github.com/quinndk/ethereum_read@v0.0.0-20181211143958-29c55eec3237/go-ethereum-master_read/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  	// 内存
    29  	store       []byte
    30  	// 最后一次的gas花费
    31  	lastGasCost uint64
    32  }
    33  
    34  // NewMemory returns a new memory memory model.
    35  func NewMemory() *Memory {
    36  	return &Memory{}
    37  }
    38  
    39  // Set sets offset + size to value
    40  func (m *Memory) Set(offset, size uint64, value []byte) {
    41  	// It's possible the offset is greater than 0 and size equals 0. This is because
    42  	// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
    43  	if size > 0 {
    44  		// length of store may never be less than offset + size.
    45  		// The store should be resized PRIOR to setting the memory
    46  		if offset+size > uint64(len(m.store)) {
    47  			panic("invalid memory: store empty")
    48  		}
    49  		copy(m.store[offset:offset+size], value)
    50  	}
    51  }
    52  
    53  // Set32 sets the 32 bytes starting at offset to the value of val, left-padded with zeroes to
    54  // 32 bytes.
    55  func (m *Memory) Set32(offset uint64, val *big.Int) {
    56  	// length of store may never be less than offset + size.
    57  	// The store should be resized PRIOR to setting the memory
    58  	if offset+32 > uint64(len(m.store)) {
    59  		panic("invalid memory: store empty")
    60  	}
    61  	// Zero the memory area
    62  	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})
    63  	// Fill in relevant bits
    64  	math.ReadBits(val, m.store[offset:offset+32])
    65  }
    66  
    67  // Resize resizes the memory to size
    68  func (m *Memory) Resize(size uint64) {
    69  	if uint64(m.Len()) < size {
    70  		m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
    71  	}
    72  }
    73  
    74  // Get returns offset + size as a new slice
    75  func (m *Memory) Get(offset, size int64) (cpy []byte) {
    76  	if size == 0 {
    77  		return nil
    78  	}
    79  
    80  	if len(m.store) > int(offset) {
    81  		cpy = make([]byte, size)
    82  		copy(cpy, m.store[offset:offset+size])
    83  
    84  		return
    85  	}
    86  
    87  	return
    88  }
    89  
    90  // GetPtr returns the offset + size
    91  func (m *Memory) GetPtr(offset, size int64) []byte {
    92  	if size == 0 {
    93  		return nil
    94  	}
    95  
    96  	if len(m.store) > int(offset) {
    97  		return m.store[offset : offset+size]
    98  	}
    99  
   100  	return nil
   101  }
   102  
   103  // Len returns the length of the backing slice
   104  func (m *Memory) Len() int {
   105  	return len(m.store)
   106  }
   107  
   108  // Data returns the backing slice
   109  func (m *Memory) Data() []byte {
   110  	return m.store
   111  }
   112  
   113  // Print dumps the content of the memory.
   114  func (m *Memory) Print() {
   115  	fmt.Printf("### mem %d bytes ###\n", len(m.store))
   116  	if len(m.store) > 0 {
   117  		addr := 0
   118  		for i := 0; i+32 <= len(m.store); i += 32 {
   119  			fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
   120  			addr++
   121  		}
   122  	} else {
   123  		fmt.Println("-- empty --")
   124  	}
   125  	fmt.Println("####################")
   126  }