IMG_xpm.c

/*
    SDL_image:  An example image loading library for use with SDL
    Copyright (C) 1997-2006 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/

/*
 * XPM (X PixMap) image loader:
 *
 * Supports the XPMv3 format, EXCEPT:
 * - hotspot coordinates are ignored
 * - only colour ('c') colour symbols are used
 * - rgb.txt is not used (for portability), so only RGB colours
 *   are recognized (#rrggbb etc) - only a few basic colour names are
 *   handled
 *
 * The result is an 8bpp indexed surface if possible, otherwise 32bpp.
 * The colourkey is correctly set if transparency is used.
 * 
 * Besides the standard API, also provides
 *
 *     SDL_Surface *IMG_ReadXPMFromArray(char **xpm)
 *
 * that reads the image data from an XPM file included in the C source.
 *
 * TODO: include rgb.txt here. The full table (from solaris 2.6) only
 * requires about 13K in binary form.
 */

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

#include "SDL_image.h"

#ifdef LOAD_XPM

/* See if an image is contained in a data source */
int IMG_isXPM(SDL_RWops *src)
{
	int start;
	int is_XPM;
	char magic[9];

	if ( !src )
		return 0;
	start = SDL_RWtell(src);
	is_XPM = 0;
	if ( SDL_RWread(src, magic, sizeof(magic), 1) ) {
		if ( memcmp(magic, "/* XPM */", sizeof(magic)) == 0 ) {
			is_XPM = 1;
		}
	}
	SDL_RWseek(src, start, SEEK_SET);
	return(is_XPM);
}

/* Hash table to look up colors from pixel strings */
#define STARTING_HASH_SIZE 256

struct hash_entry {
	char *key;
	Uint32 color;
	struct hash_entry *next;
};

struct color_hash {
	struct hash_entry **table;
	struct hash_entry *entries; /* array of all entries */
	struct hash_entry *next_free;
	int size;
	int maxnum;
};

static int hash_key(const char *key, int cpp, int size)
{
	int hash;

	hash = 0;
	while ( cpp-- > 0 ) {
		hash = hash * 33 + *key++;
	}
	return hash & (size - 1);
}

static struct color_hash *create_colorhash(int maxnum)
{
	int bytes, s;
	struct color_hash *hash;

	/* we know how many entries we need, so we can allocate
	   everything here */
	hash = malloc(sizeof *hash);
	if(!hash)
		return NULL;

	/* use power-of-2 sized hash table for decoding speed */
	for(s = STARTING_HASH_SIZE; s < maxnum; s <<= 1)
		;
	hash->size = s;
	hash->maxnum = maxnum;
	bytes = hash->size * sizeof(struct hash_entry **);
	hash->entries = NULL;	/* in case malloc fails */
	hash->table = malloc(bytes);
	if(!hash->table)
		return NULL;
	memset(hash->table, 0, bytes);
	hash->entries = malloc(maxnum * sizeof(struct hash_entry));
	if(!hash->entries)
		return NULL;
	hash->next_free = hash->entries;
	return hash;
}

static int add_colorhash(struct color_hash *hash,
                         char *key, int cpp, Uint32 color)
{
	int index = hash_key(key, cpp, hash->size);
	struct hash_entry *e = hash->next_free++;
	e->color = color;
	e->key = key;
	e->next = hash->table[index];
	hash->table[index] = e;
	return 1;
}

/* fast lookup that works if cpp == 1 */
#define QUICK_COLORHASH(hash, key) ((hash)->table[*(Uint8 *)(key)]->color)

static Uint32 get_colorhash(struct color_hash *hash, const char *key, int cpp)
{
	struct hash_entry *entry = hash->table[hash_key(key, cpp, hash->size)];
	while(entry) {
		if(memcmp(key, entry->key, cpp) == 0)
			return entry->color;
		entry = entry->next;
	}
	return 0;		/* garbage in - garbage out */
}

static void free_colorhash(struct color_hash *hash)
{
	if(hash && hash->table) {
		free(hash->table);
		free(hash->entries);
		free(hash);
	}
}

/* portable case-insensitive string comparison */
static int string_equal(const char *a, const char *b, int n)
{
	while(*a && *b && n) {
		if(toupper((unsigned char)*a) != toupper((unsigned char)*b))
			return 0;
		a++;
		b++;
		n--;
	}
	return *a == *b;
}

#define ARRAYSIZE(a) (int)(sizeof(a) / sizeof((a)[0]))

/*
 * convert colour spec to RGB (in 0xrrggbb format).
 * return 1 if successful.
 */
static int color_to_rgb(char *spec, int speclen, Uint32 *rgb)
{
	/* poor man's rgb.txt */
	static struct { char *name; Uint32 rgb; } known[] = {
		{"none",  0xffffffff},
		{"black", 0x00000000},
		{"white", 0x00ffffff},
		{"red",   0x00ff0000},
		{"green", 0x0000ff00},
		{"blue",  0x000000ff}
	};

	if(spec[0] == '#') {
		char buf[7];
		switch(speclen) {
		case 4:
			buf[0] = buf[1] = spec[1];
			buf[2] = buf[3] = spec[2];
			buf[4] = buf[5] = spec[3];
			break;
		case 7:
			memcpy(buf, spec + 1, 6);
			break;
		case 13:
			buf[0] = spec[1];
			buf[1] = spec[2];
			buf[2] = spec[5];
			buf[3] = spec[6];
			buf[4] = spec[9];
			buf[5] = spec[10];
			break;
		}
		buf[6] = '\0';
		*rgb = strtol(buf, NULL, 16);
		return 1;
	} else {
		int i;
		for(i = 0; i < ARRAYSIZE(known); i++)
			if(string_equal(known[i].name, spec, speclen)) {
				*rgb = known[i].rgb;
				return 1;
			}
		return 0;
	}
}

#ifndef MAX
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#endif

static char *linebuf;
static int buflen;
static char *error;

/*
 * Read next line from the source.
 * If len > 0, it's assumed to be at least len chars (for efficiency).
 * Return NULL and set error upon EOF or parse error.
 */
static char *get_next_line(char ***lines, SDL_RWops *src, int len)
{
	if(lines) {
		return *(*lines)++;
	} else {
		char c;
		int n;
		do {
			if(SDL_RWread(src, &c, 1, 1) <= 0) {
				error = "Premature end of data";
				return NULL;
			}
		} while(c != '"');
		if(len) {
			len += 4;	/* "\",\n\0" */
			if(len > buflen){
				buflen = len;
				linebuf = realloc(linebuf, buflen);
				if(!linebuf) {
					error = "Out of memory";
					return NULL;
				}
			}
			if(SDL_RWread(src, linebuf, len - 1, 1) <= 0) {
				error = "Premature end of data";
				return NULL;
			}
			n = len - 2;
		} else {
			n = 0;
			do {
				if(n >= buflen - 1) {
					if(buflen == 0)
						buflen = 16;
					buflen *= 2;
					linebuf = realloc(linebuf, buflen);
					if(!linebuf) {
						error = "Out of memory";
						return NULL;
					}
				}
				if(SDL_RWread(src, linebuf + n, 1, 1) <= 0) {
					error = "Premature end of data";
					return NULL;
				}
			} while(linebuf[n++] != '"');
			n--;
		}
		linebuf[n] = '\0';
		return linebuf;
	}
}

#define SKIPSPACE(p)				\
do {						\
	while(isspace((unsigned char)*(p)))	\
	      ++(p);				\
} while(0)

#define SKIPNONSPACE(p)					\
do {							\
	while(!isspace((unsigned char)*(p)) && *p)	\
	      ++(p);					\
} while(0)

/* read XPM from either array or RWops */
static SDL_Surface *load_xpm(char **xpm, SDL_RWops *src)
{
	int start = 0;
	SDL_Surface *image = NULL;
	int index;
	int x, y;
	int w, h, ncolors, cpp;
	int indexed;
	Uint8 *dst;
	struct color_hash *colors = NULL;
	SDL_Color *im_colors = NULL;
	char *keystrings = NULL, *nextkey;
	char *line;
	char ***xpmlines = NULL;
	int pixels_len;

	error = NULL;
	linebuf = NULL;
	buflen = 0;

	if ( src ) 
		start = SDL_RWtell(src);

	if(xpm)
		xpmlines = &xpm;

	line = get_next_line(xpmlines, src, 0);
	if(!line)
		goto done;
	/*
	 * The header string of an XPMv3 image has the format
	 *
	 * <width> <height> <ncolors> <cpp> [ <hotspot_x> <hotspot_y> ]
	 *
	 * where the hotspot coords are intended for mouse cursors.
	 * Right now we don't use the hotspots but it should be handled
	 * one day.
	 */
	if(sscanf(line, "%d %d %d %d", &w, &h, &ncolors, &cpp) != 4
	   || w <= 0 || h <= 0 || ncolors <= 0 || cpp <= 0) {
		error = "Invalid format description";
		goto done;
	}

	keystrings = malloc(ncolors * cpp);
	if(!keystrings) {
		error = "Out of memory";
		goto done;
	}
	nextkey = keystrings;

	/* Create the new surface */
	if(ncolors <= 256) {
		indexed = 1;
		image = SDL_CreateRGBSurface(SDL_SWSURFACE, w, h, 8,
					     0, 0, 0, 0);
		im_colors = image->format->palette->colors;
		image->format->palette->ncolors = ncolors;
	} else {
		indexed = 0;
		image = SDL_CreateRGBSurface(SDL_SWSURFACE, w, h, 32,
					     0xff0000, 0x00ff00, 0x0000ff, 0);
	}
	if(!image) {
		/* Hmm, some SDL error (out of memory?) */
		goto done;
	}

	/* Read the colors */
	colors = create_colorhash(ncolors);
	if (!colors) {
		error = "Out of memory";
		goto done;
	}
	for(index = 0; index < ncolors; ++index ) {
		char *p;
		line = get_next_line(xpmlines, src, 0);
		if(!line)
			goto done;

		p = line + cpp + 1;

		/* parse a colour definition */
		for(;;) {
			char nametype;
			char *colname;
			Uint32 rgb, pixel;

			SKIPSPACE(p);
			if(!*p) {
				error = "colour parse error";
				goto done;
			}
			nametype = *p;
			SKIPNONSPACE(p);
			SKIPSPACE(p);
			colname = p;
			SKIPNONSPACE(p);
			if(nametype == 's')
				continue;      /* skip symbolic colour names */

			if(!color_to_rgb(colname, p - colname, &rgb))
				continue;

			memcpy(nextkey, line, cpp);
			if(indexed) {
				SDL_Color *c = im_colors + index;
				c->r = (Uint8)(rgb >> 16);
				c->g = (Uint8)(rgb >> 8);
				c->b = (Uint8)(rgb);
				pixel = index;
			} else
				pixel = rgb;
			add_colorhash(colors, nextkey, cpp, pixel);
			nextkey += cpp;
			if(rgb == 0xffffffff)
				SDL_SetColorKey(image, SDL_SRCCOLORKEY, pixel);
			break;
		}
	}

	/* Read the pixels */
	pixels_len = w * cpp;
	dst = image->pixels;
	for(y = 0; y < h; y++) {
		line = get_next_line(xpmlines, src, pixels_len);
		if(indexed) {
			/* optimization for some common cases */
			if(cpp == 1)
				for(x = 0; x < w; x++)
					dst[x] = (Uint8)QUICK_COLORHASH(colors,
								 line + x);
			else
				for(x = 0; x < w; x++)
					dst[x] = (Uint8)get_colorhash(colors,
							       line + x * cpp,
							       cpp);
		} else {
			for (x = 0; x < w; x++)
				((Uint32*)dst)[x] = get_colorhash(colors,
								line + x * cpp,
								  cpp);
		}
		dst += image->pitch;
	}

done:
	if(error) {
		if ( src )
			SDL_RWseek(src, start, SEEK_SET);
		if ( image ) {
			SDL_FreeSurface(image);
			image = NULL;
		}
		IMG_SetError(error);
	}
	free(keystrings);
	free_colorhash(colors);
	free(linebuf);
	return(image);
}

/* Load a XPM type image from an RWops datasource */
SDL_Surface *IMG_LoadXPM_RW(SDL_RWops *src)
{
	if ( !src ) {
		/* The error message has been set in SDL_RWFromFile */
		return NULL;
	}
	return load_xpm(NULL, src);
}

SDL_Surface *IMG_ReadXPMFromArray(char **xpm)
{
	return load_xpm(xpm, NULL);
}

#else  /* not LOAD_XPM */

/* See if an image is contained in a data source */
int IMG_isXPM(SDL_RWops *src)
{
	return(0);
}


/* Load a XPM type image from an SDL datasource */
SDL_Surface *IMG_LoadXPM_RW(SDL_RWops *src)
{
	return(NULL);
}

SDL_Surface *IMG_ReadXPMFromArray(char **xpm)
{
    return NULL;
}
#endif /* not LOAD_XPM */