src/video/SDL_stretch.c
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FUNCTIONS
This source file includes following functions.
- generate_rowbytes
- DEFINE_COPY_ROW
- DEFINE_COPY_ROW
- SDL_SoftStretch
1 /*
2 SDL - Simple DirectMedia Layer
3 Copyright (C) 1997, 1998, 1999, 2000, 2001 Sam Lantinga
4
5 This library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Library General Public
7 License as published by the Free Software Foundation; either
8 version 2 of the License, or (at your option) any later version.
9
10 This library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Library General Public License for more details.
14
15 You should have received a copy of the GNU Library General Public
16 License along with this library; if not, write to the Free
17 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18
19 Sam Lantinga
20 slouken@devolution.com
21 */
22
23 #ifdef SAVE_RCSID
24 static char rcsid =
25 "@(#) $Id: SDL_stretch.c,v 1.1.2.10 2001/02/22 00:21:51 hercules Exp $";
26 #endif
27
28 /* This a stretch blit implementation based on ideas given to me by
29 Tomasz Cejner - thanks! :)
30
31 April 27, 2000 - Sam Lantinga
32 */
33
34 #include "SDL_error.h"
35 #include "SDL_video.h"
36 #include "SDL_blit.h"
37
38 /* This isn't ready for general consumption yet - it should be folded
39 into the general blitting mechanism.
40 */
41
42 #if (defined(WIN32) && !defined(_M_ALPHA) && !defined(_WIN32_WCE)) || \
43 defined(i386) && defined(__GNUC__) && defined(USE_ASMBLIT)
44 #define USE_ASM_STRETCH
45 #endif
46
47 #ifdef USE_ASM_STRETCH
48
49 #if defined(WIN32) || defined(i386)
50 #define PREFIX16 0x66
51 #define STORE_BYTE 0xAA
52 #define STORE_WORD 0xAB
53 #define LOAD_BYTE 0xAC
54 #define LOAD_WORD 0xAD
55 #define RETURN 0xC3
56 #else
57 #error Need assembly opcodes for this architecture
58 #endif
59
60 #if defined(__ELF__) && defined(__GNUC__)
61 extern unsigned char _copy_row[4096] __attribute__ ((alias ("copy_row")));
62 #endif
63 static unsigned char copy_row[4096];
64
65 static int generate_rowbytes(int src_w, int dst_w, int bpp)
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66 {
67 static struct {
68 int bpp;
69 int src_w;
70 int dst_w;
71 } last;
72
73 int i;
74 int pos, inc;
75 unsigned char *eip;
76 unsigned char load, store;
77
78 /* See if we need to regenerate the copy buffer */
79 if ( (src_w == last.src_w) &&
80 (dst_w == last.src_w) && (bpp == last.bpp) ) {
81 return(0);
82 }
83 last.bpp = bpp;
84 last.src_w = src_w;
85 last.dst_w = dst_w;
86
87 switch (bpp) {
88 case 1:
89 load = LOAD_BYTE;
90 store = STORE_BYTE;
91 break;
92 case 2:
93 case 4:
94 load = LOAD_WORD;
95 store = STORE_WORD;
96 break;
97 default:
98 SDL_SetError("ASM stretch of %d bytes isn't supported\n", bpp);
99 return(-1);
100 }
101 pos = 0x10000;
102 inc = (src_w << 16) / dst_w;
103 eip = copy_row;
104 for ( i=0; i<dst_w; ++i ) {
105 while ( pos >= 0x10000L ) {
106 if ( bpp == 2 ) {
107 *eip++ = PREFIX16;
108 }
109 *eip++ = load;
110 pos -= 0x10000L;
111 }
112 if ( bpp == 2 ) {
113 *eip++ = PREFIX16;
114 }
115 *eip++ = store;
116 pos += inc;
117 }
118 *eip++ = RETURN;
119
120 /* Verify that we didn't overflow (too late) */
121 if ( eip > (copy_row+sizeof(copy_row)) ) {
122 SDL_SetError("Copy buffer overflow");
123 return(-1);
124 }
125 return(0);
126 }
127
128 #else
129
130 #define DEFINE_COPY_ROW(name, type) \
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131 void name(type *src, int src_w, type *dst, int dst_w) \
132 { \
133 int i; \
134 int pos, inc; \
135 type pixel = 0; \
136 \
137 pos = 0x10000; \
138 inc = (src_w << 16) / dst_w; \
139 for ( i=dst_w; i>0; --i ) { \
140 while ( pos >= 0x10000L ) { \
141 pixel = *src++; \
142 pos -= 0x10000L; \
143 } \
144 *dst++ = pixel; \
145 pos += inc; \
146 } \
147 }
148 DEFINE_COPY_ROW(copy_row1, Uint8)
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149 DEFINE_COPY_ROW(copy_row2, Uint16)
150 DEFINE_COPY_ROW(copy_row4, Uint32)
151
152 #endif /* USE_ASM_STRETCH */
153
154 /* The ASM code doesn't handle 24-bpp stretch blits */
155 void copy_row3(Uint8 *src, int src_w, Uint8 *dst, int dst_w)
156 {
157 int i;
158 int pos, inc;
159 Uint8 pixel[3];
160
161 pos = 0x10000;
162 inc = (src_w << 16) / dst_w;
163 for ( i=dst_w; i>0; --i ) {
164 while ( pos >= 0x10000L ) {
165 pixel[0] = *src++;
166 pixel[1] = *src++;
167 pixel[2] = *src++;
168 pos -= 0x10000L;
169 }
170 *dst++ = pixel[0];
171 *dst++ = pixel[1];
172 *dst++ = pixel[2];
173 pos += inc;
174 }
175 }
176
177 /* Perform a stretch blit between two surfaces of the same format.
178 NOTE: This function is not safe to call from multiple threads!
179 */
180 int SDL_SoftStretch(SDL_Surface *src, SDL_Rect *srcrect,
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181 SDL_Surface *dst, SDL_Rect *dstrect)
182 {
183 int pos, inc;
184 int dst_width;
185 int dst_maxrow;
186 int src_row, dst_row;
187 Uint8 *srcp = NULL;
188 Uint8 *dstp;
189 SDL_Rect full_src;
190 SDL_Rect full_dst;
191 #if defined(USE_ASM_STRETCH) && defined(__GNUC__)
192 int u1, u2;
193 #endif
194 const int bpp = dst->format->BytesPerPixel;
195
196 if ( src->format->BitsPerPixel != dst->format->BitsPerPixel ) {
197 SDL_SetError("Only works with same format surfaces");
198 return(-1);
199 }
200
201 /* Verify the blit rectangles */
202 if ( srcrect ) {
203 if ( (srcrect->x < 0) || (srcrect->y < 0) ||
204 ((srcrect->x+srcrect->w) > src->w) ||
205 ((srcrect->y+srcrect->h) > src->h) ) {
206 SDL_SetError("Invalid source blit rectangle");
207 return(-1);
208 }
209 } else {
210 full_src.x = 0;
211 full_src.y = 0;
212 full_src.w = src->w;
213 full_src.h = src->h;
214 srcrect = &full_src;
215 }
216 if ( dstrect ) {
217 if ( (dstrect->x < 0) || (dstrect->y < 0) ||
218 ((dstrect->x+dstrect->w) > dst->w) ||
219 ((dstrect->y+dstrect->h) > dst->h) ) {
220 SDL_SetError("Invalid destination blit rectangle");
221 return(-1);
222 }
223 } else {
224 full_dst.x = 0;
225 full_dst.y = 0;
226 full_dst.w = dst->w;
227 full_dst.h = dst->h;
228 dstrect = &full_dst;
229 }
230
231 /* Set up the data... */
232 pos = 0x10000;
233 inc = (srcrect->h << 16) / dstrect->h;
234 src_row = srcrect->y;
235 dst_row = dstrect->y;
236 dst_width = dstrect->w*bpp;
237
238 #ifdef USE_ASM_STRETCH
239 /* Write the opcodes for this stretch */
240 if ( (bpp != 3) &&
241 (generate_rowbytes(srcrect->w, dstrect->w, bpp) < 0) ) {
242 return(-1);
243 }
244 #endif
245
246 /* Perform the stretch blit */
247 for ( dst_maxrow = dst_row+dstrect->h; dst_row<dst_maxrow; ++dst_row ) {
248 dstp = (Uint8 *)dst->pixels + (dst_row*dst->pitch)
249 + (dstrect->x*bpp);
250 while ( pos >= 0x10000L ) {
251 srcp = (Uint8 *)src->pixels + (src_row*src->pitch)
252 + (srcrect->x*bpp);
253 ++src_row;
254 pos -= 0x10000L;
255 }
256 #ifdef USE_ASM_STRETCH
257 switch (bpp) {
258 case 3:
259 copy_row3(srcp, srcrect->w, dstp, dstrect->w);
260 break;
261 default:
262 #ifdef __GNUC__
263 __asm__ __volatile__ ("
264 call _copy_row
265 "
266 : "=&D" (u1), "=&S" (u2)
267 : "0" (dstp), "1" (srcp)
268 : "memory" );
269 #else
270 #ifdef WIN32
271 { void *code = ©_row;
272 __asm {
273 push edi
274 push esi
275
276 mov edi, dstp
277 mov esi, srcp
278 call dword ptr code
279
280 pop esi
281 pop edi
282 }
283 }
284 #else
285 #error Need inline assembly for this compiler
286 #endif
287 #endif /* __GNUC__ */
288 break;
289 }
290 #else
291 switch (bpp) {
292 case 1:
293 copy_row1(srcp, srcrect->w, dstp, dstrect->w);
294 break;
295 case 2:
296 copy_row2((Uint16 *)srcp, srcrect->w,
297 (Uint16 *)dstp, dstrect->w);
298 break;
299 case 3:
300 copy_row3(srcp, srcrect->w, dstp, dstrect->w);
301 break;
302 case 4:
303 copy_row4((Uint32 *)srcp, srcrect->w,
304 (Uint32 *)dstp, dstrect->w);
305 break;
306 }
307 #endif
308 pos += inc;
309 }
310 return(0);
311 }
312