#include <stdio.h>
#include <stdlib.h>

static const char usage[] = /* .. */
    {"zzipsetstub <zipfile> <zipsfxstub>... \n"
     " overwrite the header of the zipfile with the sfxstub code.\n"
     " this is usually the last step in creating a selfextract archive\n"
     " or an application with all its data appended as a zip.\n"};

int
main(int argc, char** argv)
{
    int argn;
    if (argc <= 2) {
        printf(usage);
        exit(0);
    }

    {
        char  buf[17];
        int   n;
        char* zipfile = 0;
        FILE* zipFILE = 0;
        char* sfxfile = 0;
        FILE* sfxFILE = 0;

        for (argn = 1; argn < argc; argn++) {
            if (argv[argn][0] == '-')
                continue;
            if (! zipfile) {
                zipfile = argv[argn];
                continue;
            }
            if (! sfxfile) {
                sfxfile = argv[argn];
                continue;
            }
            /* superflous argument */
        }

        zipFILE = fopen(zipfile, "r+b");
        if (! zipFILE) {
            perror(zipfile);
            return 1;
        }

        sfxFILE = fopen(sfxfile, "rb");
        if (! sfxFILE) {
            perror(sfxfile);
            return 1;
        }

        while (0 < (n = fread(buf, 1, 16, sfxFILE))) {
            buf[n] = '\0';
            fwrite(buf, 1, n, zipFILE);
        }

        if (n == -1)
            perror(argv[argn]);

        fclose(sfxFILE);
        fclose(zipFILE);
    }

    return 0;
}
