commit d0a2114cd0f9dda0212b0195364e81fb5e69a68d
from: Oliver Lowe <o@olowe.co>
date: Sat Dec 21 06:07:49 2024 UTC

add package for WAVE files

commit - 74364bb7c33ecf3fdef8c8a361310c2f1992c1bd
commit + d0a2114cd0f9dda0212b0195364e81fb5e69a68d
blob - /dev/null
blob + 96d779bdc07609d730676c1c3c48bd1f0beaa542 (mode 644)
Binary files /dev/null and wav/test.wav differ
blob - /dev/null
blob + f1b47d3c3c7c83af3ccdd5e90da8ee7d827d04ef (mode 644)
--- /dev/null
+++ wav/wav.go
@@ -0,0 +1,114 @@
+// Package wav provides an encoder and decoder of WAVE data.
+// https://en.wikipedia.org/wiki/WAV
+package wav
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+)
+
+type File struct {
+	Header    Header
+	Bitstream io.Reader
+}
+
+type Header struct {
+	FileSize uint32
+
+	BlocSize       uint32
+	AudioFormat    uint16
+	ChannelCount   uint16
+	Frequency      uint32
+	BytesPerSecond uint32
+	BytesPerBloc   uint16
+	BitsPerSample  uint16
+
+	DataSize uint32
+}
+
+type header struct {
+	FileBlocID   [4]byte
+	FileSize     uint32
+	FileFormatID [4]byte
+
+	FormatBlocID   [4]byte
+	BlocSize       uint32
+	AudioFormat    uint16
+	ChannelCount   uint16
+	Frequency      uint32
+	BytesPerSecond uint32
+	BytesPerBloc   uint16
+	BitsPerSample  uint16
+
+	DataBlocID [4]byte
+	DataSize   uint32
+}
+
+var (
+	fileBlocID   = [4]byte{'R', 'I', 'F', 'F'}
+	fileFormatID = [4]byte{'W', 'A', 'V', 'E'}
+)
+
+var formatBlocID = [4]byte{'f', 'm', 't', ' '}
+
+var dataBlocID = [4]byte{'d', 'a', 't', 'a'}
+
+func readHeader(rd io.Reader) (*header, error) {
+	var h header
+	if err := binary.Read(rd, binary.LittleEndian, &h); err != nil {
+		return nil, err
+	}
+	if h.FileBlocID != fileBlocID {
+		return nil, fmt.Errorf("bad file block id %x", h.FileBlocID)
+	} else if h.FileFormatID != fileFormatID {
+		return nil, fmt.Errorf("bad file format id %x", h.FileFormatID)
+	} else if h.FormatBlocID != formatBlocID {
+		return nil, fmt.Errorf("bad format block id %x", h.FileFormatID)
+	} else if h.DataBlocID != dataBlocID {
+		return nil, fmt.Errorf("bad data block id %x", h.DataBlocID)
+	}
+	return &h, nil
+}
+
+func EncodeHeader(hdr Header) [44]byte {
+	var buf [44]byte
+	h := header{
+		fileBlocID,
+		hdr.FileSize,
+		fileFormatID,
+		formatBlocID,
+		hdr.BlocSize,
+		hdr.AudioFormat,
+		hdr.ChannelCount,
+		hdr.Frequency,
+		hdr.BytesPerSecond,
+		hdr.BytesPerBloc,
+		hdr.BitsPerSample,
+		dataBlocID,
+		hdr.DataSize,
+	}
+	binary.Encode(buf[:], binary.LittleEndian, h)
+	return buf
+}
+
+func ReadFile(r io.Reader) (*File, error) {
+	h, err := readHeader(r)
+	if err != nil {
+		return nil, fmt.Errorf("read header: %w", err)
+	}
+	return &File{
+		Header: Header{
+			h.FileSize,
+			h.BlocSize,
+			h.AudioFormat,
+			h.ChannelCount,
+			h.Frequency,
+			h.BytesPerSecond,
+			h.BytesPerBloc,
+			h.BitsPerSample,
+			h.DataSize,
+		},
+		Bitstream: r,
+	}, nil
+}
blob - /dev/null
blob + 17d0e50710ffa13942ad76429c8fcc586e3d87e7 (mode 644)
--- /dev/null
+++ wav/wav_test.go
@@ -0,0 +1,31 @@
+package wav
+
+import (
+	"io"
+	"os"
+	"testing"
+)
+
+func TestDecodeEncode(t *testing.T) {
+	var source [44]byte
+	f, err := os.Open("test.wav")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	if _, err := io.ReadFull(f, source[:]); err != nil {
+		t.Fatalf("copy header bytes: %v", err)
+	}
+
+	if _, err := f.Seek(0, 0); err != nil {
+		t.Fatal(err)
+	}
+	file, err := ReadFile(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	header := EncodeHeader(file.Header)
+	if source != header {
+		t.Errorf("encode header: want %v, got %v", source, header)
+	}
+}