java.security > DigestInputStream :: 자주 쓰이는 메소드및 API 를 정리합니다.[SSISO Community]

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자주 쓰이는 메소드및 API 를 정리합니다.

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등록일:2008-03-18 15:31:29

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제목:java.security > DigestInputStream

new  DigestInputStream(InputStream  stream,  MessageDigest  digest)

import  java.io.BufferedInputStream;
import  java.io.FileInputStream;
import  java.io.IOException;
import  java.security.DigestInputStream;
import  java.security.MessageDigest;
import  java.security.NoSuchAlgorithmException;
import  java.security.Provider;
import  java.security.Security;
import  java.util.zip.CRC32;

public  class  MainClass  {
    static  private  String  hexDigit(byte  x)  {
        StringBuffer  sb  =  new  StringBuffer();
        char  c;
        //  First  nibble
        c  =  (char)  ((x  >>  4)  &  0xf);
        if  (c  >  9)  {
            c  =  (char)  ((c  -  10)  +  'a');
        }  else  {
            c  =  (char)  (c  +  '0');
        }
        sb.append(c);
        //  Second  nibble
        c  =  (char)  (x  &  0xf);
        if  (c  >  9)  {
            c  =  (char)  ((c  -  10)  +  'a');
        }  else  {
            c  =  (char)  (c  +  '0');
        }
        sb.append(c);
        return  sb.toString();
    }

    static  private  String  computeDigest(MessageDigest  algorithm,  String  filename)  {
        String  returnValue  =  "";
        try  {
            algorithm.reset();
            FileInputStream  fis  =  new  FileInputStream(filename);
            BufferedInputStream  bis  =  new  BufferedInputStream(fis);
            DigestInputStream  dis  =  new  DigestInputStream(bis,  algorithm);
            int  ch;
            while  ((ch  =  dis.read())  !=  -1)
                ;
            StringBuffer  hexString  =  new  StringBuffer();
            byte  digest[]  =  algorithm.digest();
            int  digestLength  =  digest.length;
            for  (int  i  =  0;  i  <  digestLength;  i++)  {
                hexString.append(hexDigit(digest[i]));
                hexString.append("  ");
            }
            returnValue  =  hexString.toString();
        }  catch  (IOException  e)  {
            System.err.println("Error  generating  digest  for:  "  +  filename);
        }
        return  returnValue;
    }

    public  static  void  main(String  args[])  {
        MessageDigest  algorithm  =  null;
        Security.addProvider(new  MyProvider());
        try  {
            algorithm  =  MessageDigest.getInstance("CRC32");
        }  catch  (NoSuchAlgorithmException  e)  {
            System.err.println("Invalid  algorithm");
            System.exit(-1);
        }
        int  argsLength  =  args.length;
        for  (int  i  =  0;  i  <  argsLength;  i++)  {
            String  digest  =  computeDigest(algorithm,  args[i]);
            System.out.println(args[i]  +  "  :  "  +  digest);

        }
    }
}

class  MyProvider  extends  Provider  {
    public  MyProvider()  {
        super("MyProvider",  1.0,  "Java2s.com  Collections  Example");
        put("CRC32",  "CRC");
    }
}

class  CRC  extends  MessageDigest  {
    CRC32  crc;

    public  CRC()  {
        super("CRC");
        crc  =  new  CRC32();
    }

    protected  void  engineReset()  {
        crc.reset();
    }

    protected  void  engineUpdate(byte  input)  {
        crc.update(input);
    }

    protected  void  engineUpdate(byte[]  input,  int  offset,  int  len)  {
        crc.update(input,  offset,  len);
    }

    protected  byte[]  engineDigest()  {
        long  l  =  crc.getValue();
        byte[]  bytes  =  new  byte[4];
        bytes[3]  =  (byte)  ((l  &  0xFF000000)  >>  24);
        bytes[2]  =  (byte)  ((l  &  0x00FF0000)  >>  16);
        bytes[1]  =  (byte)  ((l  &  0x0000FF00)  >>  8);
        bytes[0]  =  (byte)  ((l  &  0x000000FF)  >>  0);
        return  bytes;
    }
}

[본문링크] java.security > DigestInputStream

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