// Copyright 2014 The go-ethereum Authors // This file is part of the go-ethereum library. // // The go-ethereum library is free software: you can redistribute it and/or modify // it under the terms of the GNU Lesser General Public License as published by // the Free Software Foundation, either version 3 of the License, or // (at your option) any later version. // // The go-ethereum library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU Lesser General Public License for more details. // // You should have received a copy of the GNU Lesser General Public License // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. package vm // bitvec is a bit vector which maps bytes in a program. // An unset bit means the byte is an opcode, a set bit means // it's data (i.e. argument of PUSHxx). type bitvec []byte func (bits *bitvec) set(pos uint64) { (*bits)[pos/8] |= 0x80 >> (pos % 8) } func (bits *bitvec) set8(pos uint64) { (*bits)[pos/8] |= 0xFF >> (pos % 8) (*bits)[pos/8+1] |= ^(0xFF >> (pos % 8)) } // codeSegment checks if the position is in a code segment. func (bits *bitvec) codeSegment(pos uint64) bool { return ((*bits)[pos/8] & (0x80 >> (pos % 8))) == 0 } // codeBitmap collects data locations in code. func codeBitmap(code []byte) bitvec { // The bitmap is 4 bytes longer than necessary, in case the code // ends with a PUSH32, the algorithm will push zeroes onto the // bitvector outside the bounds of the actual code. bits := make(bitvec, len(code)/8+1+4) for pc := uint64(0); pc < uint64(len(code)); { op := OpCode(code[pc]) if op >= PUSH1 && op <= PUSH32 { numbits := op - PUSH1 + 1 pc++ for ; numbits >= 8; numbits -= 8 { bits.set8(pc) // 8 pc += 8 } for ; numbits > 0; numbits-- { bits.set(pc) pc++ } } else { pc++ } } return bits }