IMG_xpm.c

/*
  SDL_image:  An example image loading library for use with SDL
  Copyright (C) 1997-2012 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/

/*
 * 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, RW_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) {
		free(hash->table);
		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)
{
	char *linebufnew;

	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;
				linebufnew = realloc(linebuf, buflen);
				if(!linebufnew) {
					free(linebuf);
					error = "Out of memory";
					return NULL;
				}
				linebuf = linebufnew;
			}
			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;
					linebufnew = realloc(linebuf, buflen);
					if(!linebufnew) {
						free(linebuf);
						error = "Out of memory";
						return NULL;
					}
					linebuf = linebufnew;
				}
				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);
	} else {
		error = "src is NULL";
		goto done;
	}

	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, RW_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 */