/* Simple PPM library ----------------------------------------------------------
 * Based on specification: http://netpbm.sourceforge.net/doc/ppm.html
 * -------------------------------------------------------------------------- */

#include "ppm.h"

#include <ctype.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define PPM_FLIP	1
#define PPM_LINE_MAX	4096

/* PPM write ---------------------------------------------------------------- */

int
ppm_write(const char *fname, unsigned char *buffer, size_t width, size_t height)
{
    FILE *fs = NULL;
    int result = 0;

    fs = fopen(fname, "w+");
    if (!fs) 
    	goto pgm_write_cleanup;

    fprintf(fs, "P6\n");			/* Magic Number */
    fprintf(fs, "# Simple PPM library\n");	/* Comment */
    fprintf(fs, "%lu %lu\n", width, height);	/* Image width, height */
    fprintf(fs, "255\n");			/* Maximum color value */

    /* Pixel values */
#if PPM_FLIP
    size_t r;
    for (r = 0; r < height; r++)
    	fwrite(&buffer[width*(height - r - 1)*3], sizeof(unsigned char), width * 3, fs);
#else
    fwrite(buffer, sizeof(unsigned char), width * height * 3, fs);
#endif
    result = 1;

pgm_write_cleanup:
    if (fs) fclose(fs);
    return result;
}

char *
ppm_read_token(FILE *fs)
{
    static char buffer[PPM_LINE_MAX] = "";
    static char *front = buffer;
    static char *back  = buffer;

    if (*back == 0) {
    	if (!fgets(buffer, sizeof(char) * PPM_LINE_MAX, fs))
    	    goto ppm_read_token_failure;
    	buffer[strlen(buffer) - 1] = 0;
    	front = buffer;
    	back  = buffer;
    }
    
    if (*front == '#') {
    	*front = 0;
    	return ppm_read_token(fs);
    }
    
    for (front = back; *front != 0 && isspace(*front); front++);
    for (back = front; *back  != 0 && !isspace(*back); back++);

    if (*back != 0)
    	*back++ = 0;

    return front;

ppm_read_token_failure:
    return NULL;
}

int
ppm_read(const char *fname, unsigned char **buffer, size_t *width, size_t *height)
{
    FILE *fs = NULL;
    char *token = NULL;
    int max_value;

    fs = fopen(fname, "r");
    if (!fs) {
    	fprintf(stderr, "ppm_read: could not open file %s = %s\n", fname, strerror(errno));
    	goto ppm_read_cleanup;
    }

    token = ppm_read_token(fs);
    if (strcmp(token, "P6") != 0) {
    	fprintf(stderr, "ppm_read: file %s has wrong magic number %s\n", fname, token);
    	goto ppm_read_cleanup;
    }

    token = ppm_read_token(fs);
    if (!token) {
    	fprintf(stderr, "ppm_read: could not read width\n");
    	goto ppm_read_cleanup;
    }
    *width = strtol(token, NULL, 10);
    
    token = ppm_read_token(fs);
    if (!token) {
    	fprintf(stderr, "ppm_read: could not read height\n");
    	goto ppm_read_cleanup;
    }
    *height = strtol(token, NULL, 10);
    
    token = ppm_read_token(fs);
    if (!token) {
    	fprintf(stderr, "ppm_read: could not read max_value\n");
    	goto ppm_read_cleanup;
    }
    max_value = strtol(token, NULL, 10);

    *buffer = (unsigned char *)malloc(sizeof(unsigned char) * (*width) * (*height) * 3);
    if (!*buffer) {
    	fprintf(stderr, "ppm_read: could not allocate memory for image buffer = %s\n", strerror(errno));
    	goto ppm_read_cleanup;
    }

#if PPM_FLIP
    size_t r;
    for (r = 0; r < *height; r++) {
    	fread(&(*buffer)[(*width)*((*height) - r - 1)*3], sizeof(unsigned char), (*width) * 3, fs);
    }
#else
    fread(*buffer, sizeof(unsigned char), (*width) * (*height) * 3, fs);
#endif
    return 1;

ppm_read_cleanup:
    if (fs) fclose(fs);
    return 0;
}

/* vim: set sts=4 sw=4 ts=8 ft=cpp: ----------------------------------------- */