path: root/core/vm/evm/analysis.go

// 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 evm

import (
    "github.com/dexon-foundation/dexon/core/vm"
)

// codeBitmap collects data locations in code.
func codeBitmap(code []byte) vm.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(vm.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
}