libguile/read.c

   1 /*      Copyright (C) 1995,1996,1997, 1999, 2000 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_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 "")
  83 #define FUNC_NAME s_scm_read_options
  84 {
  85   SCM ans = scm_options (setting,
  86                          scm_read_opts,
  87                          SCM_N_READ_OPTIONS,
  88                          FUNC_NAME);
  89   if (SCM_COPY_SOURCE_P)
  90     SCM_RECORD_POSITIONS_P = 1;
  91   return ans;
  92 }
  93 #undef FUNC_NAME
  94
  95 /* An association list mapping extra hash characters to procedures.  */
  96 static SCM *scm_read_hash_procedures;
  97
  98 SCM_DEFINE (scm_read, "read", 0, 1, 0,
  99             (SCM port),
 100 "")
 101 #define FUNC_NAME s_scm_read
 102 {
 103   int c;
 104   SCM tok_buf, copy;
 105
 106   if (SCM_UNBNDP (port))
 107     port = scm_cur_inp;
 108   SCM_VALIDATE_OPINPORT (1,port);
 109
 110   c = scm_flush_ws (port, (char *) NULL);
 111   if (EOF == c)
 112     return SCM_EOF_VAL;
 113   scm_ungetc (c, port);
 114
 115   tok_buf = scm_makstr (30L, 0);
 116   return scm_lreadr (&tok_buf, port, &copy);
 117 }
 118 #undef FUNC_NAME
 119
 120
 121
 122 char *
 123 scm_grow_tok_buf (SCM *tok_buf)
 124 {
 125   unsigned long int oldlen = SCM_STRING_LENGTH (*tok_buf);
 126   SCM newstr = scm_makstr (2 * oldlen, 0);
 127   unsigned long int i;
 128
 129   for (i = 0; i != oldlen; ++i)
 130     SCM_STRING_CHARS (newstr) [i] = SCM_STRING_CHARS (*tok_buf) [i];
 131
 132   *tok_buf = newstr;
 133   return SCM_STRING_CHARS (newstr);
 134 }
 135
 136
 137
 138 int
 139 scm_flush_ws (SCM port, const char *eoferr)
 140 {
 141   register int c;
 142   while (1)
 143     switch (c = scm_getc (port))
 144       {
 145       case EOF:
 146       goteof:
 147         if (eoferr)
 148           {
 149             if (!SCM_FALSEP (SCM_FILENAME (port)))
 150               scm_misc_error (eoferr,
 151                               "end of file in ~A",
 152                               SCM_LIST1 (SCM_FILENAME (port)));
 153             else
 154               scm_misc_error (eoferr, "end of file", SCM_EOL);
 155           }
 156         return c;
 157       case ';':
 158       lp:
 159         switch (c = scm_getc (port))
 160           {
 161           case EOF:
 162             goto goteof;
 163           default:
 164             goto lp;
 165           case SCM_LINE_INCREMENTORS:
 166             break;
 167           }
 168         break;
 169       case SCM_LINE_INCREMENTORS:
 170       case SCM_SINGLE_SPACES:
 171       case '\t':
 172         break;
 173       default:
 174         return c;
 175       }
 176 }
 177
 178
 179
 180 int
 181 scm_casei_streq (char *s1, char *s2)
 182 {
 183   while (*s1 && *s2)
 184     if (scm_downcase((int)*s1) != scm_downcase((int)*s2))
 185       return 0;
 186     else
 187       {
 188         ++s1;
 189         ++s2;
 190       }
 191   return !(*s1 || *s2);
 192 }
 193
 194
 195 /* recsexpr is used when recording expressions
 196  * constructed by read:sharp.
 197  */
 198 #ifndef DEBUG_EXTENSIONS
 199 #define recsexpr(obj, line, column, filename) (obj)
 200 #else
 201 static SCM
 202 recsexpr (SCM obj,int line,int column,SCM filename)
 203 {
 204   if (!SCM_CONSP(obj)) {
 205     return obj;
 206   } else {
 207     SCM tmp = obj, copy;
 208     /* If this sexpr is visible in the read:sharp source, we want to
 209        keep that information, so only record non-constant cons cells
 210        which haven't previously been read by the reader. */
 211     if (SCM_FALSEP (scm_whash_lookup (scm_source_whash, obj)))
 212       {
 213         if (SCM_COPY_SOURCE_P)
 214           {
 215             copy = scm_cons (recsexpr (SCM_CAR (obj), line, column, filename),
 216                              SCM_UNDEFINED);
 217             while ((tmp = SCM_CDR (tmp)) && SCM_CONSP (tmp))
 218               {
 219                 SCM_SETCDR (copy, scm_cons (recsexpr (SCM_CAR (tmp),
 220                                                       line,
 221                                                       column,
 222                                                       filename),
 223                                             SCM_UNDEFINED));
 224                 copy = SCM_CDR (copy);
 225               }
 226             SCM_SETCDR (copy, tmp);
 227           }
 228         else
 229           {
 230             recsexpr (SCM_CAR (obj), line, column, filename);
 231             while ((tmp = SCM_CDR (tmp)) && SCM_CONSP (tmp))
 232               recsexpr (SCM_CAR (tmp), line, column, filename);
 233             copy = SCM_UNDEFINED;
 234           }
 235         scm_whash_insert (scm_source_whash,
 236                           obj,
 237                           scm_make_srcprops (line,
 238                                              column,
 239                                              filename,
 240                                              copy,
 241                                              SCM_EOL));
 242       }
 243     return obj;
 244   }
 245 }
 246 #endif
 247
 248 /* Consume an SCSH-style block comment.  Assume that we've already
 249    read the initial `#!', and eat characters until we get a
 250    newline/exclamation-point/sharp-sign/newline sequence.  */
 251
 252 static void
 253 skip_scsh_block_comment (SCM port)
 254 {
 255   /* Is this portable?  Dear God, spare me from the non-eight-bit
 256      characters.  But is it tasteful?  */
 257   long history = 0;
 258
 259   for (;;)
 260     {
 261       int c = scm_getc (port);
 262
 263       if (c == EOF)
 264         scm_wta (SCM_UNDEFINED,
 265                  "unterminated `#! ... !#' comment", "read");
 266       history = ((history << 8) | (c & 0xff)) & 0xffffffff;
 267
 268       /* Were the last four characters read "\n!#\n"?  */
 269       if (history == (('\n' << 24) | ('!' << 16) | ('#' << 8) | '\n'))
 270         return;
 271     }
 272 }
 273
 274 static SCM scm_get_hash_procedure(int c);
 275
 276 static char s_list[]="list";
 277
 278 SCM
 279 scm_lreadr (SCM *tok_buf,SCM port,SCM *copy)
 280 {
 281   int c;
 282   scm_sizet j;
 283   SCM p;
 284
 285 tryagain:
 286   c = scm_flush_ws (port, s_scm_read);
 287 tryagain_no_flush_ws:
 288   switch (c)
 289     {
 290     case EOF:
 291       return SCM_EOF_VAL;
 292
 293     case '(':
 294       return SCM_RECORD_POSITIONS_P
 295              ? scm_lreadrecparen (tok_buf, port, s_list, copy)
 296              : scm_lreadparen (tok_buf, port, s_list, copy);
 297     case ')':
 298       scm_wta (SCM_UNDEFINED, "unexpected \")\"", "read");
 299       goto tryagain;
 300
 301     case '\'':
 302       p = scm_sym_quote;
 303       goto recquote;
 304     case '`':
 305       p = scm_sym_quasiquote;
 306       goto recquote;
 307     case ',':
 308       c = scm_getc (port);
 309       if ('@' == c)
 310         p = scm_sym_uq_splicing;
 311       else
 312         {
 313           scm_ungetc (c, port);
 314           p = scm_sym_unquote;
 315         }
 316     recquote:
 317       p = scm_cons2 (p,
 318                      scm_lreadr (tok_buf, port, copy),
 319                      SCM_EOL);
 320       if (SCM_RECORD_POSITIONS_P)
 321         scm_whash_insert (scm_source_whash,
 322                           p,
 323                           scm_make_srcprops (SCM_LINUM (port),
 324                                              SCM_COL (port) - 1,
 325                                              SCM_FILENAME (port),
 326                                              SCM_COPY_SOURCE_P
 327                                              ? (*copy = scm_cons2 (SCM_CAR (p),
 328                                                                    SCM_CAR (SCM_CDR (p)),
 329                                                                    SCM_EOL))
 330                                              : SCM_UNDEFINED,
 331                                              SCM_EOL));
 332       return p;
 333     case '#':
 334       c = scm_getc (port);
 335       switch (c)
 336         {
 337         case '(':
 338           p = scm_lreadparen (tok_buf, port, "vector", copy);
 339           return SCM_NULLP (p) ? scm_nullvect : scm_vector (p);
 340
 341         case 't':
 342         case 'T':
 343           return SCM_BOOL_T;
 344         case 'f':
 345         case 'F':
 346           return SCM_BOOL_F;
 347
 348         case 'b':
 349         case 'B':
 350         case 'o':
 351         case 'O':
 352         case 'd':
 353         case 'D':
 354         case 'x':
 355         case 'X':
 356         case 'i':
 357         case 'I':
 358         case 'e':
 359         case 'E':
 360           scm_ungetc (c, port);
 361           c = '#';
 362           goto num;
 363
 364         case '!':
 365           /* start of a shell script.  Parse as a block comment,
 366              terminated by !#, just like SCSH.  */
 367           skip_scsh_block_comment (port);
 368           /* EOF is not an error here */
 369           c = scm_flush_ws (port, (char *)NULL);
 370           goto tryagain_no_flush_ws;
 371
 372 #ifdef HAVE_ARRAYS
 373         case '*':
 374           j = scm_read_token (c, tok_buf, port, 0);
 375           p = scm_istr2bve (SCM_STRING_CHARS (*tok_buf) + 1, (long) (j - 1));
 376           if (SCM_NFALSEP (p))
 377             return p;
 378           else
 379             goto unkshrp;
 380 #endif
 381
 382         case '{':
 383           j = scm_read_token (c, tok_buf, port, 1);
 384           return scm_mem2symbol (SCM_STRING_CHARS (*tok_buf), j);
 385
 386         case '\\':
 387           c = scm_getc (port);
 388           j = scm_read_token (c, tok_buf, port, 0);
 389           if (j == 1)
 390             return SCM_MAKE_CHAR (c);
 391           if (c >= '0' && c < '8')
 392             {
 393               p = scm_istr2int (SCM_STRING_CHARS (*tok_buf), (long) j, 8);
 394               if (SCM_NFALSEP (p))
 395                 return SCM_MAKE_CHAR (SCM_INUM (p));
 396             }
 397           for (c = 0; c < scm_n_charnames; c++)
 398             if (scm_charnames[c]
 399                 && (scm_casei_streq (scm_charnames[c], SCM_STRING_CHARS (*tok_buf))))
 400               return SCM_MAKE_CHAR (scm_charnums[c]);
 401           scm_wta (SCM_UNDEFINED, "unknown # object: #\\", SCM_STRING_CHARS (*tok_buf));
 402
 403           /* #:SYMBOL is a syntax for keywords supported in all contexts.  */
 404         case ':':
 405           j = scm_read_token ('-', tok_buf, port, 0);
 406           p = scm_mem2symbol (SCM_STRING_CHARS (*tok_buf), j);
 407           return scm_make_keyword_from_dash_symbol (p);
 408
 409         default:
 410         callshrp:
 411           {
 412             SCM sharp = scm_get_hash_procedure (c);
 413
 414             if (SCM_NIMP (sharp))
 415               {
 416                 int line = SCM_LINUM (port);
 417                 int column = SCM_COL (port) - 2;
 418                 SCM got;
 419
 420                 got = scm_apply (sharp,
 421                                  SCM_MAKE_CHAR (c),
 422                                  scm_acons (port, SCM_EOL, SCM_EOL));
 423                 if (SCM_EQ_P (got, SCM_UNSPECIFIED))
 424                   goto unkshrp;
 425                 if (SCM_RECORD_POSITIONS_P)
 426                   return *copy = recsexpr (got, line, column,
 427                                            SCM_FILENAME (port));
 428                 else
 429                   return got;
 430               }
 431           }
 432         unkshrp:
 433           scm_misc_error (s_scm_read, "Unknown # object: ~S",
 434                           scm_listify (SCM_MAKE_CHAR (c), SCM_UNDEFINED));
 435         }
 436
 437     case '"':
 438       j = 0;
 439       while ('"' != (c = scm_getc (port)))
 440         {
 441           SCM_ASSERT (EOF != c, SCM_UNDEFINED, "end of file in ", "string");
 442
 443           while (j + 2 >= SCM_STRING_LENGTH (*tok_buf))
 444             scm_grow_tok_buf (tok_buf);
 445
 446           if (c == '\\')
 447             switch (c = scm_getc (port))
 448               {
 449               case '\n':
 450                 continue;
 451               case '0':
 452                 c = '\0';
 453                 break;
 454               case 'f':
 455                 c = '\f';
 456                 break;
 457               case 'n':
 458                 c = '\n';
 459                 break;
 460               case 'r':
 461                 c = '\r';
 462                 break;
 463               case 't':
 464                 c = '\t';
 465                 break;
 466               case 'a':
 467                 c = '\007';
 468                 break;
 469               case 'v':
 470                 c = '\v';
 471                 break;
 472               }
 473           SCM_STRING_CHARS (*tok_buf)[j] = c;
 474           ++j;
 475         }
 476       if (j == 0)
 477         return scm_nullstr;
 478       SCM_STRING_CHARS (*tok_buf)[j] = 0;
 479       {
 480         SCM str;
 481         str = scm_makfromstr (SCM_STRING_CHARS (*tok_buf), j, 0);
 482         return str;
 483       }
 484
 485     case'0':case '1':case '2':case '3':case '4':
 486     case '5':case '6':case '7':case '8':case '9':
 487     case '.':
 488     case '-':
 489     case '+':
 490     num:
 491       j = scm_read_token (c, tok_buf, port, 0);
 492       p = scm_istring2number (SCM_STRING_CHARS (*tok_buf), (long) j, 10L);
 493       if (SCM_NFALSEP (p))
 494         return p;
 495       if (c == '#')
 496         {
 497           if ((j == 2) && (scm_getc (port) == '('))
 498             {
 499               scm_ungetc ('(', port);
 500               c = SCM_STRING_CHARS (*tok_buf)[1];
 501               goto callshrp;
 502             }
 503           scm_wta (SCM_UNDEFINED, "unknown # object", SCM_STRING_CHARS (*tok_buf));
 504         }
 505       goto tok;
 506
 507     case ':':
 508       if (SCM_EQ_P (SCM_PACK (SCM_KEYWORD_STYLE), scm_keyword_prefix))
 509         {
 510           j = scm_read_token ('-', tok_buf, port, 0);
 511           p = scm_mem2symbol (SCM_STRING_CHARS (*tok_buf), j);
 512           return scm_make_keyword_from_dash_symbol (p);
 513         }
 514       /* fallthrough */
 515     default:
 516       j = scm_read_token (c, tok_buf, port, 0);
 517       /* fallthrough */
 518
 519     tok:
 520       return scm_mem2symbol (SCM_STRING_CHARS (*tok_buf), j);
 521     }
 522 }
 523
 524 #ifdef _UNICOS
 525 _Pragma ("noopt");              /* # pragma _CRI noopt */
 526 #endif
 527
 528 scm_sizet
 529 scm_read_token (int ic, SCM *tok_buf, SCM port, int weird)
 530 {
 531   register scm_sizet j;
 532   register int c;
 533   register char *p;
 534
 535   c = (SCM_CASE_INSENSITIVE_P ? scm_downcase(ic) : ic);
 536   p = SCM_STRING_CHARS (*tok_buf);
 537
 538   if (weird)
 539     j = 0;
 540   else
 541     {
 542       j = 0;
 543       while (j + 2 >= SCM_STRING_LENGTH (*tok_buf))
 544         p = scm_grow_tok_buf (tok_buf);
 545       p[j] = c;
 546       ++j;
 547     }
 548
 549   while (1)
 550     {
 551       while (j + 2 >= SCM_STRING_LENGTH (*tok_buf))
 552         p = scm_grow_tok_buf (tok_buf);
 553       c = scm_getc (port);
 554       switch (c)
 555         {
 556         case '(':
 557         case ')':
 558         case '"':
 559         case ';':
 560         case SCM_WHITE_SPACES:
 561         case SCM_LINE_INCREMENTORS:
 562           if (weird)
 563             goto default_case;
 564
 565           scm_ungetc (c, port);
 566         case EOF:
 567         eof_case:
 568           p[j] = 0;
 569           return j;
 570         case '\\':
 571           if (!weird)
 572             goto default_case;
 573           else
 574             {
 575               c = scm_getc (port);
 576               if (c == EOF)
 577                 goto eof_case;
 578               else
 579                 goto default_case;
 580             }
 581         case '}':
 582           if (!weird)
 583             goto default_case;
 584
 585           c = scm_getc (port);
 586           if (c == '#')
 587             {
 588               p[j] = 0;
 589               return j;
 590             }
 591           else
 592             {
 593               scm_ungetc (c, port);
 594               c = '}';
 595               goto default_case;
 596             }
 597
 598         default:
 599         default_case:
 600           {
 601             c = (SCM_CASE_INSENSITIVE_P ? scm_downcase(c) : c);
 602             p[j] = c;
 603             ++j;
 604           }
 605
 606         }
 607     }
 608 }
 609
 610 #ifdef _UNICOS
 611 _Pragma ("opt");                /* # pragma _CRI opt */
 612 #endif
 613
 614 SCM
 615 scm_lreadparen (SCM *tok_buf, SCM port, char *name, SCM *copy)
 616 {
 617   SCM tmp;
 618   SCM tl;
 619   SCM ans;
 620   int c;
 621
 622   c = scm_flush_ws (port, name);
 623   if (')' == c)
 624     return SCM_EOL;
 625   scm_ungetc (c, port);
 626   if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 627     {
 628       ans = scm_lreadr (tok_buf, port, copy);
 629     closeit:
 630       if (')' != (c = scm_flush_ws (port, name)))
 631         scm_wta (SCM_UNDEFINED, "missing close paren", "");
 632       return ans;
 633     }
 634   ans = tl = scm_cons (tmp, SCM_EOL);
 635   while (')' != (c = scm_flush_ws (port, name)))
 636     {
 637       scm_ungetc (c, port);
 638       if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 639         {
 640           SCM_SETCDR (tl, scm_lreadr (tok_buf, port, copy));
 641           goto closeit;
 642         }
 643       SCM_SETCDR (tl, scm_cons (tmp, SCM_EOL));
 644       tl = SCM_CDR (tl);
 645     }
 646   return ans;
 647 }
 648
 649
 650 SCM
 651 scm_lreadrecparen (SCM *tok_buf, SCM port, char *name, SCM *copy)
 652 {
 653   register int c;
 654   register SCM tmp;
 655   register SCM tl, tl2 = SCM_EOL;
 656   SCM ans, ans2 = SCM_EOL;
 657   /* Need to capture line and column numbers here. */
 658   int line = SCM_LINUM (port);
 659   int column = SCM_COL (port) - 1;
 660
 661   c = scm_flush_ws (port, name);
 662   if (')' == c)
 663     return SCM_EOL;
 664   scm_ungetc (c, port);
 665   if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 666     {
 667       ans = scm_lreadr (tok_buf, port, copy);
 668       if (')' != (c = scm_flush_ws (port, name)))
 669         scm_wta (SCM_UNDEFINED, "missing close paren", "");
 670       return ans;
 671     }
 672   /* Build the head of the list structure. */
 673   ans = tl = scm_cons (tmp, SCM_EOL);
 674   if (SCM_COPY_SOURCE_P)
 675     ans2 = tl2 = scm_cons (SCM_CONSP (tmp)
 676                            ? *copy
 677                            : tmp,
 678                            SCM_EOL);
 679   while (')' != (c = scm_flush_ws (port, name)))
 680     {
 681       SCM new_tail;
 682
 683       scm_ungetc (c, port);
 684       if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 685         {
 686           SCM_SETCDR (tl, tmp = scm_lreadr (tok_buf, port, copy));
 687           if (SCM_COPY_SOURCE_P)
 688             SCM_SETCDR (tl2, scm_cons (SCM_CONSP (tmp)
 689                                        ? *copy
 690                                        : tmp,
 691                                        SCM_EOL));
 692           if (')' != (c = scm_flush_ws (port, name)))
 693             scm_wta (SCM_UNDEFINED, "missing close paren", "");
 694           goto exit;
 695         }
 696
 697       new_tail = scm_cons (tmp, SCM_EOL);
 698       SCM_SETCDR (tl, new_tail);
 699       tl = new_tail;
 700
 701       if (SCM_COPY_SOURCE_P)
 702         {
 703           SCM new_tail2 = scm_cons (SCM_CONSP (tmp) ? *copy : tmp, SCM_EOL);
 704           SCM_SETCDR (tl2, new_tail2);
 705           tl2 = new_tail2;
 706         }
 707     }
 708 exit:
 709   scm_whash_insert (scm_source_whash,
 710                     ans,
 711                     scm_make_srcprops (line,
 712                                        column,
 713                                        SCM_FILENAME (port),
 714                                        SCM_COPY_SOURCE_P
 715                                        ? *copy = ans2
 716                                        : SCM_UNDEFINED,
 717                                        SCM_EOL));
 718   return ans;
 719 }
 720
 721
 722 \f
 723
 724 /* Manipulate the read-hash-procedures alist.  This could be written in
 725    Scheme, but maybe it will also be used by C code during initialisation.  */
 726 SCM_DEFINE (scm_read_hash_extend, "read-hash-extend", 2, 0, 0,
 727             (SCM chr, SCM proc),
 728 "")
 729 #define FUNC_NAME s_scm_read_hash_extend
 730 {
 731   SCM this;
 732   SCM prev;
 733
 734   SCM_VALIDATE_CHAR (1,chr);
 735   SCM_ASSERT (SCM_FALSEP (proc) || SCM_NIMP(proc), proc, SCM_ARG2,
 736               FUNC_NAME);
 737
 738   /* Check if chr is already in the alist.  */
 739   this = *scm_read_hash_procedures;
 740   prev = SCM_BOOL_F;
 741   while (1)
 742     {
 743       if (SCM_NULLP (this))
 744         {
 745           /* not found, so add it to the beginning.  */
 746           if (SCM_NFALSEP (proc))
 747             {
 748               *scm_read_hash_procedures =
 749                 scm_cons (scm_cons (chr, proc), *scm_read_hash_procedures);
 750             }
 751           break;
 752         }
 753       if (SCM_EQ_P (chr, SCM_CAAR (this)))
 754         {
 755           /* already in the alist.  */
 756           if (SCM_FALSEP (proc))
 757             {
 758               /* remove it.  */
 759               if (SCM_FALSEP (prev))
 760                 {
 761                   *scm_read_hash_procedures =
 762                     SCM_CDR (*scm_read_hash_procedures);
 763                 }
 764               else
 765                 scm_set_cdr_x (prev, SCM_CDR (this));
 766             }
 767           else
 768             {
 769               /* replace it.  */
 770               scm_set_cdr_x (SCM_CAR (this), proc);
 771             }
 772           break;
 773         }
 774       prev = this;
 775       this = SCM_CDR (this);
 776     }
 777
 778   return SCM_UNSPECIFIED;
 779 }
 780 #undef FUNC_NAME
 781
 782 /* Recover the read-hash procedure corresponding to char c.  */
 783 static SCM
 784 scm_get_hash_procedure (int c)
 785 {
 786   SCM rest = *scm_read_hash_procedures;
 787
 788   while (1)
 789     {
 790       if (SCM_NULLP (rest))
 791         return SCM_BOOL_F;
 792
 793       if (SCM_CHAR (SCM_CAAR (rest)) == c)
 794         return SCM_CDAR (rest);
 795
 796       rest = SCM_CDR (rest);
 797     }
 798 }
 799
 800 void
 801 scm_init_read ()
 802 {
 803   scm_read_hash_procedures =
 804     SCM_CDRLOC (scm_sysintern ("read-hash-procedures", SCM_EOL));
 805
 806   scm_init_opts (scm_read_options, scm_read_opts, SCM_N_READ_OPTIONS);
 807 #ifndef SCM_MAGIC_SNARFER
 808 #include "libguile/read.x"
 809 #endif
 810 }
 811
 812 /*
 813   Local Variables:
 814   c-file-style: "gnu"
 815   End:
 816 */