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// 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"
"math/big"
"github.com/ethereum/go-ethereum/common/math"
)
// Memory implements a simple memory model for the ethereum virtual machine.
type Memory struct {
store []byte
lastGasCost uint64
}
// NewMemory returns a new memory 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 *big.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
math.ReadBits(val, m.store[offset:offset+32])
}
// 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) Get(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("####################")
}
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