av/codec/mjpeg/utils.go

/*
DESCRIPTION
  utils.go provides buffer utilities used by jpeg.go.

AUTHOR
  Saxon Nelson-Milton <saxon@ausocean.org>

LICENSE
  Copyright (C) 2019 the Australian Ocean Lab (AusOcean)

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  for more details.

  You should have received a copy of the GNU General Public License
  along with revid in gpl.txt. If not, see http://www.gnu.org/licenses.
*/

package mjpeg

import (
	"encoding/binary"
	"io"
)

type putBuffer struct {
	i int
	b []byte
}

func newPutBuffer(b []byte) *putBuffer { return &putBuffer{b: b} }

func (p *putBuffer) Write(b []byte) (int, error) {
	copy(p.b[p.i:], b)
	p.i += len(b)
	return len(b), nil
}

func (p *putBuffer) writeTo(d io.Writer) (int, error) {
	n, err := d.Write(p.b[0:p.i])
	p.i -= n
	return n, err
}

func (p *putBuffer) put16(v uint16) {
	binary.BigEndian.PutUint16(p.b[p.i:], v)
	p.i += 2
}

func (p *putBuffer) put8(v uint8) {
	p.b[p.i] = byte(v)
	p.i++
}

func (p *putBuffer) putBuf(src []byte) {
	copy(p.b[p.i:], src)
	p.i += len(src)
}

func (p *putBuffer) put16At(v uint16, i int) {
	binary.BigEndian.PutUint16(p.b[i:], v)
}

func (p *putBuffer) reset() {
	p.i = 0
}

func (p *putBuffer) len() int {
	return p.i
}

type byteStream struct {
	bytes []byte
	i     int
}

func newByteStream(b []byte) *byteStream { return &byteStream{bytes: b} }

func (b *byteStream) get24() int {
	v := int(b.bytes[b.i])<<16 | int(b.bytes[b.i+1])<<8 | int(b.bytes[b.i+2])
	b.i += 3
	return v
}

func (b *byteStream) get8() int {
	v := int(b.bytes[b.i])
	b.i++
	return v
}

func (b *byteStream) get16() int {
	v := int(binary.BigEndian.Uint16(b.bytes[b.i:]))
	b.i += 2
	return v
}

func (b *byteStream) getBuf(n int) []byte {
	v := b.bytes[b.i : b.i+n]
	b.i += n
	return v
}

func (b *byteStream) remaining() int {
	return len(b.bytes) - b.i
}

func (b *byteStream) writeTo(w io.Writer, n int) error {
	_n, err := w.Write(b.bytes[b.i : b.i+n])
	b.i += _n
	if err != nil {
		return err
	}
	return nil
}