/* POSIX crc32/adler32 checksum program; requires zlib (a.k.a. libz)
 * Compile:    cc -o zsum32 zsum32.c -lz
 */

#include <zlib.h>

#include <errno.h>
#include <stdio.h>
#include <string.h>

#define BUFSIZE     (8192*4)

int
main(int argc, char **argv) {
    int estat = 0, erri = 0;
    FILE *f;
    uLong adler, crc;
    const char *errs = NULL;
    auto char buffer[BUFSIZE];

    if (argc != 2) {
        erri = EINVAL;
        errs = "Usage zsum32 FILE";
        goto jerror_noc;
    }
    ++argv;

    f = fopen(*argv, "rb");
    if (f == NULL) {
        erri = errno;
        errs = "fopen()ing the file failed";
        goto jerror_noc;
    }

    adler = adler32(0L, Z_NULL, 0);
    crc = 0;
    for (;;) {
        size_t rb = fread(buffer, 1, BUFSIZE, f);
        if (rb > 0) {
            adler = adler32(adler, (const Bytef*)buffer, (uInt)rb);
            crc = crc32(crc, (const Bytef*)buffer, (uInt)rb);
            continue;
        }
        if (feof(f))
            break;
        erri = errno;
        errs = "fread()ing the file failed";
        goto jerror;
    }
    printf("Adler-32 <%lx> CRC-32 <%lx> -- %s\n",
           (unsigned long)adler, (unsigned long)crc, *argv);

    (void)fclose(f);
jleave:
    return estat;

jerror:
    (void)fclose(f);
jerror_noc:
    fprintf(stderr, "%s: %s\n", errs, strerror(erri));
    estat = 1;
    goto jleave;
}