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