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89 lines
1.3 KiB
Go
89 lines
1.3 KiB
Go
package bit
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import (
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"io"
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)
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type bufReader struct {
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src []byte // source of data
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n uint64 // bit buffer
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bits uint // number of valid bits in n
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err error // stored error
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}
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func (r *bufReader) ReadBits(bits uint) (n uint64) {
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for bits > r.bits {
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if len(r.src) == 0 {
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r.err = io.EOF
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return 0
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}
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r.n |= uint64(r.src[0]) << r.bits
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r.src = r.src[1:]
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r.bits += 8
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}
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n = r.n & (1<<bits - 1)
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r.n >>= bits
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r.bits -= bits
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return
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}
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func (r *bufReader) ReadByte() byte {
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if r.bits == 0 {
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if len(r.src) == 0 {
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r.err = io.EOF
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return 0
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}
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b := r.src[0]
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r.src = r.src[1:]
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return b
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}
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return byte(r.ReadBits(8))
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}
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func (r *bufReader) Read(buf []byte) int {
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if r.bits == 0 {
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if len(r.src) < len(buf) {
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r.err = io.EOF
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return 0
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}
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copy(buf, r.src[:len(buf)])
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r.src = r.src[len(buf):]
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return len(buf)
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}
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for i := 0; i < len(buf); i++ {
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b := r.ReadByte()
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if r.err != nil {
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return 0
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}
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buf[i] = b
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}
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return len(buf)
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}
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func (r *bufReader) DiscardBytes(n int) {
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if r.bits == 0 {
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if len(r.src) < n {
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r.err = io.EOF
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return
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}
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r.src = r.src[n:]
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return
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}
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for r.bits > 8 {
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r.bits -= 8
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n -= 1
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}
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if len(r.src) < n {
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r.err = io.EOF
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return
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}
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r.n = uint64(r.src[n-1]) >> (8 - r.bits)
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r.src = r.src[n:]
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}
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func (r *bufReader) Err() error { return r.err }
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