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- // 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
- }
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