利用java操作系统中通过基本分页分区模拟实现内存管理,包括内存分配和回收、地址映射等功能,观察空闲分区变化情况, 加深对操作系统存储器管理内容的理解的代码
时间: 2024-02-18 17:05:09 浏览: 41
以下是一个简单的Java代码示例,实现了基本分页分区模拟,包括内存分配和回收、地址映射等功能,以及空闲分区变化情况的观察。
```java
import java.util.*;
public class MemoryManager {
private static final int PAGE_SIZE = 1024; //页大小
private int memorySize; //内存总大小
private int pageSize; //页大小
private int pageCount; //页数
private int[] memory; //内存数组
private int[] pageTable; //页表
private List<MemoryArea> freeAreas; //空闲分区列表
public MemoryManager(int memorySize) {
this.memorySize = memorySize;
this.pageSize = PAGE_SIZE;
this.pageCount = memorySize / pageSize;
this.memory = new int[memorySize];
this.pageTable = new int[pageCount];
this.freeAreas = new ArrayList<>();
this.freeAreas.add(new MemoryArea(0, memorySize));
}
//分配内存
public int allocate(int size) {
int pageCount = size / pageSize + 1;
for (MemoryArea area : freeAreas) {
if (area.getSize() >= pageCount) {
int pageIndex = area.getStart() / pageSize;
for (int i = pageIndex; i < pageIndex + pageCount; i++) {
pageTable[i] = 1;
}
area.setStart(area.getStart() + pageCount * pageSize);
if (area.getSize() == 0) {
freeAreas.remove(area);
}
return pageIndex * pageSize;
}
}
return -1;
}
//回收内存
public void free(int addr) {
int pageIndex = addr / pageSize;
pageTable[pageIndex] = 0;
MemoryArea area = new MemoryArea(addr, pageSize);
int i = 0;
for (; i < freeAreas.size(); i++) {
MemoryArea a = freeAreas.get(i);
if (area.getEnd() <= a.getStart()) {
freeAreas.add(i, area);
break;
} else if (area.getStart() >= a.getEnd()) {
continue;
} else {
throw new RuntimeException("Memory overlay!");
}
}
if (i == freeAreas.size()) {
freeAreas.add(area);
}
mergeFreeAreas();
}
//地址映射
public int translate(int addr) {
int pageIndex = addr / pageSize;
if (pageTable[pageIndex] == 0) {
throw new RuntimeException("Page fault!");
}
return pageIndex * pageSize + addr % pageSize;
}
//合并空闲分区
private void mergeFreeAreas() {
for (int i = 0; i < freeAreas.size() - 1; ) {
MemoryArea a = freeAreas.get(i);
MemoryArea b = freeAreas.get(i + 1);
if (a.getEnd() == b.getStart()) {
a.setSize(a.getSize() + b.getSize());
freeAreas.remove(b);
} else {
i++;
}
}
}
//打印空闲分区列表
public void printFreeAreas() {
System.out.println("Free areas:");
for (MemoryArea area : freeAreas) {
System.out.println(area.getStart() + "-" + area.getEnd());
}
System.out.println();
}
private static class MemoryArea {
private int start;
private int size;
public MemoryArea(int start, int size) {
this.start = start;
this.size = size;
}
public int getStart() {
return start;
}
public void setStart(int start) {
this.start = start;
}
public int getSize() {
return size;
}
public void setSize(int size) {
this.size = size;
}
public int getEnd() {
return start + size;
}
}
}
```
该代码实现了一个内存管理器类`MemoryManager`,其中包括了`allocate`方法用于分配内存、`free`方法用于回收内存、`translate`方法用于地址映射等功能。在分配和回收内存时,使用了空闲分区列表`freeAreas`来管理内存的空闲分区。在代码的末尾,还提供了一个`printFreeAreas`方法来打印空闲分区列表,以便观察空闲分区的变化情况。
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