109 lines
1.9 KiB
Go
109 lines
1.9 KiB
Go
package video
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"os"
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"github.com/photoprism/photoprism/pkg/fs"
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"github.com/sunfish-shogi/bufseekio"
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)
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// Chunk represents a fixed length file chunk.
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type Chunk [4]byte
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// Get returns the chunk as byte array.
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func (c Chunk) Get() [4]byte {
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return c
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}
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// Hex returns the chunk as hex formatted string.
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func (c Chunk) Hex() string {
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return fmt.Sprintf("0x%x", c[:])
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}
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// String returns the chunk as string.
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func (c Chunk) String() string {
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return string(c[:])
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}
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// Bytes returns the chunk as byte slice.
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func (c Chunk) Bytes() []byte {
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return c[:]
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}
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// Uint32 returns the chunk as unsigned integer.
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func (c Chunk) Uint32() uint32 {
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return binary.BigEndian.Uint32(c.Bytes())
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}
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// Equal compares the chunk with a byte slice.
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func (c Chunk) Equal(b []byte) bool {
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return bytes.Equal(c.Bytes(), b)
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}
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// FileOffset returns the index of the chunk, or -1 if it was not found.
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func (c Chunk) FileOffset(fileName string) (int, error) {
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if !fs.FileExists(fileName) {
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return -1, errors.New("file not found")
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}
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file, err := os.Open(fileName)
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if err != nil {
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return -1, err
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}
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defer file.Close()
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index, err := c.DataOffset(file)
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return index, err
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}
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// DataOffset returns the index of the chunk in file, or -1 if it was not found.
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func (c Chunk) DataOffset(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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data := c.Bytes()
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dataSize := len(data)
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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, dataSize)
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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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// Return data index, if found.
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if i := bytes.Index(buffer, data); i >= 0 {
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return offset + i, 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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