github.com/aigarnetwork/aigar@v0.0.0-20191115204914-d59a6eb70f8e/core/vm/memory.go (about)

     1  //  Copyright 2018 The go-ethereum Authors
     2  //  Copyright 2019 The go-aigar Authors
     3  //  This file is part of the go-aigar library.
     4  //
     5  //  The go-aigar library is free software: you can redistribute it and/or modify
     6  //  it under the terms of the GNU Lesser General Public License as published by
     7  //  the Free Software Foundation, either version 3 of the License, or
     8  //  (at your option) any later version.
     9  //
    10  //  The go-aigar library is distributed in the hope that it will be useful,
    11  //  but WITHOUT ANY WARRANTY; without even the implied warranty of
    12  //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    13  //  GNU Lesser General Public License for more details.
    14  //
    15  //  You should have received a copy of the GNU Lesser General Public License
    16  //  along with the go-aigar library. If not, see <http://www.gnu.org/licenses/>.
    17  
    18  package vm
    19  
    20  import (
    21  	"fmt"
    22  	"math/big"
    23  
    24  	"github.com/AigarNetwork/aigar/common/math"
    25  )
    26  
    27  // Memory implements a simple memory model for the ethereum virtual machine.
    28  type Memory struct {
    29  	store       []byte
    30  	lastGasCost uint64
    31  }
    32  
    33  // NewMemory returns a new memory model.
    34  func NewMemory() *Memory {
    35  	return &Memory{}
    36  }
    37  
    38  // Set sets offset + size to value
    39  func (m *Memory) Set(offset, size uint64, value []byte) {
    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  		// length of store may never be less than offset + size.
    44  		// The store should be resized PRIOR to setting the memory
    45  		if offset+size > uint64(len(m.store)) {
    46  			panic("invalid memory: store empty")
    47  		}
    48  		copy(m.store[offset:offset+size], value)
    49  	}
    50  }
    51  
    52  // Set32 sets the 32 bytes starting at offset to the value of val, left-padded with zeroes to
    53  // 32 bytes.
    54  func (m *Memory) Set32(offset uint64, val *big.Int) {
    55  	// length of store may never be less than offset + size.
    56  	// The store should be resized PRIOR to setting the memory
    57  	if offset+32 > uint64(len(m.store)) {
    58  		panic("invalid memory: store empty")
    59  	}
    60  	// Zero the memory area
    61  	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})
    62  	// Fill in relevant bits
    63  	math.ReadBits(val, m.store[offset:offset+32])
    64  }
    65  
    66  // Resize resizes the memory to size
    67  func (m *Memory) Resize(size uint64) {
    68  	if uint64(m.Len()) < size {
    69  		m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
    70  	}
    71  }
    72  
    73  // Get returns offset + size as a new slice
    74  func (m *Memory) GetCopy(offset, size int64) (cpy []byte) {
    75  	if size == 0 {
    76  		return nil
    77  	}
    78  
    79  	if len(m.store) > int(offset) {
    80  		cpy = make([]byte, size)
    81  		copy(cpy, m.store[offset:offset+size])
    82  
    83  		return
    84  	}
    85  
    86  	return
    87  }
    88  
    89  // GetPtr returns the offset + size
    90  func (m *Memory) GetPtr(offset, size int64) []byte {
    91  	if size == 0 {
    92  		return nil
    93  	}
    94  
    95  	if len(m.store) > int(offset) {
    96  		return m.store[offset : offset+size]
    97  	}
    98  
    99  	return nil
   100  }
   101  
   102  // Len returns the length of the backing slice
   103  func (m *Memory) Len() int {
   104  	return len(m.store)
   105  }
   106  
   107  // Data returns the backing slice
   108  func (m *Memory) Data() []byte {
   109  	return m.store
   110  }
   111  
   112  // Print dumps the content of the memory.
   113  func (m *Memory) Print() {
   114  	fmt.Printf("### mem %d bytes ###\n", len(m.store))
   115  	if len(m.store) > 0 {
   116  		addr := 0
   117  		for i := 0; i+32 <= len(m.store); i += 32 {
   118  			fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
   119  			addr++
   120  		}
   121  	} else {
   122  		fmt.Println("-- empty --")
   123  	}
   124  	fmt.Println("####################")
   125  }