94 lines
1.6 KiB
Go
94 lines
1.6 KiB
Go
package video
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import (
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"bytes"
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"errors"
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"io"
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"github.com/sunfish-shogi/bufseekio"
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)
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// Chunks represents a list of file chunks.
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type Chunks []Chunk
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// Contains tests if the chunk is contained in this list.
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func (c Chunks) Contains(s [4]byte) bool {
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if len(c) == 0 {
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return false
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}
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// Find matches.
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for i := range c {
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if s == c[i] {
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return true
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}
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}
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return false
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}
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// ContainsAny checks if at least one common chunk exists in this list.
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func (c Chunks) ContainsAny(b [][4]byte) bool {
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if len(c) == 0 || len(b) == 0 {
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return false
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}
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// Find matches.
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for i := range c {
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for j := range b {
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if b[j] == c[i] {
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return true
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}
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}
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}
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// Not found.
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return false
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}
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// FileTypeOffset returns the file type start offset in f, or -1 if it was not found.
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func (c Chunks) FileTypeOffset(file io.ReadSeeker) (int, error) {
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if file == nil {
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return -1, errors.New("file is nil")
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}
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ftyp := ChunkFTYP.Bytes()
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blockSize := 128 * 1024
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buffer := make([]byte, blockSize)
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// Create buffered read seeker.
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r := bufseekio.NewReadSeeker(file, blockSize, 8)
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// Index offset.
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var offset int
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// Search in batches.
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for {
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n, err := r.Read(buffer)
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buffer = buffer[:n]
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if err != nil {
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if err != io.EOF {
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return -1, err
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}
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break
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} else if n == 0 {
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break
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}
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// Find ftyp chunk.
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if i := bytes.Index(buffer, ftyp); i < 0 {
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// Not found.
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} else if j := i + 4; j < 8 || len(buffer) < j+4 {
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// Skip.
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} else if k := j + 4; c.Contains(*(*[4]byte)(buffer[j:k])) {
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return offset + i - 4, nil
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}
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offset += n
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}
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return -1, nil
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}
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