github.com/FusionFoundation/efsn/v4@v4.2.0/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  	"github.com/holiman/uint256"
    22  )
    23  
    24  // Memory implements a simple memory model for the ethereum virtual machine.
    25  type Memory struct {
    26  	store       []byte
    27  	lastGasCost uint64
    28  }
    29  
    30  // NewMemory returns a new memory memory model.
    31  func NewMemory() *Memory {
    32  	return &Memory{}
    33  }
    34  
    35  // Set sets offset + size to value
    36  func (m *Memory) Set(offset, size uint64, value []byte) {
    37  	// It's possible the offset is greater than 0 and size equals 0. This is because
    38  	// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
    39  	if size > 0 {
    40  		// length of store may never be less than offset + size.
    41  		// The store should be resized PRIOR to setting the memory
    42  		if offset+size > uint64(len(m.store)) {
    43  			panic("invalid memory: store empty")
    44  		}
    45  		copy(m.store[offset:offset+size], value)
    46  	}
    47  }
    48  
    49  // Set32 sets the 32 bytes starting at offset to the value of val, left-padded with zeroes to
    50  // 32 bytes.
    51  func (m *Memory) Set32(offset uint64, val *uint256.Int) {
    52  	// length of store may never be less than offset + size.
    53  	// The store should be resized PRIOR to setting the memory
    54  	if offset+32 > uint64(len(m.store)) {
    55  		panic("invalid memory: store empty")
    56  	}
    57  	// Zero the memory area
    58  	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})
    59  	// Fill in relevant bits
    60  	val.WriteToSlice(m.store[offset:])
    61  }
    62  
    63  // Resize resizes the memory to size
    64  func (m *Memory) Resize(size uint64) {
    65  	if uint64(m.Len()) < size {
    66  		m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
    67  	}
    68  }
    69  
    70  // Get returns offset + size as a new slice
    71  func (m *Memory) GetCopy(offset, size int64) (cpy []byte) {
    72  	if size == 0 {
    73  		return nil
    74  	}
    75  
    76  	if len(m.store) > int(offset) {
    77  		cpy = make([]byte, size)
    78  		copy(cpy, m.store[offset:offset+size])
    79  
    80  		return
    81  	}
    82  
    83  	return
    84  }
    85  
    86  // GetPtr returns the offset + size
    87  func (m *Memory) GetPtr(offset, size int64) []byte {
    88  	if size == 0 {
    89  		return nil
    90  	}
    91  
    92  	if len(m.store) > int(offset) {
    93  		return m.store[offset : offset+size]
    94  	}
    95  
    96  	return nil
    97  }
    98  
    99  // Len returns the length of the backing slice
   100  func (m *Memory) Len() int {
   101  	return len(m.store)
   102  }
   103  
   104  // Data returns the backing slice
   105  func (m *Memory) Data() []byte {
   106  	return m.store
   107  }
   108  
   109  // Print dumps the content of the memory.
   110  func (m *Memory) Print() {
   111  	fmt.Printf("### mem %d bytes ###\n", len(m.store))
   112  	if len(m.store) > 0 {
   113  		addr := 0
   114  		for i := 0; i+32 <= len(m.store); i += 32 {
   115  			fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
   116  			addr++
   117  		}
   118  	} else {
   119  		fmt.Println("-- empty --")
   120  	}
   121  	fmt.Println("####################")
   122  }