198
199
200 /*
201 * Figure F.12: extend sign bit.
202 * On some machines, a shift and add will be faster than a table lookup.
203 */
204
205 #ifdef AVOID_TABLES
206
207 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))
208
209 #else
210
211 #define HUFF_EXTEND(x,s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))
212
213 static const int extend_test[16] = /* entry n is 2**(n-1) */
214 { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
215 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };
216
217 static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
218 { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,
219 ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1,
220 ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1,
221 ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 };
222
223 #endif /* AVOID_TABLES */
224
225
226 /*
227 * Check for a restart marker & resynchronize decoder.
228 * Returns FALSE if must suspend.
229 */
230
231 LOCAL(boolean)
232 process_restart (j_decompress_ptr cinfo)
233 {
234 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
235 int ci;
236
237 /* Throw away any unused bits remaining in bit buffer; */
238 /* include any full bytes in next_marker's count of discarded bytes */
239 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
240 entropy->bitstate.bits_left = 0;
241
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198
199
200 /*
201 * Figure F.12: extend sign bit.
202 * On some machines, a shift and add will be faster than a table lookup.
203 */
204
205 #ifdef AVOID_TABLES
206
207 #define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))
208
209 #else
210
211 #define HUFF_EXTEND(x,s) ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))
212
213 static const int extend_test[16] = /* entry n is 2**(n-1) */
214 { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,
215 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };
216
217 static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */
218 { 0,
219 (int)(((unsigned)(~0)<<1) + 1), (int)(((unsigned)(~0)<<2) + 1),
220 (int)(((unsigned)(~0)<<3) + 1), (int)(((unsigned)(~0)<<4) + 1),
221 (int)(((unsigned)(~0)<<5) + 1), (int)(((unsigned)(~0)<<6) + 1),
222 (int)(((unsigned)(~0)<<7) + 1), (int)(((unsigned)(~0)<<8) + 1),
223 (int)(((unsigned)(~0)<<9) + 1), (int)(((unsigned)(~0)<<10) + 1),
224 (int)(((unsigned)(~0)<<11) + 1), (int)(((unsigned)(~0)<<12) + 1),
225 (int)(((unsigned)(~0)<<13) + 1), (int)(((unsigned)(~0)<<14) + 1),
226 (int)(((unsigned)(~0)<<15) + 1) };
227
228 #endif /* AVOID_TABLES */
229
230
231 /*
232 * Check for a restart marker & resynchronize decoder.
233 * Returns FALSE if must suspend.
234 */
235
236 LOCAL(boolean)
237 process_restart (j_decompress_ptr cinfo)
238 {
239 phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
240 int ci;
241
242 /* Throw away any unused bits remaining in bit buffer; */
243 /* include any full bytes in next_marker's count of discarded bytes */
244 cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
245 entropy->bitstate.bits_left = 0;
246
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