LRU算法的简单实现

group02/812350401/.gitignore

@@ -1,4 +1,6 @@
 target/
 .idea/
 src/main/java/train/
-src/main/resources/
+!src/main/resources/**/*.class
+!src/main/resources/**/*.xml
+src/main/resources/**/*.png

group02/812350401/pom.xml

@@ -7,6 +7,7 @@
     <groupId>coding2017</groupId>
     <artifactId>812350401</artifactId>
     <version>1.0-SNAPSHOT</version>
+    <packaging>jar</packaging>
     <build>
         <plugins>
             <plugin>
@@ -32,7 +33,20 @@
             <artifactId>dom4j</artifactId>
             <version>1.6.1</version>
         </dependency>
+        <dependency>
+            <groupId>org.jetbrains</groupId>
+            <artifactId>annotations</artifactId>
+            <version>RELEASE</version>
+        </dependency>
+        <!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
+        <dependency>
+            <groupId>commons-io</groupId>
+            <artifactId>commons-io</artifactId>
+            <version>2.5</version>
+        </dependency>
+
     </dependencies>
 
 
+
 </project>

group02/812350401/src/main/java/com/github/miniyk2012/coding2017/basic/linklist/LRUPageFrame.java

@@ -0,0 +1,148 @@
+package com.github.miniyk2012.coding2017.basic.linklist;
+
+/**
+ * 用双向链表实现LRU算法
+ * @author liuxin
+ *
+ */
+public class LRUPageFrame {
+
+	private static class Node {
+
+		Node prev;
+		Node next;
+		int pageNum;
+
+		Node() {
+		}
+
+		Node(int pageNum) {
+		    this.pageNum = pageNum;
+        }
+	}
+
+	private int capacity;
+	private int size;
+
+	private Node first;// 链表头
+	private Node last;// 链表尾
+
+
+	public LRUPageFrame(int capacity) {
+
+		this.capacity = capacity;
+
+	}
+
+	/**
+	 * 获取缓存中对象
+	 * 
+	 * @param pageNum: page值
+	 * @return
+	 */
+	public void access(int pageNum) {
+        Node hitNode = get(pageNum);
+        if (null == hitNode) {
+            hitNode = new Node(pageNum);
+            addTop(hitNode);
+            if (size > capacity) {
+                delBottom();
+            }
+        } else {
+            switchTop(hitNode);
+        }
+	}
+
+    /**
+     * 获取值为pageNum的Node，如果没有返回null
+     * @param pageNum
+     * @return
+     */
+	private Node get(int pageNum) {
+	    Node currentNode = first;
+		while (currentNode != null) {
+		    if (currentNode.pageNum == pageNum) return currentNode;
+		    currentNode = currentNode.next;
+        }
+        return null;
+	}
+
+    /**
+     * 往顶部放一个Node
+     * @param node
+     */
+	private void addTop(Node node) {
+        size++;
+        if (first == null) {
+            first = last = node;
+        } else {
+            node.next = first;
+            first.prev = node;
+            first = node;
+        }
+	}
+
+    /**
+     * 把node和顶部做交换
+     * @param node
+     */
+	private void switchTop(Node node) {
+        if (node == first) return;
+        Node preNode = node.prev;
+        Node nextNode = node.next;
+        preNode.next = nextNode;
+        if (nextNode != null) {
+            nextNode.prev = preNode;
+        } else {
+            last = preNode;
+        }
+        node.next = node.prev = null;
+        addTop(node);
+        size--;
+    }
+
+    /**
+     * 把底部的踢掉
+     */
+    private void delBottom() {
+        size--;
+        if (last == first) first = null;
+        Node temp = last;
+        last = last.prev;
+        temp.prev = null;
+        last.next = null;
+    }
+
+	public String toString(){
+		StringBuilder buffer = new StringBuilder();
+		Node node = first;
+		while(node != null){
+			buffer.append(node.pageNum);			
+
+			node = node.next;
+			if(node != null){
+				buffer.append(",");
+			}
+		}
+		return buffer.toString();
+	}
+
+    /**
+     * 测试双向链表逆序输出
+     * @return
+     */
+    public String lastToString(){
+        StringBuilder buffer = new StringBuilder();
+        Node node = last;
+        while(node != null){
+            buffer.append(node.pageNum);
+
+            node = node.prev;
+            if(node != null){
+                buffer.append(",");
+            }
+        }
+        return buffer.toString();
+    }
+
+}

group02/812350401/src/main/java/com/github/miniyk2012/coding2017/basic/linklist/LRUPageFrameTest.java

@@ -0,0 +1,62 @@
+package com.github.miniyk2012.coding2017.basic.linklist;
+
+import  org.junit.Assert;
+
+import org.junit.Test;
+
+
+public class LRUPageFrameTest {
+
+	@Test
+	public void testAccess() {
+		LRUPageFrame frame = new LRUPageFrame(3);
+		frame.access(7);
+		frame.access(0);
+		Assert.assertEquals("0,7", frame.toString());
+		Assert.assertEquals("7,0", frame.lastToString());
+		frame.access(1);
+		Assert.assertEquals("1,0,7", frame.toString());
+		Assert.assertEquals("7,0,1", frame.lastToString());
+		frame.access(2);
+		Assert.assertEquals("2,1,0", frame.toString());
+		Assert.assertEquals("0,1,2", frame.lastToString());
+		frame.access(0);
+		Assert.assertEquals("0,2,1", frame.toString());
+		Assert.assertEquals("1,2,0", frame.lastToString());
+		frame.access(0);
+		Assert.assertEquals("0,2,1", frame.toString());
+		Assert.assertEquals("1,2,0", frame.lastToString());
+		frame.access(3);
+		Assert.assertEquals("3,0,2", frame.toString());
+		Assert.assertEquals("2,0,3", frame.lastToString());
+		frame.access(0);
+		Assert.assertEquals("0,3,2", frame.toString());
+		Assert.assertEquals("2,3,0", frame.lastToString());
+		frame.access(4);
+		Assert.assertEquals("4,0,3", frame.toString());
+		Assert.assertEquals("3,0,4", frame.lastToString());
+		frame.access(4);
+		Assert.assertEquals("4,0,3", frame.toString());
+		Assert.assertEquals("3,0,4", frame.lastToString());
+		frame.access(4);
+		Assert.assertEquals("4,0,3", frame.toString());
+		Assert.assertEquals("3,0,4", frame.lastToString());
+		frame.access(0);
+		Assert.assertEquals("0,4,3", frame.toString());
+		Assert.assertEquals("3,4,0", frame.lastToString());
+		frame.access(7);
+		Assert.assertEquals("7,0,4", frame.toString());
+		Assert.assertEquals("4,0,7", frame.lastToString());
+		frame.access(4);
+		Assert.assertEquals("4,7,0", frame.toString());
+		Assert.assertEquals("0,7,4", frame.lastToString());
+
+		LRUPageFrame frame2 = new LRUPageFrame(1);
+		Assert.assertEquals("", frame2.toString());
+		frame2.access(7);
+		Assert.assertEquals("7", frame2.toString());
+		frame2.access(0);
+		Assert.assertEquals("0", frame2.toString());
+	}
+
+}

group02/812350401/src/main/java/com/github/miniyk2012/coding2017/coderising/jvm/loader/ClassFileLoader.java

@@ -0,0 +1,63 @@
+package com.github.miniyk2012.coding2017.coderising.jvm.loader;
+
+import org.apache.commons.io.FileUtils;
+import java.io.*;
+import java.util.ArrayList;
+import java.util.List;
+
+public class ClassFileLoader {
+
+	private List<String> clzPaths = new ArrayList<String>();
+
+	public byte[] readBinaryCode(String className) {
+//        InputStream is = null;
+//        ByteArrayOutputStream bas = null;
+//        byte[] ret = null;
+//		try {
+//            is = new BufferedInputStream(getClass().getClassLoader().getResourceAsStream(className));
+//            bas = new ByteArrayOutputStream();
+//            byte[] buf = new byte[1024];
+//            int bytesRead = 0;
+//            while ((bytesRead = is.read(buf)) != -1) {
+//                bas.write(buf, 0, bytesRead);
+//            }
+//            ret = bas.toByteArray();
+//        } catch (IOException e) {
+//		    e.printStackTrace();
+//        } finally {
+//		    try {
+//                if (is != null)
+//                    is.close();
+//                if (bas != null)
+//                    bas.close();
+//            } catch (IOException e) {
+//                e.printStackTrace();
+//            }
+//        }
+//        return ret;
+        int lastIndexDot = className.lastIndexOf(".");
+        String classPath = className.substring(0, lastIndexDot).replace(".", File.separator)
+                + className.substring(lastIndexDot);
+        for (String parentPath: clzPaths) {
+            try {
+                String fullPath = parentPath + File.separator + classPath;
+                return FileUtils.readFileToByteArray(new File(fullPath));
+            } catch (IOException e) {
+                continue;
+            }
+        }
+        return null;
+    }
+
+	public void addClassPath(String path) {
+		clzPaths.add(path);
+	}
+
+	public String getClassPath(){
+		return String.join(";", clzPaths);
+	}
+
+    public static void main(String[] args) {
+        new ClassFileLoader().readBinaryCode("");
+    }
+}

group02/812350401/src/main/java/com/github/miniyk2012/coding2017/coderising/jvm/test/ClassFileloaderTest.java

@@ -0,0 +1,83 @@
+package com.github.miniyk2012.coding2017.coderising.jvm.test;
+
+import com.github.miniyk2012.coding2017.coderising.jvm.loader.ClassFileLoader;
+import org.junit.After;
+import  org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+
+public class ClassFileloaderTest {
+
+
+	static String path1 = ClassFileloaderTest.class.getClassLoader().getResource("struts").getPath();
+	static String path2 = ClassFileloaderTest.class.getClassLoader().getResource("jvm").getPath();
+
+	@Before
+	public void setUp() throws Exception {		 
+	}
+
+	@After
+	public void tearDown() throws Exception {
+	}
+
+	@Test
+	public void testClassPath(){		
+
+		ClassFileLoader loader = new ClassFileLoader();
+		loader.addClassPath(path1);
+		loader.addClassPath(path2);
+
+		String clzPath = loader.getClassPath();
+
+		Assert.assertEquals(path1+";"+path2,clzPath);
+
+	}
+
+	@Test
+	public void testClassFileLength() {		
+
+		ClassFileLoader loader = new ClassFileLoader();
+        loader.addClassPath(path1);
+        loader.addClassPath(path2);
+
+		String className = "com.github.miniyk2012.coding2017.jvm.test.EmployeeV1.class";
+
+		byte[] byteCodes = loader.readBinaryCode(className);
+
+		// 注意：这个字节数可能和你的JVM版本有关系， 你可以看看编译好的类到底有多大
+		Assert.assertEquals(1114, byteCodes.length);
+
+	}
+
+    @Test	
+	public void testMagicNumber(){
+    	ClassFileLoader loader = new ClassFileLoader();
+		loader.addClassPath(path1);
+		loader.addClassPath(path2);
+		String className = "com.github.miniyk2012.coding2017.jvm.test.EmployeeV1.class";
+		byte[] byteCodes = loader.readBinaryCode(className);
+		byte[] codes = new byte[]{byteCodes[0],byteCodes[1],byteCodes[2],byteCodes[3]};
+
+
+		String acctualValue = this.byteToHexString(codes);
+
+		Assert.assertEquals("cafebabe", acctualValue);
+	}
+
+	@org.jetbrains.annotations.NotNull
+	private String byteToHexString(byte[] codes ){
+		StringBuffer buffer = new StringBuffer();
+		for(int i=0;i<codes.length;i++){
+			byte b = codes[i];
+			int value = b & 0xFF;
+			String strHex = Integer.toHexString(value);
+			if(strHex.length()< 2){
+				strHex = "0" + strHex;
+			}		
+			buffer.append(strHex);
+		}
+		return buffer.toString();
+	}
+
+}