github.com/ontio/ontology@v1.14.4/vm/evm/analysis.go (about)

     1  // Copyright (C) 2021 The Ontology Authors
     2  // Copyright 2014 The go-ethereum Authors
     3  // This file is part of the go-ethereum library.
     4  //
     5  // The go-ethereum library is free software: you can redistribute it and/or modify
     6  // it under the terms of the GNU Lesser General Public License as published by
     7  // the Free Software Foundation, either version 3 of the License, or
     8  // (at your option) any later version.
     9  //
    10  // The go-ethereum library is distributed in the hope that it will be useful,
    11  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    12  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    13  // GNU Lesser General Public License for more details.
    14  //
    15  // You should have received a copy of the GNU Lesser General Public License
    16  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    17  
    18  package evm
    19  
    20  // bitvec is a bit vector which maps bytes in a program.
    21  // An unset bit means the byte is an opcode, a set bit means
    22  // it's data (i.e. argument of PUSHxx).
    23  type bitvec []byte
    24  
    25  func (bits *bitvec) set(pos uint64) {
    26  	(*bits)[pos/8] |= 0x80 >> (pos % 8)
    27  }
    28  func (bits *bitvec) set8(pos uint64) {
    29  	(*bits)[pos/8] |= 0xFF >> (pos % 8)
    30  	(*bits)[pos/8+1] |= ^(0xFF >> (pos % 8))
    31  }
    32  
    33  // codeSegment checks if the position is in a code segment.
    34  func (bits *bitvec) codeSegment(pos uint64) bool {
    35  	return ((*bits)[pos/8] & (0x80 >> (pos % 8))) == 0
    36  }
    37  
    38  // codeBitmap collects data locations in code.
    39  func codeBitmap(code []byte) bitvec {
    40  	// The bitmap is 4 bytes longer than necessary, in case the code
    41  	// ends with a PUSH32, the algorithm will push zeroes onto the
    42  	// bitvector outside the bounds of the actual code.
    43  	bits := make(bitvec, len(code)/8+1+4)
    44  	for pc := uint64(0); pc < uint64(len(code)); {
    45  		op := OpCode(code[pc])
    46  
    47  		if op >= PUSH1 && op <= PUSH32 {
    48  			numbits := op - PUSH1 + 1
    49  			pc++
    50  			for ; numbits >= 8; numbits -= 8 {
    51  				bits.set8(pc) // 8
    52  				pc += 8
    53  			}
    54  			for ; numbits > 0; numbits-- {
    55  				bits.set(pc)
    56  				pc++
    57  			}
    58  		} else {
    59  			pc++
    60  		}
    61  	}
    62  	return bits
    63  }