github.com/MetalBlockchain/subnet-evm@v0.4.9/core/vm/common.go (about)

     1  // (c) 2019-2020, Ava Labs, Inc.
     2  //
     3  // This file is a derived work, based on the go-ethereum library whose original
     4  // notices appear below.
     5  //
     6  // It is distributed under a license compatible with the licensing terms of the
     7  // original code from which it is derived.
     8  //
     9  // Much love to the original authors for their work.
    10  // **********
    11  // Copyright 2014 The go-ethereum Authors
    12  // This file is part of the go-ethereum library.
    13  //
    14  // The go-ethereum library is free software: you can redistribute it and/or modify
    15  // it under the terms of the GNU Lesser General Public License as published by
    16  // the Free Software Foundation, either version 3 of the License, or
    17  // (at your option) any later version.
    18  //
    19  // The go-ethereum library is distributed in the hope that it will be useful,
    20  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    21  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    22  // GNU Lesser General Public License for more details.
    23  //
    24  // You should have received a copy of the GNU Lesser General Public License
    25  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    26  
    27  package vm
    28  
    29  import (
    30  	"github.com/ethereum/go-ethereum/common"
    31  	"github.com/ethereum/go-ethereum/common/math"
    32  	"github.com/holiman/uint256"
    33  )
    34  
    35  // calcMemSize64 calculates the required memory size, and returns
    36  // the size and whether the result overflowed uint64
    37  func calcMemSize64(off, l *uint256.Int) (uint64, bool) {
    38  	if !l.IsUint64() {
    39  		return 0, true
    40  	}
    41  	return calcMemSize64WithUint(off, l.Uint64())
    42  }
    43  
    44  // calcMemSize64WithUint calculates the required memory size, and returns
    45  // the size and whether the result overflowed uint64
    46  // Identical to calcMemSize64, but length is a uint64
    47  func calcMemSize64WithUint(off *uint256.Int, length64 uint64) (uint64, bool) {
    48  	// if length is zero, memsize is always zero, regardless of offset
    49  	if length64 == 0 {
    50  		return 0, false
    51  	}
    52  	// Check that offset doesn't overflow
    53  	offset64, overflow := off.Uint64WithOverflow()
    54  	if overflow {
    55  		return 0, true
    56  	}
    57  	val := offset64 + length64
    58  	// if value < either of it's parts, then it overflowed
    59  	return val, val < offset64
    60  }
    61  
    62  // getData returns a slice from the data based on the start and size and pads
    63  // up to size with zero's. This function is overflow safe.
    64  func getData(data []byte, start uint64, size uint64) []byte {
    65  	length := uint64(len(data))
    66  	if start > length {
    67  		start = length
    68  	}
    69  	end := start + size
    70  	if end > length {
    71  		end = length
    72  	}
    73  	return common.RightPadBytes(data[start:end], int(size))
    74  }
    75  
    76  // toWordSize returns the ceiled word size required for memory expansion.
    77  func toWordSize(size uint64) uint64 {
    78  	if size > math.MaxUint64-31 {
    79  		return math.MaxUint64/32 + 1
    80  	}
    81  
    82  	return (size + 31) / 32
    83  }
    84  
    85  func allZero(b []byte) bool {
    86  	for _, byte := range b {
    87  		if byte != 0 {
    88  			return false
    89  		}
    90  	}
    91  	return true
    92  }