zpipe.c with modified magic numbers

zpipe.c

/* zpipe.c: example of proper use of zlib's inflate() and deflate()
   Not copyrighted -- provided to the public domain
   Version 1.2  9 November 2004  Mark Adler */

/* Version history:
   1.0  30 Oct 2004  First version
   1.1   8 Nov 2004  Add void casting for unused return values
                     Use switch statement for inflate() return values
   1.2   9 Nov 2004  Add assertions to document zlib guarantees
   1.3   6 Apr 2005  Remove incorrect assertion in inf()
 */

#include <stdio.h>
#include <string.h>
#include <assert.h>
#include "zlib.h"

#include <sys/types.h>
#include <sys/stat.h>

#define CHUNK 16384

/* Compress from file source to file dest until EOF on source.
   def() returns Z_OK on success, Z_MEM_ERROR if memory could not be
   allocated for processing, Z_STREAM_ERROR if an invalid compression
   level is supplied, Z_VERSION_ERROR if the version of zlib.h and the
   version of the library linked do not match, or Z_ERRNO if there is
   an error reading or writing the files. */
int def(FILE *source, FILE *dest, int level)
{
    int ret, flush;
    unsigned have;
    z_stream strm;
    char in[CHUNK];
    char out[CHUNK];
    char *buf;
    unsigned long dest_size;
    unsigned long indx = 0;
    struct stat sb;

    have = fileno(source);

    if (fstat(have, &sb) < 0)
        return Z_ERRNO;

    if (!S_ISREG(sb.st_mode))
        return Z_ERRNO;

    if ((dest_size = (unsigned long)sb.st_size) <= 0)
        return Z_ERRNO;

    if (fwrite(&dest_size, 4, 1, dest) != 1 || ferror(dest))
        return Z_ERRNO;

    /* allocate deflate state */
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    ret = deflateInit2(&strm, level, Z_DEFLATED, -MAX_WBITS, 8, Z_DEFAULT_STRATEGY);
    if (ret != Z_OK)
        return ret;

    /* compress until end of file */
    do {
        strm.avail_in = fread(in, 1, CHUNK, source);
        if (ferror(source)) {
            (void)deflateEnd(&strm);
            return Z_ERRNO;
        }
        flush = feof(source) ? Z_FINISH : Z_NO_FLUSH;
        strm.next_in = in;

        /* run deflate() on input until output buffer not full, finish
           compression if all of source has been read in */
        do {
            strm.avail_out = CHUNK;
            strm.next_out = out;
            ret = deflate(&strm, flush);    /* no bad return value */
            assert(ret != Z_STREAM_ERROR);  /* state not clobbered */
            have = CHUNK - strm.avail_out;
            if (have > 0) {
                buf = out;

                do {
                    if (dest_size > indx++) {
                        switch (indx) {
                        case 1:
                            *buf ^= 0x92;
                            break;
                        case 2:
                            *buf ^= 0x65;
                            break;
                        case 3:
                            *buf ^= 0x67;
                            break;
                        case 4:
                            *buf ^= 0x57;
                        }
                    }
                } while (*buf++);

                if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
                    (void)deflateEnd(&strm);
                    return Z_ERRNO;
                }
            }
        } while (strm.avail_out == 0);
        assert(strm.avail_in == 0);     /* all input will be used */

        /* done when last data in file processed */
    } while (flush != Z_FINISH);
    assert(ret == Z_STREAM_END);        /* stream will be complete */

    /* clean up and return */
    (void)deflateEnd(&strm);
    return Z_OK;
}

/* Decompress from file source to file dest until stream ends or EOF.
   inf() returns Z_OK on success, Z_MEM_ERROR if memory could not be
   allocated for processing, Z_DATA_ERROR if the deflate data is
   invalid or incomplete, Z_VERSION_ERROR if the version of zlib.h and
   the version of the library linked do not match, or Z_ERRNO if there
   is an error reading or writing the files. */
int inf(FILE *source, FILE *dest)
{
    int ret;
    unsigned have;
    z_stream strm;
    char in[CHUNK];
    char out[CHUNK];
    char *buf;
    unsigned long dest_size;
    unsigned long indx = 0;

    have = fread(in, 1, 4, source);

    if (have != 4 || ferror(source)) {
        return Z_ERRNO;
    }

    dest_size = ((unsigned long)in[0]) |
                ((unsigned long)in[1] << 8) | 
                ((unsigned long)in[2] << 16) | 
                ((unsigned long)in[3] << 24);

    /* allocate inflate state */
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    strm.avail_in = 0;
    strm.next_in = Z_NULL;
    ret = inflateInit2(&strm, -MAX_WBITS);
    if (ret != Z_OK)
        return ret;

    /* decompress until deflate stream ends or end of file */
    do {
        strm.avail_in = fread(in, 1, CHUNK, source);
        if (ferror(source)) {
            (void)inflateEnd(&strm);
            return Z_ERRNO;
        }
        if (strm.avail_in == 0)
            break;

        buf = in;

        do {
            if (dest_size > indx++) {
                switch (indx) {
                case 1:
                    *buf ^= 0x92;
                    break;
                case 2:
                    *buf ^= 0x65;
                    break;
                case 3:
                    *buf ^= 0x67;
                    break;
                case 4:
                    *buf ^= 0x57;
                }
            }
        } while (*buf++);

        strm.next_in = in;

        /* run inflate() on input until output buffer not full */
        do {
            strm.avail_out = CHUNK;
            strm.next_out = out;
            ret = inflate(&strm, Z_NO_FLUSH);
            assert(ret != Z_STREAM_ERROR);  /* state not clobbered */
            switch (ret) {
            case Z_NEED_DICT:
                ret = Z_DATA_ERROR;     /* and fall through */
            case Z_DATA_ERROR:
            case Z_MEM_ERROR:
                (void)inflateEnd(&strm);
                return ret;
            }
            have = CHUNK - strm.avail_out;
            if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
                (void)inflateEnd(&strm);
                return Z_ERRNO;
            }
        } while (strm.avail_out == 0);

        /* done when inflate() says it's done */
    } while (ret != Z_STREAM_END);

    /* clean up and return */
    (void)inflateEnd(&strm);
    return ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR;
}

/* report a zlib or i/o error */
void zerr(int ret)
{
    fputs("zpipe: ", stderr);
    switch (ret) {
    case Z_ERRNO:
        if (ferror(stdin))
            fputs("error reading stdin\n", stderr);
        if (ferror(stdout))
            fputs("error writing stdout\n", stderr);
        break;
    case Z_STREAM_ERROR:
        fputs("invalid compression level\n", stderr);
        break;
    case Z_DATA_ERROR:
        fputs("invalid or incomplete deflate data\n", stderr);
        break;
    case Z_MEM_ERROR:
        fputs("out of memory\n", stderr);
        break;
    case Z_VERSION_ERROR:
        fputs("zlib version mismatch!\n", stderr);
    }
}

/* compress or decompress from stdin to stdout */
int main(int argc, char **argv)
{
    int ret;

    /* do compression if no arguments */
    if (argc == 1) {
        ret = def(stdin, stdout, Z_DEFAULT_COMPRESSION);
        if (ret != Z_OK)
            zerr(ret);
        return ret;
    }

    /* do decompression if -d specified */
    else if (argc == 2 && strcmp(argv[1], "-d") == 0) {
        ret = inf(stdin, stdout);
        if (ret != Z_OK)
            zerr(ret);
        return ret;
    }

    /* otherwise, report usage */
    else {
        fputs("zpipe usage: zpipe [-d] < source > dest\n", stderr);
        return 1;
    }
}