all: unify big.Int zero checks, use common/math in more places (#3716)

* common/math: optimize PaddedBigBytes, use it more

name              old time/op    new time/op    delta
PaddedBigBytes-8    71.1ns ± 5%    46.1ns ± 1%  -35.15%  (p=0.000 n=20+19)

name              old alloc/op   new alloc/op   delta
PaddedBigBytes-8     48.0B ± 0%     32.0B ± 0%  -33.33%  (p=0.000 n=20+20)

* all: unify big.Int zero checks

Various checks were in use. This commit replaces them all with Int.Sign,
which is cheaper and less code.

eg templates:

    func before(x *big.Int) bool { return x.BitLen() == 0 }
    func after(x *big.Int) bool  { return x.Sign() == 0 }

    func before(x *big.Int) bool { return x.BitLen() > 0 }
    func after(x *big.Int) bool  { return x.Sign() != 0 }

    func before(x *big.Int) int { return x.Cmp(common.Big0) }
    func after(x *big.Int) int  { return x.Sign() }

* common/math, crypto/secp256k1: make ReadBits public in package math
This commit is contained in:
Felix Lange
2017-02-28 15:09:11 +01:00
committed by Jeffrey Wilcke
parent d4f60d362b
commit 5f7826270c
30 changed files with 104 additions and 114 deletions

View File

@ -36,6 +36,8 @@ import (
"math/big"
"sync"
"unsafe"
"github.com/ethereum/go-ethereum/common/math"
)
/*
@ -230,8 +232,8 @@ func (BitCurve *BitCurve) ScalarMult(Bx, By *big.Int, scalar []byte) (*big.Int,
// Do the multiplication in C, updating point.
point := make([]byte, 64)
readBits(point[:32], Bx)
readBits(point[32:], By)
math.ReadBits(Bx, point[:32])
math.ReadBits(By, point[32:])
pointPtr := (*C.uchar)(unsafe.Pointer(&point[0]))
scalarPtr := (*C.uchar)(unsafe.Pointer(&scalar[0]))
res := C.secp256k1_pubkey_scalar_mul(context, pointPtr, scalarPtr)

View File

@ -1,39 +0,0 @@
// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package secp256k1
import (
"bytes"
"encoding/hex"
"math/big"
"testing"
)
func TestReadBits(t *testing.T) {
check := func(input string) {
want, _ := hex.DecodeString(input)
int, _ := new(big.Int).SetString(input, 16)
buf := make([]byte, len(want))
readBits(buf, int)
if !bytes.Equal(buf, want) {
t.Errorf("have: %x\nwant: %x", buf, want)
}
}
check("000000000000000000000000000000000000000000000000000000FEFCF3F8F0")
check("0000000000012345000000000000000000000000000000000000FEFCF3F8F0")
check("18F8F8F1000111000110011100222004330052300000000000000000FEFCF3F8F0")
}

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@ -38,7 +38,6 @@ import "C"
import (
"errors"
"math/big"
"unsafe"
)
@ -129,16 +128,3 @@ func checkSignature(sig []byte) error {
}
return nil
}
// reads num into buf as big-endian bytes.
func readBits(buf []byte, num *big.Int) {
const wordLen = int(unsafe.Sizeof(big.Word(0)))
i := len(buf)
for _, d := range num.Bits() {
for j := 0; j < wordLen && i > 0; j++ {
i--
buf[i] = byte(d)
d >>= 8
}
}
}

View File

@ -24,6 +24,7 @@ import (
"encoding/hex"
"testing"
"github.com/ethereum/go-ethereum/common/math"
"github.com/ethereum/go-ethereum/crypto/randentropy"
)
@ -35,9 +36,7 @@ func generateKeyPair() (pubkey, privkey []byte) {
panic(err)
}
pubkey = elliptic.Marshal(S256(), key.X, key.Y)
privkey = make([]byte, 32)
readBits(privkey, key.D)
return pubkey, privkey
return pubkey, math.PaddedBigBytes(key.D, 32)
}
func randSig() []byte {

View File

@ -23,7 +23,7 @@ import (
"crypto/elliptic"
"fmt"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/math"
"github.com/ethereum/go-ethereum/crypto/secp256k1"
)
@ -53,7 +53,7 @@ func Sign(hash []byte, prv *ecdsa.PrivateKey) (sig []byte, err error) {
if len(hash) != 32 {
return nil, fmt.Errorf("hash is required to be exactly 32 bytes (%d)", len(hash))
}
seckey := common.LeftPadBytes(prv.D.Bytes(), prv.Params().BitSize/8)
seckey := math.PaddedBigBytes(prv.D, prv.Params().BitSize/8)
defer zeroBytes(seckey)
return secp256k1.Sign(hash, seckey)
}