github.com/bamzi/go-ethereum@v1.6.7-0.20170704111104-138f26c93af1/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 "fmt"
    20  
    21  // Memory implements a simple memory model for the ethereum virtual machine.
    22  type Memory struct {
    23  	store       []byte
    24  	lastGasCost uint64
    25  	lastReturn  []byte
    26  }
    27  
    28  func NewMemory() *Memory {
    29  	return &Memory{}
    30  }
    31  
    32  // Set sets offset + size to value
    33  func (m *Memory) Set(offset, size uint64, value []byte) {
    34  	// length of store may never be less than offset + size.
    35  	// The store should be resized PRIOR to setting the memory
    36  	if size > uint64(len(m.store)) {
    37  		panic("INVALID memory: store empty")
    38  	}
    39  
    40  	// It's possible the offset is greater than 0 and size equals 0. This is because
    41  	// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
    42  	if size > 0 {
    43  		copy(m.store[offset:offset+size], value)
    44  	}
    45  }
    46  
    47  // Resize resizes the memory to size
    48  func (m *Memory) Resize(size uint64) {
    49  	if uint64(m.Len()) < size {
    50  		m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
    51  	}
    52  }
    53  
    54  // Get returns offset + size as a new slice
    55  func (self *Memory) Get(offset, size int64) (cpy []byte) {
    56  	if size == 0 {
    57  		return nil
    58  	}
    59  
    60  	if len(self.store) > int(offset) {
    61  		cpy = make([]byte, size)
    62  		copy(cpy, self.store[offset:offset+size])
    63  
    64  		return
    65  	}
    66  
    67  	return
    68  }
    69  
    70  // GetPtr returns the offset + size
    71  func (self *Memory) GetPtr(offset, size int64) []byte {
    72  	if size == 0 {
    73  		return nil
    74  	}
    75  
    76  	if len(self.store) > int(offset) {
    77  		return self.store[offset : offset+size]
    78  	}
    79  
    80  	return nil
    81  }
    82  
    83  // Len returns the length of the backing slice
    84  func (m *Memory) Len() int {
    85  	return len(m.store)
    86  }
    87  
    88  // Data returns the backing slice
    89  func (m *Memory) Data() []byte {
    90  	return m.store
    91  }
    92  
    93  func (m *Memory) Print() {
    94  	fmt.Printf("### mem %d bytes ###\n", len(m.store))
    95  	if len(m.store) > 0 {
    96  		addr := 0
    97  		for i := 0; i+32 <= len(m.store); i += 32 {
    98  			fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
    99  			addr++
   100  		}
   101  	} else {
   102  		fmt.Println("-- empty --")
   103  	}
   104  	fmt.Println("####################")
   105  }