四种拷贝方式

1. 不同io
2. buffer io
3. mmap 零拷贝
4. sendfile 零拷贝

核心代码

java">package com.itzhongzi.io;import java.io.*;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Files;
import java.nio.file.Paths;/*** @author Administrator* @description* @since 2024-04-23 19:30* <p>* 运行方式: java IOTest.java "io" "source" "target"*/
public class IOTest {public static void main(String[] args) {String type = args[0];String inputFilePath = args[1];String outputFilePath = args[2];if ("io".equalsIgnoreCase(type)) {inputStreamCopyFile(inputFilePath, outputFilePath);} else if ("buffer".equalsIgnoreCase(type)) {bufferInputStreamCopyFile(inputFilePath, outputFilePath);} else if ("mmap".equalsIgnoreCase(type)) {mmapInputStreamCopyFile(inputFilePath, outputFilePath);} else if ("sendfile".equalsIgnoreCase(type)) {sendfileInputStreamCopyFile(inputFilePath, outputFilePath);}}/*** 普通io** @param inputFilePath* @param outputFilePath*/private static void inputStreamCopyFile(String inputFilePath, String outputFilePath) {long start = System.currentTimeMillis();try (FileInputStream fis = new FileInputStream(inputFilePath);FileOutputStream fos = new FileOutputStream(outputFilePath)) {byte[] buf = new byte[1024];int len;;while ((len = fis.read(buf)) != -1) {fos.write(buf);}} catch (Exception e) {e.printStackTrace();}long end = System.currentTimeMillis();System.out.println("耗时" + (end - start) + "ms");}/*** buffer io** @param inputFilePath* @param outputFilePath*/private static void bufferInputStreamCopyFile(String inputFilePath, String outputFilePath) {long start = System.currentTimeMillis();try (BufferedInputStream bis = new BufferedInputStream(Files.newInputStream(Paths.get(inputFilePath)));BufferedOutputStream bos = new BufferedOutputStream(Files.newOutputStream(Paths.get(outputFilePath)));) {byte[] buf = new byte[1024];int len;while ((len = bis.read(buf)) != -1) {bos.write(buf);}} catch (Exception e) {e.printStackTrace();}long end = System.currentTimeMillis();System.out.println("耗时" + (end - start) + "ms");}/*** mmap 零拷贝io** @param inputFilePath* @param outputFilePath*/private static void mmapInputStreamCopyFile(String inputFilePath, String outputFilePath) {try (FileChannel channelIn = new FileInputStream(inputFilePath).getChannel();FileChannel channelOut = new RandomAccessFile(outputFilePath, "rw").getChannel();) {long size = channelIn.size();System.out.println("mmap size:" + size);MappedByteBuffer mappedInByteBuffer = channelIn.map(FileChannel.MapMode.READ_ONLY, 0, size);MappedByteBuffer mappedOutByteBuffer = channelOut.map(FileChannel.MapMode.READ_WRITE, 0, size);for (int i = 0; i < size; i++) {mappedOutByteBuffer.put(mappedInByteBuffer.get(i));}} catch (Exception e) {e.printStackTrace();}}/*** sendfile 零拷贝io** @param inputFilePath* @param outputFilePath*/private static void sendfileInputStreamCopyFile(String inputFilePath, String outputFilePath) {try (FileChannel channelIn = new FileInputStream(inputFilePath).getChannel();FileChannel channelOut = new FileOutputStream(outputFilePath).getChannel()// FileChannel channelOut = new RandomAccessFile(outputFilePath, "rw").getChannel();) {// 方式一// 针对小于 2G 文件,超过 2G，超出部分会丢弃// long transferSize = channelIn.transferTo(0, channelIn.size(), channelOut);// 方式二: 针对大于2G的文件，分多次读写// 获取文件总大小long size = channelIn.size();for (long left = size; left > 0; ) {// 真实拷贝的长度， size - left 计算下次拷贝的位置long transferSize = channelIn.transferTo(size - left, left, channelOut);left = size - transferSize;}} catch (Exception e) {e.printStackTrace();}}}