mirror of
https://github.com/wader/fq.git
synced 2024-11-28 03:02:55 +03:00
113 lines
2.3 KiB
Go
113 lines
2.3 KiB
Go
package mpeg
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import (
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"bytes"
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"io"
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"github.com/wader/fq/pkg/bitio"
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"github.com/wader/fq/pkg/decode"
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"github.com/wader/fq/pkg/interp"
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)
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func init() {
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interp.RegisterFunc0("nal_unescape", makeBinaryTransformFn(func(r io.Reader) (io.Reader, error) {
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return &nalUnescapeReader{Reader: r}, nil
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}))
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}
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// transform to binary using fn
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func makeBinaryTransformFn(fn func(r io.Reader) (io.Reader, error)) func(i *interp.Interp, c any) any {
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return func(_ *interp.Interp, c any) any {
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inBR, err := interp.ToBitReader(c)
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if err != nil {
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return err
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}
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r, err := fn(bitio.NewIOReader(inBR))
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if err != nil {
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return err
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}
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outBuf := &bytes.Buffer{}
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if _, err := io.Copy(outBuf, r); err != nil {
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return err
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}
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outBR := bitio.NewBitReader(outBuf.Bytes(), -1)
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bb, err := interp.NewBinaryFromBitReader(outBR, 8, 0)
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if err != nil {
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return err
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}
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return bb
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}
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}
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func decodeEscapeValueFn(add int, b1 int, b2 int, b3 int) func(d *decode.D) uint64 {
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return func(d *decode.D) uint64 {
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n1 := d.U(b1)
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n := n1
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if n1 == (1<<b1)-1 {
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n2 := d.U(b2)
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if add != -1 {
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n += n2 + uint64(add)
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} else {
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n = n2
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}
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if n2 == (1<<b2)-1 {
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n3 := d.U(b3)
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if add != -1 {
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n += n3 + uint64(add)
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} else {
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n = n3
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}
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}
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}
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return n
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}
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}
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// use last non-escaped value
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func decodeEscapeValueAbsFn(b1 int, b2 int, b3 int) func(d *decode.D) uint64 {
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return decodeEscapeValueFn(-1, b1, b2, b3)
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}
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// add values and escaped values
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//nolint: deadcode,unused
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func decodeEscapeValueAddFn(b1 int, b2 int, b3 int) func(d *decode.D) uint64 {
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return decodeEscapeValueFn(0, b1, b2, b3)
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}
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// add values and escaped values+1
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func decodeEscapeValueCarryFn(b1 int, b2 int, b3 int) func(d *decode.D) uint64 {
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return decodeEscapeValueFn(1, b1, b2, b3)
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}
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// TODO: move?
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// TODO: make generic replace reader? share with id3v2 unsync?
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type nalUnescapeReader struct {
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io.Reader
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lastTwoZeros [2]bool
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}
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func (r nalUnescapeReader) Read(p []byte) (n int, err error) {
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n, err = r.Reader.Read(p)
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ni := 0
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for i, b := range p[0:n] {
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if r.lastTwoZeros[0] && r.lastTwoZeros[1] && b == 0x03 {
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n--
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r.lastTwoZeros[0] = false
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r.lastTwoZeros[1] = false
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continue
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} else {
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r.lastTwoZeros[1] = r.lastTwoZeros[0]
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r.lastTwoZeros[0] = b == 0
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}
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p[ni] = p[i]
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ni++
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}
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return n, err
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}
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