github.com/SmartMeshFoundation/Spectrum@v0.0.0-20220621030607-452a266fee1e/core/vm/common.go (about)

     1  // Copyright 2014 The Spectrum Authors
     2  // This file is part of the Spectrum library.
     3  //
     4  // The Spectrum 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 Spectrum 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 Spectrum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package vm
    18  
    19  import (
    20  	"github.com/holiman/uint256"
    21  	"math/big"
    22  
    23  	"github.com/SmartMeshFoundation/Spectrum/common"
    24  	"github.com/SmartMeshFoundation/Spectrum/common/math"
    25  )
    26  
    27  // calcMemSize64 calculates the required memory size, and returns
    28  // the size and whether the result overflowed uint64
    29  func calcMemSize64(off, l *uint256.Int) (uint64, bool) {
    30  	if !l.IsUint64() {
    31  		return 0, true
    32  	}
    33  	return calcMemSize64WithUint(off, l.Uint64())
    34  }
    35  
    36  // calcMemSize64WithUint calculates the required memory size, and returns
    37  // the size and whether the result overflowed uint64
    38  // Identical to calcMemSize64, but length is a uint64
    39  func calcMemSize64WithUint(off *uint256.Int, length64 uint64) (uint64, bool) {
    40  	// if length is zero, memsize is always zero, regardless of offset
    41  	if length64 == 0 {
    42  		return 0, false
    43  	}
    44  	// Check that offset doesn't overflow
    45  	offset64, overflow := off.Uint64WithOverflow()
    46  	if overflow {
    47  		return 0, true
    48  	}
    49  	val := offset64 + length64
    50  	// if value < either of it's parts, then it overflowed
    51  	return val, val < offset64
    52  }
    53  
    54  // calculates the memory size required for a step
    55  func calcMemSize(off, l *big.Int) *big.Int {
    56  	if l.Sign() == 0 {
    57  		return common.Big0
    58  	}
    59  
    60  	return new(big.Int).Add(off, l)
    61  }
    62  
    63  // getData returns a slice from the data based on the start and size and pads
    64  // up to size with zero's. This function is overflow safe.
    65  func getData(data []byte, start uint64, size uint64) []byte {
    66  	length := uint64(len(data))
    67  	if start > length {
    68  		start = length
    69  	}
    70  	end := start + size
    71  	if end > length {
    72  		end = length
    73  	}
    74  	return common.RightPadBytes(data[start:end], int(size))
    75  }
    76  
    77  // getDataBig returns a slice from the data based on the start and size and pads
    78  // up to size with zero's. This function is overflow safe.
    79  func getDataBig(data []byte, start *big.Int, size *big.Int) []byte {
    80  	dlen := big.NewInt(int64(len(data)))
    81  
    82  	s := math.BigMin(start, dlen)
    83  	e := math.BigMin(new(big.Int).Add(s, size), dlen)
    84  	return common.RightPadBytes(data[s.Uint64():e.Uint64()], int(size.Uint64()))
    85  }
    86  
    87  // bigUint64 returns the integer casted to a uint64 and returns whether it
    88  // overflowed in the process.
    89  func bigUint64(v *big.Int) (uint64, bool) {
    90  	return v.Uint64(), v.BitLen() > 64
    91  }
    92  
    93  // toWordSize returns the ceiled word size required for memory expansion.
    94  func toWordSize(size uint64) uint64 {
    95  	if size > math.MaxUint64-31 {
    96  		return math.MaxUint64/32 + 1
    97  	}
    98  
    99  	return (size + 31) / 32
   100  }
   101  
   102  func allZero(b []byte) bool {
   103  	for _, byte := range b {
   104  		if byte != 0 {
   105  			return false
   106  		}
   107  	}
   108  	return true
   109  }