#include "imglib.h"

#define PPMREADBUFLEN 256
image get_ppm(FILE *pf)
{
        char buf[PPMREADBUFLEN], *t;
        image img;
        unsigned int w, h, d;
        int r;

        if (pf == NULL) return NULL;
        t = fgets(buf, PPMREADBUFLEN, pf);
        /* the code fails if the white space following "P6" is not '\n' */
        if ( (t == NULL) || ( strncmp(buf, "P6\n", 3) != 0 ) ) return NULL;
        do
        { /* Px formats can have # comments after first line */
           t = fgets(buf, PPMREADBUFLEN, pf);
           if ( t == NULL ) return NULL;
        } while ( strncmp(buf, "#", 1) == 0 );
        r = sscanf(buf, "%u %u", &w, &h);
        if ( r < 2 ) return NULL;

        r = fscanf(pf, "%u", &d);
        if ( (r < 1) || ( d != 255 ) ) return NULL;
        fseek(pf, 1, SEEK_CUR); /* skip one byte, should be whitespace */

        img = alloc_img(w, h);
        if ( img != NULL )
        {
            size_t rd = fread(img->buf, sizeof(pixel), w*h, pf);
            if ( rd < w*h )
            {
               free_img(img);
               return NULL;
            }
            return img;
        }
}