libguile/symbols.c

   1 /* Copyright (C) 1995,1996,1997,1998,2000,2001, 2003, 2004, 2006 Free Software Foundation, Inc.
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public
   5  * License as published by the Free Software Foundation; either
   6  * version 2.1 of the License, or (at your option) any later version.
   7  *
   8  * This library 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 GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  16  */
  17
  18
  19 \f
  20 #if HAVE_CONFIG_H
  21 #  include <config.h>
  22 #endif
  23
  24 #include "libguile/_scm.h"
  25 #include "libguile/chars.h"
  26 #include "libguile/eval.h"
  27 #include "libguile/hash.h"
  28 #include "libguile/smob.h"
  29 #include "libguile/variable.h"
  30 #include "libguile/alist.h"
  31 #include "libguile/fluids.h"
  32 #include "libguile/strings.h"
  33 #include "libguile/vectors.h"
  34 #include "libguile/hashtab.h"
  35 #include "libguile/weaks.h"
  36 #include "libguile/modules.h"
  37 #include "libguile/read.h"
  38 #include "libguile/srfi-13.h"
  39
  40 #include "libguile/validate.h"
  41 #include "libguile/symbols.h"
  42
  43 #ifdef HAVE_STRING_H
  44 #include <string.h>
  45 #endif
  46
  47 \f
  48
  49 static SCM symbols;
  50
  51 #ifdef GUILE_DEBUG
  52 SCM_DEFINE (scm_sys_symbols, "%symbols", 0, 0, 0,
  53             (),
  54             "Return the system symbol obarray.")
  55 #define FUNC_NAME s_scm_sys_symbols
  56 {
  57   return symbols;
  58 }
  59 #undef FUNC_NAME
  60 #endif
  61
  62 \f
  63
  64 /* {Symbols}
  65  */
  66
  67 /* In order to optimize reading speed, this function breaks part of
  68  * the hashtable abstraction.  The optimizations are:
  69  *
  70  * 1. The argument string can be compared directly to symbol objects
  71  *    without first creating an SCM string object.  (This would have
  72  *    been necessary if we had used the hashtable API in hashtab.h.)
  73  *
  74  * 2. We can use the raw hash value stored in scm_i_symbol_hash (sym)
  75  *    to speed up lookup.
  76  *
  77  * Both optimizations might be possible without breaking the
  78  * abstraction if the API in hashtab.c is improved.
  79  */
  80
  81 unsigned long
  82 scm_i_hash_symbol (SCM obj, unsigned long n, void *closure)
  83 {
  84   return scm_i_symbol_hash (obj) % n;
  85 }
  86
  87 static SCM
  88 lookup_interned_symbol (const char *name, size_t len,
  89                         unsigned long raw_hash)
  90 {
  91   /* Try to find the symbol in the symbols table */
  92   SCM l;
  93   unsigned long hash = raw_hash % SCM_HASHTABLE_N_BUCKETS (symbols);
  94
  95   for (l = SCM_HASHTABLE_BUCKET (symbols, hash);
  96        !scm_is_null (l);
  97        l = SCM_CDR (l))
  98     {
  99       SCM sym = SCM_CAAR (l);
 100       if (scm_i_symbol_hash (sym) == raw_hash
 101           && scm_i_symbol_length (sym) == len)
 102         {
 103           const char *chrs = scm_i_symbol_chars (sym);
 104           size_t i = len;
 105
 106           while (i != 0)
 107             {
 108               --i;
 109               if (name[i] != chrs[i])
 110                 goto next_symbol;
 111             }
 112
 113           return sym;
 114         }
 115     next_symbol:
 116       ;
 117     }
 118
 119   return SCM_BOOL_F;
 120 }
 121
 122 static SCM
 123 scm_i_c_mem2symbol (const char *name, size_t len)
 124 {
 125   SCM symbol;
 126   size_t raw_hash = scm_string_hash ((const unsigned char *) name, len);
 127   size_t hash = raw_hash % SCM_HASHTABLE_N_BUCKETS (symbols);
 128
 129   symbol = lookup_interned_symbol (name, len, raw_hash);
 130   if (symbol != SCM_BOOL_F)
 131     return symbol;
 132
 133   {
 134     /* The symbol was not found - create it. */
 135     SCM symbol = scm_i_c_make_symbol (name, len, 0, raw_hash,
 136                                       scm_cons (SCM_BOOL_F, SCM_EOL));
 137
 138     SCM slot = SCM_HASHTABLE_BUCKET (symbols, hash);
 139     SCM cell = scm_cons (symbol, SCM_UNDEFINED);
 140     SCM_SET_HASHTABLE_BUCKET (symbols, hash, scm_cons (cell, slot));
 141     SCM_HASHTABLE_INCREMENT (symbols);
 142     if (SCM_HASHTABLE_N_ITEMS (symbols) > SCM_HASHTABLE_UPPER (symbols))
 143       scm_i_rehash (symbols, scm_i_hash_symbol, 0, "scm_mem2symbol");
 144
 145     return symbol;
 146   }
 147 }
 148
 149 static SCM
 150 scm_i_mem2symbol (SCM str)
 151 {
 152   SCM symbol;
 153   const char *name = scm_i_string_chars (str);
 154   size_t len = scm_i_string_length (str);
 155   size_t raw_hash = scm_string_hash ((const unsigned char *) name, len);
 156   size_t hash = raw_hash % SCM_HASHTABLE_N_BUCKETS (symbols);
 157
 158   symbol = lookup_interned_symbol (name, len, raw_hash);
 159   if (symbol != SCM_BOOL_F)
 160     return symbol;
 161
 162   {
 163     /* The symbol was not found - create it. */
 164     SCM symbol = scm_i_make_symbol (str, 0, raw_hash,
 165                                     scm_cons (SCM_BOOL_F, SCM_EOL));
 166
 167     SCM slot = SCM_HASHTABLE_BUCKET (symbols, hash);
 168     SCM cell = scm_cons (symbol, SCM_UNDEFINED);
 169     SCM_SET_HASHTABLE_BUCKET (symbols, hash, scm_cons (cell, slot));
 170     SCM_HASHTABLE_INCREMENT (symbols);
 171     if (SCM_HASHTABLE_N_ITEMS (symbols) > SCM_HASHTABLE_UPPER (symbols))
 172       scm_i_rehash (symbols, scm_i_hash_symbol, 0, "scm_mem2symbol");
 173
 174     return symbol;
 175   }
 176 }
 177
 178
 179 static SCM
 180 scm_i_mem2uninterned_symbol (SCM str)
 181 {
 182   const char *name = scm_i_string_chars (str);
 183   size_t len = scm_i_string_length (str);
 184   size_t raw_hash = scm_string_hash ((const unsigned char *) name, len);
 185
 186   return scm_i_make_symbol (str, SCM_I_F_SYMBOL_UNINTERNED,
 187                             raw_hash, scm_cons (SCM_BOOL_F, SCM_EOL));
 188 }
 189
 190 SCM_DEFINE (scm_symbol_p, "symbol?", 1, 0, 0,
 191             (SCM obj),
 192             "Return @code{#t} if @var{obj} is a symbol, otherwise return\n"
 193             "@code{#f}.")
 194 #define FUNC_NAME s_scm_symbol_p
 195 {
 196   return scm_from_bool (scm_is_symbol (obj));
 197 }
 198 #undef FUNC_NAME
 199
 200 SCM_DEFINE (scm_symbol_interned_p, "symbol-interned?", 1, 0, 0,
 201             (SCM symbol),
 202             "Return @code{#t} if @var{symbol} is interned, otherwise return\n"
 203             "@code{#f}.")
 204 #define FUNC_NAME s_scm_symbol_interned_p
 205 {
 206   SCM_VALIDATE_SYMBOL (1, symbol);
 207   return scm_from_bool (scm_i_symbol_is_interned (symbol));
 208 }
 209 #undef FUNC_NAME
 210
 211 SCM_DEFINE (scm_make_symbol, "make-symbol", 1, 0, 0,
 212             (SCM name),
 213             "Return a new uninterned symbol with the name @var{name}.  "
 214             "The returned symbol is guaranteed to be unique and future "
 215             "calls to @code{string->symbol} will not return it.")
 216 #define FUNC_NAME s_scm_make_symbol
 217 {
 218   SCM_VALIDATE_STRING (1, name);
 219   return scm_i_mem2uninterned_symbol (name);
 220 }
 221 #undef FUNC_NAME
 222
 223 SCM_DEFINE (scm_symbol_to_string, "symbol->string", 1, 0, 0,
 224            (SCM s),
 225             "Return the name of @var{symbol} as a string.  If the symbol was\n"
 226             "part of an object returned as the value of a literal expression\n"
 227             "(section @pxref{Literal expressions,,,r5rs, The Revised^5\n"
 228             "Report on Scheme}) or by a call to the @code{read} procedure,\n"
 229             "and its name contains alphabetic characters, then the string\n"
 230             "returned will contain characters in the implementation's\n"
 231             "preferred standard case---some implementations will prefer\n"
 232             "upper case, others lower case.  If the symbol was returned by\n"
 233             "@code{string->symbol}, the case of characters in the string\n"
 234             "returned will be the same as the case in the string that was\n"
 235             "passed to @code{string->symbol}.  It is an error to apply\n"
 236             "mutation procedures like @code{string-set!} to strings returned\n"
 237             "by this procedure.\n"
 238             "\n"
 239             "The following examples assume that the implementation's\n"
 240             "standard case is lower case:\n"
 241             "\n"
 242             "@lisp\n"
 243             "(symbol->string 'flying-fish)    @result{} \"flying-fish\"\n"
 244             "(symbol->string 'Martin)         @result{}  \"martin\"\n"
 245             "(symbol->string\n"
 246             "   (string->symbol \"Malvina\")) @result{} \"Malvina\"\n"
 247             "@end lisp")
 248 #define FUNC_NAME s_scm_symbol_to_string
 249 {
 250   SCM_VALIDATE_SYMBOL (1, s);
 251   return scm_i_symbol_substring (s, 0, scm_i_symbol_length (s));
 252 }
 253 #undef FUNC_NAME
 254
 255
 256 SCM_DEFINE (scm_string_to_symbol, "string->symbol", 1, 0, 0,
 257             (SCM string),
 258             "Return the symbol whose name is @var{string}. This procedure\n"
 259             "can create symbols with names containing special characters or\n"
 260             "letters in the non-standard case, but it is usually a bad idea\n"
 261             "to create such symbols because in some implementations of\n"
 262             "Scheme they cannot be read as themselves.  See\n"
 263             "@code{symbol->string}.\n"
 264             "\n"
 265             "The following examples assume that the implementation's\n"
 266             "standard case is lower case:\n"
 267             "\n"
 268             "@lisp\n"
 269             "(eq? 'mISSISSIppi 'mississippi) @result{} #t\n"
 270             "(string->symbol \"mISSISSIppi\") @result{} @r{the symbol with name \"mISSISSIppi\"}\n"
 271             "(eq? 'bitBlt (string->symbol \"bitBlt\")) @result{} #f\n"
 272             "(eq? 'JollyWog\n"
 273             "  (string->symbol (symbol->string 'JollyWog))) @result{} #t\n"
 274             "(string=? \"K. Harper, M.D.\"\n"
 275             "  (symbol->string\n"
 276             "    (string->symbol \"K. Harper, M.D.\"))) @result{}#t\n"
 277             "@end lisp")
 278 #define FUNC_NAME s_scm_string_to_symbol
 279 {
 280   SCM_VALIDATE_STRING (1, string);
 281   return scm_i_mem2symbol (string);
 282 }
 283 #undef FUNC_NAME
 284
 285 SCM_DEFINE (scm_string_ci_to_symbol, "string-ci->symbol", 1, 0, 0,
 286             (SCM str),
 287             "Return the symbol whose name is @var{str}.  @var{str} is\n"
 288             "converted to lowercase before the conversion is done, if Guile\n"
 289             "is currently reading symbols case-insensitively.")
 290 #define FUNC_NAME s_scm_string_ci_to_symbol
 291 {
 292   return scm_string_to_symbol (SCM_CASE_INSENSITIVE_P
 293                                ? scm_string_downcase(str)
 294                                : str);
 295 }
 296 #undef FUNC_NAME
 297
 298 #define MAX_PREFIX_LENGTH 30
 299
 300 SCM_DEFINE (scm_gensym, "gensym", 0, 1, 0,
 301             (SCM prefix),
 302             "Create a new symbol with a name constructed from a prefix and\n"
 303             "a counter value. The string @var{prefix} can be specified as\n"
 304             "an optional argument. Default prefix is @code{ g}.  The counter\n"
 305             "is increased by 1 at each call. There is no provision for\n"
 306             "resetting the counter.")
 307 #define FUNC_NAME s_scm_gensym
 308 {
 309   static int gensym_counter = 0;
 310
 311   SCM suffix, name;
 312   int n, n_digits;
 313   char buf[SCM_INTBUFLEN];
 314
 315   if (SCM_UNBNDP (prefix))
 316     prefix = scm_from_locale_string (" g");
 317
 318   /* mutex in case another thread looks and incs at the exact same moment */
 319   scm_i_scm_pthread_mutex_lock (&scm_i_misc_mutex);
 320   n = gensym_counter++;
 321   scm_i_pthread_mutex_unlock (&scm_i_misc_mutex);
 322
 323   n_digits = scm_iint2str (n, 10, buf);
 324   suffix = scm_from_locale_stringn (buf, n_digits);
 325   name = scm_string_append (scm_list_2 (prefix, suffix));
 326   return scm_string_to_symbol (name);
 327 }
 328 #undef FUNC_NAME
 329
 330 SCM_DEFINE (scm_symbol_hash, "symbol-hash", 1, 0, 0,
 331             (SCM symbol),
 332             "Return a hash value for @var{symbol}.")
 333 #define FUNC_NAME s_scm_symbol_hash
 334 {
 335   SCM_VALIDATE_SYMBOL (1, symbol);
 336   return scm_from_ulong (scm_i_symbol_hash (symbol));
 337 }
 338 #undef FUNC_NAME
 339
 340 SCM_DEFINE (scm_symbol_fref, "symbol-fref", 1, 0, 0,
 341            (SCM s),
 342             "Return the contents of @var{symbol}'s @dfn{function slot}.")
 343 #define FUNC_NAME s_scm_symbol_fref
 344 {
 345   SCM_VALIDATE_SYMBOL (1, s);
 346   return SCM_CAR (SCM_CELL_OBJECT_3 (s));
 347 }
 348 #undef FUNC_NAME
 349
 350
 351 SCM_DEFINE (scm_symbol_pref, "symbol-pref", 1, 0, 0,
 352            (SCM s),
 353             "Return the @dfn{property list} currently associated with @var{symbol}.")
 354 #define FUNC_NAME s_scm_symbol_pref
 355 {
 356   SCM_VALIDATE_SYMBOL (1, s);
 357   return SCM_CDR (SCM_CELL_OBJECT_3 (s));
 358 }
 359 #undef FUNC_NAME
 360
 361
 362 SCM_DEFINE (scm_symbol_fset_x, "symbol-fset!", 2, 0, 0,
 363            (SCM s, SCM val),
 364             "Change the binding of @var{symbol}'s function slot.")
 365 #define FUNC_NAME s_scm_symbol_fset_x
 366 {
 367   SCM_VALIDATE_SYMBOL (1, s);
 368   SCM_SETCAR (SCM_CELL_OBJECT_3 (s), val);
 369   return SCM_UNSPECIFIED;
 370 }
 371 #undef FUNC_NAME
 372
 373
 374 SCM_DEFINE (scm_symbol_pset_x, "symbol-pset!", 2, 0, 0,
 375            (SCM s, SCM val),
 376             "Change the binding of @var{symbol}'s property slot.")
 377 #define FUNC_NAME s_scm_symbol_pset_x
 378 {
 379   SCM_VALIDATE_SYMBOL (1, s);
 380   SCM_SETCDR (SCM_CELL_OBJECT_3 (s), val);
 381   return SCM_UNSPECIFIED;
 382 }
 383 #undef FUNC_NAME
 384
 385 SCM
 386 scm_from_locale_symbol (const char *sym)
 387 {
 388   return scm_i_c_mem2symbol (sym, strlen (sym));
 389 }
 390
 391 SCM
 392 scm_from_locale_symboln (const char *sym, size_t len)
 393 {
 394   return scm_i_c_mem2symbol (sym, len);
 395 }
 396
 397 SCM
 398 scm_take_locale_symboln (char *sym, size_t len)
 399 {
 400   SCM res;
 401   unsigned long raw_hash;
 402
 403   if (len == (size_t)-1)
 404     len = strlen (sym);
 405   else
 406     {
 407       /* Ensure STR is null terminated.  A realloc for 1 extra byte should
 408          often be satisfied from the alignment padding after the block, with
 409          no actual data movement.  */
 410       sym = scm_realloc (sym, len+1);
 411       sym[len] = '\0';
 412     }
 413
 414   raw_hash = scm_string_hash ((unsigned char *)sym, len);
 415   res = lookup_interned_symbol (sym, len, raw_hash);
 416   if (res != SCM_BOOL_F)
 417     {
 418       free (sym);
 419       return res;
 420     }
 421
 422   res = scm_i_c_take_symbol (sym, len, 0, raw_hash,
 423                              scm_cons (SCM_BOOL_F, SCM_EOL));
 424
 425   return res;
 426 }
 427
 428 SCM
 429 scm_take_locale_symbol (char *sym)
 430 {
 431   return scm_take_locale_symboln (sym, (size_t)-1);
 432 }
 433
 434 void
 435 scm_symbols_prehistory ()
 436 {
 437   symbols = scm_make_weak_key_hash_table (scm_from_int (2139));
 438   scm_permanent_object (symbols);
 439 }
 440
 441
 442 void
 443 scm_init_symbols ()
 444 {
 445 #include "libguile/symbols.x"
 446 }
 447
 448 /*
 449   Local Variables:
 450   c-file-style: "gnu"
 451   End:
 452 */