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slicewriter.go
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slicewriter.go
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package mp4
import (
"encoding/binary"
)
// SliceWriter - write numbers to a []byte slice
type SliceWriter struct {
buf []byte
pos int
}
// NewSliceWriter - create writer around slice
func NewSliceWriter(data []byte) *SliceWriter {
return &SliceWriter{
buf: data,
pos: 0,
}
}
// WriteUint8 - write byte to slice
func (b *SliceWriter) WriteUint8(n byte) {
b.buf[b.pos] = n
b.pos++
}
// WriteUint16 - write uint16 to slice
func (b *SliceWriter) WriteUint16(n uint16) {
binary.BigEndian.PutUint16(b.buf[b.pos:], n)
b.pos += 2
}
// WriteInt16 - write int16 to slice
func (b *SliceWriter) WriteInt16(n int16) {
binary.BigEndian.PutUint16(b.buf[b.pos:], uint16(n))
b.pos += 2
}
// WriteUint24 - write uint24 to slice
func (b *SliceWriter) WriteUint24(n uint32) {
b.WriteUint8(byte(n >> 16))
b.WriteUint16(uint16(n & 0xffff))
}
// WriteUint32 - write uint32 to slice
func (b *SliceWriter) WriteUint32(n uint32) {
binary.BigEndian.PutUint32(b.buf[b.pos:], n)
b.pos += 4
}
// WriteInt32 - write int32 to slice
func (b *SliceWriter) WriteInt32(n int32) {
binary.BigEndian.PutUint32(b.buf[b.pos:], uint32(n))
b.pos += 4
}
// WriteUint64 - write uint64 to slice
func (b *SliceWriter) WriteUint64(n uint64) {
binary.BigEndian.PutUint64(b.buf[b.pos:], n)
b.pos += 8
}
// WriteInt64 - write int64 to slice
func (b *SliceWriter) WriteInt64(n int64) {
binary.BigEndian.PutUint64(b.buf[b.pos:], uint64(n))
b.pos += 8
}
// WriteString - write string to slice with or without zero end
func (b *SliceWriter) WriteString(s string, addZeroEnd bool) {
for _, c := range s {
b.buf[b.pos] = byte(c)
b.pos++
}
if addZeroEnd {
b.buf[b.pos] = 0
b.pos++
}
}
// WriteZeroBytes - write n byte of zeroes
func (b *SliceWriter) WriteZeroBytes(n int) {
for i := 0; i < n; i++ {
b.buf[b.pos] = 0
b.pos++
}
}
// WriteBytes - write []byte
func (b *SliceWriter) WriteBytes(byteSlice []byte) {
for _, c := range byteSlice {
b.buf[b.pos] = c
b.pos++
}
}
// WriteUnityMatrix - write a unity matrix for mvhd or tkhd
func (b *SliceWriter) WriteUnityMatrix() {
b.WriteUint32(0x00010000) // = 1 fixed 16.16
b.WriteUint32(0)
b.WriteUint32(0)
b.WriteUint32(0)
b.WriteUint32(0x00010000) // = 1 fixed 16.16
b.WriteUint32(0)
b.WriteUint32(0)
b.WriteUint32(0)
b.WriteUint32(0x40000000) // = 1 fixed 2.30
}