Triforce Heroes SaveData checksum fixer

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

const unsigned int poly = 0x04C11DB7;

unsigned int reflect(unsigned int data, int bits) {
    unsigned int ret = 0;
    int i;
    for(i = bits-1; i>=0; i--) {
        if(data & 1) ret |= (1 << i);
        data >>= 1;
    }
    return ret;
}

unsigned int crc32(char* msg, int len) {
    unsigned int crc = 0xffffffff;
    int i, j;
    for(i = 0; i < len; i++) {
        crc ^= ((char)reflect(msg[i], 8) << 24);
        for(j = 8; j; j--) {
            crc = (crc << 1) ^ ((crc & 0x80000000) ? poly : 0x0);
        }
    }
    return reflect(crc, 32) ^ 0xffffffff;
}

int main(int argc, char **argv){
    if(argc < 2){
        printf("Usage: %s [SaveData.bin]\n", argv[0]);
        return -1;
    }

    FILE *fp;
    fp = fopen(argv[1], "rb+");
    if(!fp) return -1;
    int crc1 = 0, crc2 = 0, crc3 = 0;
    unsigned char *firstChunk = malloc(0x1FC);
    unsigned char *secondChunk = malloc(0x17FC);
    unsigned char *thirdChunk = malloc(0x11FC);
    //Get chunks
    fread(firstChunk, 1, 0x1FC, fp);
    fseek(fp, 0x200, SEEK_SET);
    fread(secondChunk, 1, 0x17FC, fp);
    fseek(fp, 0x1A00, SEEK_SET);
    fread(thirdChunk, 1, 0x11FC, fp);
    //Get CRCs
    crc1 = crc32(firstChunk, 0x1FC);
    crc2 = crc32(secondChunk, 0x17FC);
    crc3 = crc32(thirdChunk, 0x11FC);
    //Write CRCs
    fseek(fp, 0x1FC, SEEK_SET);
    fwrite(&crc1, sizeof(int),1, fp);
    fseek(fp, 0x19FC, SEEK_SET);
    fwrite(&crc2, sizeof(int),1, fp);
    fseek(fp, 0x2BFC, SEEK_SET);
    fwrite(&crc3, sizeof(int),1, fp);
    fclose(fp);
    printf("First check = 0x%08X\n", crc1);
    printf("Second check = 0x%08X\n", crc2);
    printf("Third check = 0x%08X\n", crc3);
    free(firstChunk);
    free(secondChunk);
    free(thirdChunk);
    return 0;
}