/*
    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
*/

/* This is a JPEG image file loading framework */

#include <stdio.h>
#include <string.h>
#include <setjmp.h>

#include "SDL_image.h"

#ifdef LOAD_JPG

#include <jpeglib.h>

/* Define this for fast loading and not as good image quality */
/*#define FAST_JPEG*/

/* Define this for quicker (but less perfect) JPEG identification */
#define FAST_IS_JPEG

static struct {
	int loaded;
	void *handle;
	void (*jpeg_calc_output_dimensions) (j_decompress_ptr cinfo);
	void (*jpeg_CreateDecompress) (j_decompress_ptr cinfo, int version, size_t structsize);
	void (*jpeg_destroy_decompress) (j_decompress_ptr cinfo);
	boolean (*jpeg_finish_decompress) (j_decompress_ptr cinfo);
	int (*jpeg_read_header) (j_decompress_ptr cinfo, boolean require_image);
	JDIMENSION (*jpeg_read_scanlines) (j_decompress_ptr cinfo, JSAMPARRAY scanlines, JDIMENSION max_lines);
	boolean (*jpeg_resync_to_restart) (j_decompress_ptr cinfo, int desired);
	boolean (*jpeg_start_decompress) (j_decompress_ptr cinfo);
	struct jpeg_error_mgr * (*jpeg_std_error) (struct jpeg_error_mgr * err);
} lib;

#ifdef LOAD_JPG_DYNAMIC
int IMG_InitJPG()
{
	if ( lib.loaded == 0 ) {
		lib.handle = SDL_LoadObject(LOAD_JPG_DYNAMIC);
		if ( lib.handle == NULL ) {
			return -1;
		}
		lib.jpeg_calc_output_dimensions =
			(void (*) (j_decompress_ptr))
			SDL_LoadFunction(lib.handle, "jpeg_calc_output_dimensions");
		if ( lib.jpeg_calc_output_dimensions == NULL ) {
			SDL_UnloadObject(lib.handle);
			return -1;
		}
		lib.jpeg_CreateDecompress = 
			(void (*) (j_decompress_ptr, int, size_t))
			SDL_LoadFunction(lib.handle, "jpeg_CreateDecompress");
		if ( lib.jpeg_CreateDecompress == NULL ) {
			SDL_UnloadObject(lib.handle);
			return -1;
		}
		lib.jpeg_destroy_decompress = 
			(void (*) (j_decompress_ptr))
			SDL_LoadFunction(lib.handle, "jpeg_destroy_decompress");
		if ( lib.jpeg_destroy_decompress == NULL ) {
			SDL_UnloadObject(lib.handle);
			return -1;
		}
		lib.jpeg_finish_decompress = 
			(boolean (*) (j_decompress_ptr))
			SDL_LoadFunction(lib.handle, "jpeg_finish_decompress");
		if ( lib.jpeg_finish_decompress == NULL ) {
			SDL_UnloadObject(lib.handle);
			return -1;
		}
		lib.jpeg_read_header = 
			(int (*) (j_decompress_ptr, boolean))
			SDL_LoadFunction(lib.handle, "jpeg_read_header");
		if ( lib.jpeg_read_header == NULL ) {
			SDL_UnloadObject(lib.handle);
			return -1;
		}
		lib.jpeg_read_scanlines = 
			(JDIMENSION (*) (j_decompress_ptr, JSAMPARRAY, JDIMENSION))
			SDL_LoadFunction(lib.handle, "jpeg_read_scanlines");
		if ( lib.jpeg_read_scanlines == NULL ) {
			SDL_UnloadObject(lib.handle);
			return -1;
		}
		lib.jpeg_resync_to_restart = 
			(boolean (*) (j_decompress_ptr, int))
			SDL_LoadFunction(lib.handle, "jpeg_resync_to_restart");
		if ( lib.jpeg_resync_to_restart == NULL ) {
			SDL_UnloadObject(lib.handle);
			return -1;
		}
		lib.jpeg_start_decompress = 
			(boolean (*) (j_decompress_ptr))
			SDL_LoadFunction(lib.handle, "jpeg_start_decompress");
		if ( lib.jpeg_start_decompress == NULL ) {
			SDL_UnloadObject(lib.handle);
			return -1;
		}
		lib.jpeg_std_error = 
			(struct jpeg_error_mgr * (*) (struct jpeg_error_mgr *))
			SDL_LoadFunction(lib.handle, "jpeg_std_error");
		if ( lib.jpeg_std_error == NULL ) {
			SDL_UnloadObject(lib.handle);
			return -1;
		}
	}
	++lib.loaded;

	return 0;
}
void IMG_QuitJPG()
{
	if ( lib.loaded == 0 ) {
		return;
	}
	if ( lib.loaded == 1 ) {
		SDL_UnloadObject(lib.handle);
	}
	--lib.loaded;
}
#else
int IMG_InitJPG()
{
	if ( lib.loaded == 0 ) {
		lib.jpeg_calc_output_dimensions = jpeg_calc_output_dimensions;
		lib.jpeg_CreateDecompress = jpeg_CreateDecompress;
		lib.jpeg_destroy_decompress = jpeg_destroy_decompress;
		lib.jpeg_finish_decompress = jpeg_finish_decompress;
		lib.jpeg_read_header = jpeg_read_header;
		lib.jpeg_read_scanlines = jpeg_read_scanlines;
		lib.jpeg_resync_to_restart = jpeg_resync_to_restart;
		lib.jpeg_start_decompress = jpeg_start_decompress;
		lib.jpeg_std_error = jpeg_std_error;
	}
	++lib.loaded;

	return 0;
}
void IMG_QuitJPG()
{
	if ( lib.loaded == 0 ) {
		return;
	}
	if ( lib.loaded == 1 ) {
	}
	--lib.loaded;
}
#endif /* LOAD_JPG_DYNAMIC */

/* See if an image is contained in a data source */
int IMG_isJPG(SDL_RWops *src)
{
	int start;
	int is_JPG;
	int in_scan;
	Uint8 magic[4];

	/* This detection code is by Steaphan Greene <stea@cs.binghamton.edu> */
	/* Blame me, not Sam, if this doesn't work right. */
	/* And don't forget to report the problem to the the sdl list too! */

	if ( !src )
		return 0;
	start = SDL_RWtell(src);
	is_JPG = 0;
	in_scan = 0;
	if ( SDL_RWread(src, magic, 2, 1) ) {
		if ( (magic[0] == 0xFF) && (magic[1] == 0xD8) ) {
			is_JPG = 1;
			while (is_JPG == 1) {
				if(SDL_RWread(src, magic, 1, 2) != 2) {
					is_JPG = 0;
				} else if( (magic[0] != 0xFF) && (in_scan == 0) ) {
					is_JPG = 0;
				} else if( (magic[0] != 0xFF) || (magic[1] == 0xFF) ) {
					/* Extra padding in JPEG (legal) */
					/* or this is data and we are scanning */
					SDL_RWseek(src, -1, SEEK_CUR);
				} else if(magic[1] == 0xD9) {
					/* Got to end of good JPEG */
					break;
				} else if( (in_scan == 1) && (magic[1] == 0x00) ) {
					/* This is an encoded 0xFF within the data */
				} else if( (magic[1] >= 0xD0) && (magic[1] < 0xD9) ) {
					/* These have nothing else */
				} else if(SDL_RWread(src, magic+2, 1, 2) != 2) {
					is_JPG = 0;
				} else {
					/* Yes, it's big-endian */
					Uint32 start;
					Uint32 size;
					Uint32 end;
					start = SDL_RWtell(src);
					size = (magic[2] << 8) + magic[3];
					end = SDL_RWseek(src, size-2, SEEK_CUR);
					if ( end != start + size - 2 ) is_JPG = 0;
					if ( magic[1] == 0xDA ) {
						/* Now comes the actual JPEG meat */
#ifdef	FAST_IS_JPEG
						/* Ok, I'm convinced.  It is a JPEG. */
						break;
#else
						/* I'm not convinced.  Prove it! */
						in_scan = 1;
#endif
					}
				}
			}
		}
	}
	SDL_RWseek(src, start, SEEK_SET);
	return(is_JPG);
}

#define INPUT_BUFFER_SIZE	4096
typedef struct {
	struct jpeg_source_mgr pub;

	SDL_RWops *ctx;
	Uint8 buffer[INPUT_BUFFER_SIZE];
} my_source_mgr;

/*
 * Initialize source --- called by jpeg_read_header
 * before any data is actually read.
 */
static void init_source (j_decompress_ptr cinfo)
{
	/* We don't actually need to do anything */
	return;
}

/*
 * Fill the input buffer --- called whenever buffer is emptied.
 */
static int fill_input_buffer (j_decompress_ptr cinfo)
{
	my_source_mgr * src = (my_source_mgr *) cinfo->src;
	int nbytes;

	nbytes = SDL_RWread(src->ctx, src->buffer, 1, INPUT_BUFFER_SIZE);
	if (nbytes <= 0) {
		/* Insert a fake EOI marker */
		src->buffer[0] = (Uint8) 0xFF;
		src->buffer[1] = (Uint8) JPEG_EOI;
		nbytes = 2;
	}
	src->pub.next_input_byte = src->buffer;
	src->pub.bytes_in_buffer = nbytes;

	return TRUE;
}


/*
 * Skip data --- used to skip over a potentially large amount of
 * uninteresting data (such as an APPn marker).
 *
 * Writers of suspendable-input applications must note that skip_input_data
 * is not granted the right to give a suspension return.  If the skip extends
 * beyond the data currently in the buffer, the buffer can be marked empty so
 * that the next read will cause a fill_input_buffer call that can suspend.
 * Arranging for additional bytes to be discarded before reloading the input
 * buffer is the application writer's problem.
 */
static void skip_input_data (j_decompress_ptr cinfo, long num_bytes)
{
	my_source_mgr * src = (my_source_mgr *) cinfo->src;

	/* Just a dumb implementation for now.	Could use fseek() except
	 * it doesn't work on pipes.  Not clear that being smart is worth
	 * any trouble anyway --- large skips are infrequent.
	 */
	if (num_bytes > 0) {
		while (num_bytes > (long) src->pub.bytes_in_buffer) {
			num_bytes -= (long) src->pub.bytes_in_buffer;
			(void) src->pub.fill_input_buffer(cinfo);
			/* note we assume that fill_input_buffer will never
			 * return FALSE, so suspension need not be handled.
			 */
		}
		src->pub.next_input_byte += (size_t) num_bytes;
		src->pub.bytes_in_buffer -= (size_t) num_bytes;
	}
}

/*
 * Terminate source --- called by jpeg_finish_decompress
 * after all data has been read.
 */
static void term_source (j_decompress_ptr cinfo)
{
	/* We don't actually need to do anything */
	return;
}

/*
 * Prepare for input from a stdio stream.
 * The caller must have already opened the stream, and is responsible
 * for closing it after finishing decompression.
 */
static void jpeg_SDL_RW_src (j_decompress_ptr cinfo, SDL_RWops *ctx)
{
  my_source_mgr *src;

  /* The source object and input buffer are made permanent so that a series
   * of JPEG images can be read from the same file by calling jpeg_stdio_src
   * only before the first one.  (If we discarded the buffer at the end of
   * one image, we'd likely lose the start of the next one.)
   * This makes it unsafe to use this manager and a different source
   * manager serially with the same JPEG object.  Caveat programmer.
   */
  if (cinfo->src == NULL) {	/* first time for this JPEG object? */
    cinfo->src = (struct jpeg_source_mgr *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
				  sizeof(my_source_mgr));
    src = (my_source_mgr *) cinfo->src;
  }

  src = (my_source_mgr *) cinfo->src;
  src->pub.init_source = init_source;
  src->pub.fill_input_buffer = fill_input_buffer;
  src->pub.skip_input_data = skip_input_data;
  src->pub.resync_to_restart = lib.jpeg_resync_to_restart; /* use default method */
  src->pub.term_source = term_source;
  src->ctx = ctx;
  src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
  src->pub.next_input_byte = NULL; /* until buffer loaded */
}

struct my_error_mgr {
	struct jpeg_error_mgr errmgr;
	jmp_buf escape;
};

static void my_error_exit(j_common_ptr cinfo)
{
	struct my_error_mgr *err = (struct my_error_mgr *)cinfo->err;
	longjmp(err->escape, 1);
}

static void output_no_message(j_common_ptr cinfo)
{
	/* do nothing */
}

/* Load a JPEG type image from an SDL datasource */
SDL_Surface *IMG_LoadJPG_RW(SDL_RWops *src)
{
	int start;
	struct jpeg_decompress_struct cinfo;
	JSAMPROW rowptr[1];
	SDL_Surface *volatile surface = NULL;
	struct my_error_mgr jerr;

	if ( !src ) {
		/* The error message has been set in SDL_RWFromFile */
		return NULL;
	}
	start = SDL_RWtell(src);

	if ( IMG_InitJPG() < 0 ) {
		return NULL;
	}

	/* Create a decompression structure and load the JPEG header */
	cinfo.err = lib.jpeg_std_error(&jerr.errmgr);
	jerr.errmgr.error_exit = my_error_exit;
	jerr.errmgr.output_message = output_no_message;
	if(setjmp(jerr.escape)) {
		/* If we get here, libjpeg found an error */
		lib.jpeg_destroy_decompress(&cinfo);
		if ( surface != NULL ) {
			SDL_FreeSurface(surface);
		}
		SDL_RWseek(src, start, SEEK_SET);
		IMG_QuitJPG();
		IMG_SetError("JPEG loading error");
		return NULL;
	}

	lib.jpeg_create_decompress(&cinfo);
	jpeg_SDL_RW_src(&cinfo, src);
	lib.jpeg_read_header(&cinfo, TRUE);

	if(cinfo.num_components == 4) {
		/* Set 32-bit Raw output */
		cinfo.out_color_space = JCS_CMYK;
		cinfo.quantize_colors = FALSE;
		lib.jpeg_calc_output_dimensions(&cinfo);

		/* Allocate an output surface to hold the image */
		surface = SDL_AllocSurface(SDL_SWSURFACE,
		        cinfo.output_width, cinfo.output_height, 32,
#if SDL_BYTEORDER == SDL_LIL_ENDIAN
		                   0x00FF0000, 0x0000FF00, 0x000000FF, 0xFF000000);
#else
		                   0x0000FF00, 0x00FF0000, 0xFF000000, 0x000000FF);
#endif
	} else {
		/* Set 24-bit RGB output */
		cinfo.out_color_space = JCS_RGB;
		cinfo.quantize_colors = FALSE;
#ifdef FAST_JPEG
		cinfo.scale_num   = 1;
		cinfo.scale_denom = 1;
		cinfo.dct_method = JDCT_FASTEST;
		cinfo.do_fancy_upsampling = FALSE;
#endif
		lib.jpeg_calc_output_dimensions(&cinfo);

		/* Allocate an output surface to hold the image */
		surface = SDL_AllocSurface(SDL_SWSURFACE,
		        cinfo.output_width, cinfo.output_height, 24,
#if SDL_BYTEORDER == SDL_LIL_ENDIAN
		                   0x0000FF, 0x00FF00, 0xFF0000,
#else
		                   0xFF0000, 0x00FF00, 0x0000FF,
#endif
		                   0);
	}

	if ( surface == NULL ) {
		lib.jpeg_destroy_decompress(&cinfo);
		SDL_RWseek(src, start, SEEK_SET);
		IMG_QuitJPG();
		IMG_SetError("Out of memory");
		return NULL;
	}

	/* Decompress the image */
	lib.jpeg_start_decompress(&cinfo);
	while ( cinfo.output_scanline < cinfo.output_height ) {
		rowptr[0] = (JSAMPROW)(Uint8 *)surface->pixels +
		                    cinfo.output_scanline * surface->pitch;
		lib.jpeg_read_scanlines(&cinfo, rowptr, (JDIMENSION) 1);
	}
	lib.jpeg_finish_decompress(&cinfo);
	lib.jpeg_destroy_decompress(&cinfo);

	IMG_QuitJPG();

	return(surface);
}

#else

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

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

#endif /* LOAD_JPG */
