Support multiple hash sizes in one build

1 files changed, 33 insertions, 10 deletions

diff --git a/hash.go b/hash.go
index 3c6ff6ac..336d5322 100644
--- a/hash.go
+++ b/hash.go
@@ -1,17 +1,40 @@
 package furgit
 
 import (
+	"crypto/sha1"
+	"crypto/sha256"
 	"encoding/hex"
 	"fmt"
 )
 
+const maxHashSize = 32
+
 // Hash represents a Git object identifier.
-type Hash [HashSize]byte
+type Hash [maxHashSize]byte
+
+// hashFunc is a function that computes a hash from input data.
+type hashFunc func([]byte) [maxHashSize]byte
+
+// hashFuncs maps hash size to hash function.
+var hashFuncs = map[int]hashFunc{
+	sha1.Size: func(data []byte) [maxHashSize]byte {
+		var result [maxHashSize]byte
+		sum := sha1.Sum(data)
+		copy(result[:], sum[:])
+		return result
+	},
+	sha256.Size: func(data []byte) [maxHashSize]byte {
+		var result [maxHashSize]byte
+		sum := sha256.Sum256(data)
+		copy(result[:], sum[:])
+		return result
+	},
+}
 
-// ParseHash converts a hex string into an Hash.
-func ParseHash(s string) (Hash, error) {
+// ParseHashWithSize converts a hex string into a Hash for a given hash size.
+func ParseHashWithSize(s string, hashSize int) (Hash, error) {
 	var id Hash
-	if len(s) != HashSize*2 {
+	if len(s) != hashSize*2 {
 		return id, fmt.Errorf("furgit: invalid hash length %d", len(s))
 	}
 	data, err := hex.DecodeString(s)
@@ -22,12 +45,12 @@ func ParseHash(s string) (Hash, error) {
 	return id, nil
 }
 
-// String renders the ID as hex.
-func (id Hash) String() string {
-	return hex.EncodeToString(id[:])
+// StringWithSize returns the ID as hex for a given hash size.
+func (id Hash) StringWithSize(hashSize int) string {
+	return hex.EncodeToString(id[:hashSize])
 }
 
-// Bytes returns a mutable copy of the underlying bytes.
-func (id Hash) Bytes() []byte {
-	return append([]byte(nil), id[:]...)
+// BytesWithSize returns a mutable copy of the underlying bytes for a given hash size.
+func (id Hash) BytesWithSize(hashSize int) []byte {
+	return append([]byte(nil), id[:hashSize]...)
 }