src/doc.c

   1 /* Record indices of function doc strings stored in a file.
   2
   3 Copyright (C) 1985-1986, 1993-1995, 1997-2013 Free Software Foundation,
   4 Inc.
   5
   6 This file is part of GNU Emacs.
   7
   8 GNU Emacs is free software: you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation, either version 3 of the License, or
  11 (at your option) any later version.
  12
  13 GNU Emacs is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21
  22 #include <config.h>
  23
  24 #include <errno.h>
  25 #include <sys/types.h>
  26 #include <sys/file.h>   /* Must be after sys/types.h for USG.  */
  27 #include <fcntl.h>
  28 #include <unistd.h>
  29
  30 #include <c-ctype.h>
  31
  32 #include "lisp.h"
  33 #include "character.h"
  34 #include "buffer.h"
  35 #include "keyboard.h"
  36 #include "keymap.h"
  37
  38 Lisp_Object Qfunction_documentation;
  39
  40 /* Buffer used for reading from documentation file.  */
  41 static char *get_doc_string_buffer;
  42 static ptrdiff_t get_doc_string_buffer_size;
  43
  44 static unsigned char *read_bytecode_pointer;
  45
  46 /* `readchar' in lread.c calls back here to fetch the next byte.
  47    If UNREADFLAG is 1, we unread a byte.  */
  48
  49 int
  50 read_bytecode_char (bool unreadflag)
  51 {
  52   if (unreadflag)
  53     {
  54       read_bytecode_pointer--;
  55       return 0;
  56     }
  57   return *read_bytecode_pointer++;
  58 }
  59
  60 /* Extract a doc string from a file.  FILEPOS says where to get it.
  61    If it is an integer, use that position in the standard DOC file.
  62    If it is (FILE . INTEGER), use FILE as the file name
  63    and INTEGER as the position in that file.
  64    But if INTEGER is negative, make it positive.
  65    (A negative integer is used for user variables, so we can distinguish
  66    them without actually fetching the doc string.)
  67
  68    If the location does not point to the beginning of a docstring
  69    (e.g. because the file has been modified and the location is stale),
  70    return nil.
  71
  72    If UNIBYTE, always make a unibyte string.
  73
  74    If DEFINITION, assume this is for reading
  75    a dynamic function definition; convert the bytestring
  76    and the constants vector with appropriate byte handling,
  77    and return a cons cell.  */
  78
  79 Lisp_Object
  80 get_doc_string (Lisp_Object filepos, bool unibyte, bool definition)
  81 {
  82   char *from, *to, *name, *p, *p1;
  83   int fd;
  84   ptrdiff_t minsize;
  85   int offset;
  86   EMACS_INT position;
  87   Lisp_Object file, tem, pos;
  88   ptrdiff_t count;
  89   USE_SAFE_ALLOCA;
  90
  91   if (INTEGERP (filepos))
  92     {
  93       file = Vdoc_file_name;
  94       pos = filepos;
  95     }
  96   else if (CONSP (filepos))
  97     {
  98       file = XCAR (filepos);
  99       pos = XCDR (filepos);
 100     }
 101   else
 102     return Qnil;
 103
 104   position = eabs (XINT (pos));
 105
 106   if (!STRINGP (Vdoc_directory))
 107     return Qnil;
 108
 109   if (!STRINGP (file))
 110     return Qnil;
 111
 112   /* Put the file name in NAME as a C string.
 113      If it is relative, combine it with Vdoc_directory.  */
 114
 115   tem = Ffile_name_absolute_p (file);
 116   file = ENCODE_FILE (file);
 117   if (NILP (tem))
 118     {
 119       Lisp_Object docdir = ENCODE_FILE (Vdoc_directory);
 120       minsize = SCHARS (docdir);
 121       /* sizeof ("../etc/") == 8 */
 122       if (minsize < 8)
 123         minsize = 8;
 124       name = SAFE_ALLOCA (minsize + SCHARS (file) + 8);
 125       strcpy (name, SSDATA (docdir));
 126       strcat (name, SSDATA (file));
 127     }
 128   else
 129     {
 130       name = SSDATA (file);
 131     }
 132
 133   fd = emacs_open (name, O_RDONLY, 0);
 134   if (fd < 0)
 135     {
 136 #ifndef CANNOT_DUMP
 137       if (!NILP (Vpurify_flag))
 138         {
 139           /* Preparing to dump; DOC file is probably not installed.
 140              So check in ../etc.  */
 141           strcpy (name, "../etc/");
 142           strcat (name, SSDATA (file));
 143
 144           fd = emacs_open (name, O_RDONLY, 0);
 145         }
 146 #endif
 147       if (fd < 0)
 148         {
 149           SAFE_FREE ();
 150           return concat3 (build_string ("Cannot open doc string file \""),
 151                           file, build_string ("\"\n"));
 152         }
 153     }
 154   count = SPECPDL_INDEX ();
 155   record_unwind_protect_int (close_file_unwind, fd);
 156
 157   /* Seek only to beginning of disk block.  */
 158   /* Make sure we read at least 1024 bytes before `position'
 159      so we can check the leading text for consistency.  */
 160   offset = min (position, max (1024, position % (8 * 1024)));
 161   if (TYPE_MAXIMUM (off_t) < position
 162       || lseek (fd, position - offset, 0) < 0)
 163     error ("Position %"pI"d out of range in doc string file \"%s\"",
 164            position, name);
 165
 166   /* Read the doc string into get_doc_string_buffer.
 167      P points beyond the data just read.  */
 168
 169   p = get_doc_string_buffer;
 170   while (1)
 171     {
 172       ptrdiff_t space_left = (get_doc_string_buffer_size - 1
 173                               - (p - get_doc_string_buffer));
 174       int nread;
 175
 176       /* Allocate or grow the buffer if we need to.  */
 177       if (space_left <= 0)
 178         {
 179           ptrdiff_t in_buffer = p - get_doc_string_buffer;
 180           get_doc_string_buffer
 181             = xpalloc (get_doc_string_buffer, &get_doc_string_buffer_size,
 182                        16 * 1024, -1, 1);
 183           p = get_doc_string_buffer + in_buffer;
 184           space_left = (get_doc_string_buffer_size - 1
 185                         - (p - get_doc_string_buffer));
 186         }
 187
 188       /* Read a disk block at a time.
 189          If we read the same block last time, maybe skip this?  */
 190       if (space_left > 1024 * 8)
 191         space_left = 1024 * 8;
 192       nread = emacs_read (fd, p, space_left);
 193       if (nread < 0)
 194         report_file_error ("Read error on documentation file", file);
 195       p[nread] = 0;
 196       if (!nread)
 197         break;
 198       if (p == get_doc_string_buffer)
 199         p1 = strchr (p + offset, '\037');
 200       else
 201         p1 = strchr (p, '\037');
 202       if (p1)
 203         {
 204           *p1 = 0;
 205           p = p1;
 206           break;
 207         }
 208       p += nread;
 209     }
 210   unbind_to (count, Qnil);
 211   SAFE_FREE ();
 212
 213   /* Sanity checking.  */
 214   if (CONSP (filepos))
 215     {
 216       int test = 1;
 217       /* A dynamic docstring should be either at the very beginning of a "#@
 218          comment" or right after a dynamic docstring delimiter (in case we
 219          pack several such docstrings within the same comment).  */
 220       if (get_doc_string_buffer[offset - test] != '\037')
 221         {
 222           if (get_doc_string_buffer[offset - test++] != ' ')
 223             return Qnil;
 224           while (get_doc_string_buffer[offset - test] >= '0'
 225                  && get_doc_string_buffer[offset - test] <= '9')
 226             test++;
 227           if (get_doc_string_buffer[offset - test++] != '@'
 228               || get_doc_string_buffer[offset - test] != '#')
 229             return Qnil;
 230         }
 231     }
 232   else
 233     {
 234       int test = 1;
 235       if (get_doc_string_buffer[offset - test++] != '\n')
 236         return Qnil;
 237       while (get_doc_string_buffer[offset - test] > ' ')
 238         test++;
 239       if (get_doc_string_buffer[offset - test] != '\037')
 240         return Qnil;
 241     }
 242
 243   /* Scan the text and perform quoting with ^A (char code 1).
 244      ^A^A becomes ^A, ^A0 becomes a null char, and ^A_ becomes a ^_.  */
 245   from = get_doc_string_buffer + offset;
 246   to = get_doc_string_buffer + offset;
 247   while (from != p)
 248     {
 249       if (*from == 1)
 250         {
 251           int c;
 252
 253           from++;
 254           c = *from++;
 255           if (c == 1)
 256             *to++ = c;
 257           else if (c == '0')
 258             *to++ = 0;
 259           else if (c == '_')
 260             *to++ = 037;
 261           else
 262             {
 263               unsigned char uc = c;
 264               error ("\
 265 Invalid data in documentation file -- %c followed by code %03o",
 266                      1, uc);
 267             }
 268         }
 269       else
 270         *to++ = *from++;
 271     }
 272
 273   /* If DEFINITION, read from this buffer
 274      the same way we would read bytes from a file.  */
 275   if (definition)
 276     {
 277       read_bytecode_pointer = (unsigned char *) get_doc_string_buffer + offset;
 278       return Fread (Qlambda);
 279     }
 280
 281   if (unibyte)
 282     return make_unibyte_string (get_doc_string_buffer + offset,
 283                                 to - (get_doc_string_buffer + offset));
 284   else
 285     {
 286       /* The data determines whether the string is multibyte.  */
 287       ptrdiff_t nchars
 288         = multibyte_chars_in_text (((unsigned char *) get_doc_string_buffer
 289                                     + offset),
 290                                    to - (get_doc_string_buffer + offset));
 291       return make_string_from_bytes (get_doc_string_buffer + offset,
 292                                      nchars,
 293                                      to - (get_doc_string_buffer + offset));
 294     }
 295 }
 296
 297 /* Get a string from position FILEPOS and pass it through the Lisp reader.
 298    We use this for fetching the bytecode string and constants vector
 299    of a compiled function from the .elc file.  */
 300
 301 Lisp_Object
 302 read_doc_string (Lisp_Object filepos)
 303 {
 304   return get_doc_string (filepos, 0, 1);
 305 }
 306
 307 static bool
 308 reread_doc_file (Lisp_Object file)
 309 {
 310 #if 0
 311   Lisp_Object reply, prompt[3];
 312   struct gcpro gcpro1;
 313   GCPRO1 (file);
 314   prompt[0] = build_string ("File ");
 315   prompt[1] = NILP (file) ? Vdoc_file_name : file;
 316   prompt[2] = build_string (" is out of sync.  Reload? ");
 317   reply = Fy_or_n_p (Fconcat (3, prompt));
 318   UNGCPRO;
 319   if (NILP (reply))
 320     return 0;
 321 #endif
 322
 323   if (NILP (file))
 324     Fsnarf_documentation (Vdoc_file_name);
 325   else
 326     Fload (file, Qt, Qt, Qt, Qnil);
 327
 328   return 1;
 329 }
 330
 331 DEFUN ("documentation", Fdocumentation, Sdocumentation, 1, 2, 0,
 332        doc: /* Return the documentation string of FUNCTION.
 333 Unless a non-nil second argument RAW is given, the
 334 string is passed through `substitute-command-keys'.  */)
 335   (Lisp_Object function, Lisp_Object raw)
 336 {
 337   Lisp_Object fun;
 338   Lisp_Object funcar;
 339   Lisp_Object doc;
 340   bool try_reload = 1;
 341
 342  documentation:
 343
 344   doc = Qnil;
 345
 346   if (SYMBOLP (function))
 347     {
 348       Lisp_Object tem = Fget (function, Qfunction_documentation);
 349       if (!NILP (tem))
 350         return Fdocumentation_property (function, Qfunction_documentation,
 351                                         raw);
 352     }
 353
 354   fun = Findirect_function (function, Qnil);
 355   if (CONSP (fun) && EQ (XCAR (fun), Qmacro))
 356     fun = XCDR (fun);
 357   if (SUBRP (fun))
 358     {
 359       if (XSUBR (fun)->doc == 0)
 360         return Qnil;
 361       /* FIXME: This is not portable, as it assumes that string
 362          pointers have the top bit clear.  */
 363       else if ((intptr_t) XSUBR (fun)->doc >= 0)
 364         doc = build_string (XSUBR (fun)->doc);
 365       else
 366         doc = make_number ((intptr_t) XSUBR (fun)->doc);
 367     }
 368   else if (COMPILEDP (fun))
 369     {
 370       if ((ASIZE (fun) & PSEUDOVECTOR_SIZE_MASK) <= COMPILED_DOC_STRING)
 371         return Qnil;
 372       else
 373         {
 374           Lisp_Object tem = AREF (fun, COMPILED_DOC_STRING);
 375           if (STRINGP (tem))
 376             doc = tem;
 377           else if (NATNUMP (tem) || CONSP (tem))
 378             doc = tem;
 379           else
 380             return Qnil;
 381         }
 382     }
 383   else if (STRINGP (fun) || VECTORP (fun))
 384     {
 385       return build_string ("Keyboard macro.");
 386     }
 387   else if (CONSP (fun))
 388     {
 389       funcar = XCAR (fun);
 390       if (!SYMBOLP (funcar))
 391         xsignal1 (Qinvalid_function, fun);
 392       else if (EQ (funcar, Qkeymap))
 393         return build_string ("Prefix command (definition is a keymap associating keystrokes with commands).");
 394       else if (EQ (funcar, Qlambda)
 395                || (EQ (funcar, Qclosure) && (fun = XCDR (fun), 1))
 396                || EQ (funcar, Qautoload))
 397         {
 398           Lisp_Object tem1 = Fcdr (Fcdr (fun));
 399           Lisp_Object tem = Fcar (tem1);
 400           if (STRINGP (tem))
 401             doc = tem;
 402           /* Handle a doc reference--but these never come last
 403              in the function body, so reject them if they are last.  */
 404           else if ((NATNUMP (tem) || (CONSP (tem) && INTEGERP (XCDR (tem))))
 405                    && !NILP (XCDR (tem1)))
 406             doc = tem;
 407           else
 408             return Qnil;
 409         }
 410       else
 411         goto oops;
 412     }
 413   else
 414     {
 415     oops:
 416       xsignal1 (Qinvalid_function, fun);
 417     }
 418
 419   /* Check for a dynamic docstring.  These come with
 420      a dynamic-docstring-function text property.  */
 421   if (STRINGP (doc))
 422     {
 423       Lisp_Object func
 424         = Fget_text_property (make_number (0),
 425                               intern ("dynamic-docstring-function"),
 426                                       doc);
 427       if (!NILP (func))
 428         /* Pass both `doc' and `function' since `function' can be needed, and
 429            finding `doc' can be annoying: calling `documentation' is not an
 430            option because it would infloop.  */
 431         doc = call2 (func, doc, function);
 432     }
 433
 434   /* If DOC is 0, it's typically because of a dumped file missing
 435      from the DOC file (bug in src/Makefile.in).  */
 436   if (EQ (doc, make_number (0)))
 437     doc = Qnil;
 438   if (INTEGERP (doc) || CONSP (doc))
 439     {
 440       Lisp_Object tem;
 441       tem = get_doc_string (doc, 0, 0);
 442       if (NILP (tem) && try_reload)
 443         {
 444           /* The file is newer, we need to reset the pointers.  */
 445           struct gcpro gcpro1, gcpro2;
 446           GCPRO2 (function, raw);
 447           try_reload = reread_doc_file (Fcar_safe (doc));
 448           UNGCPRO;
 449           if (try_reload)
 450             {
 451               try_reload = 0;
 452               goto documentation;
 453             }
 454         }
 455       else
 456         doc = tem;
 457     }
 458
 459   if (NILP (raw))
 460     doc = Fsubstitute_command_keys (doc);
 461   return doc;
 462 }
 463
 464 DEFUN ("documentation-property", Fdocumentation_property,
 465        Sdocumentation_property, 2, 3, 0,
 466        doc: /* Return the documentation string that is SYMBOL's PROP property.
 467 Third argument RAW omitted or nil means pass the result through
 468 `substitute-command-keys' if it is a string.
 469
 470 This differs from `get' in that it can refer to strings stored in the
 471 `etc/DOC' file; and that it evaluates documentation properties that
 472 aren't strings.  */)
 473   (Lisp_Object symbol, Lisp_Object prop, Lisp_Object raw)
 474 {
 475   bool try_reload = 1;
 476   Lisp_Object tem;
 477
 478  documentation_property:
 479
 480   tem = Fget (symbol, prop);
 481   if (EQ (tem, make_number (0)))
 482     tem = Qnil;
 483   if (INTEGERP (tem) || (CONSP (tem) && INTEGERP (XCDR (tem))))
 484     {
 485       Lisp_Object doc = tem;
 486       tem = get_doc_string (tem, 0, 0);
 487       if (NILP (tem) && try_reload)
 488         {
 489           /* The file is newer, we need to reset the pointers.  */
 490           struct gcpro gcpro1, gcpro2, gcpro3;
 491           GCPRO3 (symbol, prop, raw);
 492           try_reload = reread_doc_file (Fcar_safe (doc));
 493           UNGCPRO;
 494           if (try_reload)
 495             {
 496               try_reload = 0;
 497               goto documentation_property;
 498             }
 499         }
 500     }
 501   else if (!STRINGP (tem))
 502     /* Feval protects its argument.  */
 503     tem = Feval (tem, Qnil);
 504
 505   if (NILP (raw) && STRINGP (tem))
 506     tem = Fsubstitute_command_keys (tem);
 507   return tem;
 508 }
 509 \f
 510 /* Scanning the DOC files and placing docstring offsets into functions.  */
 511
 512 static void
 513 store_function_docstring (Lisp_Object obj, ptrdiff_t offset)
 514 {
 515   /* Don't use indirect_function here, or defaliases will apply their
 516      docstrings to the base functions (Bug#2603).  */
 517   Lisp_Object fun = SYMBOLP (obj) ? XSYMBOL (obj)->function : obj;
 518
 519   /* The type determines where the docstring is stored.  */
 520
 521   /* Lisp_Subrs have a slot for it.  */
 522   if (SUBRP (fun))
 523     {
 524       intptr_t negative_offset = - offset;
 525       XSUBR (fun)->doc = (char *) negative_offset;
 526     }
 527
 528   /* If it's a lisp form, stick it in the form.  */
 529   else if (CONSP (fun))
 530     {
 531       Lisp_Object tem;
 532
 533       tem = XCAR (fun);
 534       if (EQ (tem, Qlambda) || EQ (tem, Qautoload)
 535           || (EQ (tem, Qclosure) && (fun = XCDR (fun), 1)))
 536         {
 537           tem = Fcdr (Fcdr (fun));
 538           if (CONSP (tem) && INTEGERP (XCAR (tem)))
 539             /* FIXME: This modifies typically pure hash-cons'd data, so its
 540                correctness is quite delicate.  */
 541             XSETCAR (tem, make_number (offset));
 542         }
 543       else if (EQ (tem, Qmacro))
 544         store_function_docstring (XCDR (fun), offset);
 545     }
 546
 547   /* Bytecode objects sometimes have slots for it.  */
 548   else if (COMPILEDP (fun))
 549     {
 550       /* This bytecode object must have a slot for the
 551          docstring, since we've found a docstring for it.  */
 552       if ((ASIZE (fun) & PSEUDOVECTOR_SIZE_MASK) > COMPILED_DOC_STRING)
 553         ASET (fun, COMPILED_DOC_STRING, make_number (offset));
 554     }
 555 }
 556
 557
 558 DEFUN ("Snarf-documentation", Fsnarf_documentation, Ssnarf_documentation,
 559        1, 1, 0,
 560        doc: /* Used during Emacs initialization to scan the `etc/DOC...' file.
 561 This searches the `etc/DOC...' file for doc strings and
 562 records them in function and variable definitions.
 563 The function takes one argument, FILENAME, a string;
 564 it specifies the file name (without a directory) of the DOC file.
 565 That file is found in `../etc' now; later, when the dumped Emacs is run,
 566 the same file name is found in the `doc-directory'.  */)
 567   (Lisp_Object filename)
 568 {
 569   int fd;
 570   char buf[1024 + 1];
 571   int filled;
 572   EMACS_INT pos;
 573   Lisp_Object sym;
 574   char *p, *name;
 575   bool skip_file = 0;
 576   ptrdiff_t count;
 577
 578   CHECK_STRING (filename);
 579
 580   if
 581 #ifndef CANNOT_DUMP
 582     (!NILP (Vpurify_flag))
 583 #else /* CANNOT_DUMP */
 584       (0)
 585 #endif /* CANNOT_DUMP */
 586     {
 587       name = alloca (SCHARS (filename) + 14);
 588       strcpy (name, "../etc/");
 589     }
 590   else
 591     {
 592       CHECK_STRING (Vdoc_directory);
 593       name = alloca (SCHARS (filename) + SCHARS (Vdoc_directory) + 1);
 594       strcpy (name, SSDATA (Vdoc_directory));
 595     }
 596   strcat (name, SSDATA (filename));     /*** Add this line ***/
 597
 598   /* Vbuild_files is nil when temacs is run, and non-nil after that.  */
 599   if (NILP (Vbuild_files))
 600     {
 601       static char const *const buildobj[] =
 602         {
 603           #include "buildobj.h"
 604         };
 605       int i = sizeof buildobj / sizeof *buildobj;
 606       while (0 <= --i)
 607         Vbuild_files = Fcons (build_string (buildobj[i]), Vbuild_files);
 608       Vbuild_files = Fpurecopy (Vbuild_files);
 609     }
 610
 611   fd = emacs_open (name, O_RDONLY, 0);
 612   if (fd < 0)
 613     {
 614       int open_errno = errno;
 615       report_file_errno ("Opening doc string file", build_string (name),
 616                          open_errno);
 617     }
 618   count = SPECPDL_INDEX ();
 619   record_unwind_protect_int (close_file_unwind, fd);
 620   Vdoc_file_name = filename;
 621   filled = 0;
 622   pos = 0;
 623   while (1)
 624     {
 625       register char *end;
 626       if (filled < 512)
 627         filled += emacs_read (fd, &buf[filled], sizeof buf - 1 - filled);
 628       if (!filled)
 629         break;
 630
 631       buf[filled] = 0;
 632       end = buf + (filled < 512 ? filled : filled - 128);
 633       p = memchr (buf, '\037', end - buf);
 634       /* p points to ^_Ffunctionname\n or ^_Vvarname\n or ^_Sfilename\n.  */
 635       if (p)
 636         {
 637           end = strchr (p, '\n');
 638
 639           /* See if this is a file name, and if it is a file in build-files.  */
 640           if (p[1] == 'S')
 641             {
 642               skip_file = 0;
 643               if (end - p > 4 && end[-2] == '.'
 644                   && (end[-1] == 'o' || end[-1] == 'c'))
 645                 {
 646                   ptrdiff_t len = end - p - 2;
 647                   char *fromfile = alloca (len + 1);
 648                   memcpy (fromfile, &p[2], len);
 649                   fromfile[len] = 0;
 650                   if (fromfile[len-1] == 'c')
 651                     fromfile[len-1] = 'o';
 652
 653                   skip_file = NILP (Fmember (build_string (fromfile),
 654                                              Vbuild_files));
 655                 }
 656             }
 657
 658           sym = oblookup (Vobarray, p + 2,
 659                           multibyte_chars_in_text ((unsigned char *) p + 2,
 660                                                    end - p - 2),
 661                           end - p - 2);
 662           /* Check skip_file so that when a function is defined several
 663              times in different files (typically, once in xterm, once in
 664              w32term, ...), we only pay attention to the one that
 665              matters.  */
 666           if (! skip_file && SYMBOLP (sym))
 667             {
 668               /* Attach a docstring to a variable?  */
 669               if (p[1] == 'V')
 670                 {
 671                   /* Install file-position as variable-documentation property
 672                      and make it negative for a user-variable
 673                      (doc starts with a `*').  */
 674                   if (!NILP (Fboundp (sym)))
 675                     Fput (sym, Qvariable_documentation,
 676                           make_number ((pos + end + 1 - buf)
 677                                        * (end[1] == '*' ? -1 : 1)));
 678                 }
 679
 680               /* Attach a docstring to a function?  */
 681               else if (p[1] == 'F')
 682                 {
 683                   if (!NILP (Ffboundp (sym)))
 684                     store_function_docstring (sym, pos + end + 1 - buf);
 685                 }
 686               else if (p[1] == 'S')
 687                 ; /* Just a source file name boundary marker.  Ignore it.  */
 688
 689               else
 690                 error ("DOC file invalid at position %"pI"d", pos);
 691             }
 692         }
 693       pos += end - buf;
 694       filled -= end - buf;
 695       memmove (buf, end, filled);
 696     }
 697   return unbind_to (count, Qnil);
 698 }
 699 \f
 700 DEFUN ("substitute-command-keys", Fsubstitute_command_keys,
 701        Ssubstitute_command_keys, 1, 1, 0,
 702        doc: /* Substitute key descriptions for command names in STRING.
 703 Each substring of the form \\=\\[COMMAND] is replaced by either a
 704 keystroke sequence that invokes COMMAND, or "M-x COMMAND" if COMMAND
 705 is not on any keys.
 706
 707 Each substring of the form \\=\\{MAPVAR} is replaced by a summary of
 708 the value of MAPVAR as a keymap.  This summary is similar to the one
 709 produced by `describe-bindings'.  The summary ends in two newlines
 710 \(used by the helper function `help-make-xrefs' to find the end of the
 711 summary).
 712
 713 Each substring of the form \\=\\<MAPVAR> specifies the use of MAPVAR
 714 as the keymap for future \\=\\[COMMAND] substrings.
 715 \\=\\= quotes the following character and is discarded;
 716 thus, \\=\\=\\=\\= puts \\=\\= into the output, and \\=\\=\\=\\[ puts \\=\\[ into the output.
 717
 718 Return the original STRING if no substitutions are made.
 719 Otherwise, return a new string, without any text properties.  */)
 720   (Lisp_Object string)
 721 {
 722   char *buf;
 723   bool changed = 0;
 724   unsigned char *strp;
 725   char *bufp;
 726   ptrdiff_t idx;
 727   ptrdiff_t bsize;
 728   Lisp_Object tem;
 729   Lisp_Object keymap;
 730   unsigned char *start;
 731   ptrdiff_t length, length_byte;
 732   Lisp_Object name;
 733   struct gcpro gcpro1, gcpro2, gcpro3, gcpro4;
 734   bool multibyte;
 735   ptrdiff_t nchars;
 736
 737   if (NILP (string))
 738     return Qnil;
 739
 740   CHECK_STRING (string);
 741   tem = Qnil;
 742   keymap = Qnil;
 743   name = Qnil;
 744   GCPRO4 (string, tem, keymap, name);
 745
 746   multibyte = STRING_MULTIBYTE (string);
 747   nchars = 0;
 748
 749   /* KEYMAP is either nil (which means search all the active keymaps)
 750      or a specified local map (which means search just that and the
 751      global map).  If non-nil, it might come from Voverriding_local_map,
 752      or from a \\<mapname> construct in STRING itself..  */
 753   keymap = Voverriding_local_map;
 754
 755   bsize = SBYTES (string);
 756   bufp = buf = xmalloc (bsize);
 757
 758   strp = SDATA (string);
 759   while (strp < SDATA (string) + SBYTES (string))
 760     {
 761       if (strp[0] == '\\' && strp[1] == '=')
 762         {
 763           /* \= quotes the next character;
 764              thus, to put in \[ without its special meaning, use \=\[.  */
 765           changed = 1;
 766           strp += 2;
 767           if (multibyte)
 768             {
 769               int len;
 770
 771               STRING_CHAR_AND_LENGTH (strp, len);
 772               if (len == 1)
 773                 *bufp = *strp;
 774               else
 775                 memcpy (bufp, strp, len);
 776               strp += len;
 777               bufp += len;
 778               nchars++;
 779             }
 780           else
 781             *bufp++ = *strp++, nchars++;
 782         }
 783       else if (strp[0] == '\\' && strp[1] == '[')
 784         {
 785           ptrdiff_t start_idx;
 786           bool follow_remap = 1;
 787
 788           changed = 1;
 789           strp += 2;            /* skip \[ */
 790           start = strp;
 791           start_idx = start - SDATA (string);
 792
 793           while ((strp - SDATA (string)
 794                   < SBYTES (string))
 795                  && *strp != ']')
 796             strp++;
 797           length_byte = strp - start;
 798
 799           strp++;               /* skip ] */
 800
 801           /* Save STRP in IDX.  */
 802           idx = strp - SDATA (string);
 803           name = Fintern (make_string ((char *) start, length_byte), Qnil);
 804
 805         do_remap:
 806           tem = Fwhere_is_internal (name, keymap, Qt, Qnil, Qnil);
 807
 808           if (VECTORP (tem) && ASIZE (tem) > 1
 809               && EQ (AREF (tem, 0), Qremap) && SYMBOLP (AREF (tem, 1))
 810               && follow_remap)
 811             {
 812               name = AREF (tem, 1);
 813               follow_remap = 0;
 814               goto do_remap;
 815             }
 816
 817           /* Note the Fwhere_is_internal can GC, so we have to take
 818              relocation of string contents into account.  */
 819           strp = SDATA (string) + idx;
 820           start = SDATA (string) + start_idx;
 821
 822           if (NILP (tem))       /* but not on any keys */
 823             {
 824               ptrdiff_t offset = bufp - buf;
 825               if (STRING_BYTES_BOUND - 4 < bsize)
 826                 string_overflow ();
 827               buf = xrealloc (buf, bsize += 4);
 828               bufp = buf + offset;
 829               memcpy (bufp, "M-x ", 4);
 830               bufp += 4;
 831               nchars += 4;
 832               if (multibyte)
 833                 length = multibyte_chars_in_text (start, length_byte);
 834               else
 835                 length = length_byte;
 836               goto subst;
 837             }
 838           else
 839             {                   /* function is on a key */
 840               tem = Fkey_description (tem, Qnil);
 841               goto subst_string;
 842             }
 843         }
 844       /* \{foo} is replaced with a summary of the keymap (symbol-value foo).
 845          \<foo> just sets the keymap used for \[cmd].  */
 846       else if (strp[0] == '\\' && (strp[1] == '{' || strp[1] == '<'))
 847         {
 848           struct buffer *oldbuf;
 849           ptrdiff_t start_idx;
 850           /* This is for computing the SHADOWS arg for describe_map_tree.  */
 851           Lisp_Object active_maps = Fcurrent_active_maps (Qnil, Qnil);
 852           Lisp_Object earlier_maps;
 853
 854           changed = 1;
 855           strp += 2;            /* skip \{ or \< */
 856           start = strp;
 857           start_idx = start - SDATA (string);
 858
 859           while ((strp - SDATA (string) < SBYTES (string))
 860                  && *strp != '}' && *strp != '>')
 861             strp++;
 862
 863           length_byte = strp - start;
 864           strp++;                       /* skip } or > */
 865
 866           /* Save STRP in IDX.  */
 867           idx = strp - SDATA (string);
 868
 869           /* Get the value of the keymap in TEM, or nil if undefined.
 870              Do this while still in the user's current buffer
 871              in case it is a local variable.  */
 872           name = Fintern (make_string ((char *) start, length_byte), Qnil);
 873           tem = Fboundp (name);
 874           if (! NILP (tem))
 875             {
 876               tem = Fsymbol_value (name);
 877               if (! NILP (tem))
 878                 {
 879                   tem = get_keymap (tem, 0, 1);
 880                   /* Note that get_keymap can GC.  */
 881                   strp = SDATA (string) + idx;
 882                   start = SDATA (string) + start_idx;
 883                 }
 884             }
 885
 886           /* Now switch to a temp buffer.  */
 887           oldbuf = current_buffer;
 888           set_buffer_internal (XBUFFER (Vprin1_to_string_buffer));
 889
 890           if (NILP (tem))
 891             {
 892               name = Fsymbol_name (name);
 893               insert_string ("\nUses keymap `");
 894               insert_from_string (name, 0, 0,
 895                                   SCHARS (name),
 896                                   SBYTES (name), 1);
 897               insert_string ("', which is not currently defined.\n");
 898               if (start[-1] == '<') keymap = Qnil;
 899             }
 900           else if (start[-1] == '<')
 901             keymap = tem;
 902           else
 903             {
 904               /* Get the list of active keymaps that precede this one.
 905                  If this one's not active, get nil.  */
 906               earlier_maps = Fcdr (Fmemq (tem, Freverse (active_maps)));
 907               describe_map_tree (tem, 1, Fnreverse (earlier_maps),
 908                                  Qnil, 0, 1, 0, 0, 1);
 909             }
 910           tem = Fbuffer_string ();
 911           Ferase_buffer ();
 912           set_buffer_internal (oldbuf);
 913
 914         subst_string:
 915           start = SDATA (tem);
 916           length = SCHARS (tem);
 917           length_byte = SBYTES (tem);
 918         subst:
 919           {
 920             ptrdiff_t offset = bufp - buf;
 921             if (STRING_BYTES_BOUND - length_byte < bsize)
 922               string_overflow ();
 923             buf = xrealloc (buf, bsize += length_byte);
 924             bufp = buf + offset;
 925             memcpy (bufp, start, length_byte);
 926             bufp += length_byte;
 927             nchars += length;
 928             /* Check STRING again in case gc relocated it.  */
 929             strp = SDATA (string) + idx;
 930           }
 931         }
 932       else if (! multibyte)             /* just copy other chars */
 933         *bufp++ = *strp++, nchars++;
 934       else
 935         {
 936           int len;
 937
 938           STRING_CHAR_AND_LENGTH (strp, len);
 939           if (len == 1)
 940             *bufp = *strp;
 941           else
 942             memcpy (bufp, strp, len);
 943           strp += len;
 944           bufp += len;
 945           nchars++;
 946         }
 947     }
 948
 949   if (changed)                  /* don't bother if nothing substituted */
 950     tem = make_string_from_bytes (buf, nchars, bufp - buf);
 951   else
 952     tem = string;
 953   xfree (buf);
 954   RETURN_UNGCPRO (tem);
 955 }
 956 \f
 957 void
 958 syms_of_doc (void)
 959 {
 960   DEFSYM (Qfunction_documentation, "function-documentation");
 961
 962   DEFVAR_LISP ("internal-doc-file-name", Vdoc_file_name,
 963                doc: /* Name of file containing documentation strings of built-in symbols.  */);
 964   Vdoc_file_name = Qnil;
 965
 966   DEFVAR_LISP ("build-files", Vbuild_files,
 967                doc: /* A list of files used to build this Emacs binary.  */);
 968   Vbuild_files = Qnil;
 969
 970   defsubr (&Sdocumentation);
 971   defsubr (&Sdocumentation_property);
 972   defsubr (&Ssnarf_documentation);
 973   defsubr (&Ssubstitute_command_keys);
 974 }