PSET 4 Recover - Only recovering part of the photo?

Question

My program to recover JPGs runs and creates the files, but was failing check50. So I ran the debugger, and it looks like it's only recovering a small portion of each JPG. Not sure what I'm doing wrong, and having a hard enough time wrapping my head around this PSET in general, so fixing it has proven to be super frustrating. Help would be appreciated!

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

typedef uint8_t BYTE;

int main(int argc, char *argv[])
{
    //check argc to ensure only 1 (technically 2) command line arguments are present
        //if more or less, return Usage: ./recover image
    if (argc != 2)
    {
        printf("Error: Must include file name to recover from only.\n");
        return 1;
    }

    //open memory card in read mode
    FILE *card = fopen(argv[1], "r");

    //if it can't find the file, return error
    if (card == NULL)
    {
        printf("Error: Cannot read file.\n");
        return 2;
    }

    // Open our first file.
    int counter = 0;

    FILE *output = NULL;

    // Create a 512 byte buffer.
    BYTE buffer[512];

    // while we're not at the end of the card.raw file, read 512 bytes {
    while (fread(buffer, sizeof(BYTE), 512, card))
    {
      // at this point we have 512 bytes of the file.
      // check the first 3 to see is a JPG AND.. if we convert hex to binary, then check the high 4 bit and it's 1110  {
      if (buffer[0] == 0xff
          && buffer[1] == 0xd8
          && buffer[2] == 0xff
          && (buffer[3] >= 0xe0 && buffer[3] < 0xf0))
          {

          // YES
          // are we working on another jpg?
          if (output) {
            fclose(output);
          }

        // YES: close the other file.
        // start a new jpg file outout
        counter++;
        char filename[8];
        sprintf(filename, "%03d.jpg", (counter - 1));
        output = fopen(filename, "w");

      //  char filename[8] = ("output%d.jpg", counter); // output0.jpg, output1.jpg...
      //  FILE *output = fopen(filename, "w");

        // copy the 512 to the new jpg output
        fwrite(buffer, 512, 1, output);
      }
      if (output != NULL)
      {
        // NO
        // continue copying
        fwrite(buffer, 512, 1, output);
      }

    }

    // also close the very last file.
    fclose(output);

    // close the card.raw file
    fclose(card);

}

Answer 1

You should do a little indentation in your code to make it more readable. You can use 'style50' from cs50 IDE. If you do that, you'll see that you missed an 'else' condition someplace in your code, that is causing that 'fwrite'is executing twice every loop iteration.