libguile/read.c

   1 /* Copyright (C) 1995,1996,1997,1999,2000,2001 Free Software Foundation, Inc.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2, or (at your option)
   6  * any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this software; see the file COPYING.  If not, write to
  15  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  16  * Boston, MA 02111-1307 USA
  17  *
  18  * As a special exception, the Free Software Foundation gives permission
  19  * for additional uses of the text contained in its release of GUILE.
  20  *
  21  * The exception is that, if you link the GUILE library with other files
  22  * to produce an executable, this does not by itself cause the
  23  * resulting executable to be covered by the GNU General Public License.
  24  * Your use of that executable is in no way restricted on account of
  25  * linking the GUILE library code into it.
  26  *
  27  * This exception does not however invalidate any other reasons why
  28  * the executable file might be covered by the GNU General Public License.
  29  *
  30  * This exception applies only to the code released by the
  31  * Free Software Foundation under the name GUILE.  If you copy
  32  * code from other Free Software Foundation releases into a copy of
  33  * GUILE, as the General Public License permits, the exception does
  34  * not apply to the code that you add in this way.  To avoid misleading
  35  * anyone as to the status of such modified files, you must delete
  36  * this exception notice from them.
  37  *
  38  * If you write modifications of your own for GUILE, it is your choice
  39  * whether to permit this exception to apply to your modifications.
  40  * If you do not wish that, delete this exception notice.  */
  41
  42 /* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
  43    gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
  44
  45 \f
  46
  47 #include <stdio.h>
  48 #include "libguile/_scm.h"
  49 #include "libguile/chars.h"
  50 #include "libguile/eval.h"
  51 #include "libguile/unif.h"
  52 #include "libguile/keywords.h"
  53 #include "libguile/alist.h"
  54 #include "libguile/srcprop.h"
  55 #include "libguile/hashtab.h"
  56 #include "libguile/hash.h"
  57 #include "libguile/ports.h"
  58 #include "libguile/root.h"
  59 #include "libguile/strings.h"
  60 #include "libguile/vectors.h"
  61
  62 #include "libguile/validate.h"
  63 #include "libguile/read.h"
  64
  65 \f
  66
  67 SCM_SYMBOL (scm_keyword_prefix, "prefix");
  68
  69 scm_t_option scm_read_opts[] = {
  70   { SCM_OPTION_BOOLEAN, "copy", 0,
  71     "Copy source code expressions." },
  72   { SCM_OPTION_BOOLEAN, "positions", 0,
  73     "Record positions of source code expressions." },
  74   { SCM_OPTION_BOOLEAN, "case-insensitive", 0,
  75     "Convert symbols to lower case."},
  76   { SCM_OPTION_SCM, "keywords", SCM_UNPACK (SCM_BOOL_F),
  77     "Style of keyword recognition: #f or 'prefix"}
  78 };
  79
  80 SCM_DEFINE (scm_read_options, "read-options-interface", 0, 1, 0,
  81             (SCM setting),
  82             "Option interface for the read options. Instead of using\n"
  83             "this procedure directly, use the procedures @code{read-enable},\n"
  84             "@code{read-disable}, @code{read-set!} and @var{read-options}.")
  85 #define FUNC_NAME s_scm_read_options
  86 {
  87   SCM ans = scm_options (setting,
  88                          scm_read_opts,
  89                          SCM_N_READ_OPTIONS,
  90                          FUNC_NAME);
  91   if (SCM_COPY_SOURCE_P)
  92     SCM_RECORD_POSITIONS_P = 1;
  93   return ans;
  94 }
  95 #undef FUNC_NAME
  96
  97 /* An association list mapping extra hash characters to procedures.  */
  98 static SCM *scm_read_hash_procedures;
  99
 100 SCM_DEFINE (scm_read, "read", 0, 1, 0,
 101             (SCM port),
 102             "Read an s-expression from the input port @var{port}, or from\n"
 103             "the current input port if @var{port} is not specified.\n"
 104             "Any whitespace before the next token is discarded.")
 105 #define FUNC_NAME s_scm_read
 106 {
 107   int c;
 108   SCM tok_buf, copy;
 109
 110   if (SCM_UNBNDP (port))
 111     port = scm_cur_inp;
 112   SCM_VALIDATE_OPINPORT (1,port);
 113
 114   c = scm_flush_ws (port, (char *) NULL);
 115   if (EOF == c)
 116     return SCM_EOF_VAL;
 117   scm_ungetc (c, port);
 118
 119   tok_buf = scm_allocate_string (30);
 120   return scm_lreadr (&tok_buf, port, &copy);
 121 }
 122 #undef FUNC_NAME
 123
 124
 125
 126 char *
 127 scm_grow_tok_buf (SCM *tok_buf)
 128 {
 129   size_t oldlen = SCM_STRING_LENGTH (*tok_buf);
 130   SCM newstr = scm_allocate_string (2 * oldlen);
 131   size_t i;
 132
 133   for (i = 0; i != oldlen; ++i)
 134     SCM_STRING_CHARS (newstr) [i] = SCM_STRING_CHARS (*tok_buf) [i];
 135
 136   *tok_buf = newstr;
 137   return SCM_STRING_CHARS (newstr);
 138 }
 139
 140
 141
 142 int
 143 scm_flush_ws (SCM port, const char *eoferr)
 144 {
 145   register int c;
 146   while (1)
 147     switch (c = scm_getc (port))
 148       {
 149       case EOF:
 150       goteof:
 151         if (eoferr)
 152           {
 153             if (!SCM_FALSEP (SCM_FILENAME (port)))
 154               scm_misc_error (eoferr,
 155                               "end of file in ~A",
 156                               SCM_LIST1 (SCM_FILENAME (port)));
 157             else
 158               scm_misc_error (eoferr, "end of file", SCM_EOL);
 159           }
 160         return c;
 161       case ';':
 162       lp:
 163         switch (c = scm_getc (port))
 164           {
 165           case EOF:
 166             goto goteof;
 167           default:
 168             goto lp;
 169           case SCM_LINE_INCREMENTORS:
 170             break;
 171           }
 172         break;
 173       case SCM_LINE_INCREMENTORS:
 174       case SCM_SINGLE_SPACES:
 175       case '\t':
 176         break;
 177       default:
 178         return c;
 179       }
 180 }
 181
 182
 183
 184 int
 185 scm_casei_streq (char *s1, char *s2)
 186 {
 187   while (*s1 && *s2)
 188     if (scm_downcase((int)*s1) != scm_downcase((int)*s2))
 189       return 0;
 190     else
 191       {
 192         ++s1;
 193         ++s2;
 194       }
 195   return !(*s1 || *s2);
 196 }
 197
 198
 199 /* recsexpr is used when recording expressions
 200  * constructed by read:sharp.
 201  */
 202 #ifndef DEBUG_EXTENSIONS
 203 #define recsexpr(obj, line, column, filename) (obj)
 204 #else
 205 static SCM
 206 recsexpr (SCM obj, long line, int column, SCM filename)
 207 {
 208   if (!SCM_CONSP(obj)) {
 209     return obj;
 210   } else {
 211     SCM tmp = obj, copy;
 212     /* If this sexpr is visible in the read:sharp source, we want to
 213        keep that information, so only record non-constant cons cells
 214        which haven't previously been read by the reader. */
 215     if (SCM_FALSEP (scm_whash_lookup (scm_source_whash, obj)))
 216       {
 217         if (SCM_COPY_SOURCE_P)
 218           {
 219             copy = scm_cons (recsexpr (SCM_CAR (obj), line, column, filename),
 220                              SCM_UNDEFINED);
 221             while ((tmp = SCM_CDR (tmp)) && SCM_CONSP (tmp))
 222               {
 223                 SCM_SETCDR (copy, scm_cons (recsexpr (SCM_CAR (tmp),
 224                                                       line,
 225                                                       column,
 226                                                       filename),
 227                                             SCM_UNDEFINED));
 228                 copy = SCM_CDR (copy);
 229               }
 230             SCM_SETCDR (copy, tmp);
 231           }
 232         else
 233           {
 234             recsexpr (SCM_CAR (obj), line, column, filename);
 235             while ((tmp = SCM_CDR (tmp)) && SCM_CONSP (tmp))
 236               recsexpr (SCM_CAR (tmp), line, column, filename);
 237             copy = SCM_UNDEFINED;
 238           }
 239         scm_whash_insert (scm_source_whash,
 240                           obj,
 241                           scm_make_srcprops (line,
 242                                              column,
 243                                              filename,
 244                                              copy,
 245                                              SCM_EOL));
 246       }
 247     return obj;
 248   }
 249 }
 250 #endif
 251
 252 /* Consume an SCSH-style block comment.  Assume that we've already
 253    read the initial `#!', and eat characters until we get a
 254    newline/exclamation-point/sharp-sign/newline sequence.  */
 255
 256 static void
 257 skip_scsh_block_comment (SCM port)
 258 #define FUNC_NAME "skip_scsh_block_comment"
 259 {
 260   /* Is this portable?  Dear God, spare me from the non-eight-bit
 261      characters.  But is it tasteful?  */
 262   long history = 0;
 263
 264   for (;;)
 265     {
 266       int c = scm_getc (port);
 267
 268       if (c == EOF)
 269         SCM_MISC_ERROR ("unterminated `#! ... !#' comment", SCM_EOL);
 270       history = ((history << 8) | (c & 0xff)) & 0xffffffff;
 271
 272       /* Were the last four characters read "\n!#\n"?  */
 273       if (history == (('\n' << 24) | ('!' << 16) | ('#' << 8) | '\n'))
 274         return;
 275     }
 276 }
 277 #undef FUNC_NAME
 278
 279
 280 static SCM scm_get_hash_procedure(int c);
 281
 282 static char s_list[]="list";
 283
 284 SCM
 285 scm_lreadr (SCM *tok_buf,SCM port,SCM *copy)
 286 #define FUNC_NAME "scm_lreadr"
 287 {
 288   int c;
 289   size_t j;
 290   SCM p;
 291
 292 tryagain:
 293   c = scm_flush_ws (port, s_scm_read);
 294 tryagain_no_flush_ws:
 295   switch (c)
 296     {
 297     case EOF:
 298       return SCM_EOF_VAL;
 299
 300     case '(':
 301       return SCM_RECORD_POSITIONS_P
 302              ? scm_lreadrecparen (tok_buf, port, s_list, copy)
 303              : scm_lreadparen (tok_buf, port, s_list, copy);
 304     case ')':
 305       SCM_MISC_ERROR ("unexpected \")\"", SCM_EOL);
 306       goto tryagain;
 307
 308     case '\'':
 309       p = scm_sym_quote;
 310       goto recquote;
 311     case '`':
 312       p = scm_sym_quasiquote;
 313       goto recquote;
 314     case ',':
 315       c = scm_getc (port);
 316       if ('@' == c)
 317         p = scm_sym_uq_splicing;
 318       else
 319         {
 320           scm_ungetc (c, port);
 321           p = scm_sym_unquote;
 322         }
 323     recquote:
 324       p = scm_cons2 (p,
 325                      scm_lreadr (tok_buf, port, copy),
 326                      SCM_EOL);
 327       if (SCM_RECORD_POSITIONS_P)
 328         scm_whash_insert (scm_source_whash,
 329                           p,
 330                           scm_make_srcprops (SCM_LINUM (port),
 331                                              SCM_COL (port) - 1,
 332                                              SCM_FILENAME (port),
 333                                              SCM_COPY_SOURCE_P
 334                                              ? (*copy = scm_cons2 (SCM_CAR (p),
 335                                                                    SCM_CAR (SCM_CDR (p)),
 336                                                                    SCM_EOL))
 337                                              : SCM_UNDEFINED,
 338                                              SCM_EOL));
 339       return p;
 340     case '#':
 341       c = scm_getc (port);
 342       switch (c)
 343         {
 344         case '(':
 345           p = scm_lreadparen (tok_buf, port, "vector", copy);
 346           return SCM_NULLP (p) ? scm_nullvect : scm_vector (p);
 347
 348         case 't':
 349         case 'T':
 350           return SCM_BOOL_T;
 351         case 'f':
 352         case 'F':
 353           return SCM_BOOL_F;
 354
 355         case 'b':
 356         case 'B':
 357         case 'o':
 358         case 'O':
 359         case 'd':
 360         case 'D':
 361         case 'x':
 362         case 'X':
 363         case 'i':
 364         case 'I':
 365         case 'e':
 366         case 'E':
 367           scm_ungetc (c, port);
 368           c = '#';
 369           goto num;
 370
 371         case '!':
 372           /* start of a shell script.  Parse as a block comment,
 373              terminated by !#, just like SCSH.  */
 374           skip_scsh_block_comment (port);
 375           /* EOF is not an error here */
 376           c = scm_flush_ws (port, (char *)NULL);
 377           goto tryagain_no_flush_ws;
 378
 379 #ifdef HAVE_ARRAYS
 380         case '*':
 381           j = scm_read_token (c, tok_buf, port, 0);
 382           p = scm_istr2bve (SCM_STRING_CHARS (*tok_buf) + 1, (long) (j - 1));
 383           if (!SCM_FALSEP (p))
 384             return p;
 385           else
 386             goto unkshrp;
 387 #endif
 388
 389         case '{':
 390           j = scm_read_token (c, tok_buf, port, 1);
 391           return scm_mem2symbol (SCM_STRING_CHARS (*tok_buf), j);
 392
 393         case '\\':
 394           c = scm_getc (port);
 395           j = scm_read_token (c, tok_buf, port, 0);
 396           if (j == 1)
 397             return SCM_MAKE_CHAR (c);
 398           if (c >= '0' && c < '8')
 399             {
 400               p = scm_istr2int (SCM_STRING_CHARS (*tok_buf), (long) j, 8);
 401               if (!SCM_FALSEP (p))
 402                 return SCM_MAKE_CHAR (SCM_INUM (p));
 403             }
 404           for (c = 0; c < scm_n_charnames; c++)
 405             if (scm_charnames[c]
 406                 && (scm_casei_streq (scm_charnames[c], SCM_STRING_CHARS (*tok_buf))))
 407               return SCM_MAKE_CHAR (scm_charnums[c]);
 408           SCM_MISC_ERROR ("unknown # object", SCM_EOL);
 409
 410           /* #:SYMBOL is a syntax for keywords supported in all contexts.  */
 411         case ':':
 412           j = scm_read_token ('-', tok_buf, port, 0);
 413           p = scm_mem2symbol (SCM_STRING_CHARS (*tok_buf), j);
 414           return scm_make_keyword_from_dash_symbol (p);
 415
 416         default:
 417         callshrp:
 418           {
 419             SCM sharp = scm_get_hash_procedure (c);
 420
 421             if (!SCM_FALSEP (sharp))
 422               {
 423                 int line = SCM_LINUM (port);
 424                 int column = SCM_COL (port) - 2;
 425                 SCM got;
 426
 427                 got = scm_apply (sharp,
 428                                  SCM_MAKE_CHAR (c),
 429                                  scm_acons (port, SCM_EOL, SCM_EOL));
 430                 if (SCM_EQ_P (got, SCM_UNSPECIFIED))
 431                   goto unkshrp;
 432                 if (SCM_RECORD_POSITIONS_P)
 433                   return *copy = recsexpr (got, line, column,
 434                                            SCM_FILENAME (port));
 435                 else
 436                   return got;
 437               }
 438           }
 439         unkshrp:
 440           scm_misc_error (s_scm_read, "Unknown # object: ~S",
 441                           SCM_LIST1 (SCM_MAKE_CHAR (c)));
 442         }
 443
 444     case '"':
 445       j = 0;
 446       while ('"' != (c = scm_getc (port)))
 447         {
 448           if (c == EOF)
 449             SCM_MISC_ERROR ("end of file in string constant", SCM_EOL);
 450
 451           while (j + 2 >= SCM_STRING_LENGTH (*tok_buf))
 452             scm_grow_tok_buf (tok_buf);
 453
 454           if (c == '\\')
 455             switch (c = scm_getc (port))
 456               {
 457               case '\n':
 458                 continue;
 459               case '0':
 460                 c = '\0';
 461                 break;
 462               case 'f':
 463                 c = '\f';
 464                 break;
 465               case 'n':
 466                 c = '\n';
 467                 break;
 468               case 'r':
 469                 c = '\r';
 470                 break;
 471               case 't':
 472                 c = '\t';
 473                 break;
 474               case 'a':
 475                 c = '\007';
 476                 break;
 477               case 'v':
 478                 c = '\v';
 479                 break;
 480               }
 481           SCM_STRING_CHARS (*tok_buf)[j] = c;
 482           ++j;
 483         }
 484       if (j == 0)
 485         return scm_nullstr;
 486       SCM_STRING_CHARS (*tok_buf)[j] = 0;
 487       return scm_mem2string (SCM_STRING_CHARS (*tok_buf), j);
 488
 489     case'0':case '1':case '2':case '3':case '4':
 490     case '5':case '6':case '7':case '8':case '9':
 491     case '.':
 492     case '-':
 493     case '+':
 494     num:
 495       j = scm_read_token (c, tok_buf, port, 0);
 496       p = scm_istring2number (SCM_STRING_CHARS (*tok_buf), (long) j, 10L);
 497       if (!SCM_FALSEP (p))
 498         return p;
 499       if (c == '#')
 500         {
 501           if ((j == 2) && (scm_getc (port) == '('))
 502             {
 503               scm_ungetc ('(', port);
 504               c = SCM_STRING_CHARS (*tok_buf)[1];
 505               goto callshrp;
 506             }
 507           SCM_MISC_ERROR ("unknown # object", SCM_EOL);
 508         }
 509       goto tok;
 510
 511     case ':':
 512       if (SCM_EQ_P (SCM_PACK (SCM_KEYWORD_STYLE), scm_keyword_prefix))
 513         {
 514           j = scm_read_token ('-', tok_buf, port, 0);
 515           p = scm_mem2symbol (SCM_STRING_CHARS (*tok_buf), j);
 516           return scm_make_keyword_from_dash_symbol (p);
 517         }
 518       /* fallthrough */
 519     default:
 520       j = scm_read_token (c, tok_buf, port, 0);
 521       /* fallthrough */
 522
 523     tok:
 524       return scm_mem2symbol (SCM_STRING_CHARS (*tok_buf), j);
 525     }
 526 }
 527 #undef FUNC_NAME
 528
 529
 530 #ifdef _UNICOS
 531 _Pragma ("noopt");              /* # pragma _CRI noopt */
 532 #endif
 533
 534 size_t
 535 scm_read_token (int ic, SCM *tok_buf, SCM port, int weird)
 536 {
 537   register size_t j;
 538   register int c;
 539   register char *p;
 540
 541   c = (SCM_CASE_INSENSITIVE_P ? scm_downcase(ic) : ic);
 542   p = SCM_STRING_CHARS (*tok_buf);
 543
 544   if (weird)
 545     j = 0;
 546   else
 547     {
 548       j = 0;
 549       while (j + 2 >= SCM_STRING_LENGTH (*tok_buf))
 550         p = scm_grow_tok_buf (tok_buf);
 551       p[j] = c;
 552       ++j;
 553     }
 554
 555   while (1)
 556     {
 557       while (j + 2 >= SCM_STRING_LENGTH (*tok_buf))
 558         p = scm_grow_tok_buf (tok_buf);
 559       c = scm_getc (port);
 560       switch (c)
 561         {
 562         case '(':
 563         case ')':
 564         case '"':
 565         case ';':
 566         case SCM_WHITE_SPACES:
 567         case SCM_LINE_INCREMENTORS:
 568           if (weird)
 569             goto default_case;
 570
 571           scm_ungetc (c, port);
 572         case EOF:
 573         eof_case:
 574           p[j] = 0;
 575           return j;
 576         case '\\':
 577           if (!weird)
 578             goto default_case;
 579           else
 580             {
 581               c = scm_getc (port);
 582               if (c == EOF)
 583                 goto eof_case;
 584               else
 585                 goto default_case;
 586             }
 587         case '}':
 588           if (!weird)
 589             goto default_case;
 590
 591           c = scm_getc (port);
 592           if (c == '#')
 593             {
 594               p[j] = 0;
 595               return j;
 596             }
 597           else
 598             {
 599               scm_ungetc (c, port);
 600               c = '}';
 601               goto default_case;
 602             }
 603
 604         default:
 605         default_case:
 606           {
 607             c = (SCM_CASE_INSENSITIVE_P ? scm_downcase(c) : c);
 608             p[j] = c;
 609             ++j;
 610           }
 611
 612         }
 613     }
 614 }
 615
 616 #ifdef _UNICOS
 617 _Pragma ("opt");                /* # pragma _CRI opt */
 618 #endif
 619
 620 SCM
 621 scm_lreadparen (SCM *tok_buf, SCM port, char *name, SCM *copy)
 622 #define FUNC_NAME "scm_lreadparen"
 623 {
 624   SCM tmp;
 625   SCM tl;
 626   SCM ans;
 627   int c;
 628
 629   c = scm_flush_ws (port, name);
 630   if (')' == c)
 631     return SCM_EOL;
 632   scm_ungetc (c, port);
 633   if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 634     {
 635       ans = scm_lreadr (tok_buf, port, copy);
 636     closeit:
 637       if (')' != (c = scm_flush_ws (port, name)))
 638         SCM_MISC_ERROR ("missing close paren", SCM_EOL);
 639       return ans;
 640     }
 641   ans = tl = scm_cons (tmp, SCM_EOL);
 642   while (')' != (c = scm_flush_ws (port, name)))
 643     {
 644       scm_ungetc (c, port);
 645       if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 646         {
 647           SCM_SETCDR (tl, scm_lreadr (tok_buf, port, copy));
 648           goto closeit;
 649         }
 650       SCM_SETCDR (tl, scm_cons (tmp, SCM_EOL));
 651       tl = SCM_CDR (tl);
 652     }
 653   return ans;
 654 }
 655 #undef FUNC_NAME
 656
 657
 658 SCM
 659 scm_lreadrecparen (SCM *tok_buf, SCM port, char *name, SCM *copy)
 660 #define FUNC_NAME "scm_lreadrecparen"
 661 {
 662   register int c;
 663   register SCM tmp;
 664   register SCM tl, tl2 = SCM_EOL;
 665   SCM ans, ans2 = SCM_EOL;
 666   /* Need to capture line and column numbers here. */
 667   int line = SCM_LINUM (port);
 668   int column = SCM_COL (port) - 1;
 669
 670   c = scm_flush_ws (port, name);
 671   if (')' == c)
 672     return SCM_EOL;
 673   scm_ungetc (c, port);
 674   if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 675     {
 676       ans = scm_lreadr (tok_buf, port, copy);
 677       if (')' != (c = scm_flush_ws (port, name)))
 678         SCM_MISC_ERROR ("missing close paren", SCM_EOL);
 679       return ans;
 680     }
 681   /* Build the head of the list structure. */
 682   ans = tl = scm_cons (tmp, SCM_EOL);
 683   if (SCM_COPY_SOURCE_P)
 684     ans2 = tl2 = scm_cons (SCM_CONSP (tmp)
 685                            ? *copy
 686                            : tmp,
 687                            SCM_EOL);
 688   while (')' != (c = scm_flush_ws (port, name)))
 689     {
 690       SCM new_tail;
 691
 692       scm_ungetc (c, port);
 693       if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 694         {
 695           SCM_SETCDR (tl, tmp = scm_lreadr (tok_buf, port, copy));
 696           if (SCM_COPY_SOURCE_P)
 697             SCM_SETCDR (tl2, scm_cons (SCM_CONSP (tmp)
 698                                        ? *copy
 699                                        : tmp,
 700                                        SCM_EOL));
 701           if (')' != (c = scm_flush_ws (port, name)))
 702             SCM_MISC_ERROR ("missing close paren", SCM_EOL);
 703           goto exit;
 704         }
 705
 706       new_tail = scm_cons (tmp, SCM_EOL);
 707       SCM_SETCDR (tl, new_tail);
 708       tl = new_tail;
 709
 710       if (SCM_COPY_SOURCE_P)
 711         {
 712           SCM new_tail2 = scm_cons (SCM_CONSP (tmp) ? *copy : tmp, SCM_EOL);
 713           SCM_SETCDR (tl2, new_tail2);
 714           tl2 = new_tail2;
 715         }
 716     }
 717 exit:
 718   scm_whash_insert (scm_source_whash,
 719                     ans,
 720                     scm_make_srcprops (line,
 721                                        column,
 722                                        SCM_FILENAME (port),
 723                                        SCM_COPY_SOURCE_P
 724                                        ? *copy = ans2
 725                                        : SCM_UNDEFINED,
 726                                        SCM_EOL));
 727   return ans;
 728 }
 729 #undef FUNC_NAME
 730
 731
 732 \f
 733
 734 /* Manipulate the read-hash-procedures alist.  This could be written in
 735    Scheme, but maybe it will also be used by C code during initialisation.  */
 736 SCM_DEFINE (scm_read_hash_extend, "read-hash-extend", 2, 0, 0,
 737             (SCM chr, SCM proc),
 738             "Install the procedure @var{proc} for reading expressions\n"
 739             "starting with the character sequence @code{#} and @var{chr}.\n"
 740             "@var{proc} will be called with two arguments:  the character\n"
 741             "@var{chr} and the port to read further data from. The object\n"
 742             "returned will be the return value of @code{read}.")
 743 #define FUNC_NAME s_scm_read_hash_extend
 744 {
 745   SCM this;
 746   SCM prev;
 747
 748   SCM_VALIDATE_CHAR (1, chr);
 749   SCM_ASSERT (SCM_FALSEP (proc)
 750               || SCM_EQ_P (scm_procedure_p (proc), SCM_BOOL_T),
 751               proc, SCM_ARG2, FUNC_NAME);
 752
 753   /* Check if chr is already in the alist.  */
 754   this = *scm_read_hash_procedures;
 755   prev = SCM_BOOL_F;
 756   while (1)
 757     {
 758       if (SCM_NULLP (this))
 759         {
 760           /* not found, so add it to the beginning.  */
 761           if (!SCM_FALSEP (proc))
 762             {
 763               *scm_read_hash_procedures =
 764                 scm_cons (scm_cons (chr, proc), *scm_read_hash_procedures);
 765             }
 766           break;
 767         }
 768       if (SCM_EQ_P (chr, SCM_CAAR (this)))
 769         {
 770           /* already in the alist.  */
 771           if (SCM_FALSEP (proc))
 772             {
 773               /* remove it.  */
 774               if (SCM_FALSEP (prev))
 775                 {
 776                   *scm_read_hash_procedures =
 777                     SCM_CDR (*scm_read_hash_procedures);
 778                 }
 779               else
 780                 scm_set_cdr_x (prev, SCM_CDR (this));
 781             }
 782           else
 783             {
 784               /* replace it.  */
 785               scm_set_cdr_x (SCM_CAR (this), proc);
 786             }
 787           break;
 788         }
 789       prev = this;
 790       this = SCM_CDR (this);
 791     }
 792
 793   return SCM_UNSPECIFIED;
 794 }
 795 #undef FUNC_NAME
 796
 797 /* Recover the read-hash procedure corresponding to char c.  */
 798 static SCM
 799 scm_get_hash_procedure (int c)
 800 {
 801   SCM rest = *scm_read_hash_procedures;
 802
 803   while (1)
 804     {
 805       if (SCM_NULLP (rest))
 806         return SCM_BOOL_F;
 807
 808       if (SCM_CHAR (SCM_CAAR (rest)) == c)
 809         return SCM_CDAR (rest);
 810
 811       rest = SCM_CDR (rest);
 812     }
 813 }
 814
 815 void
 816 scm_init_read ()
 817 {
 818   scm_read_hash_procedures =
 819     SCM_VARIABLE_LOC (scm_c_define ("read-hash-procedures", SCM_EOL));
 820
 821   scm_init_opts (scm_read_options, scm_read_opts, SCM_N_READ_OPTIONS);
 822 #ifndef SCM_MAGIC_SNARFER
 823 #include "libguile/read.x"
 824 #endif
 825 }
 826
 827 /*
 828   Local Variables:
 829   c-file-style: "gnu"
 830   End:
 831 */