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|
package wav
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"io/ioutil"
"os"
)
type WavFile struct {
Header Header
Format FormatChunk
Data DataChunk
}
type Header struct {
GroupID [4]uint8
FileLength uint32
RiffType [4]uint8
}
type FormatChunk struct {
GroupID [4]uint8
ChunkSize uint32
FormatTag uint16
Channels uint16
SampleRate uint32
ByteRate uint32
Alignment uint16
BitDensity uint32
}
type DataChunk struct {
GroupID [4]uint8
ChunkSize uint32
Samples io.Reader
}
func Load(filename string) (*WavFile, error) {
file, err := os.Open(filename)
if err != nil {
return nil, err
}
load16 := func(b []byte) (uint16, error) {
var out uint16
err := binary.Read(bytes.NewBuffer(b), binary.LittleEndian, &out)
return out, err
}
load32 := func(b []byte) (uint32, error) {
var out uint32
err := binary.Read(bytes.NewBuffer(b), binary.LittleEndian, &out)
return out, err
}
b, err := ioutil.ReadAll(io.LimitReader(file, 40))
if err != nil {
return nil, err
}
h := Header{}
h.FileLength, err = load32(b[4:36])
if err != nil {
return nil, err
}
h.FileLength -= 8 // subtract RIFF/WAVE markers
for i := 0; i < 4; i++ {
h.GroupID[i] = b[i]
h.RiffType[i] = b[i+36]
}
fmt.Println(h)
fmt.Println(string(h.RiffType[:]))
if string(h.GroupID[:]) != "RIFF" { // || string(h.RiffType[:]) != "WAVE" {
return nil, fmt.Errorf("invalid header!")
}
f := FormatChunk{}
file.Seek(40, io.SeekStart)
b, err = ioutil.ReadAll(io.LimitReader(file, 36))
if err != nil {
return nil, err
}
for i := 0; i < 4; i++ {
f.GroupID[i] = b[i]
}
f.ChunkSize, err = load32(b[4:36])
if err != nil {
return nil, err
}
file.Seek(76, io.SeekStart)
b, err = ioutil.ReadAll(io.LimitReader(file, int64(f.ChunkSize)))
if err != nil {
return nil, err
}
f.FormatTag, err = load16(b[36:52])
if err != nil {
return nil, err
}
f.Channels, err = load16(b[52:68])
if err != nil {
return nil, err
}
f.SampleRate, err = load32(b[68:100])
if err != nil {
return nil, err
}
f.ByteRate, err = load32(b[100:132])
if err != nil {
return nil, err
}
f.Alignment, err = load16(b[132:148])
if err != nil {
return nil, err
}
f.BitDensity, err = load32(b[138:180])
if err != nil {
return nil, err
}
if string(f.GroupID[:]) != "fmt " ||
f.FormatTag != 1 ||
f.Alignment != uint16((uint32(f.Channels)*f.BitDensity/8)&0xff) {
return nil, fmt.Errorf("invalid format block!")
}
if f.BitDensity != 16 || f.Channels != 2 || f.SampleRate != 44100 {
return nil, fmt.Errorf("wrong pcm format!")
}
d := DataChunk{}
file.Seek(220, io.SeekStart)
b, err = ioutil.ReadAll(io.LimitReader(file, 36))
if err != nil {
return nil, err
}
for i := 0; i < 4; i++ {
d.GroupID[i] = b[i]
}
d.ChunkSize, err = load32(b[4:])
if err != nil {
return nil, err
}
if string(f.GroupID[:]) != "fmt " {
return nil, fmt.Errorf("invalid data block!")
}
file.Seek(256, io.SeekStart)
d.Samples = io.LimitReader(file, int64(d.ChunkSize))
return &WavFile{
Header: h,
Format: f,
Data: d,
}, nil
}
|
