82 lines
2.1 KiB
Go
82 lines
2.1 KiB
Go
// Copyright 2023 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 internal
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import (
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"errors"
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"fmt"
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"github.com/holiman/uint256"
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)
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const (
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memoryPadLimit = 1024 * 1024
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)
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// GetMemoryCopyPadded returns offset + size as a new slice.
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// It zero-pads the slice if it extends beyond memory bounds.
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func GetMemoryCopyPadded(m []byte, offset, size int64) ([]byte, error) {
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if offset < 0 || size < 0 {
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return nil, errors.New("offset or size must not be negative")
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}
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length := int64(len(m))
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if offset+size < length { // slice fully inside memory
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return memoryCopy(m, offset, size), nil
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}
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paddingNeeded := offset + size - length
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if paddingNeeded > memoryPadLimit {
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return nil, fmt.Errorf("reached limit for padding memory slice: %d", paddingNeeded)
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}
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cpy := make([]byte, size)
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if overlap := length - offset; overlap > 0 {
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copy(cpy, MemoryPtr(m, offset, overlap))
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}
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return cpy, nil
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}
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func memoryCopy(m []byte, offset, size int64) (cpy []byte) {
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if size == 0 {
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return nil
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}
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if len(m) > int(offset) {
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cpy = make([]byte, size)
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copy(cpy, m[offset:offset+size])
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return
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}
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return
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}
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// MemoryPtr returns a pointer to a slice of memory.
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func MemoryPtr(m []byte, offset, size int64) []byte {
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if size == 0 {
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return nil
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}
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if len(m) > int(offset) {
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return m[offset : offset+size]
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}
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return nil
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}
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// Back returns the n'th item in stack
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func StackBack(st []uint256.Int, n int) *uint256.Int {
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return &st[len(st)-n-1]
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}
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