Исходники и презентации

lessons/contexts/context_with_timeout_implementation/main.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"sync/atomic"
+	"time"
+)
+
+type Context struct {
+	done   chan struct{}
+	closed int32
+}
+
+func WithTimeout(parent Context, duration time.Duration) (*Context, func()) {
+	if atomic.LoadInt32(&parent.closed) == 1 {
+		return nil, nil // don't use nil
+	}
+
+	ctx := &Context{
+		done: make(chan struct{}),
+	}
+
+	cancel := func() {
+		if atomic.CompareAndSwapInt32(&ctx.closed, 0, 1) {
+			close(ctx.done)
+		}
+	}
+
+	go func() {
+		timer := time.NewTimer(duration)
+		defer timer.Stop()
+
+		select {
+		case <-parent.Done():
+		case <-timer.C:
+		}
+
+		cancel()
+	}()
+
+	return ctx, cancel
+}
+
+func (c *Context) Done() <-chan struct{} {
+	return c.done
+}
+
+func (c *Context) Err() error {
+	select {
+	case <-c.done:
+		return errors.New("context deadline exceeded")
+	default:
+		return nil
+	}
+}
+
+func (c *Context) Deadline() (time.Time, bool) {
+	// not implemented
+	return time.Time{}, false
+}
+
+func (c *Context) Value(any) any {
+	// not implemented
+	return nil
+}
+
+func main() {
+	ctx, cancel := WithTimeout(Context{}, time.Second)
+	defer cancel()
+
+	timer := time.NewTimer(5 * time.Second)
+	defer timer.Stop()
+
+	select {
+	case <-timer.C:
+		fmt.Println("finished")
+	case <-ctx.Done():
+		fmt.Println("canceled")
+	}
+}