/
memory.go
88 lines (72 loc) · 1.85 KB
/
memory.go
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package vm
import "fmt"
// Memory implements a simple memory model for the lemochain virtual machine.
type Memory struct {
store []byte
lastGasCost uint64
}
func NewMemory() *Memory {
return &Memory{}
}
// Set sets offset + size to value
func (m *Memory) Set(offset, size uint64, value []byte) {
// length of store may never be less than offset + size.
// The store should be resized PRIOR to setting the memory
if size > uint64(len(m.store)) {
panic("INVALID memory: store empty")
}
// It's possible the offset is greater than 0 and size equals 0. This is because
// the calcMemSize (common.go) could potentially return 0 when size is zero (NO-OP)
if size > 0 {
copy(m.store[offset:offset+size], value)
}
}
// Resize resizes the memory to size
func (m *Memory) Resize(size uint64) {
if uint64(m.Len()) < size {
m.store = append(m.store, make([]byte, size-uint64(m.Len()))...)
}
}
// Get returns offset + size as a new slice
func (self *Memory) Get(offset, size int64) (cpy []byte) {
if size == 0 {
return nil
}
if len(self.store) > int(offset) {
cpy = make([]byte, size)
copy(cpy, self.store[offset:offset+size])
return
}
return
}
// GetPtr returns the offset + size
func (self *Memory) GetPtr(offset, size int64) []byte {
if size == 0 {
return nil
}
if len(self.store) > int(offset) {
return self.store[offset : offset+size]
}
return nil
}
// Len returns the length of the backing slice
func (m *Memory) Len() int {
return len(m.store)
}
// Data returns the backing slice
func (m *Memory) Data() []byte {
return m.store
}
func (m *Memory) Print() {
fmt.Printf("### mem %d bytes ###\n", len(m.store))
if len(m.store) > 0 {
addr := 0
for i := 0; i+32 <= len(m.store); i += 32 {
fmt.Printf("%03d: % x\n", addr, m.store[i:i+32])
addr++
}
} else {
fmt.Println("-- empty --")
}
fmt.Println("####################")
}