129 lines
3.6 KiB
Go
129 lines
3.6 KiB
Go
// Copyright 2015 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package vm
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import (
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"sync"
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"github.com/holiman/uint256"
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)
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var memoryPool = sync.Pool{
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New: func() any {
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return &Memory{}
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},
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}
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// Memory implements a simple memory model for the ethereum virtual machine.
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type Memory struct {
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store []byte
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lastGasCost uint64
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}
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// NewMemory returns a new memory model.
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func NewMemory() *Memory {
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return memoryPool.Get().(*Memory)
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}
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// Free returns the memory to the pool.
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func (m *Memory) Free() {
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// To reduce peak allocation, return only smaller memory instances to the pool.
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const maxBufferSize = 16 << 10
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if cap(m.store) <= maxBufferSize {
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m.store = m.store[:0]
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m.lastGasCost = 0
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memoryPool.Put(m)
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}
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}
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// Set sets offset + size to value
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func (m *Memory) Set(offset, size uint64, value []byte) {
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// It's possible the offset is greater than 0 and size equals 0. This is because
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// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
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if size > 0 {
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// length of store may never be less than offset + size.
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// The store should be resized PRIOR to setting the memory
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if offset+size > uint64(len(m.store)) {
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panic("invalid memory: store empty")
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}
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copy(m.store[offset:offset+size], value)
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}
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}
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// Set32 sets the 32 bytes starting at offset to the value of val, left-padded with zeroes to
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// 32 bytes.
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func (m *Memory) Set32(offset uint64, val *uint256.Int) {
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// length of store may never be less than offset + size.
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// The store should be resized PRIOR to setting the memory
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if offset+32 > uint64(len(m.store)) {
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panic("invalid memory: store empty")
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}
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// Fill in relevant bits
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b32 := val.Bytes32()
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copy(m.store[offset:], b32[:])
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}
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// Resize resizes the memory to size
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func (m *Memory) Resize(size uint64) {
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if uint64(m.Len()) < size {
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m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
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}
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}
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// GetCopy returns offset + size as a new slice
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func (m *Memory) GetCopy(offset, size uint64) (cpy []byte) {
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if size == 0 {
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return nil
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}
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// memory is always resized before being accessed, no need to check bounds
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cpy = make([]byte, size)
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copy(cpy, m.store[offset:offset+size])
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return
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}
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// GetPtr returns the offset + size
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func (m *Memory) GetPtr(offset, size uint64) []byte {
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if size == 0 {
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return nil
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}
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// memory is always resized before being accessed, no need to check bounds
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return m.store[offset : offset+size]
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}
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// Len returns the length of the backing slice
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func (m *Memory) Len() int {
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return len(m.store)
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}
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// Data returns the backing slice
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func (m *Memory) Data() []byte {
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return m.store
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}
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// Copy copies data from the src position slice into the dst position.
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// The source and destination may overlap.
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// OBS: This operation assumes that any necessary memory expansion has already been performed,
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// and this method may panic otherwise.
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func (m *Memory) Copy(dst, src, len uint64) {
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if len == 0 {
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return
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}
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copy(m.store[dst:], m.store[src:src+len])
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}
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