hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 1 | /* |
| 2 | * jchuff.c |
| 3 | * |
noel@chromium.org | 3395bcc | 2014-04-14 06:56:00 +0000 | [diff] [blame] | 4 | * This file was part of the Independent JPEG Group's software: |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 5 | * Copyright (C) 1991-1997, Thomas G. Lane. |
noel@chromium.org | 3395bcc | 2014-04-14 06:56:00 +0000 | [diff] [blame] | 6 | * libjpeg-turbo Modifications: |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 7 | * Copyright (C) 2009-2011, D. R. Commander. |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 8 | * For conditions of distribution and use, see the accompanying README file. |
| 9 | * |
| 10 | * This file contains Huffman entropy encoding routines. |
| 11 | * |
| 12 | * Much of the complexity here has to do with supporting output suspension. |
| 13 | * If the data destination module demands suspension, we want to be able to |
| 14 | * back up to the start of the current MCU. To do this, we copy state |
| 15 | * variables into local working storage, and update them back to the |
| 16 | * permanent JPEG objects only upon successful completion of an MCU. |
| 17 | */ |
| 18 | |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 19 | #define JPEG_INTERNALS |
| 20 | #include "jinclude.h" |
| 21 | #include "jpeglib.h" |
| 22 | #include "jchuff.h" /* Declarations shared with jcphuff.c */ |
| 23 | #include <limits.h> |
| 24 | |
noel@chromium.org | 841fff8 | 2014-05-23 23:38:59 +0000 | [diff] [blame] | 25 | /* |
| 26 | * NOTE: If USE_CLZ_INTRINSIC is defined, then clz/bsr instructions will be |
| 27 | * used for bit counting rather than the lookup table. This will reduce the |
| 28 | * memory footprint by 64k, which is important for some mobile applications |
| 29 | * that create many isolated instances of libjpeg-turbo (web browsers, for |
| 30 | * instance.) This may improve performance on some mobile platforms as well. |
| 31 | * This feature is enabled by default only on ARM processors, because some x86 |
| 32 | * chips have a slow implementation of bsr, and the use of clz/bsr cannot be |
| 33 | * shown to have a significant performance impact even on the x86 chips that |
| 34 | * have a fast implementation of it. When building for ARMv6, you can |
| 35 | * explicitly disable the use of clz/bsr by adding -mthumb to the compiler |
| 36 | * flags (this defines __thumb__). |
| 37 | */ |
| 38 | |
| 39 | /* NOTE: Both GCC and Clang define __GNUC__ */ |
| 40 | #if defined __GNUC__ && defined __arm__ |
| 41 | #if !defined __thumb__ || defined __thumb2__ |
| 42 | #define USE_CLZ_INTRINSIC |
| 43 | #endif |
| 44 | #endif |
| 45 | |
| 46 | #ifdef USE_CLZ_INTRINSIC |
| 47 | #define JPEG_NBITS_NONZERO(x) (32 - __builtin_clz(x)) |
| 48 | #define JPEG_NBITS(x) (x ? JPEG_NBITS_NONZERO(x) : 0) |
| 49 | #else |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 50 | static unsigned char jpeg_nbits_table[65536]; |
| 51 | static int jpeg_nbits_table_init = 0; |
noel@chromium.org | 841fff8 | 2014-05-23 23:38:59 +0000 | [diff] [blame] | 52 | #define JPEG_NBITS(x) (jpeg_nbits_table[x]) |
| 53 | #define JPEG_NBITS_NONZERO(x) JPEG_NBITS(x) |
| 54 | #endif |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 55 | |
| 56 | #ifndef min |
| 57 | #define min(a,b) ((a)<(b)?(a):(b)) |
| 58 | #endif |
| 59 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 60 | |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 61 | /* Expanded entropy encoder object for Huffman encoding. |
| 62 | * |
| 63 | * The savable_state subrecord contains fields that change within an MCU, |
| 64 | * but must not be updated permanently until we complete the MCU. |
| 65 | */ |
| 66 | |
| 67 | typedef struct { |
| 68 | size_t put_buffer; /* current bit-accumulation buffer */ |
| 69 | int put_bits; /* # of bits now in it */ |
| 70 | int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ |
| 71 | } savable_state; |
| 72 | |
| 73 | /* This macro is to work around compilers with missing or broken |
| 74 | * structure assignment. You'll need to fix this code if you have |
| 75 | * such a compiler and you change MAX_COMPS_IN_SCAN. |
| 76 | */ |
| 77 | |
| 78 | #ifndef NO_STRUCT_ASSIGN |
| 79 | #define ASSIGN_STATE(dest,src) ((dest) = (src)) |
| 80 | #else |
| 81 | #if MAX_COMPS_IN_SCAN == 4 |
| 82 | #define ASSIGN_STATE(dest,src) \ |
| 83 | ((dest).put_buffer = (src).put_buffer, \ |
| 84 | (dest).put_bits = (src).put_bits, \ |
| 85 | (dest).last_dc_val[0] = (src).last_dc_val[0], \ |
| 86 | (dest).last_dc_val[1] = (src).last_dc_val[1], \ |
| 87 | (dest).last_dc_val[2] = (src).last_dc_val[2], \ |
| 88 | (dest).last_dc_val[3] = (src).last_dc_val[3]) |
| 89 | #endif |
| 90 | #endif |
| 91 | |
| 92 | |
| 93 | typedef struct { |
| 94 | struct jpeg_entropy_encoder pub; /* public fields */ |
| 95 | |
| 96 | savable_state saved; /* Bit buffer & DC state at start of MCU */ |
| 97 | |
| 98 | /* These fields are NOT loaded into local working state. */ |
| 99 | unsigned int restarts_to_go; /* MCUs left in this restart interval */ |
| 100 | int next_restart_num; /* next restart number to write (0-7) */ |
| 101 | |
| 102 | /* Pointers to derived tables (these workspaces have image lifespan) */ |
| 103 | c_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS]; |
| 104 | c_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS]; |
| 105 | |
| 106 | #ifdef ENTROPY_OPT_SUPPORTED /* Statistics tables for optimization */ |
| 107 | long * dc_count_ptrs[NUM_HUFF_TBLS]; |
| 108 | long * ac_count_ptrs[NUM_HUFF_TBLS]; |
| 109 | #endif |
| 110 | } huff_entropy_encoder; |
| 111 | |
| 112 | typedef huff_entropy_encoder * huff_entropy_ptr; |
| 113 | |
| 114 | /* Working state while writing an MCU. |
| 115 | * This struct contains all the fields that are needed by subroutines. |
| 116 | */ |
| 117 | |
| 118 | typedef struct { |
| 119 | JOCTET * next_output_byte; /* => next byte to write in buffer */ |
| 120 | size_t free_in_buffer; /* # of byte spaces remaining in buffer */ |
| 121 | savable_state cur; /* Current bit buffer & DC state */ |
| 122 | j_compress_ptr cinfo; /* dump_buffer needs access to this */ |
| 123 | } working_state; |
| 124 | |
| 125 | |
| 126 | /* Forward declarations */ |
| 127 | METHODDEF(boolean) encode_mcu_huff JPP((j_compress_ptr cinfo, |
| 128 | JBLOCKROW *MCU_data)); |
| 129 | METHODDEF(void) finish_pass_huff JPP((j_compress_ptr cinfo)); |
| 130 | #ifdef ENTROPY_OPT_SUPPORTED |
| 131 | METHODDEF(boolean) encode_mcu_gather JPP((j_compress_ptr cinfo, |
| 132 | JBLOCKROW *MCU_data)); |
| 133 | METHODDEF(void) finish_pass_gather JPP((j_compress_ptr cinfo)); |
| 134 | #endif |
| 135 | |
| 136 | |
| 137 | /* |
| 138 | * Initialize for a Huffman-compressed scan. |
| 139 | * If gather_statistics is TRUE, we do not output anything during the scan, |
| 140 | * just count the Huffman symbols used and generate Huffman code tables. |
| 141 | */ |
| 142 | |
| 143 | METHODDEF(void) |
| 144 | start_pass_huff (j_compress_ptr cinfo, boolean gather_statistics) |
| 145 | { |
| 146 | huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; |
| 147 | int ci, dctbl, actbl; |
| 148 | jpeg_component_info * compptr; |
| 149 | |
| 150 | if (gather_statistics) { |
| 151 | #ifdef ENTROPY_OPT_SUPPORTED |
| 152 | entropy->pub.encode_mcu = encode_mcu_gather; |
| 153 | entropy->pub.finish_pass = finish_pass_gather; |
| 154 | #else |
| 155 | ERREXIT(cinfo, JERR_NOT_COMPILED); |
| 156 | #endif |
| 157 | } else { |
| 158 | entropy->pub.encode_mcu = encode_mcu_huff; |
| 159 | entropy->pub.finish_pass = finish_pass_huff; |
| 160 | } |
| 161 | |
| 162 | for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
| 163 | compptr = cinfo->cur_comp_info[ci]; |
| 164 | dctbl = compptr->dc_tbl_no; |
| 165 | actbl = compptr->ac_tbl_no; |
| 166 | if (gather_statistics) { |
| 167 | #ifdef ENTROPY_OPT_SUPPORTED |
| 168 | /* Check for invalid table indexes */ |
| 169 | /* (make_c_derived_tbl does this in the other path) */ |
| 170 | if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS) |
| 171 | ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, dctbl); |
| 172 | if (actbl < 0 || actbl >= NUM_HUFF_TBLS) |
| 173 | ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, actbl); |
| 174 | /* Allocate and zero the statistics tables */ |
| 175 | /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */ |
| 176 | if (entropy->dc_count_ptrs[dctbl] == NULL) |
| 177 | entropy->dc_count_ptrs[dctbl] = (long *) |
| 178 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
| 179 | 257 * SIZEOF(long)); |
| 180 | MEMZERO(entropy->dc_count_ptrs[dctbl], 257 * SIZEOF(long)); |
| 181 | if (entropy->ac_count_ptrs[actbl] == NULL) |
| 182 | entropy->ac_count_ptrs[actbl] = (long *) |
| 183 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
| 184 | 257 * SIZEOF(long)); |
| 185 | MEMZERO(entropy->ac_count_ptrs[actbl], 257 * SIZEOF(long)); |
| 186 | #endif |
| 187 | } else { |
| 188 | /* Compute derived values for Huffman tables */ |
| 189 | /* We may do this more than once for a table, but it's not expensive */ |
| 190 | jpeg_make_c_derived_tbl(cinfo, TRUE, dctbl, |
| 191 | & entropy->dc_derived_tbls[dctbl]); |
| 192 | jpeg_make_c_derived_tbl(cinfo, FALSE, actbl, |
| 193 | & entropy->ac_derived_tbls[actbl]); |
| 194 | } |
| 195 | /* Initialize DC predictions to 0 */ |
| 196 | entropy->saved.last_dc_val[ci] = 0; |
| 197 | } |
| 198 | |
| 199 | /* Initialize bit buffer to empty */ |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 200 | entropy->saved.put_buffer = 0; |
| 201 | entropy->saved.put_bits = 0; |
| 202 | |
| 203 | /* Initialize restart stuff */ |
| 204 | entropy->restarts_to_go = cinfo->restart_interval; |
| 205 | entropy->next_restart_num = 0; |
| 206 | } |
| 207 | |
| 208 | |
| 209 | /* |
| 210 | * Compute the derived values for a Huffman table. |
| 211 | * This routine also performs some validation checks on the table. |
| 212 | * |
| 213 | * Note this is also used by jcphuff.c. |
| 214 | */ |
| 215 | |
| 216 | GLOBAL(void) |
| 217 | jpeg_make_c_derived_tbl (j_compress_ptr cinfo, boolean isDC, int tblno, |
| 218 | c_derived_tbl ** pdtbl) |
| 219 | { |
| 220 | JHUFF_TBL *htbl; |
| 221 | c_derived_tbl *dtbl; |
| 222 | int p, i, l, lastp, si, maxsymbol; |
| 223 | char huffsize[257]; |
| 224 | unsigned int huffcode[257]; |
| 225 | unsigned int code; |
| 226 | |
| 227 | /* Note that huffsize[] and huffcode[] are filled in code-length order, |
| 228 | * paralleling the order of the symbols themselves in htbl->huffval[]. |
| 229 | */ |
| 230 | |
| 231 | /* Find the input Huffman table */ |
| 232 | if (tblno < 0 || tblno >= NUM_HUFF_TBLS) |
| 233 | ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno); |
| 234 | htbl = |
| 235 | isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno]; |
| 236 | if (htbl == NULL) |
| 237 | ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno); |
| 238 | |
| 239 | /* Allocate a workspace if we haven't already done so. */ |
| 240 | if (*pdtbl == NULL) |
| 241 | *pdtbl = (c_derived_tbl *) |
| 242 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
| 243 | SIZEOF(c_derived_tbl)); |
| 244 | dtbl = *pdtbl; |
| 245 | |
| 246 | /* Figure C.1: make table of Huffman code length for each symbol */ |
| 247 | |
| 248 | p = 0; |
| 249 | for (l = 1; l <= 16; l++) { |
| 250 | i = (int) htbl->bits[l]; |
| 251 | if (i < 0 || p + i > 256) /* protect against table overrun */ |
| 252 | ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); |
| 253 | while (i--) |
| 254 | huffsize[p++] = (char) l; |
| 255 | } |
| 256 | huffsize[p] = 0; |
| 257 | lastp = p; |
| 258 | |
| 259 | /* Figure C.2: generate the codes themselves */ |
| 260 | /* We also validate that the counts represent a legal Huffman code tree. */ |
| 261 | |
| 262 | code = 0; |
| 263 | si = huffsize[0]; |
| 264 | p = 0; |
| 265 | while (huffsize[p]) { |
| 266 | while (((int) huffsize[p]) == si) { |
| 267 | huffcode[p++] = code; |
| 268 | code++; |
| 269 | } |
| 270 | /* code is now 1 more than the last code used for codelength si; but |
| 271 | * it must still fit in si bits, since no code is allowed to be all ones. |
| 272 | */ |
| 273 | if (((INT32) code) >= (((INT32) 1) << si)) |
| 274 | ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); |
| 275 | code <<= 1; |
| 276 | si++; |
| 277 | } |
| 278 | |
| 279 | /* Figure C.3: generate encoding tables */ |
| 280 | /* These are code and size indexed by symbol value */ |
| 281 | |
| 282 | /* Set all codeless symbols to have code length 0; |
| 283 | * this lets us detect duplicate VAL entries here, and later |
| 284 | * allows emit_bits to detect any attempt to emit such symbols. |
| 285 | */ |
| 286 | MEMZERO(dtbl->ehufsi, SIZEOF(dtbl->ehufsi)); |
| 287 | |
| 288 | /* This is also a convenient place to check for out-of-range |
| 289 | * and duplicated VAL entries. We allow 0..255 for AC symbols |
| 290 | * but only 0..15 for DC. (We could constrain them further |
| 291 | * based on data depth and mode, but this seems enough.) |
| 292 | */ |
| 293 | maxsymbol = isDC ? 15 : 255; |
| 294 | |
| 295 | for (p = 0; p < lastp; p++) { |
| 296 | i = htbl->huffval[p]; |
| 297 | if (i < 0 || i > maxsymbol || dtbl->ehufsi[i]) |
| 298 | ERREXIT(cinfo, JERR_BAD_HUFF_TABLE); |
| 299 | dtbl->ehufco[i] = huffcode[p]; |
| 300 | dtbl->ehufsi[i] = huffsize[p]; |
| 301 | } |
| 302 | |
noel@chromium.org | 841fff8 | 2014-05-23 23:38:59 +0000 | [diff] [blame] | 303 | #ifndef USE_CLZ_INTRINSIC |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 304 | if(!jpeg_nbits_table_init) { |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 305 | for(i = 0; i < 65536; i++) { |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 306 | int nbits = 0, temp = i; |
| 307 | while (temp) {temp >>= 1; nbits++;} |
| 308 | jpeg_nbits_table[i] = nbits; |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 309 | } |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 310 | jpeg_nbits_table_init = 1; |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 311 | } |
noel@chromium.org | 841fff8 | 2014-05-23 23:38:59 +0000 | [diff] [blame] | 312 | #endif |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 313 | } |
| 314 | |
| 315 | |
| 316 | /* Outputting bytes to the file */ |
| 317 | |
| 318 | /* Emit a byte, taking 'action' if must suspend. */ |
| 319 | #define emit_byte(state,val,action) \ |
| 320 | { *(state)->next_output_byte++ = (JOCTET) (val); \ |
| 321 | if (--(state)->free_in_buffer == 0) \ |
| 322 | if (! dump_buffer(state)) \ |
| 323 | { action; } } |
| 324 | |
| 325 | |
| 326 | LOCAL(boolean) |
| 327 | dump_buffer (working_state * state) |
| 328 | /* Empty the output buffer; return TRUE if successful, FALSE if must suspend */ |
| 329 | { |
| 330 | struct jpeg_destination_mgr * dest = state->cinfo->dest; |
| 331 | |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 332 | if (! (*dest->empty_output_buffer) (state->cinfo)) |
| 333 | return FALSE; |
| 334 | /* After a successful buffer dump, must reset buffer pointers */ |
| 335 | state->next_output_byte = dest->next_output_byte; |
| 336 | state->free_in_buffer = dest->free_in_buffer; |
| 337 | return TRUE; |
| 338 | } |
| 339 | |
| 340 | |
| 341 | /* Outputting bits to the file */ |
| 342 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 343 | /* These macros perform the same task as the emit_bits() function in the |
| 344 | * original libjpeg code. In addition to reducing overhead by explicitly |
| 345 | * inlining the code, additional performance is achieved by taking into |
| 346 | * account the size of the bit buffer and waiting until it is almost full |
| 347 | * before emptying it. This mostly benefits 64-bit platforms, since 6 |
| 348 | * bytes can be stored in a 64-bit bit buffer before it has to be emptied. |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 349 | */ |
| 350 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 351 | #define EMIT_BYTE() { \ |
| 352 | JOCTET c; \ |
| 353 | put_bits -= 8; \ |
| 354 | c = (JOCTET)GETJOCTET(put_buffer >> put_bits); \ |
| 355 | *buffer++ = c; \ |
| 356 | if (c == 0xFF) /* need to stuff a zero byte? */ \ |
| 357 | *buffer++ = 0; \ |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 358 | } |
| 359 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 360 | #define PUT_BITS(code, size) { \ |
| 361 | put_bits += size; \ |
| 362 | put_buffer = (put_buffer << size) | code; \ |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 363 | } |
| 364 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 365 | #define CHECKBUF15() { \ |
| 366 | if (put_bits > 15) { \ |
| 367 | EMIT_BYTE() \ |
| 368 | EMIT_BYTE() \ |
| 369 | } \ |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 370 | } |
| 371 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 372 | #define CHECKBUF31() { \ |
| 373 | if (put_bits > 31) { \ |
| 374 | EMIT_BYTE() \ |
| 375 | EMIT_BYTE() \ |
| 376 | EMIT_BYTE() \ |
| 377 | EMIT_BYTE() \ |
| 378 | } \ |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 379 | } |
| 380 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 381 | #define CHECKBUF47() { \ |
| 382 | if (put_bits > 47) { \ |
| 383 | EMIT_BYTE() \ |
| 384 | EMIT_BYTE() \ |
| 385 | EMIT_BYTE() \ |
| 386 | EMIT_BYTE() \ |
| 387 | EMIT_BYTE() \ |
| 388 | EMIT_BYTE() \ |
| 389 | } \ |
| 390 | } |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 391 | |
| 392 | #if __WORDSIZE==64 || defined(_WIN64) |
| 393 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 394 | #define EMIT_BITS(code, size) { \ |
| 395 | CHECKBUF47() \ |
| 396 | PUT_BITS(code, size) \ |
| 397 | } |
| 398 | |
| 399 | #define EMIT_CODE(code, size) { \ |
| 400 | temp2 &= (((INT32) 1)<<nbits) - 1; \ |
| 401 | CHECKBUF31() \ |
| 402 | PUT_BITS(code, size) \ |
| 403 | PUT_BITS(temp2, nbits) \ |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 404 | } |
| 405 | |
| 406 | #else |
| 407 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 408 | #define EMIT_BITS(code, size) { \ |
| 409 | PUT_BITS(code, size) \ |
| 410 | CHECKBUF15() \ |
| 411 | } |
| 412 | |
| 413 | #define EMIT_CODE(code, size) { \ |
| 414 | temp2 &= (((INT32) 1)<<nbits) - 1; \ |
| 415 | PUT_BITS(code, size) \ |
| 416 | CHECKBUF15() \ |
| 417 | PUT_BITS(temp2, nbits) \ |
| 418 | CHECKBUF15() \ |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 419 | } |
| 420 | |
| 421 | #endif |
| 422 | |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 423 | |
| 424 | #define BUFSIZE (DCTSIZE2 * 2) |
| 425 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 426 | #define LOAD_BUFFER() { \ |
| 427 | if (state->free_in_buffer < BUFSIZE) { \ |
| 428 | localbuf = 1; \ |
| 429 | buffer = _buffer; \ |
| 430 | } \ |
| 431 | else buffer = state->next_output_byte; \ |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 432 | } |
| 433 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 434 | #define STORE_BUFFER() { \ |
| 435 | if (localbuf) { \ |
| 436 | bytes = buffer - _buffer; \ |
| 437 | buffer = _buffer; \ |
| 438 | while (bytes > 0) { \ |
| 439 | bytestocopy = min(bytes, state->free_in_buffer); \ |
| 440 | MEMCOPY(state->next_output_byte, buffer, bytestocopy); \ |
| 441 | state->next_output_byte += bytestocopy; \ |
| 442 | buffer += bytestocopy; \ |
| 443 | state->free_in_buffer -= bytestocopy; \ |
| 444 | if (state->free_in_buffer == 0) \ |
| 445 | if (! dump_buffer(state)) return FALSE; \ |
| 446 | bytes -= bytestocopy; \ |
| 447 | } \ |
| 448 | } \ |
| 449 | else { \ |
| 450 | state->free_in_buffer -= (buffer - state->next_output_byte); \ |
| 451 | state->next_output_byte = buffer; \ |
| 452 | } \ |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 453 | } |
| 454 | |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 455 | |
| 456 | LOCAL(boolean) |
| 457 | flush_bits (working_state * state) |
| 458 | { |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 459 | JOCTET _buffer[BUFSIZE], *buffer; |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 460 | size_t put_buffer; int put_bits; |
| 461 | size_t bytes, bytestocopy; int localbuf = 0; |
| 462 | |
| 463 | put_buffer = state->cur.put_buffer; |
| 464 | put_bits = state->cur.put_bits; |
| 465 | LOAD_BUFFER() |
| 466 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 467 | /* fill any partial byte with ones */ |
| 468 | PUT_BITS(0x7F, 7) |
| 469 | while (put_bits >= 8) EMIT_BYTE() |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 470 | |
| 471 | state->cur.put_buffer = 0; /* and reset bit-buffer to empty */ |
| 472 | state->cur.put_bits = 0; |
| 473 | STORE_BUFFER() |
| 474 | |
| 475 | return TRUE; |
| 476 | } |
| 477 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 478 | |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 479 | /* Encode a single block's worth of coefficients */ |
| 480 | |
| 481 | LOCAL(boolean) |
| 482 | encode_one_block (working_state * state, JCOEFPTR block, int last_dc_val, |
| 483 | c_derived_tbl *dctbl, c_derived_tbl *actbl) |
| 484 | { |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 485 | int temp, temp2, temp3; |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 486 | int nbits; |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 487 | int r, code, size; |
| 488 | JOCTET _buffer[BUFSIZE], *buffer; |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 489 | size_t put_buffer; int put_bits; |
| 490 | int code_0xf0 = actbl->ehufco[0xf0], size_0xf0 = actbl->ehufsi[0xf0]; |
| 491 | size_t bytes, bytestocopy; int localbuf = 0; |
| 492 | |
| 493 | put_buffer = state->cur.put_buffer; |
| 494 | put_bits = state->cur.put_bits; |
| 495 | LOAD_BUFFER() |
| 496 | |
| 497 | /* Encode the DC coefficient difference per section F.1.2.1 */ |
| 498 | |
| 499 | temp = temp2 = block[0] - last_dc_val; |
| 500 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 501 | /* This is a well-known technique for obtaining the absolute value without a |
| 502 | * branch. It is derived from an assembly language technique presented in |
| 503 | * "How to Optimize for the Pentium Processors", Copyright (c) 1996, 1997 by |
| 504 | * Agner Fog. |
| 505 | */ |
| 506 | temp3 = temp >> (CHAR_BIT * sizeof(int) - 1); |
| 507 | temp ^= temp3; |
| 508 | temp -= temp3; |
| 509 | |
| 510 | /* For a negative input, want temp2 = bitwise complement of abs(input) */ |
| 511 | /* This code assumes we are on a two's complement machine */ |
| 512 | temp2 += temp3; |
| 513 | |
| 514 | /* Find the number of bits needed for the magnitude of the coefficient */ |
noel@chromium.org | 841fff8 | 2014-05-23 23:38:59 +0000 | [diff] [blame] | 515 | nbits = JPEG_NBITS(temp); |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 516 | |
| 517 | /* Emit the Huffman-coded symbol for the number of bits */ |
| 518 | code = dctbl->ehufco[nbits]; |
| 519 | size = dctbl->ehufsi[nbits]; |
| 520 | PUT_BITS(code, size) |
| 521 | CHECKBUF15() |
| 522 | |
| 523 | /* Mask off any extra bits in code */ |
| 524 | temp2 &= (((INT32) 1)<<nbits) - 1; |
| 525 | |
| 526 | /* Emit that number of bits of the value, if positive, */ |
| 527 | /* or the complement of its magnitude, if negative. */ |
| 528 | PUT_BITS(temp2, nbits) |
| 529 | CHECKBUF15() |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 530 | |
| 531 | /* Encode the AC coefficients per section F.1.2.2 */ |
| 532 | |
| 533 | r = 0; /* r = run length of zeros */ |
| 534 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 535 | /* Manually unroll the k loop to eliminate the counter variable. This |
| 536 | * improves performance greatly on systems with a limited number of |
| 537 | * registers (such as x86.) |
| 538 | */ |
| 539 | #define kloop(jpeg_natural_order_of_k) { \ |
| 540 | if ((temp = block[jpeg_natural_order_of_k]) == 0) { \ |
| 541 | r++; \ |
| 542 | } else { \ |
| 543 | temp2 = temp; \ |
| 544 | /* Branch-less absolute value, bitwise complement, etc., same as above */ \ |
| 545 | temp3 = temp >> (CHAR_BIT * sizeof(int) - 1); \ |
| 546 | temp ^= temp3; \ |
| 547 | temp -= temp3; \ |
| 548 | temp2 += temp3; \ |
noel@chromium.org | 841fff8 | 2014-05-23 23:38:59 +0000 | [diff] [blame] | 549 | nbits = JPEG_NBITS_NONZERO(temp); \ |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 550 | /* if run length > 15, must emit special run-length-16 codes (0xF0) */ \ |
| 551 | while (r > 15) { \ |
| 552 | EMIT_BITS(code_0xf0, size_0xf0) \ |
| 553 | r -= 16; \ |
| 554 | } \ |
| 555 | /* Emit Huffman symbol for run length / number of bits */ \ |
| 556 | temp3 = (r << 4) + nbits; \ |
| 557 | code = actbl->ehufco[temp3]; \ |
| 558 | size = actbl->ehufsi[temp3]; \ |
| 559 | EMIT_CODE(code, size) \ |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 560 | r = 0; \ |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 561 | } \ |
| 562 | } |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 563 | |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 564 | /* One iteration for each value in jpeg_natural_order[] */ |
| 565 | kloop(1); kloop(8); kloop(16); kloop(9); kloop(2); kloop(3); |
| 566 | kloop(10); kloop(17); kloop(24); kloop(32); kloop(25); kloop(18); |
| 567 | kloop(11); kloop(4); kloop(5); kloop(12); kloop(19); kloop(26); |
| 568 | kloop(33); kloop(40); kloop(48); kloop(41); kloop(34); kloop(27); |
| 569 | kloop(20); kloop(13); kloop(6); kloop(7); kloop(14); kloop(21); |
| 570 | kloop(28); kloop(35); kloop(42); kloop(49); kloop(56); kloop(57); |
| 571 | kloop(50); kloop(43); kloop(36); kloop(29); kloop(22); kloop(15); |
| 572 | kloop(23); kloop(30); kloop(37); kloop(44); kloop(51); kloop(58); |
| 573 | kloop(59); kloop(52); kloop(45); kloop(38); kloop(31); kloop(39); |
| 574 | kloop(46); kloop(53); kloop(60); kloop(61); kloop(54); kloop(47); |
| 575 | kloop(55); kloop(62); kloop(63); |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 576 | |
| 577 | /* If the last coef(s) were zero, emit an end-of-block code */ |
hbono@chromium.org | 9862697 | 2011-08-03 03:13:08 +0000 | [diff] [blame] | 578 | if (r > 0) { |
| 579 | code = actbl->ehufco[0]; |
| 580 | size = actbl->ehufsi[0]; |
| 581 | EMIT_BITS(code, size) |
| 582 | } |
hbono@chromium.org | f0c4f33 | 2010-11-01 05:14:55 +0000 | [diff] [blame] | 583 | |
| 584 | state->cur.put_buffer = put_buffer; |
| 585 | state->cur.put_bits = put_bits; |
| 586 | STORE_BUFFER() |
| 587 | |
| 588 | return TRUE; |
| 589 | } |
| 590 | |
| 591 | |
| 592 | /* |
| 593 | * Emit a restart marker & resynchronize predictions. |
| 594 | */ |
| 595 | |
| 596 | LOCAL(boolean) |
| 597 | emit_restart (working_state * state, int restart_num) |
| 598 | { |
| 599 | int ci; |
| 600 | |
| 601 | if (! flush_bits(state)) |
| 602 | return FALSE; |
| 603 | |
| 604 | emit_byte(state, 0xFF, return FALSE); |
| 605 | emit_byte(state, JPEG_RST0 + restart_num, return FALSE); |
| 606 | |
| 607 | /* Re-initialize DC predictions to 0 */ |
| 608 | for (ci = 0; ci < state->cinfo->comps_in_scan; ci++) |
| 609 | state->cur.last_dc_val[ci] = 0; |
| 610 | |
| 611 | /* The restart counter is not updated until we successfully write the MCU. */ |
| 612 | |
| 613 | return TRUE; |
| 614 | } |
| 615 | |
| 616 | |
| 617 | /* |
| 618 | * Encode and output one MCU's worth of Huffman-compressed coefficients. |
| 619 | */ |
| 620 | |
| 621 | METHODDEF(boolean) |
| 622 | encode_mcu_huff (j_compress_ptr cinfo, JBLOCKROW *MCU_data) |
| 623 | { |
| 624 | huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; |
| 625 | working_state state; |
| 626 | int blkn, ci; |
| 627 | jpeg_component_info * compptr; |
| 628 | |
| 629 | /* Load up working state */ |
| 630 | state.next_output_byte = cinfo->dest->next_output_byte; |
| 631 | state.free_in_buffer = cinfo->dest->free_in_buffer; |
| 632 | ASSIGN_STATE(state.cur, entropy->saved); |
| 633 | state.cinfo = cinfo; |
| 634 | |
| 635 | /* Emit restart marker if needed */ |
| 636 | if (cinfo->restart_interval) { |
| 637 | if (entropy->restarts_to_go == 0) |
| 638 | if (! emit_restart(&state, entropy->next_restart_num)) |
| 639 | return FALSE; |
| 640 | } |
| 641 | |
| 642 | /* Encode the MCU data blocks */ |
| 643 | for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
| 644 | ci = cinfo->MCU_membership[blkn]; |
| 645 | compptr = cinfo->cur_comp_info[ci]; |
| 646 | if (! encode_one_block(&state, |
| 647 | MCU_data[blkn][0], state.cur.last_dc_val[ci], |
| 648 | entropy->dc_derived_tbls[compptr->dc_tbl_no], |
| 649 | entropy->ac_derived_tbls[compptr->ac_tbl_no])) |
| 650 | return FALSE; |
| 651 | /* Update last_dc_val */ |
| 652 | state.cur.last_dc_val[ci] = MCU_data[blkn][0][0]; |
| 653 | } |
| 654 | |
| 655 | /* Completed MCU, so update state */ |
| 656 | cinfo->dest->next_output_byte = state.next_output_byte; |
| 657 | cinfo->dest->free_in_buffer = state.free_in_buffer; |
| 658 | ASSIGN_STATE(entropy->saved, state.cur); |
| 659 | |
| 660 | /* Update restart-interval state too */ |
| 661 | if (cinfo->restart_interval) { |
| 662 | if (entropy->restarts_to_go == 0) { |
| 663 | entropy->restarts_to_go = cinfo->restart_interval; |
| 664 | entropy->next_restart_num++; |
| 665 | entropy->next_restart_num &= 7; |
| 666 | } |
| 667 | entropy->restarts_to_go--; |
| 668 | } |
| 669 | |
| 670 | return TRUE; |
| 671 | } |
| 672 | |
| 673 | |
| 674 | /* |
| 675 | * Finish up at the end of a Huffman-compressed scan. |
| 676 | */ |
| 677 | |
| 678 | METHODDEF(void) |
| 679 | finish_pass_huff (j_compress_ptr cinfo) |
| 680 | { |
| 681 | huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; |
| 682 | working_state state; |
| 683 | |
| 684 | /* Load up working state ... flush_bits needs it */ |
| 685 | state.next_output_byte = cinfo->dest->next_output_byte; |
| 686 | state.free_in_buffer = cinfo->dest->free_in_buffer; |
| 687 | ASSIGN_STATE(state.cur, entropy->saved); |
| 688 | state.cinfo = cinfo; |
| 689 | |
| 690 | /* Flush out the last data */ |
| 691 | if (! flush_bits(&state)) |
| 692 | ERREXIT(cinfo, JERR_CANT_SUSPEND); |
| 693 | |
| 694 | /* Update state */ |
| 695 | cinfo->dest->next_output_byte = state.next_output_byte; |
| 696 | cinfo->dest->free_in_buffer = state.free_in_buffer; |
| 697 | ASSIGN_STATE(entropy->saved, state.cur); |
| 698 | } |
| 699 | |
| 700 | |
| 701 | /* |
| 702 | * Huffman coding optimization. |
| 703 | * |
| 704 | * We first scan the supplied data and count the number of uses of each symbol |
| 705 | * that is to be Huffman-coded. (This process MUST agree with the code above.) |
| 706 | * Then we build a Huffman coding tree for the observed counts. |
| 707 | * Symbols which are not needed at all for the particular image are not |
| 708 | * assigned any code, which saves space in the DHT marker as well as in |
| 709 | * the compressed data. |
| 710 | */ |
| 711 | |
| 712 | #ifdef ENTROPY_OPT_SUPPORTED |
| 713 | |
| 714 | |
| 715 | /* Process a single block's worth of coefficients */ |
| 716 | |
| 717 | LOCAL(void) |
| 718 | htest_one_block (j_compress_ptr cinfo, JCOEFPTR block, int last_dc_val, |
| 719 | long dc_counts[], long ac_counts[]) |
| 720 | { |
| 721 | register int temp; |
| 722 | register int nbits; |
| 723 | register int k, r; |
| 724 | |
| 725 | /* Encode the DC coefficient difference per section F.1.2.1 */ |
| 726 | |
| 727 | temp = block[0] - last_dc_val; |
| 728 | if (temp < 0) |
| 729 | temp = -temp; |
| 730 | |
| 731 | /* Find the number of bits needed for the magnitude of the coefficient */ |
| 732 | nbits = 0; |
| 733 | while (temp) { |
| 734 | nbits++; |
| 735 | temp >>= 1; |
| 736 | } |
| 737 | /* Check for out-of-range coefficient values. |
| 738 | * Since we're encoding a difference, the range limit is twice as much. |
| 739 | */ |
| 740 | if (nbits > MAX_COEF_BITS+1) |
| 741 | ERREXIT(cinfo, JERR_BAD_DCT_COEF); |
| 742 | |
| 743 | /* Count the Huffman symbol for the number of bits */ |
| 744 | dc_counts[nbits]++; |
| 745 | |
| 746 | /* Encode the AC coefficients per section F.1.2.2 */ |
| 747 | |
| 748 | r = 0; /* r = run length of zeros */ |
| 749 | |
| 750 | for (k = 1; k < DCTSIZE2; k++) { |
| 751 | if ((temp = block[jpeg_natural_order[k]]) == 0) { |
| 752 | r++; |
| 753 | } else { |
| 754 | /* if run length > 15, must emit special run-length-16 codes (0xF0) */ |
| 755 | while (r > 15) { |
| 756 | ac_counts[0xF0]++; |
| 757 | r -= 16; |
| 758 | } |
| 759 | |
| 760 | /* Find the number of bits needed for the magnitude of the coefficient */ |
| 761 | if (temp < 0) |
| 762 | temp = -temp; |
| 763 | |
| 764 | /* Find the number of bits needed for the magnitude of the coefficient */ |
| 765 | nbits = 1; /* there must be at least one 1 bit */ |
| 766 | while ((temp >>= 1)) |
| 767 | nbits++; |
| 768 | /* Check for out-of-range coefficient values */ |
| 769 | if (nbits > MAX_COEF_BITS) |
| 770 | ERREXIT(cinfo, JERR_BAD_DCT_COEF); |
| 771 | |
| 772 | /* Count Huffman symbol for run length / number of bits */ |
| 773 | ac_counts[(r << 4) + nbits]++; |
| 774 | |
| 775 | r = 0; |
| 776 | } |
| 777 | } |
| 778 | |
| 779 | /* If the last coef(s) were zero, emit an end-of-block code */ |
| 780 | if (r > 0) |
| 781 | ac_counts[0]++; |
| 782 | } |
| 783 | |
| 784 | |
| 785 | /* |
| 786 | * Trial-encode one MCU's worth of Huffman-compressed coefficients. |
| 787 | * No data is actually output, so no suspension return is possible. |
| 788 | */ |
| 789 | |
| 790 | METHODDEF(boolean) |
| 791 | encode_mcu_gather (j_compress_ptr cinfo, JBLOCKROW *MCU_data) |
| 792 | { |
| 793 | huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; |
| 794 | int blkn, ci; |
| 795 | jpeg_component_info * compptr; |
| 796 | |
| 797 | /* Take care of restart intervals if needed */ |
| 798 | if (cinfo->restart_interval) { |
| 799 | if (entropy->restarts_to_go == 0) { |
| 800 | /* Re-initialize DC predictions to 0 */ |
| 801 | for (ci = 0; ci < cinfo->comps_in_scan; ci++) |
| 802 | entropy->saved.last_dc_val[ci] = 0; |
| 803 | /* Update restart state */ |
| 804 | entropy->restarts_to_go = cinfo->restart_interval; |
| 805 | } |
| 806 | entropy->restarts_to_go--; |
| 807 | } |
| 808 | |
| 809 | for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) { |
| 810 | ci = cinfo->MCU_membership[blkn]; |
| 811 | compptr = cinfo->cur_comp_info[ci]; |
| 812 | htest_one_block(cinfo, MCU_data[blkn][0], entropy->saved.last_dc_val[ci], |
| 813 | entropy->dc_count_ptrs[compptr->dc_tbl_no], |
| 814 | entropy->ac_count_ptrs[compptr->ac_tbl_no]); |
| 815 | entropy->saved.last_dc_val[ci] = MCU_data[blkn][0][0]; |
| 816 | } |
| 817 | |
| 818 | return TRUE; |
| 819 | } |
| 820 | |
| 821 | |
| 822 | /* |
| 823 | * Generate the best Huffman code table for the given counts, fill htbl. |
| 824 | * Note this is also used by jcphuff.c. |
| 825 | * |
| 826 | * The JPEG standard requires that no symbol be assigned a codeword of all |
| 827 | * one bits (so that padding bits added at the end of a compressed segment |
| 828 | * can't look like a valid code). Because of the canonical ordering of |
| 829 | * codewords, this just means that there must be an unused slot in the |
| 830 | * longest codeword length category. Section K.2 of the JPEG spec suggests |
| 831 | * reserving such a slot by pretending that symbol 256 is a valid symbol |
| 832 | * with count 1. In theory that's not optimal; giving it count zero but |
| 833 | * including it in the symbol set anyway should give a better Huffman code. |
| 834 | * But the theoretically better code actually seems to come out worse in |
| 835 | * practice, because it produces more all-ones bytes (which incur stuffed |
| 836 | * zero bytes in the final file). In any case the difference is tiny. |
| 837 | * |
| 838 | * The JPEG standard requires Huffman codes to be no more than 16 bits long. |
| 839 | * If some symbols have a very small but nonzero probability, the Huffman tree |
| 840 | * must be adjusted to meet the code length restriction. We currently use |
| 841 | * the adjustment method suggested in JPEG section K.2. This method is *not* |
| 842 | * optimal; it may not choose the best possible limited-length code. But |
| 843 | * typically only very-low-frequency symbols will be given less-than-optimal |
| 844 | * lengths, so the code is almost optimal. Experimental comparisons against |
| 845 | * an optimal limited-length-code algorithm indicate that the difference is |
| 846 | * microscopic --- usually less than a hundredth of a percent of total size. |
| 847 | * So the extra complexity of an optimal algorithm doesn't seem worthwhile. |
| 848 | */ |
| 849 | |
| 850 | GLOBAL(void) |
| 851 | jpeg_gen_optimal_table (j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[]) |
| 852 | { |
| 853 | #define MAX_CLEN 32 /* assumed maximum initial code length */ |
| 854 | UINT8 bits[MAX_CLEN+1]; /* bits[k] = # of symbols with code length k */ |
| 855 | int codesize[257]; /* codesize[k] = code length of symbol k */ |
| 856 | int others[257]; /* next symbol in current branch of tree */ |
| 857 | int c1, c2; |
| 858 | int p, i, j; |
| 859 | long v; |
| 860 | |
| 861 | /* This algorithm is explained in section K.2 of the JPEG standard */ |
| 862 | |
| 863 | MEMZERO(bits, SIZEOF(bits)); |
| 864 | MEMZERO(codesize, SIZEOF(codesize)); |
| 865 | for (i = 0; i < 257; i++) |
| 866 | others[i] = -1; /* init links to empty */ |
| 867 | |
| 868 | freq[256] = 1; /* make sure 256 has a nonzero count */ |
| 869 | /* Including the pseudo-symbol 256 in the Huffman procedure guarantees |
| 870 | * that no real symbol is given code-value of all ones, because 256 |
| 871 | * will be placed last in the largest codeword category. |
| 872 | */ |
| 873 | |
| 874 | /* Huffman's basic algorithm to assign optimal code lengths to symbols */ |
| 875 | |
| 876 | for (;;) { |
| 877 | /* Find the smallest nonzero frequency, set c1 = its symbol */ |
| 878 | /* In case of ties, take the larger symbol number */ |
| 879 | c1 = -1; |
| 880 | v = 1000000000L; |
| 881 | for (i = 0; i <= 256; i++) { |
| 882 | if (freq[i] && freq[i] <= v) { |
| 883 | v = freq[i]; |
| 884 | c1 = i; |
| 885 | } |
| 886 | } |
| 887 | |
| 888 | /* Find the next smallest nonzero frequency, set c2 = its symbol */ |
| 889 | /* In case of ties, take the larger symbol number */ |
| 890 | c2 = -1; |
| 891 | v = 1000000000L; |
| 892 | for (i = 0; i <= 256; i++) { |
| 893 | if (freq[i] && freq[i] <= v && i != c1) { |
| 894 | v = freq[i]; |
| 895 | c2 = i; |
| 896 | } |
| 897 | } |
| 898 | |
| 899 | /* Done if we've merged everything into one frequency */ |
| 900 | if (c2 < 0) |
| 901 | break; |
| 902 | |
| 903 | /* Else merge the two counts/trees */ |
| 904 | freq[c1] += freq[c2]; |
| 905 | freq[c2] = 0; |
| 906 | |
| 907 | /* Increment the codesize of everything in c1's tree branch */ |
| 908 | codesize[c1]++; |
| 909 | while (others[c1] >= 0) { |
| 910 | c1 = others[c1]; |
| 911 | codesize[c1]++; |
| 912 | } |
| 913 | |
| 914 | others[c1] = c2; /* chain c2 onto c1's tree branch */ |
| 915 | |
| 916 | /* Increment the codesize of everything in c2's tree branch */ |
| 917 | codesize[c2]++; |
| 918 | while (others[c2] >= 0) { |
| 919 | c2 = others[c2]; |
| 920 | codesize[c2]++; |
| 921 | } |
| 922 | } |
| 923 | |
| 924 | /* Now count the number of symbols of each code length */ |
| 925 | for (i = 0; i <= 256; i++) { |
| 926 | if (codesize[i]) { |
| 927 | /* The JPEG standard seems to think that this can't happen, */ |
| 928 | /* but I'm paranoid... */ |
| 929 | if (codesize[i] > MAX_CLEN) |
| 930 | ERREXIT(cinfo, JERR_HUFF_CLEN_OVERFLOW); |
| 931 | |
| 932 | bits[codesize[i]]++; |
| 933 | } |
| 934 | } |
| 935 | |
| 936 | /* JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure |
| 937 | * Huffman procedure assigned any such lengths, we must adjust the coding. |
| 938 | * Here is what the JPEG spec says about how this next bit works: |
| 939 | * Since symbols are paired for the longest Huffman code, the symbols are |
| 940 | * removed from this length category two at a time. The prefix for the pair |
| 941 | * (which is one bit shorter) is allocated to one of the pair; then, |
| 942 | * skipping the BITS entry for that prefix length, a code word from the next |
| 943 | * shortest nonzero BITS entry is converted into a prefix for two code words |
| 944 | * one bit longer. |
| 945 | */ |
| 946 | |
| 947 | for (i = MAX_CLEN; i > 16; i--) { |
| 948 | while (bits[i] > 0) { |
| 949 | j = i - 2; /* find length of new prefix to be used */ |
| 950 | while (bits[j] == 0) |
| 951 | j--; |
| 952 | |
| 953 | bits[i] -= 2; /* remove two symbols */ |
| 954 | bits[i-1]++; /* one goes in this length */ |
| 955 | bits[j+1] += 2; /* two new symbols in this length */ |
| 956 | bits[j]--; /* symbol of this length is now a prefix */ |
| 957 | } |
| 958 | } |
| 959 | |
| 960 | /* Remove the count for the pseudo-symbol 256 from the largest codelength */ |
| 961 | while (bits[i] == 0) /* find largest codelength still in use */ |
| 962 | i--; |
| 963 | bits[i]--; |
| 964 | |
| 965 | /* Return final symbol counts (only for lengths 0..16) */ |
| 966 | MEMCOPY(htbl->bits, bits, SIZEOF(htbl->bits)); |
| 967 | |
| 968 | /* Return a list of the symbols sorted by code length */ |
| 969 | /* It's not real clear to me why we don't need to consider the codelength |
| 970 | * changes made above, but the JPEG spec seems to think this works. |
| 971 | */ |
| 972 | p = 0; |
| 973 | for (i = 1; i <= MAX_CLEN; i++) { |
| 974 | for (j = 0; j <= 255; j++) { |
| 975 | if (codesize[j] == i) { |
| 976 | htbl->huffval[p] = (UINT8) j; |
| 977 | p++; |
| 978 | } |
| 979 | } |
| 980 | } |
| 981 | |
| 982 | /* Set sent_table FALSE so updated table will be written to JPEG file. */ |
| 983 | htbl->sent_table = FALSE; |
| 984 | } |
| 985 | |
| 986 | |
| 987 | /* |
| 988 | * Finish up a statistics-gathering pass and create the new Huffman tables. |
| 989 | */ |
| 990 | |
| 991 | METHODDEF(void) |
| 992 | finish_pass_gather (j_compress_ptr cinfo) |
| 993 | { |
| 994 | huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy; |
| 995 | int ci, dctbl, actbl; |
| 996 | jpeg_component_info * compptr; |
| 997 | JHUFF_TBL **htblptr; |
| 998 | boolean did_dc[NUM_HUFF_TBLS]; |
| 999 | boolean did_ac[NUM_HUFF_TBLS]; |
| 1000 | |
| 1001 | /* It's important not to apply jpeg_gen_optimal_table more than once |
| 1002 | * per table, because it clobbers the input frequency counts! |
| 1003 | */ |
| 1004 | MEMZERO(did_dc, SIZEOF(did_dc)); |
| 1005 | MEMZERO(did_ac, SIZEOF(did_ac)); |
| 1006 | |
| 1007 | for (ci = 0; ci < cinfo->comps_in_scan; ci++) { |
| 1008 | compptr = cinfo->cur_comp_info[ci]; |
| 1009 | dctbl = compptr->dc_tbl_no; |
| 1010 | actbl = compptr->ac_tbl_no; |
| 1011 | if (! did_dc[dctbl]) { |
| 1012 | htblptr = & cinfo->dc_huff_tbl_ptrs[dctbl]; |
| 1013 | if (*htblptr == NULL) |
| 1014 | *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo); |
| 1015 | jpeg_gen_optimal_table(cinfo, *htblptr, entropy->dc_count_ptrs[dctbl]); |
| 1016 | did_dc[dctbl] = TRUE; |
| 1017 | } |
| 1018 | if (! did_ac[actbl]) { |
| 1019 | htblptr = & cinfo->ac_huff_tbl_ptrs[actbl]; |
| 1020 | if (*htblptr == NULL) |
| 1021 | *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo); |
| 1022 | jpeg_gen_optimal_table(cinfo, *htblptr, entropy->ac_count_ptrs[actbl]); |
| 1023 | did_ac[actbl] = TRUE; |
| 1024 | } |
| 1025 | } |
| 1026 | } |
| 1027 | |
| 1028 | |
| 1029 | #endif /* ENTROPY_OPT_SUPPORTED */ |
| 1030 | |
| 1031 | |
| 1032 | /* |
| 1033 | * Module initialization routine for Huffman entropy encoding. |
| 1034 | */ |
| 1035 | |
| 1036 | GLOBAL(void) |
| 1037 | jinit_huff_encoder (j_compress_ptr cinfo) |
| 1038 | { |
| 1039 | huff_entropy_ptr entropy; |
| 1040 | int i; |
| 1041 | |
| 1042 | entropy = (huff_entropy_ptr) |
| 1043 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |
| 1044 | SIZEOF(huff_entropy_encoder)); |
| 1045 | cinfo->entropy = (struct jpeg_entropy_encoder *) entropy; |
| 1046 | entropy->pub.start_pass = start_pass_huff; |
| 1047 | |
| 1048 | /* Mark tables unallocated */ |
| 1049 | for (i = 0; i < NUM_HUFF_TBLS; i++) { |
| 1050 | entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL; |
| 1051 | #ifdef ENTROPY_OPT_SUPPORTED |
| 1052 | entropy->dc_count_ptrs[i] = entropy->ac_count_ptrs[i] = NULL; |
| 1053 | #endif |
| 1054 | } |
| 1055 | } |