动态分区分配算法的实现 java怎么实现
时间: 2024-01-23 07:02:29 浏览: 23
动态分区分配是一种内存分配算法,可以根据进程的需求分配合适大小的内存区域。在 Java 中,可以通过使用动态数据结构来实现动态分区分配算法。
一种常见的实现方式是使用链表来维护空闲区域和已分配区域。具体实现可以参考以下代码:
```java
public class MemoryBlock {
private int startAddr; // 起始地址
private int size; // 内存块大小
private MemoryBlock next; // 下一个内存块
public MemoryBlock(int startAddr, int size) {
this.startAddr = startAddr;
this.size = size;
this.next = null;
}
public int getStartAddr() {
return startAddr;
}
public int getSize() {
return size;
}
public MemoryBlock getNext() {
return next;
}
public void setNext(MemoryBlock next) {
this.next = next;
}
}
public class MemoryAllocator {
private MemoryBlock head; // 内存块链表头
public MemoryAllocator(int size) {
// 初始化内存块链表
head = new MemoryBlock(0, size);
}
// 分配内存
public MemoryBlock allocate(int size) {
MemoryBlock prev = null;
MemoryBlock curr = head;
while (curr != null) {
if (curr.getSize() >= size) {
// 找到合适的空闲内存块
int startAddr = curr.getStartAddr();
int remainingSize = curr.getSize() - size;
if (remainingSize > 0) {
// 分割空闲内存块
MemoryBlock newBlock = new MemoryBlock(startAddr + size, remainingSize);
newBlock.setNext(curr.getNext());
curr.setSize(size);
curr.setNext(newBlock);
}
// 将分配的内存块从空闲内存块链表中移除
if (prev == null) {
head = curr.getNext();
} else {
prev.setNext(curr.getNext());
}
return curr;
}
prev = curr;
curr = curr.getNext();
}
// 没有合适的空闲内存块
return null;
}
// 释放内存
public void free(MemoryBlock block) {
MemoryBlock prev = null;
MemoryBlock curr = head;
while (curr != null) {
if (curr.getStartAddr() > block.getStartAddr()) {
// 找到 block 的插入位置
if (prev == null) {
block.setNext(head);
head = block;
} else {
block.setNext(curr);
prev.setNext(block);
}
// 合并相邻的空闲内存块
if (prev != null && prev.getStartAddr() + prev.getSize() == block.getStartAddr()) {
prev.setSize(prev.getSize() + block.getSize());
prev.setNext(block.getNext());
block = prev;
}
if (block.getNext() != null && block.getStartAddr() + block.getSize() == block.getNext().getStartAddr()) {
block.setSize(block.getSize() + block.getNext().getSize());
block.setNext(block.getNext().getNext());
}
return;
}
prev = curr;
curr = curr.getNext();
}
// block 的插入位置在链表末尾
if (prev == null) {
head = block;
} else {
prev.setNext(block);
}
}
}
```
以上代码实现了 `MemoryBlock` 类和 `MemoryAllocator` 类,其中 `MemoryBlock` 表示内存块,包括起始地址、大小和下一个内存块的指针;`MemoryAllocator` 表示内存分配器,包括内存块链表头和分配/释放内存的方法。在 `allocate` 方法中,需要遍历内存块链表,找到合适的空闲内存块并进行分配;在 `free` 方法中,需要找到释放的内存块的插入位置,并合并相邻的空闲内存块。
可以通过如下代码测试内存分配器的功能:
```java
public class TestMemoryAllocator {
public static void main(String[] args) {
MemoryAllocator allocator = new MemoryAllocator(1024);
// 分配内存
MemoryBlock block1 = allocator.allocate(256);
MemoryBlock block2 = allocator.allocate(512);
MemoryBlock block3 = allocator.allocate(128);
System.out.println(block1.getStartAddr() + " " + block1.getSize());
System.out.println(block2.getStartAddr() + " " + block2.getSize());
System.out.println(block3.getStartAddr() + " " + block3.getSize());
// 释放内存
allocator.free(block2);
MemoryBlock block4 = allocator.allocate(256);
System.out.println(block4.getStartAddr() + " " + block4.getSize());
}
}
```
以上代码分配了三个内存块,分别大小为 256、512 和 128,然后释放了第二个内存块,再分配一个大小为 256 的内存块。输出结果应该为:
```
0 256
256 512
768 128
256 256
```