github.com/arieschain/arieschain@v0.0.0-20191023063405-37c074544356/core/vm/memory.go (about)

     1  package vm
     2  
     3  import "fmt"
     4  
     5  // Memory implements a simple memory model for the quickchain virtual machine.
     6  type Memory struct {
     7  	store       []byte
     8  	lastGasCost uint64
     9  }
    10  
    11  func NewMemory() *Memory {
    12  	return &Memory{}
    13  }
    14  
    15  // Set sets offset + size to value
    16  func (m *Memory) Set(offset, size uint64, value []byte) {
    17  	// length of store may never be less than offset + size.
    18  	// The store should be resized PRIOR to setting the memory
    19  	if size > uint64(len(m.store)) {
    20  		panic("INVALID memory: store empty")
    21  	}
    22  
    23  	// It's possible the offset is greater than 0 and size equals 0. This is because
    24  	// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
    25  	if size > 0 {
    26  		copy(m.store[offset:offset+size], value)
    27  	}
    28  }
    29  
    30  // Resize resizes the memory to size
    31  func (m *Memory) Resize(size uint64) {
    32  	if uint64(m.Len()) < size {
    33  		m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
    34  	}
    35  }
    36  
    37  // Get returns offset + size as a new slice
    38  func (m *Memory) Get(offset, size int64) (cpy []byte) {
    39  	if size == 0 {
    40  		return nil
    41  	}
    42  
    43  	if len(m.store) > int(offset) {
    44  		cpy = make([]byte, size)
    45  		copy(cpy, m.store[offset:offset+size])
    46  
    47  		return
    48  	}
    49  
    50  	return
    51  }
    52  
    53  // GetPtr returns the offset + size
    54  func (m *Memory) GetPtr(offset, size int64) []byte {
    55  	if size == 0 {
    56  		return nil
    57  	}
    58  
    59  	if len(m.store) > int(offset) {
    60  		return m.store[offset : offset+size]
    61  	}
    62  
    63  	return nil
    64  }
    65  
    66  // Len returns the length of the backing slice
    67  func (m *Memory) Len() int {
    68  	return len(m.store)
    69  }
    70  
    71  // Data returns the backing slice
    72  func (m *Memory) Data() []byte {
    73  	return m.store
    74  }
    75  
    76  func (m *Memory) Print() {
    77  	fmt.Printf("### mem %d bytes ###\n", len(m.store))
    78  	if len(m.store) > 0 {
    79  		addr := 0
    80  		for i := 0; i+32 <= len(m.store); i += 32 {
    81  			fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
    82  			addr++
    83  		}
    84  	} else {
    85  		fmt.Println("-- empty --")
    86  	}
    87  	fmt.Println("####################")
    88  }