Pset4 recover produces only 2 corrupted iamges

Question

I am at Pset4 recover pset. When I run my code, it produces only 2 corrupted images

here is my code :

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

typedef uint8_t BYTE;

int main(int argc, char *argv[])
{
  // validate input number
  if( argc != 2)
  {
    printf("Usage: ./recover filename. \n");
    return 1;
  }

    // validte recovery storage file
    FILE *input = fopen(argv[1], "r");
  if( input == NULL)
  {
    printf("Coudn't open file.\n");
    return 1;
  }

  // read from input file
  // placeholder from each img block == 512 bytes
  BYTE bytes[512];
  //images counter for naming
  int numOfImgs = 0;
  // placeholder for image name "string"
  char filename[8];
  // placeholder for image data to bestored before exporting to external file
  FILE *img;
  // check if reach ennd of memory card
  while( fread(bytes, sizeof(bytes), 1, input) > 0)
  {
    // read 1 block from card
    fread(bytes, sizeof(bytes), 1, input);
    // current block is a starting of valid jpeg image
    if( bytes[0] == 0xff && bytes[1] == 0xd8 && bytes[2] == 0xff && (bytes[3] & 0xf0) == 0xe0)
    {
      // if JPEG found is the first one
      if( numOfImgs == 0)
      {
        // create a sequenced name
        sprintf(filename, "%03i.jpeg",numOfImgs);
        // open JPEG file to write in
        img = fopen(filename, "w");
        // write date in JPEG file
        fwrite(bytes, sizeof(bytes), 1, img);
        // increase number of found images
        numOfImgs++;
      } else
      {
        // if fond image is not the first which means there an image is currently open
        // close the current opened image
        fclose(img);
        // create a sequenced name
        sprintf(filename, "%03i.jpeg",numOfImgs);
        // open JPEG file to write in
        img = fopen(filename, "w");
        // write date in JPEG file
        fwrite(bytes, sizeof(bytes), 1, img);
        // increase number of found images
        numOfImgs++;
      }
    } else {
      // if current block is not a valid start for a JPEG
      // check if there is an open JPEG to add current block to
      if( numOfImgs >= 0)
      {
        // add current block to opened JPEG
        fwrite(bytes, sizeof(bytes), 1, img);
      }
    }
  }
  fclose(input);
  fclose(img);
  return 0;

}

Answer 1

This is the biggest problem in the code, and a very common error. I stopped looking once I found this. Look at this code:

 // check if reach ennd of memory card
  while( fread(bytes, sizeof(bytes), 1, input) > 0)
  {
    // read 1 block from card
    fread(bytes, sizeof(bytes), 1, input);

This is doing two sequential reads. The second one overwrites the first. That means that every other read is discarded without being processed.

Simple fix. Delete the second read.

There may be other problems, but this one is so big, I want you to have a chance to work through any others, assuming there are any. ;-)

If this answers your question, please click on the check mark to accept. Let's keep up on forum maintenance. ;-)