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digest.go
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digest.go
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package has160
// The size of a HAS-160 checksum in bytes.
const Size = 20
// The blocksize of HAS-160 in bytes.
const BlockSize = 64
type digest struct {
s [5]uint32
x [BlockSize]byte
nx int
len uint64
}
// newDigest returns a new *digest computing the HAS-160 checksum.
func newDigest() *digest {
c := new(digest)
c.Reset()
return c
}
func (this *digest) Size() int {
return Size
}
func (this *digest) BlockSize() int {
return BlockSize
}
func (this *digest) Reset() {
this.nx = 0
this.len = 0
this.s = [5]uint32{}
this.x = [BlockSize]byte{}
copy(this.s[:], initH[:])
}
func (this *digest) Write(p []byte) (nn int, err error) {
nn = len(p)
plen := len(p)
var limit = BlockSize
for this.nx + plen >= limit {
xx := limit - this.nx
copy(this.x[this.nx:], p)
this.stepBlock(this.x[:])
plen -= xx
this.len += uint64(xx)
p = p[xx:]
this.nx = 0
}
copy(this.x[this.nx:], p)
this.nx += plen
this.len += uint64(plen)
return
}
func (this *digest) Sum(p []byte) []byte {
d0 := *this
hash := d0.checkSum()
return append(p, hash[:]...)
}
func (this *digest) checkSum() (hash [20]byte) {
this.x[this.nx] = 0x80
this.nx++
zeros := make([]byte, BlockSize)
if this.nx > BlockSize - 8 {
copy(this.x[this.nx:], zeros)
this.stepBlock(this.x[:])
this.nx = 0
}
copy(this.x[this.nx:], zeros)
PUTU64(this.x[BlockSize-8:], this.len*8)
this.stepBlock(this.x[:])
sum := uint32sToBytes(this.s[:])
copy(hash[:], sum)
return
}
func (this *digest) stepBlock(block []byte) {
x := make([]uint32, 20)
blocks := bytesToUint32s(block)
copy(x, blocks)
var H [5]uint32
copy(H[:], this.s[:])
h := H[:]
// 00 ~ 19
// Round 1
x[16] = x[0] ^ x[1] ^ x[2] ^ x[3]
x[17] = x[4] ^ x[5] ^ x[6] ^ x[7]
x[18] = x[8] ^ x[9] ^ x[10] ^ x[11]
x[19] = x[12] ^ x[13] ^ x[14] ^ x[15]
for i := 0; i < 20; i++ {
f1(h[:], 4-(4+i)%5, 4-(3+i)%5, 4-(2+i)%5, 4-(1+i)%5, 4-i%5, x, i) // j = 00 + i
}
// 20 ~ 39
// Round 2
x[16] = x[3] ^ x[6] ^ x[9] ^ x[12]
x[17] = x[2] ^ x[5] ^ x[8] ^ x[15]
x[18] = x[1] ^ x[4] ^ x[11] ^ x[14]
x[19] = x[0] ^ x[7] ^ x[10] ^ x[13]
for i := 0; i < 20; i++ {
f2(h[:], 4-(4+i)%5, 4-(3+i)%5, 4-(2+i)%5, 4-(1+i)%5, 4-i%5, x, i) // j = 20 + i
}
// 40 ~ 59
// Round 3
x[16] = x[5] ^ x[7] ^ x[12] ^ x[14]
x[17] = x[0] ^ x[2] ^ x[9] ^ x[11]
x[18] = x[4] ^ x[6] ^ x[13] ^ x[15]
x[19] = x[1] ^ x[3] ^ x[8] ^ x[10]
for i := 0; i < 20; i++ {
f3(h[:], 4-(4+i)%5, 4-(3+i)%5, 4-(2+i)%5, 4-(1+i)%5, 4-i%5, x, i) // j = 40 + i
}
// 60 ~ 79
// Round 4
x[16] = x[2] ^ x[7] ^ x[8] ^ x[13]
x[17] = x[3] ^ x[4] ^ x[9] ^ x[14]
x[18] = x[0] ^ x[5] ^ x[10] ^ x[15]
x[19] = x[1] ^ x[6] ^ x[11] ^ x[12]
for i := 0; i < 20; i++ {
f4(h[:], 4-(4+i)%5, 4-(3+i)%5, 4-(2+i)%5, 4-(1+i)%5, 4-i%5, x, i) // j = 60 + i
}
this.s[0] += h[0]
this.s[1] += h[1]
this.s[2] += h[2]
this.s[3] += h[3]
this.s[4] += h[4]
}