filedes.java

DSS数字签名

package encryption;

//chp6
//FileDES.java

import java.io.*;
import java.nio.*;
import java.nio.channels.FileChannel;

public class FileDES{
      private static final boolean enc=true;    //加密
      private static final boolean dec=false;	  //解密
      private String sourceFileName;
      private String targetFileName;
      private String inKey;
      private boolean encdes;
      private File sourceFile;
      private File targetFile;
      private Des des;
      
      
      private void getpath(){
              String pathname;
              int pos=sourceFileName.lastIndexOf("/");
              pathname=sourceFileName.substring(0,pos);  //取得文件路径
              File dir=new File(pathname);
              if (!dir.exists()){       //判断是否存在
                      System.err.println(pathname+" is not exist");
                      System.exit(1);
              }else if(!dir.isDirectory()){     //判断是否为目录
                      System.err.println(pathname+" is not a directory");
                      System.exit(1);
              }

              pos=targetFileName.lastIndexOf("/");
              pathname=targetFileName.substring(0,pos);
              dir=new File(pathname);
              if (!dir.exists()){
                      if(!dir.mkdirs()){
                              System.out.println ("can not creat directory:"+pathname);
                              System.exit(1);
                      }
              }else if(!dir.isDirectory()){
                      System.err.println(pathname+" is not a directory");
                      System.exit(1);
              }
      }

      private static int bufcontent(FileChannel channel,ByteBuffer buf) throws IOException{
              long byteLeft=channel.size()-channel.position();
              if(byteLeft==0L)
                      return -1;
              buf.position(0);
              buf.limit(buf.position()+(byteLeft<8 ? (int)byteLeft :8));
              return channel.read(buf);
      }

      private void fileAction(boolean flag){
              des=new Des(inKey);
              FileOutputStream outputFile=null;
              try {
                      outputFile=new FileOutputStream(sourceFile,true);
          }catch (java.io.FileNotFoundException e) {
              e.printStackTrace(System.err);
          }
          FileChannel outChannel=outputFile.getChannel();

          try{
                  if(outChannel.size()%2!=0){
                              ByteBuffer bufTemp=ByteBuffer.allocate(1);
                              bufTemp.put((byte)32);
                              bufTemp.flip();
                              outChannel.position(outChannel.size());
                              outChannel.write(bufTemp);
                              bufTemp.clear();
                      }
              }catch(Exception ex){
                      ex.printStackTrace(System.err);
                      System.exit(1);
              }
              FileInputStream inFile=null;
              try{
                      inFile=new FileInputStream(sourceFile);
              }catch(java.io.FileNotFoundException e){
                      e.printStackTrace(System.err);
              }
              outputFile=null;
              try {
                      outputFile=new FileOutputStream(targetFile,true);
          }catch (java.io.FileNotFoundException e) {
              e.printStackTrace(System.err);
          }

          FileChannel inChannel=inFile.getChannel();
              outChannel=outputFile.getChannel();

              ByteBuffer inBuf=ByteBuffer.allocate(8);
              ByteBuffer outBuf=ByteBuffer.allocate(8);

              try{
                      String sourceStr;
                      String targetStr;
                      while(true){
                              if (bufcontent(inChannel,inBuf)==-1) break;
                              sourceStr=((ByteBuffer)(inBuf.flip())).asCharBuffer().toString();
                              inBuf.clear();
                              if (flag)     //若为true，则加密
                                      targetStr=des.enc(sourceStr,sourceStr.length());
                              else          //若为false，则解密
                                      targetStr=des.dec(sourceStr,sourceStr.length());
                          outBuf.clear();
                          if (targetStr.length()==4){
                              for (int i = 0; i<4; i++) {
                                      outBuf.putChar(targetStr.charAt(i));
                              }
                              outBuf.flip();
                          }else{
                              outBuf.position(0);
                              outBuf.limit(2*targetStr.length());
                              for (int i = 0; i<targetStr.length(); i++) {
                                      outBuf.putChar(targetStr.charAt(i));
                              }
                              outBuf.flip();
                          }

                          try {
                              outChannel.write(outBuf);
                              outBuf.clear();
                      }catch (java.io.IOException ex) {
                              ex.printStackTrace(System.err);
                      }
                      }
                      System.out.println (inChannel.size());
                      System.out.println (outChannel.size());
                      System.out.println ("EoF reached.");
                      inFile.close();
                      outputFile.close();
              }catch(java.io.IOException e){
                      e.printStackTrace(System.err);
                      System.exit(1);
              }
      }

      public void FileDes(String sourceFileName,String targetFileName,String inKey,boolean encdes){
              
    	  this.sourceFileName=sourceFileName;
          this.targetFileName=targetFileName;
          this.encdes=encdes;
              sourceFile=new File(sourceFileName);
              targetFile=new File(targetFileName);
              this.inKey=inKey;
              if (encdes==enc)
                      fileAction(enc);  //执行加密操作
              else
                      fileAction(dec);  //执行解密操作
      }

}