semaphore: init

semaphore/Makefile

@@ -0,0 +1,53 @@
+.DEFAULT_GOAL := help
+
+# ==================================================================================== #
+# HELPERS
+# ==================================================================================== #
+
+## help: print this help message
+.PHONY: help
+help:
+	@echo 'Usage:'
+	@sed -n 's/^##//p' ${MAKEFILE_LIST} | column -t -s ':' |  sed -e 's/^/ /'
+
+## all: tidy + audit + test/cover
+all: generate tidy test lint test/cover
+
+
+# ==================================================================================== #
+# QUALITY CONTROL
+# ==================================================================================== #
+
+## tidy: format code and tidy modfile
+.PHONY: tidy
+tidy:
+	go fmt ./...
+	goimports -local=$(shell cat go.mod | grep module | awk '{print $$2}')/ -w .
+	go mod tidy -v
+
+## audit: run quality control checks
+.PHONY: lint
+lint:
+	go mod verify
+	go run github.com/golangci/golangci-lint/cmd/golangci-lint@latest run -v ./...
+
+
+# ==================================================================================== #
+# DEVELOPMENT
+# ==================================================================================== #
+
+## generate: run all generators
+.PHONY: generate
+generate:
+	go generate ./...
+
+## test: run all tests
+.PHONY: test
+test:
+	go test -race -buildvcs ./...
+
+## test/cover: run all tests and display coverage
+.PHONY: test/cover
+test/cover:
+	go test -race -buildvcs -coverprofile=/tmp/coverage.out ./...
+	go tool cover -html=/tmp/coverage.out

semaphore/go.mod

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+module semaphore
+
+go 1.21.6

semaphore/main.go

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+package main
+
+import (
+	"context"
+	"sync/atomic"
+	"time"
+)
+
+type Semaphore interface {
+	Acquire(ctx context.Context) error
+	Release()
+}
+
+// ChanSemaphore implementation
+type ChanSemaphore struct {
+	C chan struct{}
+}
+
+func (s *ChanSemaphore) Acquire(ctx context.Context) error {
+	select {
+	case s.C <- struct{}{}:
+		return nil
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+}
+
+func (s *ChanSemaphore) Release() {
+	<-s.C
+}
+
+// AtomicSemaphore implementation
+type AtomicSemaphore struct {
+	acquired atomic.Bool
+	TryDelay time.Duration
+}
+
+func (s *AtomicSemaphore) Acquire(ctx context.Context) error {
+	if s.acquired.CompareAndSwap(false, true) {
+		return nil
+	}
+
+	return s.slowAcquire(ctx)
+}
+
+func (s *AtomicSemaphore) slowAcquire(ctx context.Context) error {
+	ticker := time.NewTicker(s.TryDelay)
+
+	for {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-ticker.C:
+			if s.acquired.CompareAndSwap(false, true) {
+				return nil
+			}
+		}
+	}
+}
+
+func (s *AtomicSemaphore) Release() {
+	s.acquired.Store(false)
+}

semaphore/main_test.go

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+package main
+
+import (
+	"testing"
+)
+
+func TestPipe(t *testing.T) {
+
+}