• Felix Lange's avatar
    all: unify big.Int zero checks, use common/math in more places (#3716) · 5f782627
    Felix Lange authored
    * 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
    5f782627
common.go 1.95 KB
// Copyright 2014 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 vm

import (
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/ethereum/go-ethereum/common/math"
)

// calculates the memory size required for a step
func calcMemSize(off, l *big.Int) *big.Int {
	if l.Sign() == 0 {
		return common.Big0
	}

	return new(big.Int).Add(off, l)
}

// getData returns a slice from the data based on the start and size and pads
// up to size with zero's. This function is overflow safe.
func getData(data []byte, start, size *big.Int) []byte {
	dlen := big.NewInt(int64(len(data)))

	s := math.BigMin(start, dlen)
	e := math.BigMin(new(big.Int).Add(s, size), dlen)
	return common.RightPadBytes(data[s.Uint64():e.Uint64()], int(size.Uint64()))
}

// bigUint64 returns the integer casted to a uint64 and returns whether it
// overflowed in the process.
func bigUint64(v *big.Int) (uint64, bool) {
	return v.Uint64(), v.BitLen() > 64
}

// toWordSize returns the ceiled word size required for memory expansion.
func toWordSize(size uint64) uint64 {
	if size > math.MaxUint64-31 {
		return math.MaxUint64/32 + 1
	}

	return (size + 31) / 32
}

func allZero(b []byte) bool {
	for _, byte := range b {
		if byte != 0 {
			return false
		}
	}
	return true
}