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73 lines
1.3 KiB
Go
73 lines
1.3 KiB
Go
package bitio
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// TODO: NewBuffer with []byte arg to save on alloc
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import (
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"io"
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)
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// Buffer is a bitio.Reader and bitio.Writer providing a bit buffer.
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// Similar to bytes.Buffer.
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type Buffer struct {
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buf []byte
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bufBits int64
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bitsOff int64
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}
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func (b *Buffer) Len() int64 { return b.bufBits - b.bitsOff }
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func (b *Buffer) Reset() {
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b.bufBits = 0
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b.bitsOff = 0
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}
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// Bits return unread bits in buffer
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func (b *Buffer) Bits() ([]byte, int64) {
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l := b.Len()
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buf := make([]byte, BitsByteCount(l))
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copyBufBits(buf, 0, b.buf, b.bitsOff, l, true)
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return buf, b.bufBits
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}
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func (b *Buffer) WriteBits(p []byte, nBits int64) (n int64, err error) {
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tBytes := BitsByteCount(b.bufBits + nBits)
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if tBytes > int64(len(b.buf)) {
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if tBytes <= int64(cap(b.buf)) {
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b.buf = b.buf[:tBytes]
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} else {
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buf := make([]byte, tBytes, tBytes*2)
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copy(buf, b.buf)
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b.buf = buf
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}
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}
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copyBufBits(b.buf, b.bufBits, p, 0, nBits, true)
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b.bufBits += nBits
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return nBits, nil
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}
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func (b *Buffer) empty() bool { return b.bufBits <= b.bitsOff }
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func (b *Buffer) ReadBits(p []byte, nBits int64) (n int64, err error) {
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if b.empty() {
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b.Reset()
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if nBits == 0 {
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return 0, nil
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}
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return 0, io.EOF
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}
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c := nBits
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left := b.Len()
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if c > left {
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c = left
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}
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copyBufBits(p, 0, b.buf, b.bitsOff, c, true)
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b.bitsOff += c
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return c, nil
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}
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