92 lines
2 KiB
Go
92 lines
2 KiB
Go
package tz
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import (
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"github.com/nspcc-dev/tzhash/gf127"
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)
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type digestp struct {
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x [4]GF127
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}
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// New returns a new hash.Hash computing the Tillich-Zémor checksum.
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func newPure() *digestp {
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d := new(digestp)
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d.Reset()
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return d
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}
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func (d *digestp) Sum(in []byte) []byte {
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// Make a copy of d so that caller can keep writing and summing.
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d0 := *d
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h := d0.checkSum()
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return append(in, h[:]...)
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}
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func (d *digestp) checkSum() [Size]byte {
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return d.byteArray()
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}
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func (d *digestp) byteArray() (b [Size]byte) {
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for i := 0; i < 4; i++ {
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t := d.x[i].ByteArray()
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copy(b[i*16:], t[:])
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}
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return
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}
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func (d *digestp) Reset() {
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d.x[0] = GF127{1, 0}
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d.x[1] = GF127{0, 0}
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d.x[2] = GF127{0, 0}
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d.x[3] = GF127{1, 0}
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}
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func (d *digestp) Write(data []byte) (n int, err error) {
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n = len(data)
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tmp := new(GF127)
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for _, b := range data {
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mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x80 != 0, tmp)
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mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x40 != 0, tmp)
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mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x20 != 0, tmp)
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mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x10 != 0, tmp)
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mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x08 != 0, tmp)
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mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x04 != 0, tmp)
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mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x02 != 0, tmp)
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mulBitRightPure(&d.x[0], &d.x[1], &d.x[2], &d.x[3], b&0x01 != 0, tmp)
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}
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return
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}
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func (d *digestp) Size() int {
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return Size
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}
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func (d *digestp) BlockSize() int {
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return hashBlockSize
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}
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func mulBitRightPure(c00, c01, c10, c11 *GF127, bit bool, tmp *GF127) {
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if bit {
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*tmp = *c00
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gf127.Mul10(c00, c00)
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gf127.Add(c00, c01, c00)
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gf127.Mul11(tmp, tmp)
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gf127.Add(c01, tmp, c01)
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*tmp = *c10
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gf127.Mul10(c10, c10)
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gf127.Add(c10, c11, c10)
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gf127.Mul11(tmp, tmp)
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gf127.Add(c11, tmp, c11)
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} else {
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*tmp = *c00
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gf127.Mul10(c00, c00)
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gf127.Add(c00, c01, c00)
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*c01 = *tmp
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*tmp = *c10
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gf127.Mul10(c10, c10)
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gf127.Add(c10, c11, c10)
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*c11 = *tmp
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}
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}
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