www.pudn.com > gzip.rar > gzip.c

/* gzip (GNU zip) -- compress files with zip algorithm and 'compress' interface 
 * Copyright (C) 1992-1993 Jean-loup Gailly 
 * The unzip code was written and put in the public domain by Mark Adler. 
 * Portions of the lzw code are derived from the public domain 'compress' 
 * written by Spencer Thomas, Joe Orost, James Woods, Jim McKie, Steve Davies, 
 * Ken Turkowski, Dave Mack and Peter Jannesen. 
 * 
 * See the license_msg below and the file COPYING for the software license. 
 * See the file algorithm.doc for the compression algorithms and file formats. 
 */ 
 
/* Compress files with zip algorithm and 'compress' interface. 
 * See usage() and help() functions below for all options. 
 * Outputs: 
 *        file.gz:   compressed file with same mode, owner, and utimes 
 *     or stdout with -c option or if stdin used as input. 
 * If the output file name had to be truncated, the original name is kept 
 * in the compressed file. 
 * On MSDOS, file.tmp -> file.tmz. On VMS, file.tmp -> file.tmp-gz. 
 * 
 * Using gz on MSDOS would create too many file name conflicts. For 
 * example, foo.txt -> foo.tgz (.tgz must be reserved as shorthand for 
 * tar.gz). Similarly, foo.dir and foo.doc would both be mapped to foo.dgz. 
 * I also considered 12345678.txt -> 12345txt.gz but this truncates the name 
 * too heavily. There is no ideal solution given the MSDOS 8+3 limitation. 
 * 
 * For the meaning of all compilation flags, see comments in Makefile.in. 
 */ 
#include  
#include "zipmem.h" 
#include "gzip.h" 
#include "lzw.h" 
 
/* global buffers */ 
 
DECLARE( uch, inbuf,  INBUFSIZ + INBUF_EXTRA ); 
DECLARE( uch, outbuf, OUTBUFSIZ + OUTBUF_EXTRA ); 
DECLARE( ush, d_buf,  DIST_BUFSIZE ); 
DECLARE( uch, window, 2L * WSIZE ); /* 声明 */ 
DECLARE( ush, tab_prefix, 1L << BITS ); 
 
/* local variables */ 
int quiet = 0;        /* be very quiet (-q) */ 
int maxbits = BITS;   /* max bits per code for LZW */ 
int method = DEFLATED;/* compression method */ 
int level = 6;        /* compression level */ 
int exit_code = 0;   /* program exit code */ 
int time_stamp;      /* original time stamp (modification time) */ 
 
int bytes_in = 0;             /* number of input bytes */ 
int bytes_out = 0;            /* number of output bytes */ 
int total_in = 0;         /* input bytes for all files */ 
int total_out = 0;        /* output bytes for all files */ 
unsigned insize = 0;           /* valid bytes in inbuf */ 
unsigned inptr = 0;            /* index of next byte to be processed in inbuf */ 
unsigned outcnt = 0;           /* bytes in output buffer */ 
 
local int  get_method   OF(()); 
 
int (* work ) OF(()) = zip; /* function to call */ 
 
/* ======================================================================== 
 * Compress 
 */ 
int zipmem( char * mem_inptr, int mem_insize, char * mem_outptr ) 
{ 
    time_stamp = 0; 
    ALLOC( uch, inbuf,  INBUFSIZ + INBUF_EXTRA ); 
    ALLOC( uch, outbuf, OUTBUFSIZ + OUTBUF_EXTRA ); 
    ALLOC( ush, d_buf,  DIST_BUFSIZE ); 
    ALLOC( uch, window, 2L * WSIZE ); /* 分配 */ 
    ALLOC( ush, tab_prefix, 1L << BITS ); 
    clear_bufs(); /* clear input and output buffers */ 
    zip_mem_outptr = mem_outptr; /* 输出缓存 */ 
    zip_mem_outlen = 0; /* 输出缓存大小 */ 
    zip_mem_inptr = mem_inptr; /* 输入指针 */ 
    zip_mem_insize = mem_insize; /* 输入缓存长度 */ 
    zip_mem_inpos = 0; /* 输入缓存当前位置 */ 
    zip(); 
    FREE( inbuf ); 
    FREE( outbuf ); 
    FREE( d_buf ); 
    FREE( window ); 
    FREE( tab_prefix ); 
    return zip_mem_outlen; 
} 
 
/* ======================================================================== 
 * deCompress 
 */ 
int unzipmem( char * mem_inptr, int mem_insize, char * mem_outptr ) 
{ 
    time_stamp = 0; 
    ALLOC( uch, inbuf,  INBUFSIZ + INBUF_EXTRA ); 
    ALLOC( uch, outbuf, OUTBUFSIZ + OUTBUF_EXTRA ); 
    ALLOC( ush, d_buf,  DIST_BUFSIZE ); 
    ALLOC( uch, window, 2L * WSIZE );/* 分配 */ 
    ALLOC( ush, tab_prefix, 1L << BITS ); 
    clear_bufs(); /* clear input and output buffers */ 
    zip_mem_outptr = mem_outptr; /* 输出缓存 */ 
    zip_mem_outlen = 0; /* 输出缓存大小 */ 
    /* 解压缩 */ 
    unzip_mem_inptr = mem_inptr; /* 输入指针 */ 
    unzip_mem_insize = mem_insize; /* 输入缓存长度 */ 
    unzip_mem_inpos = 0; /* 输入缓存当前位置 */ 
    get_method(); 
    unzip(); 
    FREE( inbuf ); 
    FREE( outbuf ); 
    FREE( d_buf ); 
    FREE( window ); 
    FREE( tab_prefix ); 
    return zip_mem_outlen; 
} 
 
/* ======================================================================== 
 * Check the magic number of the input file and update ofname if an 
 * original name was given and to_stdout is not set. 
 * Return the compression method, -1 for error, -2 for warning. 
 * Set inptr to the offset of the next byte to be processed. 
 * Updates time_stamp if there is one and --no-time is not used. 
 * This function may be called repeatedly for an input file consisting 
 * of several contiguous gzip'ed members. 
 * IN assertions: there is at least one remaining compressed member. 
 *   If the member is a zip file, it must be the only one. 
 */ 
local int get_method() 
{ 
    /* If --force and --stdout, zcat == cat, so do not complain about 
     * premature end of file: use try_byte instead of get_byte. 
     */ 
    ( char )get_byte(); 
    ( char )get_byte(); 
    method = - 1;                 /* unknown yet */ 
    /* assume multiple members in gzip file except for record oriented I/O */ 
 
    method = ( int )get_byte(); 
    work = unzip; 
    ( uch )get_byte(); 
    ( ulg )get_byte(); 
    (( ulg )get_byte()); 
    (( ulg )get_byte()); 
    (( ulg )get_byte()); 
    ( void )get_byte();  /* Ignore extra flags for the moment */ 
    ( void )get_byte();  /* Ignore OS type for the moment */ 
 
    return method; 
}