github.com/theQRL/go-zond@v0.1.1/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  	"github.com/holiman/uint256"
    21  )
    22  
    23  // Memory implements a simple memory model for the ethereum virtual machine.
    24  type Memory struct {
    25  	store       []byte
    26  	lastGasCost uint64
    27  }
    28  
    29  // NewMemory returns a new memory model.
    30  func NewMemory() *Memory {
    31  	return &Memory{}
    32  }
    33  
    34  // Set sets offset + size to value
    35  func (m *Memory) Set(offset, size uint64, value []byte) {
    36  	// It's possible the offset is greater than 0 and size equals 0. This is because
    37  	// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
    38  	if size > 0 {
    39  		// length of store may never be less than offset + size.
    40  		// The store should be resized PRIOR to setting the memory
    41  		if offset+size > uint64(len(m.store)) {
    42  			panic("invalid memory: store empty")
    43  		}
    44  		copy(m.store[offset:offset+size], value)
    45  	}
    46  }
    47  
    48  // Set32 sets the 32 bytes starting at offset to the value of val, left-padded with zeroes to
    49  // 32 bytes.
    50  func (m *Memory) Set32(offset uint64, val *uint256.Int) {
    51  	// length of store may never be less than offset + size.
    52  	// The store should be resized PRIOR to setting the memory
    53  	if offset+32 > uint64(len(m.store)) {
    54  		panic("invalid memory: store empty")
    55  	}
    56  	// Fill in relevant bits
    57  	b32 := val.Bytes32()
    58  	copy(m.store[offset:], b32[:])
    59  }
    60  
    61  // Resize resizes the memory to size
    62  func (m *Memory) Resize(size uint64) {
    63  	if uint64(m.Len()) < size {
    64  		m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
    65  	}
    66  }
    67  
    68  // GetCopy returns offset + size as a new slice
    69  func (m *Memory) GetCopy(offset, size int64) (cpy []byte) {
    70  	if size == 0 {
    71  		return nil
    72  	}
    73  
    74  	if len(m.store) > int(offset) {
    75  		cpy = make([]byte, size)
    76  		copy(cpy, m.store[offset:offset+size])
    77  
    78  		return
    79  	}
    80  
    81  	return
    82  }
    83  
    84  // GetPtr returns the offset + size
    85  func (m *Memory) GetPtr(offset, size int64) []byte {
    86  	if size == 0 {
    87  		return nil
    88  	}
    89  
    90  	if len(m.store) > int(offset) {
    91  		return m.store[offset : offset+size]
    92  	}
    93  
    94  	return nil
    95  }
    96  
    97  // Len returns the length of the backing slice
    98  func (m *Memory) Len() int {
    99  	return len(m.store)
   100  }
   101  
   102  // Data returns the backing slice
   103  func (m *Memory) Data() []byte {
   104  	return m.store
   105  }
   106  
   107  // Copy copies data from the src position slice into the dst position.
   108  // The source and destination may overlap.
   109  // OBS: This operation assumes that any necessary memory expansion has already been performed,
   110  // and this method may panic otherwise.
   111  func (m *Memory) Copy(dst, src, len uint64) {
   112  	if len == 0 {
   113  		return
   114  	}
   115  	copy(m.store[dst:], m.store[src:src+len])
   116  }