Add soundbox.StreamURLContext()v0.1.0

This should be the primary public API of the library to stream web radio
to soundbox devices.

3 files changed, 81 insertions, 1 deletions

diff --git a/README.md b/README.md
index c9cbb06..1fc718d 100644
--- a/README.md
+++ b/README.md
@@ -1,9 +1,11 @@
 # soundbox-go
 
-[soundbox-go][1] is a Go library to interface with [soundbox][2] devices.
+[soundbox-go][1] is a Go library to interface with [soundbox][2] devices. It
+currently requires that the [ffmpeg][3] command line utility is installed.
 
 While the repository and project name is `soundbox-go` the Go module name is
 only `soundbox` to make the resulting code more readable.
 
 [1]: https://xengineering.eu/git/soundbox-go
 [2]: https://xengineering.eu/git/soundbox
+[3]: https://ffmpeg.org
diff --git a/example_test.go b/example_test.go
new file mode 100644
index 0000000..78b2f27
--- /dev/null
+++ b/example_test.go
@@ -0,0 +1,38 @@
+package soundbox_test
+
+import (
+	"context"
+	"log"
+	"net"
+	"time"
+
+	"xengineering.eu/soundbox"
+)
+
+func ExampleStreamURLContext() {
+	ctx, cancel := context.WithCancel(context.Background())
+
+	// all soundboxes are referenced by their MAC address
+	soundboxes := []net.HardwareAddr{
+		{0x00, 0x00, 0x5E, 0x00, 0x53, 0x01},
+		{0x00, 0x00, 0x5E, 0x00, 0x53, 0x02},
+		{0x00, 0x00, 0x5E, 0x00, 0x53, 0x03},
+	}
+
+	// currently only web radio is supported
+	url := "https://example.org/radio.mp3"
+
+	// start streaming
+	go func() {
+		err := soundbox.StreamURLContext(ctx, url, soundboxes)
+		if err != nil {
+			log.Fatal(err)
+		}
+	}()
+
+	// let it play for some time
+	time.Sleep(time.Minute)
+
+	// stop it
+	cancel()
+}
diff --git a/stream.go b/stream.go
index 38b3727..ac0a189 100644
--- a/stream.go
+++ b/stream.go
@@ -1,5 +1,45 @@
 package soundbox
 
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"net"
+)
+
 // streamingPort is the default network port a soundbox is listening to for
 // incoming audio stream data.
 const streamingPort = 5316
+
+func StreamURLContext(ctx context.Context, url string, targets []net.HardwareAddr) error {
+	iface, err := getInterface()
+	if err != nil {
+		return err
+	}
+
+	cmd := []string{
+		"-re",
+		"-i",
+		url,
+	}
+
+	for _, target := range targets {
+		ip, err := toLinkLocal(target)
+		if err != nil {
+			return err
+		}
+
+		cmd = append(cmd, "-acodec")
+		cmd = append(cmd, "flac")
+		cmd = append(cmd, "-f")
+		cmd = append(cmd, "ogg")
+		cmd = append(cmd, fmt.Sprintf(
+			"tcp://[%s%%%s]:%d",
+			ip,
+			iface.Name,
+			streamingPort,
+		))
+	}
+
+	return exec.CommandContext(ctx, "ffmpeg", cmd...).Run()
+}