Firmwares checksum algorithm - Printable Version

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/* zpipe.c: example of proper use of zlib's inflate() and deflate()

   Not copyrighted -- provided to the public domain

   Version 1.4  11 December 2005  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()

   1.4  11 Dec 2005  Add hack to avoid MSDOS end-of-line conversions

                     Avoid some compiler warnings for input and output buffers

 */



#include <stdio.h>

#include <string.h>

#include <assert.h>

#include "zlib.h"



#if defined(MSDOS) || defined(OS2) || defined(WIN32) || defined(__CYGWIN__)

#  include <fcntl.h>

#  include <io.h>

#  define SET_BINARY_MODE(file) setmode(fileno(file), O_BINARY)

#else

#  define SET_BINARY_MODE(file)

#endif



#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;

    unsigned char in[CHUNK];

    unsigned char out[CHUNK];



    /* allocate deflate state */

    strm.zalloc = Z_NULL;

    strm.zfree = Z_NULL;

    strm.opaque = Z_NULL;

    ret = deflateInit(&strm, level);

    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 (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;

    unsigned char in[CHUNK];

    unsigned char out[CHUNK];



    /* 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 = inflateInit(&strm);

    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;

        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;



    /* avoid end-of-line conversions */

    SET_BINARY_MODE(stdin);

    SET_BINARY_MODE(stdout);



    /* 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;

    }

}