nativeaudio

commit 1f7e8a70d558e0b31085092b28648558188e9b21
parent 0c9c77611e8067c20f4e99b7fc374434a54904c0
Author: Jack Mordaunt <jackmordaunt.dev@gmail.com>
Date:   Wed, 16 Sep 2026 21:29:38 -0400

audio: use os.CreateTemp for the ffmpeg decode scratch file

The scratch file was named from a process-local counter, so two
processes decoding at once both wrote nativeaudio-1 and could corrupt
each other's input. os.CreateTemp guarantees a unique name and lets the
unused counter type go.

Diffstat:
M
audio_ffmpeg.go
 | 
41
+++++++++++++----------------------------

1 file changed, 13 insertions(+), 28 deletions(-)
diff --git a/audio_ffmpeg.go b/audio_ffmpeg.go
@@ -12,10 +12,8 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
-	"path/filepath"
 	"strconv"
 	"strings"
-	"sync"
 )
 
 // FFmpegPlay an audio file with ffplay.
@@ -65,26 +63,6 @@ func FFmpegLoad(path string) ([]byte, Format, error) {
 	return buffer.Bytes(), f, nil
 }
 
-var count = counter{}
-
-type counter struct {
-	count int
-	m     sync.Mutex
-}
-
-func (c *counter) Next() int {
-	c.m.Lock()
-	defer c.m.Unlock()
-	c.count++
-	return c.count
-}
-
-func (c *counter) Done() {
-	c.m.Lock()
-	defer c.m.Unlock()
-	c.count--
-}
-
 // FFmpegDecode raw PCM with ffmpeg.
 //
 //	ffmpeg -f m4a -i pipe: -f s16le -
@@ -95,14 +73,21 @@ func (c *counter) Done() {
 // NOTE(jfm): unfortunately, some formats cannot be piped, so we will
 // create a temporary file instead.
 func FFmpegDecode(by []byte) ([]byte, Format, error) {
-	// id ensures that multiple concurrent tmp files do not collide.
-	id := count.Next()
-	tmp := filepath.Join(os.TempDir(), fmt.Sprintf("nativeaudio-%d", id))
-	if err := os.WriteFile(tmp, by, 0644); err != nil {
+	// CreateTemp picks a unique name, so concurrent decodes in this or any
+	// other process cannot collide.
+	tmp, err := os.CreateTemp("", "nativeaudio-*")
+	if err != nil {
 		return nil, Format{}, fmt.Errorf("creating tmp file: %w", err)
 	}
-	defer os.Remove(tmp)
-	return FFmpegLoad(tmp)
+	defer os.Remove(tmp.Name())
+	if _, err := tmp.Write(by); err != nil {
+		tmp.Close()
+		return nil, Format{}, fmt.Errorf("writing tmp file: %w", err)
+	}
+	if err := tmp.Close(); err != nil {
+		return nil, Format{}, fmt.Errorf("closing tmp file: %w", err)
+	}
+	return FFmpegLoad(tmp.Name())
 }
 
 // probe queries the format information for a given audio file by parsing