mirror of
https://github.com/bluekeyes/go-gitdiff
synced 2026-06-08 13:18:30 +00:00
Billy Keyes
8ce8cba533
Git uses a unique Base85 encoding with different characters than the ascii85 encoding implemented by Go, so add a custom decoding function. Once decoded, use zlib instead of the raw DEFLATE algorithm to decompress the data. These issues were caught by some basic parsing tests which are added here as well.
57 lines
1.1 KiB
Go
57 lines
1.1 KiB
Go
package gitdiff
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import (
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"fmt"
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)
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const (
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base85Alphabet = "0123456789" +
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"ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
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"abcdefghijklmnopqrstuvwxyz" +
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"!#$%&()*+-;<=>?@^_`{|}~"
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)
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var (
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de85 map[byte]byte
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)
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func init() {
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de85 = make(map[byte]byte)
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for i, c := range base85Alphabet {
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de85[byte(c)] = byte(i)
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}
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}
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// base85Decode decodes Base85-encoded data from src into dst. It uses the
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// alphabet defined by base85.c in the Git source tree, which appears to be
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// unique. src must contain at least len(dst) bytes of encoded data.
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func base85Decode(dst, src []byte) error {
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var v uint32
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var n, ndst int
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for i, b := range src {
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if b, ok := de85[b]; ok {
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v = 85*v + uint32(b)
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n++
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} else {
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return fmt.Errorf("invalid base85 byte at index %d: 0x%x", i, b)
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}
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if n == 5 {
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rem := len(dst) - ndst
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for j := 0; j < 4 && j < rem; j++ {
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dst[ndst] = byte(v >> 24)
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ndst++
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v <<= 8
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}
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v = 0
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n = 0
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}
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}
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if n > 0 {
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return fmt.Errorf("base85 data terminated by underpadded sequence")
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}
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if ndst < len(dst) {
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return fmt.Errorf("base85 data is too short: %d < %d", ndst, len(dst))
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}
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return nil
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}
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