tzhash/tz/pure.go
Evgenii Stratonikov 337819d130 tz: export checksum size
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
2022-02-25 14:53:59 +03:00

92 lines
2 KiB
Go

package tz
import (
"github.com/nspcc-dev/tzhash/gf127"
)
type digestp struct {
x [4]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() [Size]byte {
return d.byteArray()
}
func (d *digestp) byteArray() (b [Size]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] = GF127{1, 0}
d.x[1] = GF127{0, 0}
d.x[2] = GF127{0, 0}
d.x[3] = GF127{1, 0}
}
func (d *digestp) Write(data []byte) (n int, err error) {
n = len(data)
tmp := new(GF127)
for _, b := range data {
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x80 != 0, tmp)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x40 != 0, tmp)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x20 != 0, tmp)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x10 != 0, tmp)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x08 != 0, tmp)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x04 != 0, tmp)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x02 != 0, tmp)
mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x01 != 0, tmp)
}
return
}
func (d *digestp) Size() int {
return Size
}
func (d *digestp) BlockSize() int {
return hashBlockSize
}
func mulBitRightPure(c00, c01, c10, c11 *GF127, bit bool, tmp *GF127) {
if bit {
*tmp = *c00
gf127.Mul10(c00, c00)
gf127.Add(c00, c01, c00)
gf127.Mul11(tmp, tmp)
gf127.Add(c01, tmp, c01)
*tmp = *c10
gf127.Mul10(c10, c10)
gf127.Add(c10, c11, c10)
gf127.Mul11(tmp, tmp)
gf127.Add(c11, tmp, c11)
} else {
*tmp = *c00
gf127.Mul10(c00, c00)
gf127.Add(c00, c01, c00)
*c01 = *tmp
*tmp = *c10
gf127.Mul10(c10, c10)
gf127.Add(c10, c11, c10)
*c11 = *tmp
}
}