aboutsummaryrefslogtreecommitdiff
path: root/vendor/golang.org/x/image/riff/riff.go
blob: 38dc0e5684da719dfcd056793e1bb752877c9dfd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
// 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
}