Bitcoin transaction file dumper

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

static FILE *f;


void doczytaj(unsigned char *p, int len) {
    if (fread(p, 1, len, f)!=len) {
        fprintf(stderr, "File too short\n");
        fclose(f);
        exit(1);
    }
}

unsigned long long getle(unsigned char *p, int bytes) {
    unsigned long long res=0;
    while (bytes--) {
        res|= p[bytes]<<(8*bytes);
    }
    return res;
}

unsigned long long getvl() {
    unsigned char b[8];
    doczytaj(b, 1);
    switch (*b) {
        case 0xfd:
            doczytaj(b, 2);
            return getle(b, 2);
        case 0xfe:
            doczytaj(b, 4);
            return getle(b, 4);
        case 0xff:
            doczytaj(b, 8);
            return getle(b, 8);
    }
    return *b;
}


void prhash(unsigned char *p, unsigned int l) {
    while (l--) printf("%02x", p[l]);
}


int main(int argc, char * argv[]) {
    static unsigned char buf[0x10000];
    unsigned long long i, sl, txcnt, v;

    if (argc!=2) {
        printf("Specify the filename of the transaction file (.btd)\n");
        return 1;
    }

    f = fopen(argv[1], "rb");
    if (!f) {
        fprintf(stderr, "File %s not found\n", argv[1]);
        return 1;
    }

    doczytaj(buf, 4);
    printf("Version: %llu\n", getle(buf, 4));

    txcnt = getvl();
    printf("TX IN cnt: %llu\n", txcnt);
    for (i=0; i<txcnt; i++) {
        doczytaj(buf, 36);
        sl = getvl();

        printf("  %lld) : ", i);
        prhash(buf, 32);
        printf(" Idx=%2lld  sl=%lld", getle(buf+32, 4), sl);
        doczytaj(buf, sl);
        doczytaj(buf, 4);

        printf(" seq=%x\n", (unsigned)getle(buf, 4));
    }

    txcnt = getvl();
    printf("TX OUT cnt: %llu\n", txcnt);
    for (i=0; i<txcnt; i++) {
        doczytaj(buf, 8);
        sl = getvl();
        v = getle(buf, 8);
        printf("  %lld) : %lld.%8lld BTC    sl=%lld\n", i, v/100000000, v%100000000, sl);
        doczytaj(buf, sl);
    }

    doczytaj(buf, 4);
    printf("Lock Time: %llu\n", getle(buf, 4));

    fclose(f);
    return 0;
}