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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] }
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