You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
53 lines
1.2 KiB
Go
53 lines
1.2 KiB
Go
8 years ago
|
package bit
|
||
|
|
|
||
|
|
import (
|
||
|
|
"bufio"
|
||
|
|
"bytes"
|
||
|
|
"io"
|
||
|
|
)
|
||
|
|
|
||
|
|
// bit.Reader allows for bit-level reading of arbitrary source data. This is
|
||
|
|
// based on the bit reader found in the standard library's bzip2 package.
|
||
|
|
// https://golang.org/src/compress/bzip2/bit_reader.go
|
||
|
|
type Reader struct {
|
||
|
|
src io.ByteReader // source of data
|
||
|
|
n uint64 // bit buffer
|
||
|
|
bits uint // number of valid bits in n
|
||
|
|
err error // stored error
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewReader creates a new bit.Reader for any arbitrary reader.
|
||
|
|
func NewReader(r io.Reader) *Reader {
|
||
|
|
br, ok := r.(io.ByteReader)
|
||
|
|
if !ok {
|
||
|
|
br = bufio.NewReader(r)
|
||
|
|
}
|
||
|
|
return &Reader{src: br}
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewByteReader creates a bit.Reader for a static slice of bytes. It's just
|
||
|
|
// using a bytes.Reader internally.
|
||
|
|
func NewBytesReader(b []byte) *Reader {
|
||
|
|
return NewReader(bytes.NewReader(b))
|
||
|
|
}
|
||
|
|
|
||
|
|
// ReadBits reads the given number of bits and returns them in the
|
||
|
|
// least-significant part of a uint64.
|
||
|
|
func (r *Reader) ReadBits(bits uint) (n uint64) {
|
||
|
|
for bits > r.bits {
|
||
|
|
b, err := r.src.ReadByte()
|
||
|
|
if err != nil {
|
||
|
|
r.err = err
|
||
|
|
return 0
|
||
|
|
}
|
||
|
|
r.n <<= 8
|
||
|
|
r.n |= uint64(b)
|
||
|
|
r.bits += 8
|
||
|
|
}
|
||
|
|
n = (r.n >> (r.bits - bits)) & ((1 << bits) - 1)
|
||
|
|
r.bits -= bits
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
func (r *Reader) Err() error { return r.err }
|