tzhash/tz/pure.go

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2019-07-19 15:59:41 +00:00
package tz
import (
"github.com/nspcc-dev/tzhash/gogf127"
)
type digestp struct {
x [4]gogf127.GF127
}
// New returns a new hash.Hash computing the Tillich-Zémor checksum.
func newPure() *digestp {
d := new(digestp)
d.Reset()
return d
}
func (d *digestp) Sum(in []byte) []byte {
// Make a copy of d so that caller can keep writing and summing.
d0 := *d
h := d0.checkSum()
return append(in, h[:]...)
}
func (d *digestp) checkSum() [hashSize]byte {
return d.byteArray()
}
func (d *digestp) byteArray() (b [hashSize]byte) {
for i := 0; i < 4; i++ {
t := d.x[i].ByteArray()
copy(b[i*16:], t[:])
}
return
}
func (d *digestp) Reset() {
d.x[0] = gogf127.GF127{1, 0}
d.x[1] = gogf127.GF127{0, 0}
d.x[2] = gogf127.GF127{0, 0}
d.x[3] = gogf127.GF127{1, 0}
}
func (d *digestp) Write(data []byte) (n int, err error) {
n = len(data)
for _, b := range data {
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x80 != 0)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x40 != 0)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x20 != 0)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x10 != 0)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x08 != 0)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x04 != 0)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x02 != 0)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x01 != 0)
}
return
}
func (d *digestp) Size() int {
return hashSize
}
func (d *digestp) BlockSize() int {
return hashBlockSize
}
func mulBitRightPure(c00, c01, c10, c11 *gogf127.GF127, bit bool) {
var tmp gogf127.GF127
if bit {
tmp = *c00
gogf127.Mul10(c00, c00)
gogf127.Add(c00, c01, c00)
gogf127.Mul11(&tmp, &tmp)
gogf127.Add(c01, &tmp, c01)
tmp = *c10
gogf127.Mul10(c10, c10)
gogf127.Add(c10, c11, c10)
gogf127.Mul11(&tmp, &tmp)
gogf127.Add(c11, &tmp, c11)
} else {
tmp = *c00
gogf127.Mul10(c00, c00)
gogf127.Add(c00, c01, c00)
*c01 = tmp
tmp = *c10
gogf127.Mul10(c10, c10)
gogf127.Add(c10, c11, c10)
*c11 = tmp
}
}