aboutsummaryrefslogtreecommitdiffstats
path: root/plumbing/hash.go
blob: 8e60877894abba0e00c40ba5d68f0fdc78a88d8f (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
package plumbing

import (
	"bytes"
	"crypto/sha1"
	"encoding/hex"
	"hash"
	"sort"
	"strconv"
)

// Hash SHA1 hased content
type Hash [20]byte

// ZeroHash is Hash with value zero
var ZeroHash Hash

// ComputeHash compute the hash for a given ObjectType and content
func ComputeHash(t ObjectType, content []byte) Hash {
	h := NewHasher(t, int64(len(content)))
	h.Write(content)
	return h.Sum()
}

// 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[:])
}

type Hasher struct {
	hash.Hash
}

func NewHasher(t ObjectType, size int64) Hasher {
	h := Hasher{sha1.New()}
	h.Write(t.Bytes())
	h.Write([]byte(" "))
	h.Write([]byte(strconv.FormatInt(size, 10)))
	h.Write([]byte{0})
	return h
}

func (h Hasher) Sum() (hash Hash) {
	copy(hash[:], h.Hash.Sum(nil))
	return
}

// HashesSort sorts a slice of Hashes in increasing order.
func HashesSort(a []Hash) {
	sort.Sort(HashSlice(a))
}

// HashSlice attaches the methods of sort.Interface to []Hash, sorting in
// increasing order.
type HashSlice []Hash

func (p HashSlice) Len() int           { return len(p) }
func (p HashSlice) Less(i, j int) bool { return bytes.Compare(p[i][:], p[j][:]) < 0 }
func (p HashSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }