libcitadel/lib/html_to_ascii.c

   1 // Functions which handle translation between HTML and plain text
   2 // Copyright (c) 2000-2022 by the citadel.org team
   3 //
   4 // This program is open source software.  Use, duplication, or disclosure
   5 // is subject to the terms of the GNU General Public License, version 3.
   6
   7 #include <stdlib.h>
   8 #include <unistd.h>
   9 #include <stdio.h>
  10 #include <signal.h>
  11 #include <sys/types.h>
  12 #include <ctype.h>
  13 #include <string.h>
  14 #include <sys/stat.h>
  15 #include <errno.h>
  16 #include <limits.h>
  17
  18 #if TIME_WITH_SYS_TIME
  19 # include <sys/time.h>
  20 # include <time.h>
  21 #else
  22 # if HAVE_SYS_TIME_H
  23 #  include <sys/time.h>
  24 # else
  25 #  include <time.h>
  26 # endif
  27 #endif
  28
  29 #include "libcitadel.h"
  30
  31
  32 // Convert HTML to plain text.
  33 //
  34 // inputmsg     = pointer to raw HTML message
  35 // msglen       = stop reading after this many bytes
  36 // screenwidth  = desired output screenwidth
  37 // ansi         = if nonzero, assume output is to a terminal that supports ANSI escape codes
  38 //
  39 char *html_to_ascii(const char *inputmsg, int msglen, int screenwidth, int ansi) {
  40         char inbuf[SIZ];
  41         int inbuf_len = 0;
  42         char outbuf[SIZ];
  43         char tag[1024];
  44         int done_reading = 0;
  45         const char *inptr;
  46         char *outptr;
  47         size_t outptr_buffer_size;
  48         size_t output_len = 0;
  49         int i, j, ch, did_out, rb, scanch;
  50         int nest = 0;                           // Bracket nesting level
  51         int blockquote = 0;                     // BLOCKQUOTE nesting level
  52         int styletag = 0;                       // STYLE tag nesting level
  53         int styletag_start = 0;
  54         int bytes_processed = 0;
  55         char nl[128];
  56
  57         tag[0] = '\0';
  58         strcpy(nl, "\n");
  59         inptr = inputmsg;
  60         strcpy(inbuf, "");
  61         strcpy(outbuf, "");
  62         if (msglen == 0) msglen = strlen(inputmsg);
  63
  64         outptr_buffer_size = strlen(inptr) + SIZ;
  65         outptr = malloc(outptr_buffer_size);
  66         if (outptr == NULL) return NULL;
  67         strcpy(outptr, "");
  68         output_len = 0;
  69
  70         do {
  71                 /* Fill the input buffer */
  72                 inbuf_len = strlen(inbuf);
  73                 if ( (done_reading == 0) && (inbuf_len < (SIZ-128)) ) {
  74
  75                         ch = *inptr++;
  76                         if (ch != 0) {
  77                                 inbuf[inbuf_len++] = ch;
  78                                 inbuf[inbuf_len] = 0;
  79                         }
  80                         else {
  81                                 done_reading = 1;
  82                         }
  83
  84                         ++bytes_processed;
  85                         if (bytes_processed > msglen) {
  86                                 done_reading = 1;
  87                         }
  88
  89                 }
  90
  91                 /* Do some parsing */
  92                 if (!IsEmptyStr(inbuf)) {
  93
  94
  95                     /* Fold in all the spacing */
  96                     for (i=0; !IsEmptyStr(&inbuf[i]); ++i) {
  97                         if (inbuf[i]==10) inbuf[i]=32;
  98                         if (inbuf[i]==13) inbuf[i]=32;
  99                         if (inbuf[i]==9) inbuf[i]=32;
 100                     }
 101                     for (i=0; !IsEmptyStr(&inbuf[i]); ++i) {
 102                         while ((inbuf[i]==32)&&(inbuf[i+1]==32)) {
 103                                 strcpy(&inbuf[i], &inbuf[i+1]);
 104                         }
 105                     }
 106
 107                     for (i=0; !IsEmptyStr(&inbuf[i]); ++i) {
 108
 109                         ch = inbuf[i];
 110
 111                         if (ch == '<') {
 112                                 ++nest;
 113                                 strcpy(tag, "");
 114                         }
 115
 116                         else if (ch == '>') {   /* We have a tag. */
 117                                 if (nest > 0) --nest;
 118
 119                                 /* Unqualify the tag (truncate at first space) */
 120                                 if (strchr(tag, ' ') != NULL) {
 121                                         strcpy(strchr(tag, ' '), "");
 122                                 }
 123
 124                                 if (!strcasecmp(tag, "P")) {
 125                                         strcat(outbuf, nl);
 126                                         strcat(outbuf, nl);
 127                                 }
 128
 129                                 if (!strcasecmp(tag, "/DIV")) {
 130                                         strcat(outbuf, nl);
 131                                         strcat(outbuf, nl);
 132                                 }
 133
 134                                 if (!strcasecmp(tag, "LI")) {
 135                                         strcat(outbuf, nl);
 136                                         strcat(outbuf, " * ");
 137                                 }
 138
 139                                 else if (!strcasecmp(tag, "/UL")) {
 140                                         strcat(outbuf, nl);
 141                                         strcat(outbuf, nl);
 142                                 }
 143
 144                                 else if (!strcasecmp(tag, "H1")) {
 145                                         strcat(outbuf, nl);
 146                                         strcat(outbuf, nl);
 147                                 }
 148
 149                                 else if (!strcasecmp(tag, "H2")) {
 150                                         strcat(outbuf, nl);
 151                                         strcat(outbuf, nl);
 152                                 }
 153
 154                                 else if (!strcasecmp(tag, "H3")) {
 155                                         strcat(outbuf, nl);
 156                                         strcat(outbuf, nl);
 157                                 }
 158
 159                                 else if (!strcasecmp(tag, "H4")) {
 160                                         strcat(outbuf, nl);
 161                                         strcat(outbuf, nl);
 162                                 }
 163
 164                                 else if (!strcasecmp(tag, "/H1")) {
 165                                         strcat(outbuf, nl);
 166                                 }
 167
 168                                 else if (!strcasecmp(tag, "/H2")) {
 169                                         strcat(outbuf, nl);
 170                                 }
 171
 172                                 else if (!strcasecmp(tag, "/H3")) {
 173                                         strcat(outbuf, nl);
 174                                 }
 175
 176                                 else if (!strcasecmp(tag, "/H4")) {
 177                                         strcat(outbuf, nl);
 178                                 }
 179
 180                                 else if (!strcasecmp(tag, "HR")) {
 181                                         strcat(outbuf, nl);
 182                                         strcat(outbuf, " ");
 183                                         for (j=0; j<screenwidth-2; ++j)
 184                                                 strcat(outbuf, "-");
 185                                         strcat(outbuf, nl);
 186                                 }
 187
 188 #if 0
 189         These seemed like a good idea at the time, but it just makes a mess.
 190
 191                                 else if (
 192                                         (!strcasecmp(tag, "B"))
 193                                         || (!strcasecmp(tag, "/B"))
 194                                         || (!strcasecmp(tag, "STRONG"))
 195                                         || (!strcasecmp(tag, "/STRONG"))
 196                                 ) {
 197                                         strcat(outbuf, "*");
 198                                 }
 199
 200                                 else if (
 201                                         (!strcasecmp(tag, "I"))
 202                                         || (!strcasecmp(tag, "/I"))
 203                                         || (!strcasecmp(tag, "EM"))
 204                                         || (!strcasecmp(tag, "/EM"))
 205                                 ) {
 206                                         strcat(outbuf, "/");
 207                                 }
 208
 209                                 else if (
 210                                         (!strcasecmp(tag, "U"))
 211                                         || (!strcasecmp(tag, "/U"))
 212                                 ) {
 213                                         strcat(outbuf, "_");
 214                                 }
 215 #endif
 216
 217                                 else if (!strcasecmp(tag, "BR")) {
 218                                         strcat(outbuf, nl);
 219                                 }
 220
 221                                 else if (!strcasecmp(tag, "TR")) {
 222                                         strcat(outbuf, nl);
 223                                 }
 224
 225                                 else if (!strcasecmp(tag, "/TABLE")) {
 226                                         strcat(outbuf, nl);
 227                                 }
 228
 229                                 else if (!strcasecmp(tag, "BLOCKQUOTE")) {
 230                                         ++blockquote;
 231                                         strcpy(nl, "\n");
 232                                         if ( (blockquote == 1) && (ansi) ) {
 233                                                 strcat(nl, "\033[2m\033[3m");
 234                                         }
 235                                         for (j=0; j<blockquote; ++j) strcat(nl, ">");
 236                                         strcat(outbuf, nl);
 237                                 }
 238
 239                                 else if (!strcasecmp(tag, "/BLOCKQUOTE")) {
 240                                         strcat(outbuf, "\n");
 241                                         --blockquote;
 242                                         if ( (blockquote == 0) && (ansi) ) {
 243                                                 strcat(outbuf, "\033[22m\033[23m");
 244                                         }
 245                                         strcpy(nl, "\n");
 246                                         for (j=0; j<blockquote; ++j) strcat(nl, ">");
 247                                         strcat(outbuf, nl);
 248                                 }
 249
 250                                 else if (!strcasecmp(tag, "STYLE")) {
 251                                         ++styletag;
 252                                         if (styletag == 1) {
 253                                                 styletag_start = strlen(outbuf);
 254                                         }
 255                                 }
 256
 257                                 else if (!strcasecmp(tag, "/STYLE")) {
 258                                         --styletag;
 259                                         if (styletag == 0) {
 260                                                 outbuf[styletag_start] = 0;
 261                                         }
 262                                 }
 263
 264                         }
 265
 266                         else if ((nest > 0) && (strlen(tag)<(sizeof(tag)-1))) {
 267                                 tag[strlen(tag)+1] = 0;
 268                                 tag[strlen(tag)] = ch;
 269                         }
 270
 271                         else if ((!nest) && (styletag == 0)) {
 272                                 outbuf[strlen(outbuf)+1] = 0;
 273                                 outbuf[strlen(outbuf)] = ch;
 274                         }
 275                     }
 276                     strcpy(inbuf, &inbuf[i]);
 277                 }
 278
 279                 /* Convert &; tags to the forbidden characters */
 280                 if (!IsEmptyStr(outbuf)) for (i=0; !IsEmptyStr(&outbuf[i]); ++i) {
 281
 282                         /* Character entity references */
 283                         if (!strncasecmp(&outbuf[i], "&nbsp;", 6)) {
 284                                 outbuf[i] = ' ';
 285                                 strcpy(&outbuf[i+1], &outbuf[i+6]);
 286                         }
 287
 288                         if (!strncasecmp(&outbuf[i], "&ensp;", 6)) {
 289                                 outbuf[i] = ' ';
 290                                 strcpy(&outbuf[i+1], &outbuf[i+6]);
 291                         }
 292
 293                         if (!strncasecmp(&outbuf[i], "&emsp;", 6)) {
 294                                 outbuf[i] = ' ';
 295                                 strcpy(&outbuf[i+1], &outbuf[i+6]);
 296                         }
 297
 298                         if (!strncasecmp(&outbuf[i], "&thinsp;", 8)) {
 299                                 outbuf[i] = ' ';
 300                                 strcpy(&outbuf[i+1], &outbuf[i+8]);
 301                         }
 302
 303                         else if (!strncasecmp(&outbuf[i], "&lt;", 4)) {
 304                                 outbuf[i] = '<';
 305                                 strcpy(&outbuf[i+1], &outbuf[i+4]);
 306                         }
 307
 308                         else if (!strncasecmp(&outbuf[i], "&gt;", 4)) {
 309                                 outbuf[i] = '>';
 310                                 strcpy(&outbuf[i+1], &outbuf[i+4]);
 311                         }
 312
 313                         else if (!strncasecmp(&outbuf[i], "&amp;", 5)) {
 314                                 strcpy(&outbuf[i+1], &outbuf[i+5]);
 315                         }
 316
 317                         else if (!strncasecmp(&outbuf[i], "&quot;", 6)) {
 318                                 outbuf[i] = '\"';
 319                                 strcpy(&outbuf[i+1], &outbuf[i+6]);
 320                         }
 321
 322                         else if (!strncasecmp(&outbuf[i], "&lsquo;", 7)) {
 323                                 outbuf[i] = '`';
 324                                 strcpy(&outbuf[i+1], &outbuf[i+7]);
 325                         }
 326
 327                         else if (!strncasecmp(&outbuf[i], "&rsquo;", 7)) {
 328                                 outbuf[i] = '\'';
 329                                 strcpy(&outbuf[i+1], &outbuf[i+7]);
 330                         }
 331
 332                         else if (!strncasecmp(&outbuf[i], "&copy;", 6)) {
 333                                 outbuf[i] = '(';
 334                                 outbuf[i+1] = 'c';
 335                                 outbuf[i+2] = ')';
 336                                 strcpy(&outbuf[i+3], &outbuf[i+6]);
 337                         }
 338
 339                         else if (!strncasecmp(&outbuf[i], "&bull;", 6)) {
 340                                 outbuf[i] = ' ';
 341                                 outbuf[i+1] = '*';
 342                                 outbuf[i+2] = ' ';
 343                                 strcpy(&outbuf[i+3], &outbuf[i+6]);
 344                         }
 345
 346                         else if (!strncasecmp(&outbuf[i], "&hellip;", 8)) {
 347                                 outbuf[i] = '.';
 348                                 outbuf[i+1] = '.';
 349                                 outbuf[i+2] = '.';
 350                                 strcpy(&outbuf[i+3], &outbuf[i+8]);
 351                         }
 352
 353                         else if (!strncasecmp(&outbuf[i], "&trade;", 7)) {
 354                                 outbuf[i] = '(';
 355                                 outbuf[i+1] = 't';
 356                                 outbuf[i+2] = 'm';
 357                                 outbuf[i+3] = ')';
 358                                 strcpy(&outbuf[i+4], &outbuf[i+7]);
 359                         }
 360
 361                         else if (!strncasecmp(&outbuf[i], "&reg;", 5)) {
 362                                 outbuf[i] = '(';
 363                                 outbuf[i+1] = 'r';
 364                                 outbuf[i+2] = ')';
 365                                 strcpy(&outbuf[i+3], &outbuf[i+5]);
 366                         }
 367
 368                         else if (!strncasecmp(&outbuf[i], "&frac14;", 8)) {
 369                                 outbuf[i] = '1';
 370                                 outbuf[i+1] = '/';
 371                                 outbuf[i+2] = '4';
 372                                 strcpy(&outbuf[i+3], &outbuf[i+8]);
 373                         }
 374
 375                         else if (!strncasecmp(&outbuf[i], "&frac12;", 8)) {
 376                                 outbuf[i] = '1';
 377                                 outbuf[i+1] = '/';
 378                                 outbuf[i+2] = '2';
 379                                 strcpy(&outbuf[i+3], &outbuf[i+8]);
 380                         }
 381
 382                         else if (!strncasecmp(&outbuf[i], "&frac34;", 8)) {
 383                                 outbuf[i] = '3';
 384                                 outbuf[i+1] = '/';
 385                                 outbuf[i+2] = '4';
 386                                 strcpy(&outbuf[i+3], &outbuf[i+8]);
 387                         }
 388
 389                         else if (!strncasecmp(&outbuf[i], "&ndash;", 7)) {
 390                                 outbuf[i] = '-';
 391                                 outbuf[i+1] = '-';
 392                                 strcpy(&outbuf[i+2], &outbuf[i+7]);
 393                         }
 394
 395                         else if (!strncasecmp(&outbuf[i], "&mdash;", 7)) {
 396                                 outbuf[i] = '-';
 397                                 outbuf[i+1] = '-';
 398                                 outbuf[i+2] = '-';
 399                                 strcpy(&outbuf[i+3], &outbuf[i+7]);
 400                         }
 401
 402                         else if (!strncmp(&outbuf[i], "&Ccedil;", 8)) {
 403                                 outbuf[i] = 'C';
 404                                 strcpy(&outbuf[i+1], &outbuf[i+8]);
 405                         }
 406
 407                         else if (!strncasecmp(&outbuf[i], "&ccedil;", 8)) {
 408                                 outbuf[i] = 'c';
 409                                 strcpy(&outbuf[i+1], &outbuf[i+8]);
 410                         }
 411
 412                         else if (!strncmp(&outbuf[i], "&Egrave;", 8)) {
 413                                 outbuf[i] = 'E';
 414                                 strcpy(&outbuf[i+1], &outbuf[i+8]);
 415                         }
 416
 417                         else if (!strncasecmp(&outbuf[i], "&egrave;", 8)) {
 418                                 outbuf[i] = 'e';
 419                                 strcpy(&outbuf[i+1], &outbuf[i+8]);
 420                         }
 421
 422                         else if (!strncmp(&outbuf[i], "&Ecirc;", 7)) {
 423                                 outbuf[i] = 'E';
 424                                 strcpy(&outbuf[i+1], &outbuf[i+7]);
 425                         }
 426
 427                         else if (!strncasecmp(&outbuf[i], "&ecirc;", 7)) {
 428                                 outbuf[i] = 'e';
 429                                 strcpy(&outbuf[i+1], &outbuf[i+7]);
 430                         }
 431
 432                         else if (!strncmp(&outbuf[i], "&Eacute;", 8)) {
 433                                 outbuf[i] = 'E';
 434                                 strcpy(&outbuf[i+1], &outbuf[i+8]);
 435                         }
 436
 437                         else if (!strncasecmp(&outbuf[i], "&eacute;", 8)) {
 438                                 outbuf[i] = 'e';
 439                                 strcpy(&outbuf[i+1], &outbuf[i+8]);
 440                         }
 441
 442                         else if (!strncmp(&outbuf[i], "&Agrave;", 8)) {
 443                                 outbuf[i] = 'A';
 444                                 strcpy(&outbuf[i+1], &outbuf[i+8]);
 445                         }
 446
 447                         else if (!strncasecmp(&outbuf[i], "&agrave;", 8)) {
 448                                 outbuf[i] = 'a';
 449                                 strcpy(&outbuf[i+1], &outbuf[i+8]);
 450                         }
 451
 452                         else if (!strncasecmp(&outbuf[i], "&ldquo;", 7)) {
 453                                 outbuf[i] = '\"';
 454                                 strcpy(&outbuf[i+1], &outbuf[i+7]);
 455                         }
 456
 457                         else if (!strncasecmp(&outbuf[i], "&rdquo;", 7)) {
 458                                 outbuf[i] = '\"';
 459                                 strcpy(&outbuf[i+1], &outbuf[i+7]);
 460                         }
 461
 462                         else if (!strncasecmp(&outbuf[i], "&acute;", 7)) {
 463                                 outbuf[i] = '\'';
 464                                 strcpy(&outbuf[i+1], &outbuf[i+7]);
 465                         }
 466
 467                         else if (!strncasecmp(&outbuf[i], "&#8217;", 7)) {
 468                                 outbuf[i] = '\'';
 469                                 strcpy(&outbuf[i+1], &outbuf[i+7]);
 470                         }
 471
 472                         else if (!strncasecmp(&outbuf[i], "&#8211;", 7)) {
 473                                 outbuf[i] = '-';
 474                                 strcpy(&outbuf[i+1], &outbuf[i+7]);
 475                         }
 476
 477                         /* two-digit decimal equivalents */
 478                         else if (outbuf[i] == '&'       &&
 479                                  outbuf[i + 1] == '#'   &&
 480                                  isdigit(outbuf[i + 2]) &&
 481                                  isdigit(outbuf[i + 3]) &&
 482                                  (outbuf[i+4] == ';') )
 483                         {
 484                                 scanch = 0;
 485                                 sscanf(&outbuf[i+2], "%02d", &scanch);
 486                                 outbuf[i] = scanch;
 487                                 strcpy(&outbuf[i+1], &outbuf[i+5]);
 488                         }
 489
 490                         /* three-digit decimal equivalents */
 491                         else if (outbuf[i] == '&'       &&
 492                                  outbuf[i + 1] == '#'   &&
 493                                  isdigit(outbuf[i + 2]) &&
 494                                  isdigit(outbuf[i + 3]) &&
 495                                  isdigit(outbuf[i + 4]) &&
 496                                  (outbuf[i + 5] == ';') )
 497                         {
 498                                 scanch = 0;
 499                                 sscanf(&outbuf[i+2], "%03d", &scanch);
 500                                 outbuf[i] = scanch;
 501                                 strcpy(&outbuf[i+1], &outbuf[i+6]);
 502                         }
 503
 504                         /* four-digit decimal equivalents */
 505                         else if (outbuf[i] == '&'       &&
 506                                  outbuf[i + 1] == '#'   &&
 507                                  isdigit(outbuf[i + 2]) &&
 508                                  isdigit(outbuf[i + 3]) &&
 509                                  isdigit(outbuf[i + 4]) &&
 510                                  isdigit(outbuf[i + 5]) &&
 511                                  (outbuf[i + 6] == ';') )
 512                         {
 513                                 scanch = 0;
 514                                 sscanf(&outbuf[i+2], "%04d", &scanch);
 515                                 outbuf[i] = scanch;
 516                                 strcpy(&outbuf[i+1], &outbuf[i+7]);
 517                         }
 518
 519                 }
 520
 521                 /* Make sure the output buffer is big enough */
 522                 if ((output_len + strlen(outbuf) + SIZ) > outptr_buffer_size) {
 523                         outptr_buffer_size += SIZ;
 524                         outptr = realloc(outptr, outptr_buffer_size);
 525                         if (outptr == NULL) {
 526                                 abort();
 527                         }
 528                 }
 529
 530                 /* Output any lines terminated with hard line breaks */
 531                 do {
 532                         did_out = 0;
 533                         if (strlen(outbuf) > 0) {
 534                             for (i = 0; i<strlen(outbuf); ++i) {
 535                                 if ( (i<(screenwidth-2)) && (outbuf[i]=='\n')) {
 536
 537                                         strncpy(&outptr[output_len], outbuf, i+1);
 538                                         output_len += (i+1);
 539
 540                                         strcpy(outbuf, &outbuf[i+1]);
 541                                         i = 0;
 542                                         did_out = 1;
 543                                 }
 544                         }
 545                     }
 546                 } while (did_out);
 547
 548                 /* Add soft line breaks */
 549                 if (strlen(outbuf) > (screenwidth - 2 )) {
 550                         rb = (-1);
 551                         for (i=0; i<(screenwidth-2); ++i) {
 552                                 if (outbuf[i]==32) rb = i;
 553                         }
 554                         if (rb>=0) {
 555                                 strncpy(&outptr[output_len], outbuf, rb);
 556                                 output_len += rb;
 557                                 strcpy(&outptr[output_len], nl);
 558                                 output_len += strlen(nl);
 559                                 strcpy(outbuf, &outbuf[rb+1]);
 560                         } else {
 561                                 strncpy(&outptr[output_len], outbuf,
 562                                         screenwidth-2);
 563                                 output_len += (screenwidth-2);
 564                                 strcpy(&outptr[output_len], nl);
 565                                 output_len += strlen(nl);
 566                                 strcpy(outbuf, &outbuf[screenwidth-2]);
 567                         }
 568                 }
 569
 570         } while (done_reading == 0);
 571
 572         strcpy(&outptr[output_len], outbuf);
 573         output_len += strlen(outbuf);
 574
 575         /* Strip leading/trailing whitespace.  We can't do this with
 576          * striplt() because it uses too many strlen()'s
 577          */
 578         while ((output_len > 0) && (isspace(outptr[0]))) {
 579                 strcpy(outptr, &outptr[1]);
 580                 --output_len;
 581         }
 582         while ((output_len > 0) && (isspace(outptr[output_len-1]))) {
 583                 outptr[output_len-1] = 0;
 584                 --output_len;
 585         }
 586
 587         if ((output_len > 0) && (outptr[output_len-1] != '\n')) {
 588                 strcat(outptr, "\n");
 589                 ++output_len;
 590         }
 591
 592         return outptr;
 593
 594 }