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  }