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76 lines
1.7 KiB
Go
76 lines
1.7 KiB
Go
package bit
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import (
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"io"
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)
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// bit.Reader allows for bit-level reading of arbitrary source data. This is
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// based on the bit reader found in the standard library's bzip2 package.
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// https://golang.org/src/compress/bzip2/bit_reader.go
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type streamReader struct {
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src io.ByteReader // 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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// ReadBits reads the given number of bits and returns them in the
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// least-significant part of a uint64.
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func (r *streamReader) ReadBits(bits uint) (n uint64) {
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for bits > r.bits {
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b, err := r.src.ReadByte()
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if err != nil {
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r.err = err
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return 0
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}
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r.n |= uint64(b) << r.bits
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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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// discards up to bits bits. returns a bool indicating wheter any errors occured.
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func (r *streamReader) DiscardBits(n int) {
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r.ReadBits(uint(n))
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}
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// ReadByte reads a single byte, regardless of alignment.
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func (r *streamReader) ReadByte() (byte, error) {
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if r.bits == 0 {
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return r.src.ReadByte()
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}
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b := byte(r.ReadBits(8))
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if err := r.Err(); err != nil {
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return 0, err
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}
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return b, nil
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}
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// Read reads like an io.Reader, taking care of alignment internally.
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func (r *streamReader) Read(buf []byte) (int, error) {
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for i := 0; i < len(buf); i++ {
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b, err := r.ReadByte()
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if err != nil {
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return 0, err
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}
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buf[i] = b
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}
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return len(buf), nil
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}
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// discards N byte of data on the reader or until EOF
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func (r *streamReader) DiscardBytes(n int) {
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for i := 0; i < n; i++ {
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_, err := r.ReadByte()
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if err != nil {
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r.err = err
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return
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}
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}
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}
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func (r *streamReader) Err() error { return r.err }
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