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package bitio
import (
"io"
)
type Writer interface {
io.Writer
// alignment:
// |-1-byte-block-|--------------|--------------|--------------|
// |<-offset->|<-------------------width---------------------->|
WriteBits(data []byte, width uint) error
WriteBit(bit bool) error
}
type writer struct {
writer io.Writer
octet byte
width uint
}
func NewWriter(w io.Writer) Writer {
return &writer{writer: w}
}
func (w *writer) Write(p []byte) (n int, err error) {
if w.width != 0 {
return 0, ErrInvalidAlignment
}
return w.writer.Write(p)
}
func (w *writer) WriteBits(data []byte, width uint) error {
length := uint(len(data)) * 8
offset := length - width
for i := offset; i < length; i++ {
oi := i / 8
if err := w.WriteBit((data[oi]>>(7-i%8))&0x01 != 0); err != nil {
return err
}
}
return nil
}
func (w *writer) WriteBit(bit bool) error {
if bit {
w.octet |= 0x1 << (7 - w.width)
}
w.width++
if w.width == 8 {
if _, err := w.writer.Write([]byte{w.octet}); err != nil {
return err
}
w.octet = 0x00
w.width = 0
}
return nil
}
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