internal -> core

1 files changed, 40 insertions, 0 deletions

diff --git a/core/hash.go b/core/hash.go
new file mode 100644
index 0000000..0b6f274
--- /dev/null
+++ b/core/hash.go
@@ -0,0 +1,40 @@
+package core
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+	"strconv"
+)
+
+// Hash SHA1 hased content
+type Hash [20]byte
+
+// ComputeHash compute the hash for a given ObjectType and content
+func ComputeHash(t ObjectType, content []byte) Hash {
+	h := t.Bytes()
+	h = append(h, ' ')
+	h = strconv.AppendInt(h, int64(len(content)), 10)
+	h = append(h, 0)
+	h = append(h, content...)
+
+	return Hash(sha1.Sum(h))
+}
+
+// NewHash return a new Hash from a hexadecimal hash representation
+func NewHash(s string) Hash {
+	b, _ := hex.DecodeString(s)
+
+	var h Hash
+	copy(h[:], b)
+
+	return h
+}
+
+func (h Hash) IsZero() bool {
+	var empty Hash
+	return h == empty
+}
+
+func (h Hash) String() string {
+	return hex.EncodeToString(h[:])
+}