jpg io in C (from harvard cs50 [dont cheat])

/**
 * recover.c
 *
 * Computer Science 50
 * Problem Set 4
 *
 * Recovers JPEGs from a forensic image.
 */
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

typedef uint8_t BYTE;

int main(void)
{
    FILE* cardptr = fopen("./card.raw","r");
    // open up file ^, check if null
    if (cardptr == NULL) {
        printf("Something went wrong!\n");
        return 1;
    }
    // init counter for file name
    int counter = 0;
    char name[10];

    BYTE* piece = malloc(sizeof(BYTE)*512);
    if (piece == NULL) {
        printf("Couldn't allocate memory for piece.\n");
        return 2;
    }
    //read the first block from the file
    while (fread(piece, sizeof(BYTE), 512, cardptr) && piece != NULL) {
        // check for jpeg header
        if (piece[0] == 0xff && piece[1] == 0xd8 && piece[2] == 0xff && (piece[3] >= 0xe0 && piece[3] <= 0xef)) {
            // update counter and name
            sprintf(name, "./%03d.jpg", counter);
            counter++; //inc counter

            // open a new file with the name ###.jpg
            FILE* jpeg = fopen(name, "w"); // dont forget w instead of r, silly goose!
            if (jpeg == NULL) {
                printf("Failed to open file %s\n", name);
                return 2;
            }
            // write the block to jpeg
            fwrite(piece, sizeof(BYTE), 512, jpeg); // write the jpg header to it

            // read piece again
            fread(piece, sizeof(BYTE), 512, cardptr);
            // while the jpg is still there, keep reading and writing 1 block at a time
            // this works because each jpg starts on a new block
            while (piece != NULL) {

                // write to file
                fwrite(piece, sizeof(BYTE), 512, jpeg);
                // check for end of file, read simult
                if (fread(piece, sizeof(BYTE), 512, cardptr) < 512) {
                    fclose(jpeg); // close and free everything
                    free(piece); // ^
                    fclose(cardptr); // ^^
                    return 0;
                }
                // check if next block is header
                if (piece[0] == 0xff && piece[1] == 0xd8 && piece[2] == 0xff && (piece[3] >= 0xe0 && piece[3] <= 0xef) ) {
                    fseek(cardptr, -512, SEEK_CUR); // roll back one, while loop reverses
                    break; // break out of inner loop
                }
            }
            fclose(jpeg); // close the file
        }
    }
    // memo frees
    free(piece);

    fclose(cardptr);
}