github.com/dominant-strategies/go-quai@v0.28.2/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  
    22  	"github.com/holiman/uint256"
    23  )
    24  
    25  // Memory implements a simple memory model for the quai virtual machine.
    26  type Memory struct {
    27  	store       []byte
    28  	lastGasCost uint64
    29  }
    30  
    31  // NewMemory returns a new memory model.
    32  func NewMemory() *Memory {
    33  	return &Memory{}
    34  }
    35  
    36  // Set sets offset + size to value
    37  func (m *Memory) Set(offset, size uint64, value []byte) {
    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  		// length of store may never be less than offset + size.
    42  		// The store should be resized PRIOR to setting the memory
    43  		if offset+size > uint64(len(m.store)) {
    44  			panic("invalid memory: store empty")
    45  		}
    46  		copy(m.store[offset:offset+size], value)
    47  	}
    48  }
    49  
    50  // Set32 sets the 32 bytes starting at offset to the value of val, left-padded with zeroes to
    51  // 32 bytes.
    52  func (m *Memory) Set32(offset uint64, val *uint256.Int) {
    53  	// length of store may never be less than offset + size.
    54  	// The store should be resized PRIOR to setting the memory
    55  	if offset+32 > uint64(len(m.store)) {
    56  		panic("invalid memory: store empty")
    57  	}
    58  	// Zero the memory area
    59  	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})
    60  	// Fill in relevant bits
    61  	val.WriteToSlice(m.store[offset:])
    62  }
    63  
    64  // Resize resizes the memory to size
    65  func (m *Memory) Resize(size uint64) {
    66  	if uint64(m.Len()) < size {
    67  		m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
    68  	}
    69  }
    70  
    71  // Get returns offset + size as a new slice
    72  func (m *Memory) GetCopy(offset, size int64) (cpy []byte) {
    73  	if size == 0 {
    74  		return nil
    75  	}
    76  
    77  	if len(m.store) > int(offset) {
    78  		cpy = make([]byte, size)
    79  		copy(cpy, m.store[offset:offset+size])
    80  
    81  		return
    82  	}
    83  
    84  	return
    85  }
    86  
    87  // GetPtr returns the offset + size
    88  func (m *Memory) GetPtr(offset, size int64) []byte {
    89  	if size == 0 {
    90  		return nil
    91  	}
    92  
    93  	if len(m.store) > int(offset) {
    94  		return m.store[offset : offset+size]
    95  	}
    96  
    97  	return nil
    98  }
    99  
   100  // Len returns the length of the backing slice
   101  func (m *Memory) Len() int {
   102  	return len(m.store)
   103  }
   104  
   105  // Data returns the backing slice
   106  func (m *Memory) Data() []byte {
   107  	return m.store
   108  }
   109  
   110  // Print dumps the content of the memory.
   111  func (m *Memory) Print() {
   112  	fmt.Printf("### mem %d bytes ###\n", len(m.store))
   113  	if len(m.store) > 0 {
   114  		addr := 0
   115  		for i := 0; i+32 <= len(m.store); i += 32 {
   116  			fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
   117  			addr++
   118  		}
   119  	} else {
   120  		fmt.Println("-- empty --")
   121  	}
   122  	fmt.Println("####################")
   123  }