recover.c

/**
 * recover.c
 * 30 Jun 17
 * 
 * Recovers JPEGs from a source file.
 * 
 */
 
#include <stdint.h> 
#include <stdio.h>

#define BLOCK 512 
#define TRUE 1
#define FALSE 0

typedef uint8_t BYTE;


int main(int argc, char* argv[])
{
    
    // check program usage
    if (argc != 2)
    {
        fprintf(stderr, "Usage:  ./recover image\n");
        return 1;
    }
    
    
    FILE* in;
    FILE* out;
    BYTE buffer[BLOCK];
    int index;
    int in_file;
    char filename[9];
    
    // open source file
    in = fopen(argv[1], "r");
    
    if (in == NULL) 
    {
        fprintf(stderr, "Unable to open source file\n");
        return 2;
    }
    
    index = 0;
    in_file = FALSE;
    
    // check source file block by block for JPEGs
    while (fread(&buffer, sizeof(BLOCK), 1, in))     
    {

        // check for start of next JPEG
        if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer[2] == 0xff && (buffer[3] & 0xf0) == 0xe0)
        {
            if (in_file)
            {
                // close current file
                fclose(out);
            }
            
            // open new image file and write buffer to it
            sprintf(filename, "%03i.jpg", index++);
            filename[8] = '\0';
            out = fopen(filename, "w"); 
            if (out == NULL)
            {
                fprintf(stderr, "Unable to open destination image file\n");
                return 3;
            }
            
            fwrite(&buffer, sizeof(BLOCK), 1, out);
            in_file = TRUE;
                    
        }
            
        else    // continue writing to current image file
        {
            if (in_file)
            {
                fwrite(&buffer, sizeof(BLOCK), 1, out);
            }
        }
    }
    
    // need to flush any bytes remaining in buffer; they belong to the last JPEG
    for (int i = 0; i < BLOCK; i++)
    {
        if ((char)buffer[i] == EOF)
        {
            fwrite(&buffer[i], sizeof(BYTE), 1, out);
//            printf("%i\n", i);
            fclose(out);
            break;
        }
        else
        {
            fwrite(&buffer[i], sizeof(BYTE), 1, out);
        }
    }
    
    
    // success
    return 0;
}