标题: Java中的Deflate/Inflate

创建: 2020-08-11 15:05
更新:
链接: https://scz.617.cn/web/202008111505.txt

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/*
 * javac -encoding GBK -g DeflateTest.java
 * java DeflateTest src dst 0
 * java DeflateTest dst src 1
 */
import java.io.*;
import java.util.zip.*;

public class DeflateTest
{
    private static void PrivateCopy ( InputStream is, OutputStream os ) throws Exception
    {
        int b;

        while ( ( b = is.read() ) != -1 )
        {
            os.write( b );
        }
        os.close();
        is.close();
    }  /* end of PrivateCopy */

    private static void DeflateFile ( String src, String dst ) throws Exception
    {
        FileInputStream         fis = new FileInputStream( src );
        FileOutputStream        fos = new FileOutputStream( dst );
        /*
         * https://docs.oracle.com/javase/8/docs/api/java/util/zip/Deflater.html
         * https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/zip/Deflater.html
         *
         * https://docs.oracle.com/javase/8/docs/api/java/util/zip/DeflaterOutputStream.html
         */
        DeflaterOutputStream    dos = new DeflaterOutputStream
        (
            fos,
            /*
             * If the parameter nowrap is true then the ZLIB header and
             * checksum fields will not be used.
             */
            new Deflater( 9, false ),
            1024 * 1024
        );
        PrivateCopy( fis, dos );
    }  /* end of DeflateFile */

    private static void InflateFile ( String src, String dst ) throws Exception
    {
        FileInputStream         fis = new FileInputStream( src );
        /*
         * https://docs.oracle.com/javase/8/docs/api/java/util/zip/Inflater.html
         * https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/zip/Inflater.html
         *
         * https://docs.oracle.com/javase/8/docs/api/java/util/zip/InflaterInputStream.html
         */
        InflaterInputStream     iis = new InflaterInputStream
        (
            fis,
            new Inflater( false ),
            1024 * 1024
        );
        FileOutputStream        fos = new FileOutputStream( dst );
        PrivateCopy( iis, fos );
    }  /* end of InflateFile */

    public static void main ( String[] argv ) throws Exception
    {
        String  src     = argv[0];
        String  dst     = argv[1];
        int     mode    = Integer.parseInt( argv[2] );

        switch ( mode )
        {
        /*
         * 压缩
         */
        case 0 :
            DeflateFile( src, dst );
            break;
        /*
         * 解压
         */
        case 1 :
            InflateFile( src, dst );
            break;
        }
    }
}
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$ xxd -g 1 src
0000000: 73 63 7a 20 69 73 20 68 65 72 65                 scz is here

压缩:

$ java DeflateTest src dst 0
$ echo -ne 'scz is here' | python2 -c 'import sys,zlib;sys.stdout.write(zlib.compress(sys.stdin.read(),9))' > dst
$ cat src | python2 -c 'import sys,zlib;sys.stdout.write(zlib.compress(sys.stdin.read(),9))' > dst

$ xxd -g 1 dst
0000000: 78 da 2b 4e ae 52 c8 2c 56 c8 48 2d 4a 05 00 18  x.+N.R.,V.H-J...
0000010: 6d 04 11                                         m..

解压:

$ java DeflateTest dst src 1
$ cat dst | python2 -c 'import sys,zlib;sys.stdout.write(zlib.decompress(sys.stdin.read()))' > src
$ openssl zlib -d < dst > src

$ printf "\x1f\x8b\x08\x00\x00\x00\x00\x00" | cat - dst | gzip -dc > src

gzip: stdin: unexpected end of file

有个警告，但解压无误。