fix(go.sum): update ResolveSpec dependency to v1.0.87

vendor/github.com/redis/go-redis/v9/internal/semaphore.go

@@ -0,0 +1,193 @@
+package internal
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+var semTimers = sync.Pool{
+	New: func() interface{} {
+		t := time.NewTimer(time.Hour)
+		t.Stop()
+		return t
+	},
+}
+
+// FastSemaphore is a channel-based semaphore optimized for performance.
+// It uses a fast path that avoids timer allocation when tokens are available.
+// The channel is pre-filled with tokens: Acquire = receive, Release = send.
+// Closing the semaphore unblocks all waiting goroutines.
+//
+// Performance: ~30 ns/op with zero allocations on fast path.
+// Fairness: Eventual fairness (no starvation) but not strict FIFO.
+type FastSemaphore struct {
+	tokens chan struct{}
+	max    int32
+}
+
+// NewFastSemaphore creates a new fast semaphore with the given capacity.
+func NewFastSemaphore(capacity int32) *FastSemaphore {
+	ch := make(chan struct{}, capacity)
+	// Pre-fill with tokens
+	for i := int32(0); i < capacity; i++ {
+		ch <- struct{}{}
+	}
+	return &FastSemaphore{
+		tokens: ch,
+		max:    capacity,
+	}
+}
+
+// TryAcquire attempts to acquire a token without blocking.
+// Returns true if successful, false if no tokens available.
+func (s *FastSemaphore) TryAcquire() bool {
+	select {
+	case <-s.tokens:
+		return true
+	default:
+		return false
+	}
+}
+
+// Acquire acquires a token, blocking if necessary until one is available.
+// Returns an error if the context is cancelled or the timeout expires.
+// Uses a fast path to avoid timer allocation when tokens are immediately available.
+func (s *FastSemaphore) Acquire(ctx context.Context, timeout time.Duration, timeoutErr error) error {
+	// Check context first
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	default:
+	}
+
+	// Try fast path first (no timer needed)
+	select {
+	case <-s.tokens:
+		return nil
+	default:
+	}
+
+	// Slow path: need to wait with timeout
+	timer := semTimers.Get().(*time.Timer)
+	defer semTimers.Put(timer)
+	timer.Reset(timeout)
+
+	select {
+	case <-s.tokens:
+		if !timer.Stop() {
+			<-timer.C
+		}
+		return nil
+	case <-ctx.Done():
+		if !timer.Stop() {
+			<-timer.C
+		}
+		return ctx.Err()
+	case <-timer.C:
+		return timeoutErr
+	}
+}
+
+// AcquireBlocking acquires a token, blocking indefinitely until one is available.
+func (s *FastSemaphore) AcquireBlocking() {
+	<-s.tokens
+}
+
+// Release releases a token back to the semaphore.
+func (s *FastSemaphore) Release() {
+	s.tokens <- struct{}{}
+}
+
+// Close closes the semaphore, unblocking all waiting goroutines.
+// After close, all Acquire calls will receive a closed channel signal.
+func (s *FastSemaphore) Close() {
+	close(s.tokens)
+}
+
+// Len returns the current number of acquired tokens.
+func (s *FastSemaphore) Len() int32 {
+	return s.max - int32(len(s.tokens))
+}
+
+// FIFOSemaphore is a channel-based semaphore with strict FIFO ordering.
+// Unlike FastSemaphore, this guarantees that threads are served in the exact order they call Acquire().
+// The channel is pre-filled with tokens: Acquire = receive, Release = send.
+// Closing the semaphore unblocks all waiting goroutines.
+//
+// Performance: ~115 ns/op with zero allocations (slower than FastSemaphore due to timer allocation).
+// Fairness: Strict FIFO ordering guaranteed by Go runtime.
+type FIFOSemaphore struct {
+	tokens chan struct{}
+	max    int32
+}
+
+// NewFIFOSemaphore creates a new FIFO semaphore with the given capacity.
+func NewFIFOSemaphore(capacity int32) *FIFOSemaphore {
+	ch := make(chan struct{}, capacity)
+	// Pre-fill with tokens
+	for i := int32(0); i < capacity; i++ {
+		ch <- struct{}{}
+	}
+	return &FIFOSemaphore{
+		tokens: ch,
+		max:    capacity,
+	}
+}
+
+// TryAcquire attempts to acquire a token without blocking.
+// Returns true if successful, false if no tokens available.
+func (s *FIFOSemaphore) TryAcquire() bool {
+	select {
+	case <-s.tokens:
+		return true
+	default:
+		return false
+	}
+}
+
+// Acquire acquires a token, blocking if necessary until one is available.
+// Returns an error if the context is cancelled or the timeout expires.
+// Always uses timer to guarantee FIFO ordering (no fast path).
+func (s *FIFOSemaphore) Acquire(ctx context.Context, timeout time.Duration, timeoutErr error) error {
+	// No fast path - always use timer to guarantee FIFO
+	timer := semTimers.Get().(*time.Timer)
+	defer semTimers.Put(timer)
+	timer.Reset(timeout)
+
+	select {
+	case <-s.tokens:
+		if !timer.Stop() {
+			<-timer.C
+		}
+		return nil
+	case <-ctx.Done():
+		if !timer.Stop() {
+			<-timer.C
+		}
+		return ctx.Err()
+	case <-timer.C:
+		return timeoutErr
+	}
+}
+
+// AcquireBlocking acquires a token, blocking indefinitely until one is available.
+func (s *FIFOSemaphore) AcquireBlocking() {
+	<-s.tokens
+}
+
+// Release releases a token back to the semaphore.
+func (s *FIFOSemaphore) Release() {
+	s.tokens <- struct{}{}
+}
+
+// Close closes the semaphore, unblocking all waiting goroutines.
+// After close, all Acquire calls will receive a closed channel signal.
+func (s *FIFOSemaphore) Close() {
+	close(s.tokens)
+}
+
+// Len returns the current number of acquired tokens.
+func (s *FIFOSemaphore) Len() int32 {
+	return s.max - int32(len(s.tokens))
+}