mirror of https://github.com/stashapp/stash.git
88 lines
1.6 KiB
Go
88 lines
1.6 KiB
Go
package utils
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"os"
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)
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const chunkSize int64 = 64 * 1024
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func oshash(size int64, head []byte, tail []byte) (string, error) {
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// put the head and tail together
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buf := append(head, tail...)
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// convert bytes into uint64
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ints := make([]uint64, len(buf)/8)
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reader := bytes.NewReader(buf)
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err := binary.Read(reader, binary.LittleEndian, &ints)
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if err != nil {
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return "", err
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}
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// sum the integers
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var sum uint64
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for _, v := range ints {
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sum += v
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}
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// add the filesize
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sum += uint64(size)
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// output as hex
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return fmt.Sprintf("%016x", sum), nil
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}
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// OSHashFromFilePath calculates the hash using the same algorithm that
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// OpenSubtitles.org uses.
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//
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// Calculation is as follows:
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// size + 64 bit checksum of the first and last 64k bytes of the file.
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func OSHashFromFilePath(filePath string) (string, error) {
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f, err := os.Open(filePath)
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if err != nil {
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return "", err
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}
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defer f.Close()
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fi, err := f.Stat()
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if err != nil {
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return "", err
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}
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fileSize := fi.Size()
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if fileSize == 0 {
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return "", nil
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}
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fileChunkSize := chunkSize
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if fileSize < fileChunkSize {
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fileChunkSize = fileSize
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}
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head := make([]byte, fileChunkSize)
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tail := make([]byte, fileChunkSize)
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// read the head of the file into the start of the buffer
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_, err = f.Read(head)
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if err != nil {
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return "", err
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}
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// seek to the end of the file - the chunk size
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_, err = f.Seek(-fileChunkSize, 2)
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if err != nil {
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return "", err
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}
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// read the tail of the file
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_, err = f.Read(tail)
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if err != nil {
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return "", err
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}
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return oshash(fileSize, head, tail)
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}
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