src/video/SDL_stretch.c
author Sam Lantinga <slouken@libsdl.org>
Fri, 14 Dec 2001 12:38:15 +0000
changeset 252 e8157fcb3114
parent 0 74212992fb08
child 274 051b991765ba
permissions -rw-r--r--
Updated the source with the correct e-mail address
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/*
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    SDL - Simple DirectMedia Layer
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    Copyright (C) 1997, 1998, 1999, 2000, 2001  Sam Lantinga
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    This library is free software; you can redistribute it and/or
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    modify it under the terms of the GNU Library General Public
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    License as published by the Free Software Foundation; either
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    version 2 of the License, or (at your option) any later version.
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    This library is distributed in the hope that it will be useful,
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    but WITHOUT ANY WARRANTY; without even the implied warranty of
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    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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    Library General Public License for more details.
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    You should have received a copy of the GNU Library General Public
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    License along with this library; if not, write to the Free
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    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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    Sam Lantinga
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    slouken@libsdl.org
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*/
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#ifdef SAVE_RCSID
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static char rcsid =
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 "@(#) $Id$";
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#endif
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/* This a stretch blit implementation based on ideas given to me by
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   Tomasz Cejner - thanks! :)
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   April 27, 2000 - Sam Lantinga
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*/
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#include "SDL_error.h"
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#include "SDL_video.h"
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#include "SDL_blit.h"
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/* This isn't ready for general consumption yet - it should be folded
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   into the general blitting mechanism.
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*/
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#if (defined(WIN32) && !defined(_M_ALPHA) && !defined(_WIN32_WCE)) || \
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    defined(i386) && defined(__GNUC__) && defined(USE_ASMBLIT)
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#define USE_ASM_STRETCH
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#endif
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#ifdef USE_ASM_STRETCH
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#if defined(WIN32) || defined(i386)
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#define PREFIX16	0x66
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#define STORE_BYTE	0xAA
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#define STORE_WORD	0xAB
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#define LOAD_BYTE	0xAC
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#define LOAD_WORD	0xAD
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#define RETURN		0xC3
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#else
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#error Need assembly opcodes for this architecture
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#endif
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#if defined(__ELF__) && defined(__GNUC__)
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extern unsigned char _copy_row[4096] __attribute__ ((alias ("copy_row")));
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#endif
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static unsigned char copy_row[4096];
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static int generate_rowbytes(int src_w, int dst_w, int bpp)
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{
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	static struct {
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		int bpp;
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		int src_w;
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		int dst_w;
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	} last;
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	int i;
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	int pos, inc;
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	unsigned char *eip;
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	unsigned char load, store;
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	/* See if we need to regenerate the copy buffer */
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	if ( (src_w == last.src_w) &&
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	     (dst_w == last.src_w) && (bpp == last.bpp) ) {
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		return(0);
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	}
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	last.bpp = bpp;
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	last.src_w = src_w;
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	last.dst_w = dst_w;
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	switch (bpp) {
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	    case 1:
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		load = LOAD_BYTE;
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		store = STORE_BYTE;
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		break;
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	    case 2:
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	    case 4:
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		load = LOAD_WORD;
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		store = STORE_WORD;
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		break;
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	    default:
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		SDL_SetError("ASM stretch of %d bytes isn't supported\n", bpp);
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		return(-1);
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	}
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	pos = 0x10000;
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	inc = (src_w << 16) / dst_w;
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	eip = copy_row;
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	for ( i=0; i<dst_w; ++i ) {
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		while ( pos >= 0x10000L ) {
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			if ( bpp == 2 ) {
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				*eip++ = PREFIX16;
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			}
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			*eip++ = load;
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			pos -= 0x10000L;
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		}
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		if ( bpp == 2 ) {
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			*eip++ = PREFIX16;
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		}
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		*eip++ = store;
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		pos += inc;
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	}
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	*eip++ = RETURN;
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	/* Verify that we didn't overflow (too late) */
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	if ( eip > (copy_row+sizeof(copy_row)) ) {
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		SDL_SetError("Copy buffer overflow");
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		return(-1);
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	}
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	return(0);
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}
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#else
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#define DEFINE_COPY_ROW(name, type)			\
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void name(type *src, int src_w, type *dst, int dst_w)	\
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{							\
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	int i;						\
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	int pos, inc;					\
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	type pixel = 0;					\
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							\
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	pos = 0x10000;					\
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	inc = (src_w << 16) / dst_w;			\
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	for ( i=dst_w; i>0; --i ) {			\
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		while ( pos >= 0x10000L ) {		\
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			pixel = *src++;			\
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			pos -= 0x10000L;		\
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		}					\
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		*dst++ = pixel;				\
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		pos += inc;				\
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	}						\
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}
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DEFINE_COPY_ROW(copy_row1, Uint8)
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DEFINE_COPY_ROW(copy_row2, Uint16)
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DEFINE_COPY_ROW(copy_row4, Uint32)
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#endif /* USE_ASM_STRETCH */
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/* The ASM code doesn't handle 24-bpp stretch blits */
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void copy_row3(Uint8 *src, int src_w, Uint8 *dst, int dst_w)
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{
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	int i;
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	int pos, inc;
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	Uint8 pixel[3];
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	pos = 0x10000;
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	inc = (src_w << 16) / dst_w;
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	for ( i=dst_w; i>0; --i ) {
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		while ( pos >= 0x10000L ) {
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			pixel[0] = *src++;
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			pixel[1] = *src++;
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			pixel[2] = *src++;
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			pos -= 0x10000L;
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		}
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		*dst++ = pixel[0];
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		*dst++ = pixel[1];
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		*dst++ = pixel[2];
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		pos += inc;
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	}
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}
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/* Perform a stretch blit between two surfaces of the same format.
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   NOTE:  This function is not safe to call from multiple threads!
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*/
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int SDL_SoftStretch(SDL_Surface *src, SDL_Rect *srcrect,
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                    SDL_Surface *dst, SDL_Rect *dstrect)
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{
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	int pos, inc;
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	int dst_width;
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	int dst_maxrow;
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	int src_row, dst_row;
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	Uint8 *srcp = NULL;
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	Uint8 *dstp;
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	SDL_Rect full_src;
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	SDL_Rect full_dst;
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#if defined(USE_ASM_STRETCH) && defined(__GNUC__)
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	int u1, u2;
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#endif
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	const int bpp = dst->format->BytesPerPixel;
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	if ( src->format->BitsPerPixel != dst->format->BitsPerPixel ) {
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		SDL_SetError("Only works with same format surfaces");
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		return(-1);
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	}
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	/* Verify the blit rectangles */
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	if ( srcrect ) {
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		if ( (srcrect->x < 0) || (srcrect->y < 0) ||
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		     ((srcrect->x+srcrect->w) > src->w) ||
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		     ((srcrect->y+srcrect->h) > src->h) ) {
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			SDL_SetError("Invalid source blit rectangle");
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			return(-1);
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		}
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	} else {
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		full_src.x = 0;
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		full_src.y = 0;
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		full_src.w = src->w;
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		full_src.h = src->h;
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		srcrect = &full_src;
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	}
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	if ( dstrect ) {
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		if ( (dstrect->x < 0) || (dstrect->y < 0) ||
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		     ((dstrect->x+dstrect->w) > dst->w) ||
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		     ((dstrect->y+dstrect->h) > dst->h) ) {
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			SDL_SetError("Invalid destination blit rectangle");
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			return(-1);
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		}
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	} else {
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		full_dst.x = 0;
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		full_dst.y = 0;
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		full_dst.w = dst->w;
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		full_dst.h = dst->h;
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		dstrect = &full_dst;
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	}
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	/* Set up the data... */
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	pos = 0x10000;
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	inc = (srcrect->h << 16) / dstrect->h;
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	src_row = srcrect->y;
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	dst_row = dstrect->y;
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	dst_width = dstrect->w*bpp;
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#ifdef USE_ASM_STRETCH
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	/* Write the opcodes for this stretch */
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	if ( (bpp != 3) &&
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	     (generate_rowbytes(srcrect->w, dstrect->w, bpp) < 0) ) {
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		return(-1);
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	}
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#endif
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	/* Perform the stretch blit */
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	for ( dst_maxrow = dst_row+dstrect->h; dst_row<dst_maxrow; ++dst_row ) {
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		dstp = (Uint8 *)dst->pixels + (dst_row*dst->pitch)
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		                            + (dstrect->x*bpp);
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		while ( pos >= 0x10000L ) {
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			srcp = (Uint8 *)src->pixels + (src_row*src->pitch)
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			                            + (srcrect->x*bpp);
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			++src_row;
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			pos -= 0x10000L;
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		}
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#ifdef USE_ASM_STRETCH
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		switch (bpp) {
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		    case 3:
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			copy_row3(srcp, srcrect->w, dstp, dstrect->w);
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			break;
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		    default:
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#ifdef __GNUC__
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			__asm__ __volatile__ ("
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				call _copy_row
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			"
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			: "=&D" (u1), "=&S" (u2)
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			: "0" (dstp), "1" (srcp)
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			: "memory" );
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#else
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#ifdef WIN32
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		{ void *code = &copy_row;
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			__asm {
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				push edi
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				push esi
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				mov edi, dstp
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				mov esi, srcp
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				call dword ptr code
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				pop esi
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				pop edi
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			}
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		}
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#else
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#error Need inline assembly for this compiler
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#endif
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#endif /* __GNUC__ */
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			break;
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		}
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#else
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		switch (bpp) {
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		    case 1:
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			copy_row1(srcp, srcrect->w, dstp, dstrect->w);
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			break;
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		    case 2:
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			copy_row2((Uint16 *)srcp, srcrect->w,
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			          (Uint16 *)dstp, dstrect->w);
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			break;
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		    case 3:
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			copy_row3(srcp, srcrect->w, dstp, dstrect->w);
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			break;
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		    case 4:
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			copy_row4((Uint32 *)srcp, srcrect->w,
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			          (Uint32 *)dstp, dstrect->w);
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			break;
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		}
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#endif
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		pos += inc;
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	}
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	return(0);
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}
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