github.com/ethereumproject/go-ethereum@v5.5.2+incompatible/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  }
    25  
    26  func NewMemory() *Memory {
    27  	return &Memory{nil}
    28  }
    29  
    30  // Set sets offset + size to value
    31  func (m *Memory) Set(offset, size uint64, value []byte) {
    32  	// length of store may never be less than offset + size.
    33  	// The store should be resized PRIOR to setting the memory
    34  	if size > uint64(len(m.store)) {
    35  		panic("INVALID memory: store empty")
    36  	}
    37  
    38  	// It's possible the offset is greater than 0 and size equals 0. This is because
    39  	// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
    40  	if size > 0 {
    41  		copy(m.store[offset:offset+size], value)
    42  	}
    43  }
    44  
    45  // Resize resizes the memory to size
    46  func (m *Memory) Resize(size uint64) {
    47  	if uint64(m.Len()) < size {
    48  		m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
    49  	}
    50  }
    51  
    52  // Get returns offset + size as a new slice
    53  func (self *Memory) Get(offset, size int64) (cpy []byte) {
    54  	if size == 0 {
    55  		return nil
    56  	}
    57  
    58  	if len(self.store) > int(offset) {
    59  		cpy = make([]byte, size)
    60  		copy(cpy, self.store[offset:offset+size])
    61  
    62  		return
    63  	}
    64  
    65  	return
    66  }
    67  
    68  // GetPtr returns the offset + size
    69  func (self *Memory) GetPtr(offset, size int64) []byte {
    70  	if size == 0 {
    71  		return nil
    72  	}
    73  
    74  	if len(self.store) > int(offset) {
    75  		return self.store[offset : offset+size]
    76  	}
    77  
    78  	return nil
    79  }
    80  
    81  // Len returns the length of the backing slice
    82  func (m *Memory) Len() int {
    83  	return len(m.store)
    84  }
    85  
    86  // Data returns the backing slice
    87  func (m *Memory) Data() []byte {
    88  	return m.store
    89  }
    90  
    91  func (m *Memory) Print() {
    92  	fmt.Printf("### mem %d bytes ###\n", len(m.store))
    93  	if len(m.store) > 0 {
    94  		addr := 0
    95  		for i := 0; i+32 <= len(m.store); i += 32 {
    96  			fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
    97  			addr++
    98  		}
    99  	} else {
   100  		fmt.Println("-- empty --")
   101  	}
   102  	fmt.Println("####################")
   103  }