html.c

   1 /*      $Id: html.c,v 1.132 2011/04/09 15:29:40 kristaps Exp $ */
   2 /*
   3  * Copyright (c) 2008, 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
   4  * Copyright (c) 2011 Ingo Schwarze <schwarze@openbsd.org>
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18 #ifdef HAVE_CONFIG_H
  19 #include "config.h"
  20 #endif
  21
  22 #include <sys/types.h>
  23
  24 #include <assert.h>
  25 #include <ctype.h>
  26 #include <stdarg.h>
  27 #include <stdio.h>
  28 #include <stdint.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31 #include <unistd.h>
  32
  33 #include "mandoc.h"
  34 #include "out.h"
  35 #include "html.h"
  36 #include "main.h"
  37
  38 struct  htmldata {
  39         const char       *name;
  40         int               flags;
  41 #define HTML_CLRLINE     (1 << 0)
  42 #define HTML_NOSTACK     (1 << 1)
  43 #define HTML_AUTOCLOSE   (1 << 2) /* Tag has auto-closure. */
  44 };
  45
  46 static  const struct htmldata htmltags[TAG_MAX] = {
  47         {"html",        HTML_CLRLINE}, /* TAG_HTML */
  48         {"head",        HTML_CLRLINE}, /* TAG_HEAD */
  49         {"body",        HTML_CLRLINE}, /* TAG_BODY */
  50         {"meta",        HTML_CLRLINE | HTML_NOSTACK | HTML_AUTOCLOSE}, /* TAG_META */
  51         {"title",       HTML_CLRLINE}, /* TAG_TITLE */
  52         {"div",         HTML_CLRLINE}, /* TAG_DIV */
  53         {"h1",          0}, /* TAG_H1 */
  54         {"h2",          0}, /* TAG_H2 */
  55         {"span",        0}, /* TAG_SPAN */
  56         {"link",        HTML_CLRLINE | HTML_NOSTACK | HTML_AUTOCLOSE}, /* TAG_LINK */
  57         {"br",          HTML_CLRLINE | HTML_NOSTACK | HTML_AUTOCLOSE}, /* TAG_BR */
  58         {"a",           0}, /* TAG_A */
  59         {"table",       HTML_CLRLINE}, /* TAG_TABLE */
  60         {"tbody",       HTML_CLRLINE}, /* TAG_TBODY */
  61         {"col",         HTML_CLRLINE | HTML_NOSTACK | HTML_AUTOCLOSE}, /* TAG_COL */
  62         {"tr",          HTML_CLRLINE}, /* TAG_TR */
  63         {"td",          HTML_CLRLINE}, /* TAG_TD */
  64         {"li",          HTML_CLRLINE}, /* TAG_LI */
  65         {"ul",          HTML_CLRLINE}, /* TAG_UL */
  66         {"ol",          HTML_CLRLINE}, /* TAG_OL */
  67         {"dl",          HTML_CLRLINE}, /* TAG_DL */
  68         {"dt",          HTML_CLRLINE}, /* TAG_DT */
  69         {"dd",          HTML_CLRLINE}, /* TAG_DD */
  70         {"blockquote",  HTML_CLRLINE}, /* TAG_BLOCKQUOTE */
  71         {"p",           HTML_CLRLINE | HTML_NOSTACK | HTML_AUTOCLOSE}, /* TAG_P */
  72         {"pre",         HTML_CLRLINE }, /* TAG_PRE */
  73         {"b",           0 }, /* TAG_B */
  74         {"i",           0 }, /* TAG_I */
  75         {"code",        0 }, /* TAG_CODE */
  76         {"small",       0 }, /* TAG_SMALL */
  77 };
  78
  79 static  const char      *const htmlattrs[ATTR_MAX] = {
  80         "http-equiv", /* ATTR_HTTPEQUIV */
  81         "content", /* ATTR_CONTENT */
  82         "name", /* ATTR_NAME */
  83         "rel", /* ATTR_REL */
  84         "href", /* ATTR_HREF */
  85         "type", /* ATTR_TYPE */
  86         "media", /* ATTR_MEDIA */
  87         "class", /* ATTR_CLASS */
  88         "style", /* ATTR_STYLE */
  89         "width", /* ATTR_WIDTH */
  90         "id", /* ATTR_ID */
  91         "summary", /* ATTR_SUMMARY */
  92         "align", /* ATTR_ALIGN */
  93         "colspan", /* ATTR_COLSPAN */
  94 };
  95
  96 static  void              print_num(struct html *, const char *, size_t);
  97 static  void              print_spec(struct html *, const char *, size_t);
  98 static  void              print_res(struct html *, const char *, size_t);
  99 static  void              print_ctag(struct html *, enum htmltag);
 100 static  void              print_doctype(struct html *);
 101 static  void              print_xmltype(struct html *);
 102 static  int               print_encode(struct html *, const char *, int);
 103 static  void              print_metaf(struct html *, enum mandoc_esc);
 104 static  void              print_attr(struct html *,
 105                                 const char *, const char *);
 106 static  void             *ml_alloc(char *, enum htmltype);
 107
 108
 109 static void *
 110 ml_alloc(char *outopts, enum htmltype type)
 111 {
 112         struct html     *h;
 113         const char      *toks[4];
 114         char            *v;
 115
 116         toks[0] = "style";
 117         toks[1] = "man";
 118         toks[2] = "includes";
 119         toks[3] = NULL;
 120
 121         h = mandoc_calloc(1, sizeof(struct html));
 122
 123         h->type = type;
 124         h->tags.head = NULL;
 125         h->symtab = chars_init(CHARS_HTML);
 126
 127         while (outopts && *outopts)
 128                 switch (getsubopt(&outopts, UNCONST(toks), &v)) {
 129                 case (0):
 130                         h->style = v;
 131                         break;
 132                 case (1):
 133                         h->base_man = v;
 134                         break;
 135                 case (2):
 136                         h->base_includes = v;
 137                         break;
 138                 default:
 139                         break;
 140                 }
 141
 142         return(h);
 143 }
 144
 145 void *
 146 html_alloc(char *outopts)
 147 {
 148
 149         return(ml_alloc(outopts, HTML_HTML_4_01_STRICT));
 150 }
 151
 152
 153 void *
 154 xhtml_alloc(char *outopts)
 155 {
 156
 157         return(ml_alloc(outopts, HTML_XHTML_1_0_STRICT));
 158 }
 159
 160
 161 void
 162 html_free(void *p)
 163 {
 164         struct tag      *tag;
 165         struct html     *h;
 166
 167         h = (struct html *)p;
 168
 169         while ((tag = h->tags.head) != NULL) {
 170                 h->tags.head = tag->next;
 171                 free(tag);
 172         }
 173
 174         if (h->symtab)
 175                 chars_free(h->symtab);
 176
 177         free(h);
 178 }
 179
 180
 181 void
 182 print_gen_head(struct html *h)
 183 {
 184         struct htmlpair  tag[4];
 185
 186         tag[0].key = ATTR_HTTPEQUIV;
 187         tag[0].val = "Content-Type";
 188         tag[1].key = ATTR_CONTENT;
 189         tag[1].val = "text/html; charset=utf-8";
 190         print_otag(h, TAG_META, 2, tag);
 191
 192         tag[0].key = ATTR_NAME;
 193         tag[0].val = "resource-type";
 194         tag[1].key = ATTR_CONTENT;
 195         tag[1].val = "document";
 196         print_otag(h, TAG_META, 2, tag);
 197
 198         if (h->style) {
 199                 tag[0].key = ATTR_REL;
 200                 tag[0].val = "stylesheet";
 201                 tag[1].key = ATTR_HREF;
 202                 tag[1].val = h->style;
 203                 tag[2].key = ATTR_TYPE;
 204                 tag[2].val = "text/css";
 205                 tag[3].key = ATTR_MEDIA;
 206                 tag[3].val = "all";
 207                 print_otag(h, TAG_LINK, 4, tag);
 208         }
 209 }
 210
 211 /* ARGSUSED */
 212 static void
 213 print_num(struct html *h, const char *p, size_t len)
 214 {
 215         const char      *rhs;
 216
 217         rhs = chars_num2char(p, len);
 218         if (rhs)
 219                 putchar((int)*rhs);
 220 }
 221
 222 static void
 223 print_spec(struct html *h, const char *p, size_t len)
 224 {
 225         int              cp;
 226         const char      *rhs;
 227         size_t           sz;
 228
 229         if ((cp = chars_spec2cp(h->symtab, p, len)) > 0) {
 230                 printf("&#%d;", cp);
 231                 return;
 232         } else if (-1 == cp && 1 == len) {
 233                 fwrite(p, 1, len, stdout);
 234                 return;
 235         } else if (-1 == cp)
 236                 return;
 237
 238         if (NULL != (rhs = chars_spec2str(h->symtab, p, len, &sz)))
 239                 fwrite(rhs, 1, sz, stdout);
 240 }
 241
 242
 243 static void
 244 print_res(struct html *h, const char *p, size_t len)
 245 {
 246         int              cp;
 247         const char      *rhs;
 248         size_t           sz;
 249
 250         if ((cp = chars_res2cp(h->symtab, p, len)) > 0) {
 251                 printf("&#%d;", cp);
 252                 return;
 253         } else if (-1 == cp)
 254                 return;
 255
 256         if (NULL != (rhs = chars_res2str(h->symtab, p, len, &sz)))
 257                 fwrite(rhs, 1, sz, stdout);
 258 }
 259
 260
 261 static void
 262 print_metaf(struct html *h, enum mandoc_esc deco)
 263 {
 264         enum htmlfont    font;
 265
 266         switch (deco) {
 267         case (ESCAPE_FONTPREV):
 268                 font = h->metal;
 269                 break;
 270         case (ESCAPE_FONTITALIC):
 271                 font = HTMLFONT_ITALIC;
 272                 break;
 273         case (ESCAPE_FONTBOLD):
 274                 font = HTMLFONT_BOLD;
 275                 break;
 276         case (ESCAPE_FONTROMAN):
 277                 font = HTMLFONT_NONE;
 278                 break;
 279         default:
 280                 abort();
 281                 /* NOTREACHED */
 282         }
 283
 284         if (h->metaf) {
 285                 print_tagq(h, h->metaf);
 286                 h->metaf = NULL;
 287         }
 288
 289         h->metal = h->metac;
 290         h->metac = font;
 291
 292         if (HTMLFONT_NONE != font)
 293                 h->metaf = HTMLFONT_BOLD == font ?
 294                         print_otag(h, TAG_B, 0, NULL) :
 295                         print_otag(h, TAG_I, 0, NULL);
 296 }
 297
 298
 299 static int
 300 print_encode(struct html *h, const char *p, int norecurse)
 301 {
 302         size_t           sz;
 303         int              len, nospace;
 304         const char      *seq;
 305         enum mandoc_esc  esc;
 306         static const char rejs[6] = { '\\', '<', '>', '&', ASCII_HYPH, '\0' };
 307
 308         nospace = 0;
 309
 310         while ('\0' != *p) {
 311                 sz = strcspn(p, rejs);
 312
 313                 fwrite(p, 1, sz, stdout);
 314                 p += (int)sz;
 315
 316                 if ('\0' == *p)
 317                         break;
 318
 319                 switch (*p++) {
 320                 case ('<'):
 321                         printf("&lt;");
 322                         continue;
 323                 case ('>'):
 324                         printf("&gt;");
 325                         continue;
 326                 case ('&'):
 327                         printf("&amp;");
 328                         continue;
 329                 case (ASCII_HYPH):
 330                         putchar('-');
 331                         continue;
 332                 default:
 333                         break;
 334                 }
 335
 336                 esc = mandoc_escape(&p, &seq, &len);
 337                 if (ESCAPE_ERROR == esc)
 338                         break;
 339
 340                 switch (esc) {
 341                 case (ESCAPE_NUMBERED):
 342                         print_num(h, seq, len);
 343                         break;
 344                 case (ESCAPE_PREDEF):
 345                         print_res(h, seq, len);
 346                         break;
 347                 case (ESCAPE_SPECIAL):
 348                         print_spec(h, seq, len);
 349                         break;
 350                 case (ESCAPE_FONTPREV):
 351                         /* FALLTHROUGH */
 352                 case (ESCAPE_FONTBOLD):
 353                         /* FALLTHROUGH */
 354                 case (ESCAPE_FONTITALIC):
 355                         /* FALLTHROUGH */
 356                 case (ESCAPE_FONTROMAN):
 357                         if (norecurse)
 358                                 break;
 359                         print_metaf(h, esc);
 360                         break;
 361                 case (ESCAPE_NOSPACE):
 362                         if ('\0' == *p)
 363                                 nospace = 1;
 364                         break;
 365                 default:
 366                         break;
 367                 }
 368         }
 369
 370         return(nospace);
 371 }
 372
 373
 374 static void
 375 print_attr(struct html *h, const char *key, const char *val)
 376 {
 377         printf(" %s=\"", key);
 378         (void)print_encode(h, val, 1);
 379         putchar('\"');
 380 }
 381
 382
 383 struct tag *
 384 print_otag(struct html *h, enum htmltag tag,
 385                 int sz, const struct htmlpair *p)
 386 {
 387         int              i;
 388         struct tag      *t;
 389
 390         /* Push this tags onto the stack of open scopes. */
 391
 392         if ( ! (HTML_NOSTACK & htmltags[tag].flags)) {
 393                 t = mandoc_malloc(sizeof(struct tag));
 394                 t->tag = tag;
 395                 t->next = h->tags.head;
 396                 h->tags.head = t;
 397         } else
 398                 t = NULL;
 399
 400         if ( ! (HTML_NOSPACE & h->flags))
 401                 if ( ! (HTML_CLRLINE & htmltags[tag].flags)) {
 402                         /* Manage keeps! */
 403                         if ( ! (HTML_KEEP & h->flags)) {
 404                                 if (HTML_PREKEEP & h->flags)
 405                                         h->flags |= HTML_KEEP;
 406                                 putchar(' ');
 407                         } else
 408                                 printf("&#160;");
 409                 }
 410
 411         if ( ! (h->flags & HTML_NONOSPACE))
 412                 h->flags &= ~HTML_NOSPACE;
 413         else
 414                 h->flags |= HTML_NOSPACE;
 415
 416         /* Print out the tag name and attributes. */
 417
 418         printf("<%s", htmltags[tag].name);
 419         for (i = 0; i < sz; i++)
 420                 print_attr(h, htmlattrs[p[i].key], p[i].val);
 421
 422         /* Add non-overridable attributes. */
 423
 424         if (TAG_HTML == tag && HTML_XHTML_1_0_STRICT == h->type) {
 425                 print_attr(h, "xmlns", "http://www.w3.org/1999/xhtml");
 426                 print_attr(h, "xml:lang", "en");
 427                 print_attr(h, "lang", "en");
 428         }
 429
 430         /* Accomodate for XML "well-formed" singleton escaping. */
 431
 432         if (HTML_AUTOCLOSE & htmltags[tag].flags)
 433                 switch (h->type) {
 434                 case (HTML_XHTML_1_0_STRICT):
 435                         putchar('/');
 436                         break;
 437                 default:
 438                         break;
 439                 }
 440
 441         putchar('>');
 442
 443         h->flags |= HTML_NOSPACE;
 444
 445         if ((HTML_AUTOCLOSE | HTML_CLRLINE) & htmltags[tag].flags)
 446                 putchar('\n');
 447
 448         return(t);
 449 }
 450
 451
 452 static void
 453 print_ctag(struct html *h, enum htmltag tag)
 454 {
 455
 456         printf("</%s>", htmltags[tag].name);
 457         if (HTML_CLRLINE & htmltags[tag].flags) {
 458                 h->flags |= HTML_NOSPACE;
 459                 putchar('\n');
 460         }
 461 }
 462
 463
 464 void
 465 print_gen_decls(struct html *h)
 466 {
 467
 468         print_xmltype(h);
 469         print_doctype(h);
 470 }
 471
 472
 473 static void
 474 print_xmltype(struct html *h)
 475 {
 476
 477         if (HTML_XHTML_1_0_STRICT == h->type)
 478                 puts("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
 479 }
 480
 481
 482 static void
 483 print_doctype(struct html *h)
 484 {
 485         const char      *doctype;
 486         const char      *dtd;
 487         const char      *name;
 488
 489         switch (h->type) {
 490         case (HTML_HTML_4_01_STRICT):
 491                 name = "HTML";
 492                 doctype = "-//W3C//DTD HTML 4.01//EN";
 493                 dtd = "http://www.w3.org/TR/html4/strict.dtd";
 494                 break;
 495         default:
 496                 name = "html";
 497                 doctype = "-//W3C//DTD XHTML 1.0 Strict//EN";
 498                 dtd = "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd";
 499                 break;
 500         }
 501
 502         printf("<!DOCTYPE %s PUBLIC \"%s\" \"%s\">\n",
 503                         name, doctype, dtd);
 504 }
 505
 506 void
 507 print_text(struct html *h, const char *word)
 508 {
 509
 510         if ( ! (HTML_NOSPACE & h->flags)) {
 511                 /* Manage keeps! */
 512                 if ( ! (HTML_KEEP & h->flags)) {
 513                         if (HTML_PREKEEP & h->flags)
 514                                 h->flags |= HTML_KEEP;
 515                         putchar(' ');
 516                 } else
 517                         printf("&#160;");
 518         }
 519
 520         assert(NULL == h->metaf);
 521         if (HTMLFONT_NONE != h->metac)
 522                 h->metaf = HTMLFONT_BOLD == h->metac ?
 523                         print_otag(h, TAG_B, 0, NULL) :
 524                         print_otag(h, TAG_I, 0, NULL);
 525
 526         assert(word);
 527         if ( ! print_encode(h, word, 0))
 528                 if ( ! (h->flags & HTML_NONOSPACE))
 529                         h->flags &= ~HTML_NOSPACE;
 530
 531         if (h->metaf) {
 532                 print_tagq(h, h->metaf);
 533                 h->metaf = NULL;
 534         }
 535
 536         h->flags &= ~HTML_IGNDELIM;
 537 }
 538
 539
 540 void
 541 print_tagq(struct html *h, const struct tag *until)
 542 {
 543         struct tag      *tag;
 544
 545         while ((tag = h->tags.head) != NULL) {
 546                 /*
 547                  * Remember to close out and nullify the current
 548                  * meta-font and table, if applicable.
 549                  */
 550                 if (tag == h->metaf)
 551                         h->metaf = NULL;
 552                 if (tag == h->tblt)
 553                         h->tblt = NULL;
 554                 print_ctag(h, tag->tag);
 555                 h->tags.head = tag->next;
 556                 free(tag);
 557                 if (until && tag == until)
 558                         return;
 559         }
 560 }
 561
 562
 563 void
 564 print_stagq(struct html *h, const struct tag *suntil)
 565 {
 566         struct tag      *tag;
 567
 568         while ((tag = h->tags.head) != NULL) {
 569                 if (suntil && tag == suntil)
 570                         return;
 571                 /*
 572                  * Remember to close out and nullify the current
 573                  * meta-font and table, if applicable.
 574                  */
 575                 if (tag == h->metaf)
 576                         h->metaf = NULL;
 577                 if (tag == h->tblt)
 578                         h->tblt = NULL;
 579                 print_ctag(h, tag->tag);
 580                 h->tags.head = tag->next;
 581                 free(tag);
 582         }
 583 }
 584
 585
 586 void
 587 bufinit(struct html *h)
 588 {
 589
 590         h->buf[0] = '\0';
 591         h->buflen = 0;
 592 }
 593
 594
 595 void
 596 bufcat_style(struct html *h, const char *key, const char *val)
 597 {
 598
 599         bufcat(h, key);
 600         bufncat(h, ":", 1);
 601         bufcat(h, val);
 602         bufncat(h, ";", 1);
 603 }
 604
 605
 606 void
 607 bufcat(struct html *h, const char *p)
 608 {
 609
 610         bufncat(h, p, strlen(p));
 611 }
 612
 613
 614 void
 615 buffmt(struct html *h, const char *fmt, ...)
 616 {
 617         va_list          ap;
 618
 619         va_start(ap, fmt);
 620         (void)vsnprintf(h->buf + (int)h->buflen,
 621                         BUFSIZ - h->buflen - 1, fmt, ap);
 622         va_end(ap);
 623         h->buflen = strlen(h->buf);
 624 }
 625
 626
 627 void
 628 bufncat(struct html *h, const char *p, size_t sz)
 629 {
 630
 631         if (h->buflen + sz > BUFSIZ - 1)
 632                 sz = BUFSIZ - 1 - h->buflen;
 633
 634         (void)strncat(h->buf, p, sz);
 635         h->buflen += sz;
 636 }
 637
 638
 639 void
 640 buffmt_includes(struct html *h, const char *name)
 641 {
 642         const char      *p, *pp;
 643
 644         pp = h->base_includes;
 645
 646         while (NULL != (p = strchr(pp, '%'))) {
 647                 bufncat(h, pp, (size_t)(p - pp));
 648                 switch (*(p + 1)) {
 649                 case('I'):
 650                         bufcat(h, name);
 651                         break;
 652                 default:
 653                         bufncat(h, p, 2);
 654                         break;
 655                 }
 656                 pp = p + 2;
 657         }
 658         if (pp)
 659                 bufcat(h, pp);
 660 }
 661
 662
 663 void
 664 buffmt_man(struct html *h,
 665                 const char *name, const char *sec)
 666 {
 667         const char      *p, *pp;
 668
 669         pp = h->base_man;
 670
 671         /* LINTED */
 672         while (NULL != (p = strchr(pp, '%'))) {
 673                 bufncat(h, pp, (size_t)(p - pp));
 674                 switch (*(p + 1)) {
 675                 case('S'):
 676                         bufcat(h, sec ? sec : "1");
 677                         break;
 678                 case('N'):
 679                         buffmt(h, name);
 680                         break;
 681                 default:
 682                         bufncat(h, p, 2);
 683                         break;
 684                 }
 685                 pp = p + 2;
 686         }
 687         if (pp)
 688                 bufcat(h, pp);
 689 }
 690
 691
 692 void
 693 bufcat_su(struct html *h, const char *p, const struct roffsu *su)
 694 {
 695         double           v;
 696         const char      *u;
 697
 698         v = su->scale;
 699
 700         switch (su->unit) {
 701         case (SCALE_CM):
 702                 u = "cm";
 703                 break;
 704         case (SCALE_IN):
 705                 u = "in";
 706                 break;
 707         case (SCALE_PC):
 708                 u = "pc";
 709                 break;
 710         case (SCALE_PT):
 711                 u = "pt";
 712                 break;
 713         case (SCALE_EM):
 714                 u = "em";
 715                 break;
 716         case (SCALE_MM):
 717                 if (0 == (v /= 100))
 718                         v = 1;
 719                 u = "em";
 720                 break;
 721         case (SCALE_EN):
 722                 u = "ex";
 723                 break;
 724         case (SCALE_BU):
 725                 u = "ex";
 726                 break;
 727         case (SCALE_VS):
 728                 u = "em";
 729                 break;
 730         default:
 731                 u = "ex";
 732                 break;
 733         }
 734
 735         /*
 736          * XXX: the CSS spec isn't clear as to which types accept
 737          * integer or real numbers, so we just make them all decimals.
 738          */
 739         buffmt(h, "%s: %.2f%s;", p, v, u);
 740 }
 741
 742
 743 void
 744 html_idcat(char *dst, const char *src, int sz)
 745 {
 746         int              ssz;
 747
 748         assert(sz > 2);
 749
 750         /* Cf. <http://www.w3.org/TR/html4/types.html#h-6.2>. */
 751
 752         /* We can't start with a number (bah). */
 753
 754         if ('#' == *dst) {
 755                 dst++;
 756                 sz--;
 757         }
 758         if ('\0' == *dst) {
 759                 *dst++ = 'x';
 760                 *dst = '\0';
 761                 sz--;
 762         }
 763
 764         for ( ; *dst != '\0' && sz; dst++, sz--)
 765                 /* Jump to end. */ ;
 766
 767         for ( ; *src != '\0' && sz > 1; src++) {
 768                 ssz = snprintf(dst, (size_t)sz, "%.2x", *src);
 769                 sz -= ssz;
 770                 dst += ssz;
 771         }
 772 }