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 "libguile/_scm.h"
  49 #include "libguile/chars.h"
  50 #include "libguile/ports.h"
  51 #include "libguile/vectors.h"
  52
  53 #include "libguile/validate.h"
  54 #include "libguile/hash.h"
  55 \f
  56
  57 #ifndef floor
  58 extern double floor();
  59 #endif
  60
  61
  62 /* Dirk:FIXME:: why downcase for characters? (2x: scm_hasher, scm_ihashv) */
  63 /* Dirk:FIXME:: scm_hasher could be made static. */
  64
  65
  66 unsigned long
  67 scm_hasher(SCM obj, unsigned long n, scm_sizet d)
  68 {
  69   switch (SCM_ITAG3 (obj)) {
  70   case scm_tc3_int_1:
  71   case scm_tc3_int_2:
  72     return SCM_INUM(obj) % n;   /* SCM_INUMP(obj) */
  73   case scm_tc3_imm24:
  74     if (SCM_CHARP(obj))
  75       return (unsigned)(scm_downcase(SCM_CHAR(obj))) % n;
  76     switch (SCM_UNPACK (obj)) {
  77 #ifndef SICP
  78     case SCM_EOL:
  79       d = 256;
  80       break;
  81 #endif
  82     case SCM_BOOL_T:
  83       d = 257;
  84       break;
  85     case SCM_BOOL_F:
  86       d = 258;
  87       break;
  88     case SCM_EOF_VAL:
  89       d = 259;
  90       break;
  91     default:
  92       d = 263;          /* perhaps should be error */
  93     }
  94     return d % n;
  95   default:
  96     return 263 % n;     /* perhaps should be error */
  97   case scm_tc3_cons:
  98     switch SCM_TYP7(obj) {
  99     default:
 100       return 263 % n;
 101     case scm_tc7_smob:
 102       switch SCM_TYP16(obj) {
 103       case scm_tc16_big:
 104         return SCM_INUM(scm_modulo(obj, SCM_MAKINUM(n)));
 105       default:
 106         return 263 % n;
 107       case scm_tc16_real:
 108         {
 109           double r = SCM_REAL_VALUE(obj);
 110           if (floor(r)==r) {
 111             obj = scm_inexact_to_exact (obj);
 112             if SCM_IMP(obj) return SCM_INUM(obj) % n;
 113             return SCM_INUM(scm_modulo(obj, SCM_MAKINUM(n)));
 114           }
 115         }
 116       case scm_tc16_complex:
 117         obj = scm_number_to_string(obj, SCM_MAKINUM(10));
 118       }
 119     case scm_tcs_symbols:
 120     case scm_tc7_string:
 121     case scm_tc7_substring:
 122       return scm_strhash(SCM_ROUCHARS(obj), (scm_sizet) SCM_ROLENGTH(obj), n);
 123     case scm_tc7_wvect:
 124     case scm_tc7_vector:
 125       {
 126         scm_sizet len = SCM_LENGTH(obj);
 127         SCM *data = SCM_VELTS(obj);
 128         if (len>5)
 129           {
 130             scm_sizet i = d/2;
 131             unsigned long h = 1;
 132             while (i--) h = ((h<<8) + (scm_hasher(data[h % len], n, 2))) % n;
 133             return h;
 134           }
 135         else
 136           {
 137             scm_sizet i = len;
 138             unsigned long h = (n)-1;
 139             while (i--) h = ((h<<8) + (scm_hasher(data[i], n, d/len))) % n;
 140             return h;
 141           }
 142       }
 143     case scm_tcs_cons_imcar:
 144     case scm_tcs_cons_nimcar:
 145       if (d) return (scm_hasher(SCM_CAR(obj), n, d/2)+scm_hasher(SCM_CDR(obj), n, d/2)) % n;
 146       else return 1;
 147     case scm_tc7_port:
 148       return ((SCM_RDNG & SCM_CELL_WORD_0 (obj)) ? 260 : 261) % n;
 149     case scm_tcs_closures:
 150     case scm_tc7_contin:
 151     case scm_tcs_subrs:
 152       return 262 % n;
 153     }
 154   }
 155 }
 156
 157
 158 \f
 159
 160
 161 unsigned int
 162 scm_ihashq (SCM obj, unsigned int n)
 163 {
 164   return (SCM_UNPACK (obj) >> 1) % n;
 165 }
 166
 167
 168 SCM_DEFINE (scm_hashq, "hashq", 2, 0, 0,
 169            (SCM key, SCM size),
 170             "Determine a hash value for KEY that is suitable for lookups in\n"
 171             "a hashtable of size SIZE, where eq? is used as the equality\n"
 172             "predicate.  The function returns an integer in the range 0 to\n"
 173             "SIZE - 1.  NOTE that `hashq' may use internal addresses.\n"
 174             "Thus two calls to hashq where the keys are eq? are not\n"
 175             "guaranteed to deliver the same value if the key object gets\n"
 176             "garbage collected in between.  This can happen, for example\n"
 177             "with symbols:  (hashq 'foo n) (gc) (hashq 'foo n) may produce two\n"
 178             "different values, since 'foo will be garbage collected.")
 179 #define FUNC_NAME s_scm_hashq
 180 {
 181   SCM_VALIDATE_INUM_MIN (2, size, 0);
 182   return SCM_MAKINUM (scm_ihashq (key, SCM_INUM (size)));
 183 }
 184 #undef FUNC_NAME
 185
 186
 187 \f
 188
 189
 190 unsigned int
 191 scm_ihashv (SCM obj, unsigned int n)
 192 {
 193   if (SCM_CHARP(obj))
 194     return ((unsigned int)(scm_downcase(SCM_CHAR(obj)))) % n; /* downcase!?!! */
 195
 196   if (SCM_NUMP(obj))
 197     return (unsigned int) scm_hasher(obj, n, 10);
 198   else
 199     return SCM_UNPACK (obj) % n;
 200 }
 201
 202
 203 SCM_DEFINE (scm_hashv, "hashv", 2, 0, 0,
 204            (SCM key, SCM size),
 205             "Determine a hash value for KEY that is suitable for lookups in\n"
 206             "a hashtable of size SIZE, where eqv? is used as the equality\n"
 207             "predicate.  The function returns an integer in the range 0 to\n"
 208             "SIZE - 1.  NOTE that (hashv key) may use internal addresses.\n"
 209             "Thus two calls to hashv where the keys are eqv? are not\n"
 210             "guaranteed to deliver the same value if the key object gets\n"
 211             "garbage collected in between.  This can happen, for example\n"
 212             "with symbols:  (hashv 'foo n) (gc) (hashv 'foo n) may produce two\n"
 213             "different values, since 'foo will be garbage collected.")
 214 #define FUNC_NAME s_scm_hashv
 215 {
 216   SCM_VALIDATE_INUM_MIN (2, size, 0);
 217   return SCM_MAKINUM (scm_ihashv (key, SCM_INUM (size)));
 218 }
 219 #undef FUNC_NAME
 220
 221
 222 \f
 223
 224
 225 unsigned int
 226 scm_ihash (SCM obj, unsigned int n)
 227 {
 228   return (unsigned int)scm_hasher (obj, n, 10);
 229 }
 230
 231 SCM_DEFINE (scm_hash, "hash", 2, 0, 0,
 232            (SCM key, SCM size),
 233             "Determine a hash value for KEY that is suitable for lookups in\n"
 234             "a hashtable of size SIZE, where equal? is used as the equality\n"
 235             "predicate.  The function returns an integer in the range 0 to\n"
 236             "SIZE - 1.")
 237 #define FUNC_NAME s_scm_hash
 238 {
 239   SCM_VALIDATE_INUM_MIN (2, size, 0);
 240   return SCM_MAKINUM (scm_ihash (key, SCM_INUM (size)));
 241 }
 242 #undef FUNC_NAME
 243
 244
 245 \f
 246
 247
 248 void
 249 scm_init_hash ()
 250 {
 251 #include "libguile/hash.x"
 252 }
 253
 254
 255 /*
 256   Local Variables:
 257   c-file-style: "gnu"
 258   End:
 259 */