cmd/livepeer_bench: fix segment path handling on Windows

CHANGELOG_PENDING.md

@@ -21,3 +21,5 @@
 #### Broadcaster
 
 #### CLI
+
+- \#1844 Fix livepeer_bench segment path handling on Windows (@lukiod)

cmd/livepeer_bench/livepeer_bench.go

@@ -6,7 +6,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
-	"path"
+	"path/filepath"
 	"strings"
 	"sync"
 	"time"
@@ -87,7 +87,6 @@ func main() {
 	ffmpeg.InitFFmpegWithLogLevel(ffmpeg.LogLevel(*log * 8))
 
 	var wg sync.WaitGroup
-	dir := path.Dir(*in)
 
 	table := tablewriter.NewWriter(os.Stderr)
 	data := [][]string{
@@ -139,7 +138,7 @@ func main() {
 					if v == nil {
 						continue
 					}
-					u := path.Join(dir, v.URI)
+					u := segmentPath(*in, v.URI)
 					in := &ffmpeg.TranscodeOptionsIn{
 						Fname: u,
 						Accel: accel,
@@ -223,6 +222,14 @@ func main() {
 	}
 }
 
+// segmentPath returns the path to a playlist segment by joining the input
+// manifest's directory with the segment's URI (which is relative to the
+// manifest). filepath is used instead of path so that Windows-style backslash
+// separators in the manifest path are handled correctly.
+func segmentPath(manifest, segmentURI string) string {
+	return filepath.Join(filepath.Dir(manifest), segmentURI)
+}
+
 func parseVideoProfiles(inp string) []ffmpeg.VideoProfile {
 	profiles := []ffmpeg.VideoProfile{}
 	if inp != "" {

cmd/livepeer_bench/livepeer_bench_test.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"path/filepath"
+	"runtime"
+	"testing"
+)
+
+func TestSegmentPath(t *testing.T) {
+	// Windows-style manifest path with backslash separators, as reported in
+	// issue #1844. On Windows the path package treats backslashes as ordinary
+	// characters, so path.Dir/path.Join produce a broken segment path;
+	// filepath handles them as separators.
+	if runtime.GOOS == "windows" {
+		const manifest = `C:\bench\media\input.m3u8`
+		want := filepath.Join(`C:\bench\media`, "seg0.ts")
+		if got := segmentPath(manifest, "seg0.ts"); got != want {
+			t.Fatalf("segmentPath(%q) = %q, want %q", manifest, got, want)
+		}
+		return
+	}
+
+	// POSIX-style manifest path: forward slashes. filepath and path agree on
+	// this input, but this guards the normal case against regression.
+	const manifest = "/tmp/bench/media/input.m3u8"
+	want := filepath.Join("/tmp/bench/media", "seg0.ts")
+	if got := segmentPath(manifest, "seg0.ts"); got != want {
+		t.Fatalf("segmentPath(%q) = %q, want %q", manifest, got, want)
+	}
+}