possible stack-trace from
// the value obtained from calling recover() within a defer
func FromPanicValue(pv any) error {
if pv == nil {
return nil
}
@timruffles
timruffles / notebook.ipynb
Created September 23, 2024 12:04
notebook
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@timruffles
timruffles / parse.txt
Last active December 12, 2025 11:11
Golang's url.Parse is very permissive: everything here parses without error
Input Hostname Protocol Path Query
"<h1>hi there</h1>" <h1>hi there</h1>
""
" "
"$ whoami" $ whoami
"not a url" not a url
"???" ??
"?://???" ://???
" ? "
" why?? : ; /" why ? : ; /
@timruffles
timruffles / operation.ts
Last active November 26, 2025 15:43
operation - like Result and various other ADTs in Haskell etc
export type Operation<T, E = Error> = typeof NotStarted | typeof Waiting | Complete<T> | Failed<E>;
export enum OperationState {
NotStartedState = "NotStarted",
WaitingState = "Waiting",
CompleteState = "Complete",
FailedState = "Failed",
}
export const NotStarted = {
@timruffles
timruffles / count_functions_loc.sh
Created June 12, 2020 14:09
A bash script that counts go function and method lines of code (including whitespace and comments)
#!/bin/bash
#
# Usage: bash count_functions_loc.sh some/directory
set -euo pipefail
main() {
for f in $(find $1 -name '*.go' -not -name 'test_*.go'); do
count_funcs < "$f" | awk "{ print \"$f\", \$1, \$2 }"
done
@timruffles
timruffles / ban_random_int.sh
Created July 11, 2019 13:33
A bad way to generate a random init in a range using only bash built-ins. Useful in a pinch when you aren't sure what external programs are available.
# Gets an int between min max inclusive very inefficiently, but
# only using bash built-ins. More inefficient the smaller the gap
#
# usage: n=$( bad_random_int 1000 2000 )
bad_random_int() {
local min=$1
local max=$2
local n=0
while [[ "$n" -lt "$min" ]] || [[ "$n" -gt "$max" ]]; do
@timruffles
timruffles / go-quiz.go
Last active August 19, 2019 07:43
What does this program output, and why? Reason it out gophers! Answers in a spoiler block - https://github.com/dear-github/dear-github/issues/166#issuecomment-236342209
package main
import "fmt"
func main() {
type person struct {
nickname string
}
ppl := []person{
@timruffles
timruffles / demo.go
Last active March 7, 2019 17:19
Go - cost of change for methods in application code. App code has many types that work together, requiring mocking.
// Let's define a type with a method that needs a fair few arguments
type Thing struct {}
func (c *Thing) Verb(a A,b B,c C,d D) {}
// We have things that depend on Thing and we want to test them, so to mock it we'll need to
// define an interface and generate a mock
type Thinger interface {
Verb(a A,b B,c C,d D)
}
@timruffles
timruffles / add.sh
Last active February 25, 2019 15:52
Go dep - adding a fork via `source`. Useful when you want to use a private fork of a public repo for instance, without updating all package paths.
SOURCE="github.com/you/thing"
FORK="github.com/other/thing"
PACKAGE="some-package"
CONSTRAINT="aabbcc"
dep ensure -add ${SOURCE}/${PACKAGE}:${FORK}.git@${CONSTRAINT}