github.com/avence12/go-ethereum@v1.5.10-0.20170320123548-1dfd65f6d047/core/vm/common.go (about) 1 // Copyright 2014 The go-ethereum Authors 2 // This file is part of the go-ethereum library. 3 // 4 // The go-ethereum library is free software: you can redistribute it and/or modify 5 // it under the terms of the GNU Lesser General Public License as published by 6 // the Free Software Foundation, either version 3 of the License, or 7 // (at your option) any later version. 8 // 9 // The go-ethereum library is distributed in the hope that it will be useful, 10 // but WITHOUT ANY WARRANTY; without even the implied warranty of 11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 // GNU Lesser General Public License for more details. 13 // 14 // You should have received a copy of the GNU Lesser General Public License 15 // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. 16 17 package vm 18 19 import ( 20 "math/big" 21 22 "github.com/ethereum/go-ethereum/common" 23 "github.com/ethereum/go-ethereum/common/math" 24 ) 25 26 // calculates the memory size required for a step 27 func calcMemSize(off, l *big.Int) *big.Int { 28 if l.Sign() == 0 { 29 return common.Big0 30 } 31 32 return new(big.Int).Add(off, l) 33 } 34 35 // getData returns a slice from the data based on the start and size and pads 36 // up to size with zero's. This function is overflow safe. 37 func getData(data []byte, start, size *big.Int) []byte { 38 dlen := big.NewInt(int64(len(data))) 39 40 s := math.BigMin(start, dlen) 41 e := math.BigMin(new(big.Int).Add(s, size), dlen) 42 return common.RightPadBytes(data[s.Uint64():e.Uint64()], int(size.Uint64())) 43 } 44 45 // bigUint64 returns the integer casted to a uint64 and returns whether it 46 // overflowed in the process. 47 func bigUint64(v *big.Int) (uint64, bool) { 48 return v.Uint64(), v.BitLen() > 64 49 } 50 51 // toWordSize returns the ceiled word size required for memory expansion. 52 func toWordSize(size uint64) uint64 { 53 if size > math.MaxUint64-31 { 54 return math.MaxUint64/32 + 1 55 } 56 57 return (size + 31) / 32 58 } 59 60 func allZero(b []byte) bool { 61 for _, byte := range b { 62 if byte != 0 { 63 return false 64 } 65 } 66 return true 67 }