My recovered IMGs doesn't match the Original in recover Pset4 recover

Question

0 down vote favorite The problem is to recover some JPGs from a .raw file.

when I run check50 I get "recovered img don't match".

:) recover.c exists. :) recover.c compiles. :) handles lack of forensic image :( recovers 000.jpg correctly – recovered image does not match :( recovers middle images correctly – recovered image does not match :( recovers 015.jpg correctly – 015.jpg not found

I really tried hard to identify the problem and every time I fail to Identify where the problem is, I hope someone can and give me a peace of advice.

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

int main(int argc, char *argv[]){

if(argc != 2){

     fprintf(stderr, "Usage: ./recover image");
    return 1;
}

//open file

FILE *inptr = fopen(argv[1], "r");
if (inptr == NULL){

    fprintf(stderr, "Could not open %s.\n", argv[1]);
    return 2;
}


int foundjpg = 0;
char filename[10];
int x=1;

//repeat until end of the card
while(x == 1){

    //buffer
    unsigned char buf[512];
    x = fread(buf, 512, 1, inptr);
    //read into buffer
    fread(buf, 512, 1, inptr);
    FILE *jpg = fopen(filename, "w");

    //start of a new jpg?
    if(buf[0]== 0xff  && buf[1] == 0xd8  && buf[2] == 0xff && (buf[3] & 0xf0) == 0xe0 ){


        if(jpg != NULL){// yes i found before

            fclose(jpg);
            sprintf(filename, "%03i.jpg" ,foundjpg );
            foundjpg++;
            jpg = fopen(filename, "w");


        }
        else{
            sprintf(filename, "%03i.jpg" ,foundjpg );
            jpg = fopen(filename , "w");
            foundjpg++;

        }
    }
    //already found a jpg?
    if(jpg != NULL && foundjpg > 0){

        fwrite(buf, 1, 512, jpg);

    }

}


fclose(inptr);

// success
return 0;

}

Answer 1

Look at the following code:

unsigned char buf[512];
x = fread(buf, 512, 1, inptr);
//read into buffer
fread(buf, 512, 1, inptr);

This is doing two consecutive freads into buf, but the data from the first read is being overwritten before it is processed. In other words, the code is throwing away half the data.

There may be other issues, but this is a very big problem. You should have a chance to resolve it and have a chance to analyze and resolve any other problems, if any, on your own.

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