内存的最先分配算法首先实现,再逐步完成最优和最坏的分配算法,编写全部程序
时间: 2023-11-28 12:48:15 浏览: 57
好的,以下是内存分配算法的实现代码:
```python
class Memory:
def __init__(self, size):
self.size = size
self.memory = [0] * size
self.free_blocks = [(0, size)]
def allocate(self, size):
for i, block in enumerate(self.free_blocks):
if block[1] >= size:
start = block[0]
end = start + size
self.free_blocks.pop(i)
if block[1] > size:
self.free_blocks.insert(i, (end, block[1] - size))
for j in range(start, end):
self.memory[j] = 1
return start
return None
def deallocate(self, start, size):
end = start + size
for i in range(start, end):
self.memory[i] = 0
if not self.free_blocks:
self.free_blocks.append((start, size))
else:
for i, block in enumerate(self.free_blocks):
if start < block[0]:
self.free_blocks.insert(i, (start, size))
break
else:
self.free_blocks.append((start, size))
# merge adjacent free blocks
i = 0
while i < len(self.free_blocks) - 1:
if self.free_blocks[i][0] + self.free_blocks[i][1] == self.free_blocks[i+1][0]:
merged_block = (self.free_blocks[i][0], self.free_blocks[i][1] + self.free_blocks[i+1][1])
self.free_blocks.pop(i+1)
self.free_blocks.pop(i)
self.free_blocks.insert(i, merged_block)
else:
i += 1
def print_memory(self):
for i, bit in enumerate(self.memory):
print(bit, end='')
if i % 10 == 9:
print()
```
上述代码中,`Memory` 类表示一块大小为 `size` 的内存,内部维护了一个 `memory` 数组来记录每个字节是否被占用,以及一个 `free_blocks` 列表来记录当前空闲块的起始位置和空闲块大小。
`allocate(size)` 方法用于分配大小为 `size` 的内存块。它遍历 `free_blocks` 列表中的每个空闲块,找到第一个大小大于等于 `size` 的块,将其分配出去,并将分配出去的块从 `free_blocks` 中移除。如果没有合适的块,则返回 `None`。
`deallocate(start, size)` 方法用于释放从起始位置为 `start` 的内存块,大小为 `size`。它将对应的 `memory` 中的位都置为 0,并将释放出来的块重新插入到 `free_blocks` 列表中。如果当前没有空闲块,则直接将该块插入到 `free_blocks` 中;否则,遍历 `free_blocks` 列表,找到第一个起始位置比释放的块小的块,并将释放的块插入到该块前面。插入后,还需要合并相邻的空闲块(如果有的话)。
`print_memory()` 方法用于打印当前内存的状态,每行显示 10 个字节的状态。
下面是使用上述 `Memory` 类实现最先分配算法的代码:
```python
class FirstFit:
def __init__(self, size):
self.memory = Memory(size)
def allocate(self, size):
return self.memory.allocate(size)
def deallocate(self, start, size):
self.memory.deallocate(start, size)
def print_memory(self):
self.memory.print_memory()
```
`FirstFit` 类表示最先分配算法,它的实现非常简单,只需要调用 `Memory` 类的对应方法即可。
最优分配算法的实现代码如下:
```python
class BestFit:
def __init__(self, size):
self.memory = Memory(size)
def allocate(self, size):
best_block = None
for block in self.memory.free_blocks:
if block[1] >= size and (best_block is None or block[1] < best_block[1]):
best_block = block
if best_block is None:
return None
start = best_block[0]
end = start + size
self.memory.free_blocks.remove(best_block)
if best_block[1] > size:
self.memory.free_blocks.append((end, best_block[1] - size))
for i in range(start, end):
self.memory.memory[i] = 1
return start
def deallocate(self, start, size):
self.memory.deallocate(start, size)
def print_memory(self):
self.memory.print_memory()
```
`BestFit` 类表示最优分配算法,它在分配时遍历所有空闲块,找到大小最接近需求大小的块,并将其分配出去。
最坏分配算法的实现代码如下:
```python
class WorstFit:
def __init__(self, size):
self.memory = Memory(size)
def allocate(self, size):
worst_block = None
for block in self.memory.free_blocks:
if block[1] >= size and (worst_block is None or block[1] > worst_block[1]):
worst_block = block
if worst_block is None:
return None
start = worst_block[0]
end = start + size
self.memory.free_blocks.remove(worst_block)
if worst_block[1] > size:
self.memory.free_blocks.append((end, worst_block[1] - size))
for i in range(start, end):
self.memory.memory[i] = 1
return start
def deallocate(self, start, size):
self.memory.deallocate(start, size)
def print_memory(self):
self.memory.print_memory()
```
`WorstFit` 类表示最坏分配算法,它在分配时遍历所有空闲块,找到大小最接近需求大小且最大的块,并将其分配出去。
完整代码如下: