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