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// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package riff implements the Resource Interchange File Format, used by media
// formats such as AVI, WAVE and WEBP.
//
// A RIFF stream contains a sequence of chunks. Each chunk consists of an 8-byte
// header (containing a 4-byte chunk type and a 4-byte chunk length), the chunk
// data (presented as an io.Reader), and some padding bytes.
//
// A detailed description of the format is at
// http://www.tactilemedia.com/info/MCI_Control_Info.html
package riff // import "golang.org/x/image/riff"
import (
"errors"
"io"
"io/ioutil"
"math"
)
var (
errMissingPaddingByte = errors.New("riff: missing padding byte")
errMissingRIFFChunkHeader = errors.New("riff: missing RIFF chunk header")
errListSubchunkTooLong = errors.New("riff: list subchunk too long")
errShortChunkData = errors.New("riff: short chunk data")
errShortChunkHeader = errors.New("riff: short chunk header")
errStaleReader = errors.New("riff: stale reader")
)
// u32 decodes the first four bytes of b as a little-endian integer.
func u32(b []byte) uint32 {
return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
}
const chunkHeaderSize = 8
// FourCC is a four character code.
type FourCC [4]byte
// LIST is the "LIST" FourCC.
var LIST = FourCC{'L', 'I', 'S', 'T'}
// NewReader returns the RIFF stream's form type, such as "AVI " or "WAVE", and
// its chunks as a *Reader.
func NewReader(r io.Reader) (formType FourCC, data *Reader, err error) {
var buf [chunkHeaderSize]byte
if _, err := io.ReadFull(r, buf[:]); err != nil {
if err == io.EOF || err == io.ErrUnexpectedEOF {
err = errMissingRIFFChunkHeader
}
return FourCC{}, nil, err
}
if buf[0] != 'R' || buf[1] != 'I' || buf[2] != 'F' || buf[3] != 'F' {
return FourCC{}, nil, errMissingRIFFChunkHeader
}
return NewListReader(u32(buf[4:]), r)
}
// NewListReader returns a LIST chunk's list type, such as "movi" or "wavl",
// and its chunks as a *Reader.
func NewListReader(chunkLen uint32, chunkData io.Reader) (listType FourCC, data *Reader, err error) {
if chunkLen < 4 {
return FourCC{}, nil, errShortChunkData
}
z := &Reader{r: chunkData}
if _, err := io.ReadFull(chunkData, z.buf[:4]); err != nil {
if err == io.EOF || err == io.ErrUnexpectedEOF {
err = errShortChunkData
}
return FourCC{}, nil, err
}
z.totalLen = chunkLen - 4
return FourCC{z.buf[0], z.buf[1], z.buf[2], z.buf[3]}, z, nil
}
// Reader reads chunks from an underlying io.Reader.
type Reader struct {
r io.Reader
err error
totalLen uint32
chunkLen uint32
chunkReader *chunkReader
buf [chunkHeaderSize]byte
padded bool
}
// Next returns the next chunk's ID, length and data. It returns io.EOF if there
// are no more chunks. The io.Reader returned becomes stale after the next Next
// call, and should no longer be used.
//
// It is valid to call Next even if all of the previous chunk's data has not
// been read.
func (z *Reader) Next() (chunkID FourCC, chunkLen uint32, chunkData io.Reader, err error) {
if z.err != nil {
return FourCC{}, 0, nil, z.err
}
// Drain the rest of the previous chunk.
if z.chunkLen != 0 {
want := z.chunkLen
var got int64
got, z.err = io.Copy(ioutil.Discard, z.chunkReader)
if z.err == nil && uint32(got) != want {
z.err = errShortChunkData
}
if z.err != nil {
return FourCC{}, 0, nil, z.err
}
}
z.chunkReader = nil
if z.padded {
if z.totalLen == 0 {
z.err = errListSubchunkTooLong
return FourCC{}, 0, nil, z.err
}
z.totalLen--
_, z.err = io.ReadFull(z.r, z.buf[:1])
if z.err != nil {
if z.err == io.EOF {
z.err = errMissingPaddingByte
}
return FourCC{}, 0, nil, z.err
}
}
// We are done if we have no more data.
if z.totalLen == 0 {
z.err = io.EOF
return FourCC{}, 0, nil, z.err
}
// Read the next chunk header.
if z.totalLen < chunkHeaderSize {
z.err = errShortChunkHeader
return FourCC{}, 0, nil, z.err
}
z.totalLen -= chunkHeaderSize
if _, z.err = io.ReadFull(z.r, z.buf[:chunkHeaderSize]); z.err != nil {
if z.err == io.EOF || z.err == io.ErrUnexpectedEOF {
z.err = errShortChunkHeader
}
return FourCC{}, 0, nil, z.err
}
chunkID = FourCC{z.buf[0], z.buf[1], z.buf[2], z.buf[3]}
z.chunkLen = u32(z.buf[4:])
if z.chunkLen > z.totalLen {
z.err = errListSubchunkTooLong
return FourCC{}, 0, nil, z.err
}
z.padded = z.chunkLen&1 == 1
z.chunkReader = &chunkReader{z}
return chunkID, z.chunkLen, z.chunkReader, nil
}
type chunkReader struct {
z *Reader
}
func (c *chunkReader) Read(p []byte) (int, error) {
if c != c.z.chunkReader {
return 0, errStaleReader
}
z := c.z
if z.err != nil {
if z.err == io.EOF {
return 0, errStaleReader
}
return 0, z.err
}
n := int(z.chunkLen)
if n == 0 {
return 0, io.EOF
}
if n < 0 {
// Converting uint32 to int overflowed.
n = math.MaxInt32
}
if n > len(p) {
n = len(p)
}
n, err := z.r.Read(p[:n])
z.totalLen -= uint32(n)
z.chunkLen -= uint32(n)
if err != io.EOF {
z.err = err
}
return n, err
}
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