Jay Brown
43 lines
996 B
Go
43 lines
996 B
Go
// Copyright 2014 <chaishushan{AT}gmail.com>. 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 tiff
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type bitsReader struct {
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buf []byte
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off int // Current offset in buf.
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v uint32 // Buffer value for reading with arbitrary bit depths.
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nbits uint // Remaining number of bits in v.
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}
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func newBitsReader(data []byte) *bitsReader {
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return &bitsReader{
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buf: data,
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}
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}
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// readBits reads n bits from the internal buffer starting at the current offset.
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func (p *bitsReader) ReadBits(n uint) (v uint32, ok bool) {
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for p.nbits < n {
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p.v <<= 8
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if p.off >= len(p.buf) {
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return 0, false
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}
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p.v |= uint32(p.buf[p.off])
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p.off++
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p.nbits += 8
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}
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p.nbits -= n
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rv := p.v >> p.nbits
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p.v &^= rv << p.nbits
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return rv, true
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}
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// flushBits discards the unread bits in the buffer used by readBits.
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// It is used at the end of a line.
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func (p *bitsReader) flushBits() {
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p.v = 0
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p.nbits = 0
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}
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