// Copyright 2015 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 import ( "fmt" "github.com/holiman/uint256" ) // Memory implements a simple memory model for the ethereum virtual machine. type Memory struct { store []byte lastGasCost uint64 } // NewMemory returns a new memory model. func NewMemory() *Memory { return &Memory{} } // Set sets offset + size to value func (m *Memory) Set(offset, size uint64, value []byte) { // It's possible the offset is greater than 0 and size equals 0. This is because // the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP) if size > 0 { // length of store may never be less than offset + size. // The store should be resized PRIOR to setting the memory if offset+size > uint64(len(m.store)) { panic("invalid memory: store empty") } copy(m.store[offset:offset+size], value) } } // Set32 sets the 32 bytes starting at offset to the value of val, left-padded with zeroes to // 32 bytes. func (m *Memory) Set32(offset uint64, val *uint256.Int) { // length of store may never be less than offset + size. // The store should be resized PRIOR to setting the memory if offset+32 > uint64(len(m.store)) { panic("invalid memory: store empty") } // Zero the memory area copy(m.store[offset:offset+32], []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}) // Fill in relevant bits val.WriteToSlice(m.store[offset:]) } // Resize resizes the memory to size func (m *Memory) Resize(size uint64) { if uint64(m.Len()) < size { m.store = append(m.store, make([]byte, size-uint64(m.Len()))...) } } // Get returns offset + size as a new slice func (m *Memory) GetCopy(offset, size int64) (cpy []byte) { if size == 0 { return nil } if len(m.store) > int(offset) { cpy = make([]byte, size) copy(cpy, m.store[offset:offset+size]) return } return } // GetPtr returns the offset + size func (m *Memory) GetPtr(offset, size int64) []byte { if size == 0 { return nil } if len(m.store) > int(offset) { return m.store[offset : offset+size] } return nil } // Len returns the length of the backing slice func (m *Memory) Len() int { return len(m.store) } // Data returns the backing slice func (m *Memory) Data() []byte { return m.store } // Print dumps the content of the memory. func (m *Memory) Print() { fmt.Printf("### mem %d bytes ###\n", len(m.store)) if len(m.store) > 0 { addr := 0 for i := 0; i+32 <= len(m.store); i += 32 { fmt.Printf("%03d: % x\n", addr, m.store[i:i+32]) addr++ } } else { fmt.Println("-- empty --") } fmt.Println("####################") }