libguile/hash.c

   1 /*      Copyright (C) 1995,1996,1997 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 "_scm.h"
  49 #include "chars.h"
  50
  51 #include "validate.h"
  52 #include "hash.h"
  53 \f
  54
  55 #ifndef floor
  56 extern double floor();
  57 #endif
  58
  59
  60 unsigned long
  61 scm_hasher(SCM obj, unsigned long n, scm_sizet d)
  62 {
  63   switch (7 & (int) obj) {
  64   case 2:
  65   case 6:
  66     return SCM_INUM(obj) % n;   /* SCM_INUMP(obj) */
  67   case 4:
  68     if SCM_CHARP(obj)
  69       return (unsigned)(scm_downcase(SCM_CHAR(obj))) % n;
  70     switch ((int) obj) {
  71 #ifndef SICP
  72     case (int) SCM_EOL:
  73       d = 256;
  74       break;
  75 #endif
  76     case (int) SCM_BOOL_T:
  77       d = 257;
  78       break;
  79     case (int) SCM_BOOL_F:
  80       d = 258;
  81       break;
  82     case (int) SCM_EOF_VAL:
  83       d = 259;
  84       break;
  85     default:
  86       d = 263;          /* perhaps should be error */
  87     }
  88     return d % n;
  89   default:
  90     return 263 % n;     /* perhaps should be error */
  91   case 0:
  92     switch SCM_TYP7(obj) {
  93     default:
  94       return 263 % n;
  95     case scm_tc7_smob:
  96       switch SCM_TYP16(obj) {
  97       case scm_tcs_bignums:
  98         return SCM_INUM(scm_modulo(obj, SCM_MAKINUM(n)));
  99       default:
 100         return 263 % n;
 101 #ifdef SCM_FLOATS
 102       case scm_tc16_flo:
 103         if SCM_REALP(obj) {
 104           double r = SCM_REALPART(obj);
 105           if (floor(r)==r) {
 106             obj = scm_inexact_to_exact (obj);
 107             if SCM_IMP(obj) return SCM_INUM(obj) % n;
 108             return SCM_INUM(scm_modulo(obj, SCM_MAKINUM(n)));
 109           }
 110         }
 111         obj = scm_number_to_string(obj, SCM_MAKINUM(10));
 112 #endif
 113       }
 114     case scm_tcs_symbols:
 115     case scm_tc7_string:
 116     case scm_tc7_substring:
 117       return scm_strhash(SCM_ROUCHARS(obj), (scm_sizet) SCM_ROLENGTH(obj), n);
 118     case scm_tc7_wvect:
 119     case scm_tc7_vector:
 120       {
 121         scm_sizet len = SCM_LENGTH(obj);
 122         SCM *data = SCM_VELTS(obj);
 123         if (len>5)
 124           {
 125             scm_sizet i = d/2;
 126             unsigned long h = 1;
 127             while (i--) h = ((h<<8) + (scm_hasher(data[h % len], n, 2))) % n;
 128             return h;
 129           }
 130         else
 131           {
 132             scm_sizet i = len;
 133             unsigned long h = (n)-1;
 134             while (i--) h = ((h<<8) + (scm_hasher(data[i], n, d/len))) % n;
 135             return h;
 136           }
 137       }
 138     case scm_tcs_cons_imcar:
 139     case scm_tcs_cons_nimcar:
 140       if (d) return (scm_hasher(SCM_CAR(obj), n, d/2)+scm_hasher(SCM_CDR(obj), n, d/2)) % n;
 141       else return 1;
 142     case scm_tc7_port:
 143       return ((SCM_RDNG & SCM_CARW(obj)) ? 260 : 261) % n;
 144     case scm_tcs_closures:
 145     case scm_tc7_contin:
 146     case scm_tcs_subrs:
 147       return 262 % n;
 148     }
 149   }
 150 }
 151
 152
 153 \f
 154
 155
 156 unsigned int
 157 scm_ihashq (SCM obj, unsigned int n)
 158 {
 159   return (((unsigned int) obj) >> 1) % n;
 160 }
 161
 162
 163 SCM_DEFINE (scm_hashq, "hashq", 2, 0, 0,
 164            (SCM key, SCM size),
 165             "Determine a hash value for KEY that is suitable for lookups in\n"
 166             "a hashtable of size SIZE, where eq? is used as the equality\n"
 167             "predicate.  The function returns an integer in the range 0 to\n"
 168             "SIZE - 1.  NOTE that `hashq' may use internal addresses.\n"
 169             "Thus two calls to hashq where the keys are eq? are not\n"
 170             "guaranteed to deliver the same value if the key object gets\n"
 171             "garbage collected in between.  This can happen, for example\n"
 172             "with symbols:  (hashq 'foo n) (gc) (hashq 'foo n) may produce two\n"
 173             "different values, since 'foo will be garbage collected.")
 174 #define FUNC_NAME s_scm_hashq
 175 {
 176   SCM_VALIDATE_INUM_MIN (2, size, 0);
 177   return SCM_MAKINUM (scm_ihashq (key, SCM_INUM (size)));
 178 }
 179 #undef FUNC_NAME
 180
 181
 182 \f
 183
 184
 185 unsigned int
 186 scm_ihashv (SCM obj, unsigned int n)
 187 {
 188   if (SCM_CHARP(obj))
 189     return ((unsigned int)(scm_downcase(SCM_CHAR(obj)))) % n; /* downcase!?!! */
 190
 191   if (SCM_NUMP(obj))
 192     return (unsigned int) scm_hasher(obj, n, 10);
 193   else
 194     return ((unsigned int)obj) % n;
 195 }
 196
 197
 198 SCM_DEFINE (scm_hashv, "hashv", 2, 0, 0,
 199            (SCM key, SCM size),
 200             "Determine a hash value for KEY that is suitable for lookups in\n"
 201             "a hashtable of size SIZE, where eqv? is used as the equality\n"
 202             "predicate.  The function returns an integer in the range 0 to\n"
 203             "SIZE - 1.  NOTE that (hashv key) may use internal addresses.\n"
 204             "Thus two calls to hashv where the keys are eqv? are not\n"
 205             "guaranteed to deliver the same value if the key object gets\n"
 206             "garbage collected in between.  This can happen, for example\n"
 207             "with symbols:  (hashv 'foo n) (gc) (hashv 'foo n) may produce two\n"
 208             "different values, since 'foo will be garbage collected.")
 209 #define FUNC_NAME s_scm_hashv
 210 {
 211   SCM_VALIDATE_INUM_MIN (2, size, 0);
 212   return SCM_MAKINUM (scm_ihashv (key, SCM_INUM (size)));
 213 }
 214 #undef FUNC_NAME
 215
 216
 217 \f
 218
 219
 220 unsigned int
 221 scm_ihash (SCM obj, unsigned int n)
 222 {
 223   return (unsigned int)scm_hasher (obj, n, 10);
 224 }
 225
 226 SCM_DEFINE (scm_hash, "hash", 2, 0, 0,
 227            (SCM key, SCM size),
 228             "Determine a hash value for KEY that is suitable for lookups in\n"
 229             "a hashtable of size SIZE, where equal? is used as the equality\n"
 230             "predicate.  The function returns an integer in the range 0 to\n"
 231             "SIZE - 1.")
 232 #define FUNC_NAME s_scm_hash
 233 {
 234   SCM_VALIDATE_INUM_MIN (2, size, 0);
 235   return SCM_MAKINUM (scm_ihash (key, SCM_INUM (size)));
 236 }
 237 #undef FUNC_NAME
 238
 239
 240 \f
 241
 242
 243 void
 244 scm_init_hash ()
 245 {
 246 #include "hash.x"
 247 }
 248