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_FILENAME (port) != SCM_BOOL_F)
 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           p = scm_intern (SCM_STRING_CHARS (*tok_buf), j);
 385           return SCM_CAR (p);
 386
 387         case '\\':
 388           c = scm_getc (port);
 389           j = scm_read_token (c, tok_buf, port, 0);
 390           if (j == 1)
 391             return SCM_MAKE_CHAR (c);
 392           if (c >= '0' && c < '8')
 393             {
 394               p = scm_istr2int (SCM_STRING_CHARS (*tok_buf), (long) j, 8);
 395               if (SCM_NFALSEP (p))
 396                 return SCM_MAKE_CHAR (SCM_INUM (p));
 397             }
 398           for (c = 0; c < scm_n_charnames; c++)
 399             if (scm_charnames[c]
 400                 && (scm_casei_streq (scm_charnames[c], SCM_STRING_CHARS (*tok_buf))))
 401               return SCM_MAKE_CHAR (scm_charnums[c]);
 402           scm_wta (SCM_UNDEFINED, "unknown # object: #\\", SCM_STRING_CHARS (*tok_buf));
 403
 404           /* #:SYMBOL is a syntax for keywords supported in all contexts.  */
 405         case ':':
 406           j = scm_read_token ('-', tok_buf, port, 0);
 407           p = scm_intern (SCM_STRING_CHARS (*tok_buf), j);
 408           return scm_make_keyword_from_dash_symbol (SCM_CAR (p));
 409
 410         default:
 411         callshrp:
 412           {
 413             SCM sharp = scm_get_hash_procedure (c);
 414
 415             if (SCM_NIMP (sharp))
 416               {
 417                 int line = SCM_LINUM (port);
 418                 int column = SCM_COL (port) - 2;
 419                 SCM got;
 420
 421                 got = scm_apply (sharp,
 422                                  SCM_MAKE_CHAR (c),
 423                                  scm_acons (port, SCM_EOL, SCM_EOL));
 424                 if (SCM_EQ_P (got, SCM_UNSPECIFIED))
 425                   goto unkshrp;
 426                 if (SCM_RECORD_POSITIONS_P)
 427                   return *copy = recsexpr (got, line, column,
 428                                            SCM_FILENAME (port));
 429                 else
 430                   return got;
 431               }
 432           }
 433         unkshrp:
 434           scm_misc_error (s_scm_read, "Unknown # object: ~S",
 435                           scm_listify (SCM_MAKE_CHAR (c), SCM_UNDEFINED));
 436         }
 437
 438     case '"':
 439       j = 0;
 440       while ('"' != (c = scm_getc (port)))
 441         {
 442           SCM_ASSERT (EOF != c, SCM_UNDEFINED, "end of file in ", "string");
 443
 444           while (j + 2 >= SCM_STRING_LENGTH (*tok_buf))
 445             scm_grow_tok_buf (tok_buf);
 446
 447           if (c == '\\')
 448             switch (c = scm_getc (port))
 449               {
 450               case '\n':
 451                 continue;
 452               case '0':
 453                 c = '\0';
 454                 break;
 455               case 'f':
 456                 c = '\f';
 457                 break;
 458               case 'n':
 459                 c = '\n';
 460                 break;
 461               case 'r':
 462                 c = '\r';
 463                 break;
 464               case 't':
 465                 c = '\t';
 466                 break;
 467               case 'a':
 468                 c = '\007';
 469                 break;
 470               case 'v':
 471                 c = '\v';
 472                 break;
 473               }
 474           SCM_STRING_CHARS (*tok_buf)[j] = c;
 475           ++j;
 476         }
 477       if (j == 0)
 478         return scm_nullstr;
 479       SCM_STRING_CHARS (*tok_buf)[j] = 0;
 480       {
 481         SCM str;
 482         str = scm_makfromstr (SCM_STRING_CHARS (*tok_buf), j, 0);
 483         return str;
 484       }
 485
 486     case'0':case '1':case '2':case '3':case '4':
 487     case '5':case '6':case '7':case '8':case '9':
 488     case '.':
 489     case '-':
 490     case '+':
 491     num:
 492       j = scm_read_token (c, tok_buf, port, 0);
 493       p = scm_istring2number (SCM_STRING_CHARS (*tok_buf), (long) j, 10L);
 494       if (SCM_NFALSEP (p))
 495         return p;
 496       if (c == '#')
 497         {
 498           if ((j == 2) && (scm_getc (port) == '('))
 499             {
 500               scm_ungetc ('(', port);
 501               c = SCM_STRING_CHARS (*tok_buf)[1];
 502               goto callshrp;
 503             }
 504           scm_wta (SCM_UNDEFINED, "unknown # object", SCM_STRING_CHARS (*tok_buf));
 505         }
 506       goto tok;
 507
 508     case ':':
 509       if (SCM_EQ_P (SCM_PACK (SCM_KEYWORD_STYLE), scm_keyword_prefix))
 510         {
 511           j = scm_read_token ('-', tok_buf, port, 0);
 512           p = scm_intern (SCM_STRING_CHARS (*tok_buf), j);
 513           return scm_make_keyword_from_dash_symbol (SCM_CAR (p));
 514         }
 515       /* fallthrough */
 516     default:
 517       j = scm_read_token (c, tok_buf, port, 0);
 518       /* fallthrough */
 519
 520     tok:
 521       p = scm_intern (SCM_STRING_CHARS (*tok_buf), j);
 522       return SCM_CAR (p);
 523     }
 524 }
 525
 526 #ifdef _UNICOS
 527 _Pragma ("noopt");              /* # pragma _CRI noopt */
 528 #endif
 529
 530 scm_sizet
 531 scm_read_token (int ic, SCM *tok_buf, SCM port, int weird)
 532 {
 533   register scm_sizet j;
 534   register int c;
 535   register char *p;
 536
 537   c = (SCM_CASE_INSENSITIVE_P ? scm_downcase(ic) : ic);
 538   p = SCM_STRING_CHARS (*tok_buf);
 539
 540   if (weird)
 541     j = 0;
 542   else
 543     {
 544       j = 0;
 545       while (j + 2 >= SCM_STRING_LENGTH (*tok_buf))
 546         p = scm_grow_tok_buf (tok_buf);
 547       p[j] = c;
 548       ++j;
 549     }
 550
 551   while (1)
 552     {
 553       while (j + 2 >= SCM_STRING_LENGTH (*tok_buf))
 554         p = scm_grow_tok_buf (tok_buf);
 555       c = scm_getc (port);
 556       switch (c)
 557         {
 558         case '(':
 559         case ')':
 560         case '"':
 561         case ';':
 562         case SCM_WHITE_SPACES:
 563         case SCM_LINE_INCREMENTORS:
 564           if (weird)
 565             goto default_case;
 566
 567           scm_ungetc (c, port);
 568         case EOF:
 569         eof_case:
 570           p[j] = 0;
 571           return j;
 572         case '\\':
 573           if (!weird)
 574             goto default_case;
 575           else
 576             {
 577               c = scm_getc (port);
 578               if (c == EOF)
 579                 goto eof_case;
 580               else
 581                 goto default_case;
 582             }
 583         case '}':
 584           if (!weird)
 585             goto default_case;
 586
 587           c = scm_getc (port);
 588           if (c == '#')
 589             {
 590               p[j] = 0;
 591               return j;
 592             }
 593           else
 594             {
 595               scm_ungetc (c, port);
 596               c = '}';
 597               goto default_case;
 598             }
 599
 600         default:
 601         default_case:
 602           {
 603             c = (SCM_CASE_INSENSITIVE_P ? scm_downcase(c) : c);
 604             p[j] = c;
 605             ++j;
 606           }
 607
 608         }
 609     }
 610 }
 611
 612 #ifdef _UNICOS
 613 _Pragma ("opt");                /* # pragma _CRI opt */
 614 #endif
 615
 616 SCM
 617 scm_lreadparen (SCM *tok_buf, SCM port, char *name, SCM *copy)
 618 {
 619   SCM tmp;
 620   SCM tl;
 621   SCM ans;
 622   int c;
 623
 624   c = scm_flush_ws (port, name);
 625   if (')' == c)
 626     return SCM_EOL;
 627   scm_ungetc (c, port);
 628   if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 629     {
 630       ans = scm_lreadr (tok_buf, port, copy);
 631     closeit:
 632       if (')' != (c = scm_flush_ws (port, name)))
 633         scm_wta (SCM_UNDEFINED, "missing close paren", "");
 634       return ans;
 635     }
 636   ans = tl = scm_cons (tmp, SCM_EOL);
 637   while (')' != (c = scm_flush_ws (port, name)))
 638     {
 639       scm_ungetc (c, port);
 640       if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 641         {
 642           SCM_SETCDR (tl, scm_lreadr (tok_buf, port, copy));
 643           goto closeit;
 644         }
 645       SCM_SETCDR (tl, scm_cons (tmp, SCM_EOL));
 646       tl = SCM_CDR (tl);
 647     }
 648   return ans;
 649 }
 650
 651
 652 SCM
 653 scm_lreadrecparen (SCM *tok_buf, SCM port, char *name, SCM *copy)
 654 {
 655   register int c;
 656   register SCM tmp;
 657   register SCM tl, tl2 = SCM_EOL;
 658   SCM ans, ans2 = SCM_EOL;
 659   /* Need to capture line and column numbers here. */
 660   int line = SCM_LINUM (port);
 661   int column = SCM_COL (port) - 1;
 662
 663   c = scm_flush_ws (port, name);
 664   if (')' == c)
 665     return SCM_EOL;
 666   scm_ungetc (c, port);
 667   if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 668     {
 669       ans = scm_lreadr (tok_buf, port, copy);
 670       if (')' != (c = scm_flush_ws (port, name)))
 671         scm_wta (SCM_UNDEFINED, "missing close paren", "");
 672       return ans;
 673     }
 674   /* Build the head of the list structure. */
 675   ans = tl = scm_cons (tmp, SCM_EOL);
 676   if (SCM_COPY_SOURCE_P)
 677     ans2 = tl2 = scm_cons (SCM_CONSP (tmp)
 678                            ? *copy
 679                            : tmp,
 680                            SCM_EOL);
 681   while (')' != (c = scm_flush_ws (port, name)))
 682     {
 683       SCM new_tail;
 684
 685       scm_ungetc (c, port);
 686       if (SCM_EQ_P (scm_sym_dot, (tmp = scm_lreadr (tok_buf, port, copy))))
 687         {
 688           SCM_SETCDR (tl, tmp = scm_lreadr (tok_buf, port, copy));
 689           if (SCM_COPY_SOURCE_P)
 690             SCM_SETCDR (tl2, scm_cons (SCM_CONSP (tmp)
 691                                        ? *copy
 692                                        : tmp,
 693                                        SCM_EOL));
 694           if (')' != (c = scm_flush_ws (port, name)))
 695             scm_wta (SCM_UNDEFINED, "missing close paren", "");
 696           goto exit;
 697         }
 698
 699       new_tail = scm_cons (tmp, SCM_EOL);
 700       SCM_SETCDR (tl, new_tail);
 701       tl = new_tail;
 702
 703       if (SCM_COPY_SOURCE_P)
 704         {
 705           SCM new_tail2 = scm_cons (SCM_CONSP (tmp) ? *copy : tmp, SCM_EOL);
 706           SCM_SETCDR (tl2, new_tail2);
 707           tl2 = new_tail2;
 708         }
 709     }
 710 exit:
 711   scm_whash_insert (scm_source_whash,
 712                     ans,
 713                     scm_make_srcprops (line,
 714                                        column,
 715                                        SCM_FILENAME (port),
 716                                        SCM_COPY_SOURCE_P
 717                                        ? *copy = ans2
 718                                        : SCM_UNDEFINED,
 719                                        SCM_EOL));
 720   return ans;
 721 }
 722
 723
 724 \f
 725
 726 /* Manipulate the read-hash-procedures alist.  This could be written in
 727    Scheme, but maybe it will also be used by C code during initialisation.  */
 728 SCM_DEFINE (scm_read_hash_extend, "read-hash-extend", 2, 0, 0,
 729             (SCM chr, SCM proc),
 730 "")
 731 #define FUNC_NAME s_scm_read_hash_extend
 732 {
 733   SCM this;
 734   SCM prev;
 735
 736   SCM_VALIDATE_CHAR (1,chr);
 737   SCM_ASSERT (SCM_FALSEP (proc) || SCM_NIMP(proc), proc, SCM_ARG2,
 738               FUNC_NAME);
 739
 740   /* Check if chr is already in the alist.  */
 741   this = *scm_read_hash_procedures;
 742   prev = SCM_BOOL_F;
 743   while (1)
 744     {
 745       if (SCM_NULLP (this))
 746         {
 747           /* not found, so add it to the beginning.  */
 748           if (SCM_NFALSEP (proc))
 749             {
 750               *scm_read_hash_procedures =
 751                 scm_cons (scm_cons (chr, proc), *scm_read_hash_procedures);
 752             }
 753           break;
 754         }
 755       if (SCM_EQ_P (chr, SCM_CAAR (this)))
 756         {
 757           /* already in the alist.  */
 758           if (SCM_FALSEP (proc))
 759             {
 760               /* remove it.  */
 761               if (SCM_FALSEP (prev))
 762                 {
 763                   *scm_read_hash_procedures =
 764                     SCM_CDR (*scm_read_hash_procedures);
 765                 }
 766               else
 767                 scm_set_cdr_x (prev, SCM_CDR (this));
 768             }
 769           else
 770             {
 771               /* replace it.  */
 772               scm_set_cdr_x (SCM_CAR (this), proc);
 773             }
 774           break;
 775         }
 776       prev = this;
 777       this = SCM_CDR (this);
 778     }
 779
 780   return SCM_UNSPECIFIED;
 781 }
 782 #undef FUNC_NAME
 783
 784 /* Recover the read-hash procedure corresponding to char c.  */
 785 static SCM
 786 scm_get_hash_procedure (int c)
 787 {
 788   SCM rest = *scm_read_hash_procedures;
 789
 790   while (1)
 791     {
 792       if (SCM_NULLP (rest))
 793         return SCM_BOOL_F;
 794
 795       if (SCM_CHAR (SCM_CAAR (rest)) == c)
 796         return SCM_CDAR (rest);
 797
 798       rest = SCM_CDR (rest);
 799     }
 800 }
 801
 802 void
 803 scm_init_read ()
 804 {
 805   scm_read_hash_procedures =
 806     SCM_CDRLOC (scm_sysintern ("read-hash-procedures", SCM_EOL));
 807
 808   scm_init_opts (scm_read_options, scm_read_opts, SCM_N_READ_OPTIONS);
 809 #include "libguile/read.x"
 810 }
 811
 812 /*
 813   Local Variables:
 814   c-file-style: "gnu"
 815   End:
 816 */