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zlib/examples/gun.c  view on Meta::CPAN

   1.0  16 Feb 2003  First version for testing of inflateBack()
   1.1  21 Feb 2005  Decompress concatenated gzip streams
                     Remove use of "this" variable (C++ keyword)
                     Fix return value for in()
                     Improve allocation failure checking
                     Add typecasting for void * structures
                     Add -h option for command version and usage
                     Add a bunch of comments
   1.2  20 Mar 2005  Add Unix compress (LZW) decompression
                     Copy file attributes from input file to output file
   1.3  12 Jun 2005  Add casts for error messages [Oberhumer]
   1.4   8 Dec 2006  LZW decompression speed improvements
   1.5   9 Feb 2008  Avoid warning in latest version of gcc
   1.6  17 Jan 2010  Avoid signed/unsigned comparison warnings
   1.7  12 Aug 2012  Update for z_const usage in zlib 1.2.8
 */

/*
   gun [ -t ] [ name ... ]

   decompresses the data in the named gzip files.  If no arguments are given,
   gun will decompress from stdin to stdout.  The names must end in .gz, -gz,
   .z, -z, _z, or .Z.  The uncompressed data will be written to a file name
   with the suffix stripped.  On success, the original file is deleted.  On
   failure, the output file is deleted.  For most failures, the command will
   continue to process the remaining names on the command line.  A memory
   allocation failure will abort the command.  If -t is specified, then the
   listed files or stdin will be tested as gzip files for integrity (without
   checking for a proper suffix), no output will be written, and no files
   will be deleted.

   Like gzip, gun allows concatenated gzip streams and will decompress them,
   writing all of the uncompressed data to the output.  Unlike gzip, gun allows
   an empty file on input, and will produce no error writing an empty output
   file.

   gun will also decompress files made by Unix compress, which uses LZW
   compression.  These files are automatically detected by virtue of their
   magic header bytes.  Since the end of Unix compress stream is marked by the
   end-of-file, they cannot be concatenated.  If a Unix compress stream is
   encountered in an input file, it is the last stream in that file.

   Like gunzip and uncompress, the file attributes of the original compressed
   file are maintained in the final uncompressed file, to the extent that the
   user permissions allow it.

   On my Mac OS X PowerPC G4, gun is almost twice as fast as gunzip (version
   1.2.4) is on the same file, when gun is linked with zlib 1.2.2.  Also the
   LZW decompression provided by gun is about twice as fast as the standard
   Unix uncompress command.
 */

/* external functions and related types and constants */
#include <stdio.h>          /* fprintf() */
#include <stdlib.h>         /* malloc(), free() */
#include <string.h>         /* strerror(), strcmp(), strlen(), memcpy() */
#include <errno.h>          /* errno */
#include <fcntl.h>          /* open() */
#include <unistd.h>         /* read(), write(), close(), chown(), unlink() */
#include <sys/types.h>
#include <sys/stat.h>       /* stat(), chmod() */
#include <utime.h>          /* utime() */
#include "zlib.h"           /* inflateBackInit(), inflateBack(), */
                            /* inflateBackEnd(), crc32() */

/* function declaration */
#define local static

/* buffer constants */
#define SIZE 32768U         /* input and output buffer sizes */
#define PIECE 16384         /* limits i/o chunks for 16-bit int case */

/* structure for infback() to pass to input function in() -- it maintains the
   input file and a buffer of size SIZE */
struct ind {
    int infile;
    unsigned char *inbuf;
};

/* Load input buffer, assumed to be empty, and return bytes loaded and a
   pointer to them.  read() is called until the buffer is full, or until it
   returns end-of-file or error.  Return 0 on error. */
local unsigned in(void *in_desc, z_const unsigned char **buf)
{
    int ret;
    unsigned len;
    unsigned char *next;
    struct ind *me = (struct ind *)in_desc;

    next = me->inbuf;
    *buf = next;
    len = 0;
    do {
        ret = PIECE;
        if ((unsigned)ret > SIZE - len)
            ret = (int)(SIZE - len);
        ret = (int)read(me->infile, next, ret);
        if (ret == -1) {
            len = 0;
            break;
        }
        next += ret;
        len += ret;
    } while (ret != 0 && len < SIZE);
    return len;
}

/* structure for infback() to pass to output function out() -- it maintains the
   output file, a running CRC-32 check on the output and the total number of
   bytes output, both for checking against the gzip trailer.  (The length in
   the gzip trailer is stored modulo 2^32, so it's ok if a long is 32 bits and
   the output is greater than 4 GB.) */
struct outd {
    int outfile;
    int check;                  /* true if checking crc and total */
    unsigned long crc;
    unsigned long total;
};

/* Write output buffer and update the CRC-32 and total bytes written.  write()
   is called until all of the output is written or an error is encountered.

zlib/examples/gun.c  view on Meta::CPAN

        }
        if (last == -1) break;

        /* set up output */
        outd.outfile = outfile;
        outd.check = 1;
        outd.crc = crc32(0L, Z_NULL, 0);
        outd.total = 0;

        /* decompress data to output */
        strm->next_in = next;
        strm->avail_in = have;
        ret = inflateBack(strm, in, indp, out, &outd);
        if (ret != Z_STREAM_END) break;
        next = strm->next_in;
        have = strm->avail_in;
        strm->next_in = Z_NULL;             /* so Z_BUF_ERROR means EOF */

        /* check trailer */
        ret = Z_BUF_ERROR;
        if (NEXT() != (int)(outd.crc & 0xff) ||
            NEXT() != (int)((outd.crc >> 8) & 0xff) ||
            NEXT() != (int)((outd.crc >> 16) & 0xff) ||
            NEXT() != (int)((outd.crc >> 24) & 0xff)) {
            /* crc error */
            if (last != -1) {
                strm->msg = (char *)"incorrect data check";
                ret = Z_DATA_ERROR;
            }
            break;
        }
        if (NEXT() != (int)(outd.total & 0xff) ||
            NEXT() != (int)((outd.total >> 8) & 0xff) ||
            NEXT() != (int)((outd.total >> 16) & 0xff) ||
            NEXT() != (int)((outd.total >> 24) & 0xff)) {
            /* length error */
            if (last != -1) {
                strm->msg = (char *)"incorrect length check";
                ret = Z_DATA_ERROR;
            }
            break;
        }

        /* go back and look for another gzip stream */
    }

    /* clean up and return */
    return ret;
}

/* Copy file attributes, from -> to, as best we can.  This is best effort, so
   no errors are reported.  The mode bits, including suid, sgid, and the sticky
   bit are copied (if allowed), the owner's user id and group id are copied
   (again if allowed), and the access and modify times are copied. */
local void copymeta(char *from, char *to)
{
    struct stat was;
    struct utimbuf when;

    /* get all of from's Unix meta data, return if not a regular file */
    if (stat(from, &was) != 0 || (was.st_mode & S_IFMT) != S_IFREG)
        return;

    /* set to's mode bits, ignore errors */
    (void)chmod(to, was.st_mode & 07777);

    /* copy owner's user and group, ignore errors */
    (void)chown(to, was.st_uid, was.st_gid);

    /* copy access and modify times, ignore errors */
    when.actime = was.st_atime;
    when.modtime = was.st_mtime;
    (void)utime(to, &when);
}

/* Decompress the file inname to the file outnname, of if test is true, just
   decompress without writing and check the gzip trailer for integrity.  If
   inname is NULL or an empty string, read from stdin.  If outname is NULL or
   an empty string, write to stdout.  strm is a pre-initialized inflateBack
   structure.  When appropriate, copy the file attributes from inname to
   outname.

   gunzip() returns 1 if there is an out-of-memory error or an unexpected
   return code from gunpipe().  Otherwise it returns 0.
 */
local int gunzip(z_stream *strm, char *inname, char *outname, int test)
{
    int ret;
    int infile, outfile;

    /* open files */
    if (inname == NULL || *inname == 0) {
        inname = "-";
        infile = 0;     /* stdin */
    }
    else {
        infile = open(inname, O_RDONLY, 0);
        if (infile == -1) {
            fprintf(stderr, "gun cannot open %s\n", inname);
            return 0;
        }
    }
    if (test)
        outfile = -1;
    else if (outname == NULL || *outname == 0) {
        outname = "-";
        outfile = 1;    /* stdout */
    }
    else {
        outfile = open(outname, O_CREAT | O_TRUNC | O_WRONLY, 0666);
        if (outfile == -1) {
            close(infile);
            fprintf(stderr, "gun cannot create %s\n", outname);
            return 0;
        }
    }
    errno = 0;

    /* decompress */
    ret = gunpipe(strm, infile, outfile);
    if (outfile > 2) close(outfile);