github.com/klaytn/klaytn@v1.12.1/blockchain/vm/analysis.go (about)

     1  // Modifications Copyright 2018 The klaytn Authors
     2  // Copyright 2015 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  // This file is derived from core/vm/analysis.go (2018/06/04).
    19  // Modified and improved for the klaytn development.
    20  
    21  package vm
    22  
    23  // bitvec is a bit vector which maps bytes in a program.
    24  // An unset bit means the byte is an opcode, a set bit means
    25  // it's data (i.e. argument of PUSHxx).
    26  type bitvec []byte
    27  
    28  func (bits *bitvec) set(pos uint64) {
    29  	(*bits)[pos/8] |= 0x80 >> (pos % 8)
    30  }
    31  
    32  func (bits *bitvec) set8(pos uint64) {
    33  	(*bits)[pos/8] |= 0xFF >> (pos % 8)
    34  	(*bits)[pos/8+1] |= ^(0xFF >> (pos % 8))
    35  }
    36  
    37  // codeSegment checks if the position is in a code segment.
    38  func (bits *bitvec) codeSegment(pos uint64) bool {
    39  	return ((*bits)[pos/8] & (0x80 >> (pos % 8))) == 0
    40  }
    41  
    42  // codeBitmap collects data locations in code.
    43  func codeBitmap(code []byte) bitvec {
    44  	// The bitmap is 4 bytes longer than necessary, in case the code
    45  	// ends with a PUSH32, the algorithm will push zeroes onto the
    46  	// bitvector outside the bounds of the actual code.
    47  	bits := make(bitvec, len(code)/8+1+4)
    48  	for pc := uint64(0); pc < uint64(len(code)); {
    49  		op := OpCode(code[pc])
    50  
    51  		if op >= PUSH1 && op <= PUSH32 {
    52  			numbits := op - PUSH1 + 1
    53  			pc++
    54  			for ; numbits >= 8; numbits -= 8 {
    55  				bits.set8(pc) // 8
    56  				pc += 8
    57  			}
    58  			for ; numbits > 0; numbits-- {
    59  				bits.set(pc)
    60  				pc++
    61  			}
    62  		} else {
    63  			pc++
    64  		}
    65  	}
    66  	return bits
    67  }