利用java内存映射文件机制实现CRC循环冗余校验

import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.zip.CRC32;
public static void main(String[] args){
try { //对

import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel; import java.util.zip.CRC32; public static void main(String[] args){ try { //对文件进行crc校验 long begin = System.currentTimeMillis(); FileInputStream in = new FileInputStream("code.py");//指定目标文件 FileChannel channel = in.getChannel(); //从文件中获取一个通道 CRC32 crc = new CRC32(); int length = (int)channel.size(); MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, length); //用只读模式从该通道获取字节缓冲，实现文件到内存的映射 for(int i = 0;i<length;i++) { int c = buffer.get(i); crc.update(c);//按字节做crc } System.out.println("crc校验和："+(Long.toHexString(crc.getValue())).toUpperCase()); long end = System.currentTimeMillis(); System.out.println("运行"+(end-begin)+"ms"); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel; import java.util.zip.CRC32; public static void main(String[] args){ try { //对文件进行crc校验 long begin = System.currentTimeMillis(); FileInputStream in = new FileInputStream("code.py");//指定目标文件 FileChannel channel = in.getChannel(); //从文件中获取一个通道 CRC32 crc = new CRC32(); int length = (int)channel.size(); MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, length); //用只读模式从该通道获取字节缓冲，实现文件到内存的映射 for(int i = 0;i<length;i++) { int c = buffer.get(i); crc.update(c);//按字节做crc } System.out.println("crc校验和："+(Long.toHexString(crc.getValue())).toUpperCase()); long end = System.currentTimeMillis(); System.out.println("运行"+(end-begin)+"ms"); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } 运行结果： crc校验和：4831ACAC 运行16ms