Method resolveHashPrefix

repository.go:1711–1750

resolveHashPrefix returns a list of potential hashes that the given string is a prefix of. It quietly swallows errors, returning nil.

(hashStr string)

// resolveHashPrefix returns a list of potential hashes that the given string
// is a prefix of. It quietly swallows errors, returning nil.
func (r *Repository) resolveHashPrefix(hashStr string) []plumbing.Hash {
	// Handle complete and partial hashes.
	// plumbing.NewHash forces args into a full 20 byte hash, which isn't suitable
	// for partial hashes since they will become zero-filled.

	if hashStr == "" {
		return nil
	}
	if len(hashStr) == len(plumbing.ZeroHash)*2 {
		// Only a full hash is possible.
		hexb, err := hex.DecodeString(hashStr)
		if err != nil {
			return nil
		}
		var h plumbing.Hash
		copy(h[:], hexb)
		return []plumbing.Hash{h}
	}

	// Partial hash.
	// hex.DecodeString only decodes to complete bytes, so only works with pairs of hex digits.
	evenHex := hashStr[:len(hashStr)&^1]
	hexb, err := hex.DecodeString(evenHex)
	if err != nil {
		return nil
	}
	candidates := expandPartialHash(r.Storer, hexb)
	if len(evenHex) == len(hashStr) {
		// The prefix was an exact number of bytes.
		return candidates
	}
	// Do another prefix check to ensure the dangling nybble is correct.
	var hashes []plumbing.Hash
	for _, h := range candidates {
		if strings.HasPrefix(h.String(), hashStr) {
			hashes = append(hashes, h)
		}
	}
	return hashes
}

type RepackConfig struct {
	// UseRefDeltas configures whether packfile encoder will use reference deltas.