libguile/hash.c

   1 /*      Copyright (C) 1995,1996,1997, 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 "_scm.h"
  49 #include "chars.h"
  50 #include "ports.h"
  51 #include "vectors.h"
  52
  53 #include "validate.h"
  54 #include "hash.h"
  55 \f
  56
  57 #ifndef floor
  58 extern double floor();
  59 #endif
  60
  61
  62 unsigned long
  63 scm_hasher(SCM obj, unsigned long n, scm_sizet d)
  64 {
  65   switch (7 & (int) obj) {
  66   case 2:
  67   case 6:
  68     return SCM_INUM(obj) % n;   /* SCM_INUMP(obj) */
  69   case 4:
  70     if SCM_CHARP(obj)
  71       return (unsigned)(scm_downcase(SCM_CHAR(obj))) % n;
  72     switch ((int) obj) {
  73 #ifndef SICP
  74     case (int) SCM_EOL:
  75       d = 256;
  76       break;
  77 #endif
  78     case (int) SCM_BOOL_T:
  79       d = 257;
  80       break;
  81     case (int) SCM_BOOL_F:
  82       d = 258;
  83       break;
  84     case (int) SCM_EOF_VAL:
  85       d = 259;
  86       break;
  87     default:
  88       d = 263;          /* perhaps should be error */
  89     }
  90     return d % n;
  91   default:
  92     return 263 % n;     /* perhaps should be error */
  93   case 0:
  94     switch SCM_TYP7(obj) {
  95     default:
  96       return 263 % n;
  97     case scm_tc7_smob:
  98       switch SCM_TYP16(obj) {
  99       case scm_tc16_big:
 100         return SCM_INUM(scm_modulo(obj, SCM_MAKINUM(n)));
 101       default:
 102         return 263 % n;
 103       case scm_tc16_real:
 104         {
 105           double r = SCM_REALPART(obj);
 106           if (floor(r)==r) {
 107             obj = scm_inexact_to_exact (obj);
 108             if SCM_IMP(obj) return SCM_INUM(obj) % n;
 109             return SCM_INUM(scm_modulo(obj, SCM_MAKINUM(n)));
 110           }
 111         }
 112       case scm_tc16_complex:
 113         obj = scm_number_to_string(obj, SCM_MAKINUM(10));
 114       }
 115     case scm_tcs_symbols:
 116     case scm_tc7_string:
 117     case scm_tc7_substring:
 118       return scm_strhash(SCM_ROUCHARS(obj), (scm_sizet) SCM_ROLENGTH(obj), n);
 119     case scm_tc7_wvect:
 120     case scm_tc7_vector:
 121       {
 122         scm_sizet len = SCM_LENGTH(obj);
 123         SCM *data = SCM_VELTS(obj);
 124         if (len>5)
 125           {
 126             scm_sizet i = d/2;
 127             unsigned long h = 1;
 128             while (i--) h = ((h<<8) + (scm_hasher(data[h % len], n, 2))) % n;
 129             return h;
 130           }
 131         else
 132           {
 133             scm_sizet i = len;
 134             unsigned long h = (n)-1;
 135             while (i--) h = ((h<<8) + (scm_hasher(data[i], n, d/len))) % n;
 136             return h;
 137           }
 138       }
 139     case scm_tcs_cons_imcar:
 140     case scm_tcs_cons_nimcar:
 141       if (d) return (scm_hasher(SCM_CAR(obj), n, d/2)+scm_hasher(SCM_CDR(obj), n, d/2)) % n;
 142       else return 1;
 143     case scm_tc7_port:
 144       return ((SCM_RDNG & SCM_UNPACK_CAR(obj)) ? 260 : 261) % n;
 145     case scm_tcs_closures:
 146     case scm_tc7_contin:
 147     case scm_tcs_subrs:
 148       return 262 % n;
 149     }
 150   }
 151 }
 152
 153
 154 \f
 155
 156
 157 unsigned int
 158 scm_ihashq (SCM obj, unsigned int n)
 159 {
 160   return (((unsigned int) obj) >> 1) % n;
 161 }
 162
 163
 164 SCM_DEFINE (scm_hashq, "hashq", 2, 0, 0,
 165            (SCM key, SCM size),
 166             "Determine a hash value for KEY that is suitable for lookups in\n"
 167             "a hashtable of size SIZE, where eq? is used as the equality\n"
 168             "predicate.  The function returns an integer in the range 0 to\n"
 169             "SIZE - 1.  NOTE that `hashq' may use internal addresses.\n"
 170             "Thus two calls to hashq where the keys are eq? are not\n"
 171             "guaranteed to deliver the same value if the key object gets\n"
 172             "garbage collected in between.  This can happen, for example\n"
 173             "with symbols:  (hashq 'foo n) (gc) (hashq 'foo n) may produce two\n"
 174             "different values, since 'foo will be garbage collected.")
 175 #define FUNC_NAME s_scm_hashq
 176 {
 177   SCM_VALIDATE_INUM_MIN (2, size, 0);
 178   return SCM_MAKINUM (scm_ihashq (key, SCM_INUM (size)));
 179 }
 180 #undef FUNC_NAME
 181
 182
 183 \f
 184
 185
 186 unsigned int
 187 scm_ihashv (SCM obj, unsigned int n)
 188 {
 189   if (SCM_CHARP(obj))
 190     return ((unsigned int)(scm_downcase(SCM_CHAR(obj)))) % n; /* downcase!?!! */
 191
 192   if (SCM_NUMP(obj))
 193     return (unsigned int) scm_hasher(obj, n, 10);
 194   else
 195     return ((unsigned int)obj) % n;
 196 }
 197
 198
 199 SCM_DEFINE (scm_hashv, "hashv", 2, 0, 0,
 200            (SCM key, SCM size),
 201             "Determine a hash value for KEY that is suitable for lookups in\n"
 202             "a hashtable of size SIZE, where eqv? is used as the equality\n"
 203             "predicate.  The function returns an integer in the range 0 to\n"
 204             "SIZE - 1.  NOTE that (hashv key) may use internal addresses.\n"
 205             "Thus two calls to hashv where the keys are eqv? are not\n"
 206             "guaranteed to deliver the same value if the key object gets\n"
 207             "garbage collected in between.  This can happen, for example\n"
 208             "with symbols:  (hashv 'foo n) (gc) (hashv 'foo n) may produce two\n"
 209             "different values, since 'foo will be garbage collected.")
 210 #define FUNC_NAME s_scm_hashv
 211 {
 212   SCM_VALIDATE_INUM_MIN (2, size, 0);
 213   return SCM_MAKINUM (scm_ihashv (key, SCM_INUM (size)));
 214 }
 215 #undef FUNC_NAME
 216
 217
 218 \f
 219
 220
 221 unsigned int
 222 scm_ihash (SCM obj, unsigned int n)
 223 {
 224   return (unsigned int)scm_hasher (obj, n, 10);
 225 }
 226
 227 SCM_DEFINE (scm_hash, "hash", 2, 0, 0,
 228            (SCM key, SCM size),
 229             "Determine a hash value for KEY that is suitable for lookups in\n"
 230             "a hashtable of size SIZE, where equal? is used as the equality\n"
 231             "predicate.  The function returns an integer in the range 0 to\n"
 232             "SIZE - 1.")
 233 #define FUNC_NAME s_scm_hash
 234 {
 235   SCM_VALIDATE_INUM_MIN (2, size, 0);
 236   return SCM_MAKINUM (scm_ihash (key, SCM_INUM (size)));
 237 }
 238 #undef FUNC_NAME
 239
 240
 241 \f
 242
 243
 244 void
 245 scm_init_hash ()
 246 {
 247 #include "hash.x"
 248 }
 249