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package furgit
import (
"crypto/sha1"
"crypto/sha256"
"encoding/hex"
)
// maxHashSize MUST be equal to (or larger than) the size of the
// largest hash supported in hashFuncs.
const maxHashSize = sha256.Size
// hashAlgorithm identifies the hash algorithm used for Git object IDs.
type hashAlgorithm uint8
// hashFuncs maps hash algorithm to hash function.
var hashFuncs = map[hashAlgorithm]hashFunc{
hashAlgoSHA1: func(data []byte) Hash {
sum := sha1.Sum(data)
var h Hash
copy(h.data[:], sum[:])
h.algo = hashAlgoSHA1
return h
},
hashAlgoSHA256: func(data []byte) Hash {
sum := sha256.Sum256(data)
var h Hash
copy(h.data[:], sum[:])
h.algo = hashAlgoSHA256
return h
},
}
const (
hashAlgoUnknown hashAlgorithm = iota
hashAlgoSHA1
hashAlgoSHA256
)
// size returns the hash size in bytes.
func (algo hashAlgorithm) size() int {
switch algo {
case hashAlgoSHA1:
return sha1.Size
case hashAlgoSHA256:
return sha256.Size
default:
return 0
}
}
// String returns the canonical name of the hash algorithm.
func (algo hashAlgorithm) String() string {
switch algo {
case hashAlgoSHA1:
return "sha1"
case hashAlgoSHA256:
return "sha256"
default:
return "unknown"
}
}
// Hash represents a Git object ID.
type Hash struct {
algo hashAlgorithm
data [maxHashSize]byte
}
// hashFunc is a function that computes a hash from input data.
type hashFunc func([]byte) Hash
// String returns a hexadecimal string representation of the hash.
func (hash Hash) String() string {
size := hash.algo.size()
if size == 0 {
return ""
}
return hex.EncodeToString(hash.data[:size])
}
// Bytes returns a copy of the hash's bytes.
func (hash Hash) Bytes() []byte {
size := hash.algo.size()
if size == 0 {
return nil
}
return append([]byte(nil), hash.data[:size]...)
}
// Size returns the hash size.
func (hash Hash) Size() int {
return hash.algo.size()
}
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