github.hscsec.cn/juliankolbe/go-ethereum@v1.9.7/core/vm/memory.go (about)

     1  // Copyright 2015 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package vm
    18  
    19  import (
    20  	"fmt"
    21  	"math/big"
    22  
    23  	"github.com/ethereum/go-ethereum/common/math"
    24  )
    25  
    26  // Memory implements a simple memory model for the ethereum virtual machine.
    27  type Memory struct {
    28  	store       []byte
    29  	lastGasCost uint64
    30  }
    31  
    32  // NewMemory returns a new memory model.
    33  func NewMemory() *Memory {
    34  	return &Memory{}
    35  }
    36  
    37  // Set sets offset + size to value
    38  func (m *Memory) Set(offset, size uint64, value []byte) {
    39  	// It's possible the offset is greater than 0 and size equals 0. This is because
    40  	// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
    41  	if size > 0 {
    42  		// length of store may never be less than offset + size.
    43  		// The store should be resized PRIOR to setting the memory
    44  		if offset+size > uint64(len(m.store)) {
    45  			panic("invalid memory: store empty")
    46  		}
    47  		copy(m.store[offset:offset+size], value)
    48  	}
    49  }
    50  
    51  // Set32 sets the 32 bytes starting at offset to the value of val, left-padded with zeroes to
    52  // 32 bytes.
    53  func (m *Memory) Set32(offset uint64, val *big.Int) {
    54  	// length of store may never be less than offset + size.
    55  	// The store should be resized PRIOR to setting the memory
    56  	if offset+32 > uint64(len(m.store)) {
    57  		panic("invalid memory: store empty")
    58  	}
    59  	// Zero the memory area
    60  	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})
    61  	// Fill in relevant bits
    62  	math.ReadBits(val, m.store[offset:offset+32])
    63  }
    64  
    65  // Resize resizes the memory to size
    66  func (m *Memory) Resize(size uint64) {
    67  	if uint64(m.Len()) < size {
    68  		m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
    69  	}
    70  }
    71  
    72  // Get returns offset + size as a new slice
    73  func (m *Memory) GetCopy(offset, size int64) (cpy []byte) {
    74  	if size == 0 {
    75  		return nil
    76  	}
    77  
    78  	if len(m.store) > int(offset) {
    79  		cpy = make([]byte, size)
    80  		copy(cpy, m.store[offset:offset+size])
    81  
    82  		return
    83  	}
    84  
    85  	return
    86  }
    87  
    88  // GetPtr returns the offset + size
    89  func (m *Memory) GetPtr(offset, size int64) []byte {
    90  	if size == 0 {
    91  		return nil
    92  	}
    93  
    94  	if len(m.store) > int(offset) {
    95  		return m.store[offset : offset+size]
    96  	}
    97  
    98  	return nil
    99  }
   100  
   101  // Len returns the length of the backing slice
   102  func (m *Memory) Len() int {
   103  	return len(m.store)
   104  }
   105  
   106  // Data returns the backing slice
   107  func (m *Memory) Data() []byte {
   108  	return m.store
   109  }
   110  
   111  // Print dumps the content of the memory.
   112  func (m *Memory) Print() {
   113  	fmt.Printf("### mem %d bytes ###\n", len(m.store))
   114  	if len(m.store) > 0 {
   115  		addr := 0
   116  		for i := 0; i+32 <= len(m.store); i += 32 {
   117  			fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
   118  			addr++
   119  		}
   120  	} else {
   121  		fmt.Println("-- empty --")
   122  	}
   123  	fmt.Println("####################")
   124  }