libguile/hash.c

   1 /*      Copyright (C) 1995,1996,1997, 2000, 2001, 2003, 2004 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  16  */
  17
  18
  19 \f
  20
  21 #include "libguile/_scm.h"
  22 #include "libguile/chars.h"
  23 #include "libguile/ports.h"
  24 #include "libguile/strings.h"
  25 #include "libguile/symbols.h"
  26 #include "libguile/vectors.h"
  27
  28 #include "libguile/validate.h"
  29 #include "libguile/hash.h"
  30 \f
  31
  32 #ifndef floor
  33 extern double floor();
  34 #endif
  35
  36
  37 unsigned long
  38 scm_string_hash (const unsigned char *str, size_t len)
  39 {
  40   /* from suggestion at: */
  41   /* http://srfi.schemers.org/srfi-13/mail-archive/msg00112.html */
  42
  43   unsigned long h = 0;
  44   while (len-- > 0)
  45     h = *str++ + h*37;
  46   return h;
  47 }
  48
  49
  50 /* Dirk:FIXME:: why downcase for characters? (2x: scm_hasher, scm_ihashv) */
  51 /* Dirk:FIXME:: scm_hasher could be made static. */
  52
  53
  54 unsigned long
  55 scm_hasher(SCM obj, unsigned long n, size_t d)
  56 {
  57   switch (SCM_ITAG3 (obj)) {
  58   case scm_tc3_int_1:
  59   case scm_tc3_int_2:
  60     return SCM_I_INUM(obj) % n;   /* SCM_INUMP(obj) */
  61   case scm_tc3_imm24:
  62     if (SCM_CHARP(obj))
  63       return (unsigned)(scm_c_downcase(SCM_CHAR(obj))) % n;
  64     switch (SCM_UNPACK (obj)) {
  65 #ifndef SICP
  66     case SCM_UNPACK(SCM_EOL):
  67       d = 256;
  68       break;
  69 #endif
  70     case SCM_UNPACK(SCM_BOOL_T):
  71       d = 257;
  72       break;
  73     case SCM_UNPACK(SCM_BOOL_F):
  74       d = 258;
  75       break;
  76     case SCM_UNPACK(SCM_EOF_VAL):
  77       d = 259;
  78       break;
  79     default:
  80       d = 263;          /* perhaps should be error */
  81     }
  82     return d % n;
  83   default:
  84     return 263 % n;     /* perhaps should be error */
  85   case scm_tc3_cons:
  86     switch SCM_TYP7(obj) {
  87     default:
  88       return 263 % n;
  89     case scm_tc7_smob:
  90       return 263 % n;
  91     case scm_tc7_number:
  92       switch SCM_TYP16 (obj) {
  93       case scm_tc16_big:
  94         return scm_to_ulong (scm_modulo (obj, scm_from_ulong (n)));
  95       case scm_tc16_real:
  96         {
  97           double r = SCM_REAL_VALUE (obj);
  98           if (floor (r) == r)
  99             {
 100               obj = scm_inexact_to_exact (obj);
 101               return scm_to_ulong (scm_modulo (obj, scm_from_ulong (n)));
 102             }
 103         }
 104         /* Fall through */
 105       case scm_tc16_complex:
 106       case scm_tc16_fraction:
 107         obj = scm_number_to_string (obj, scm_from_int (10));
 108         /* Fall through */
 109       }
 110       /* Fall through */
 111     case scm_tc7_string:
 112       {
 113         unsigned long hash =
 114           scm_string_hash ((const unsigned char *) scm_i_string_chars (obj),
 115                            scm_i_string_length (obj)) % n;
 116         scm_remember_upto_here_1 (obj);
 117         return hash;
 118       }
 119     case scm_tc7_symbol:
 120       return scm_i_symbol_hash (obj) % n;
 121     case scm_tc7_wvect:
 122     case scm_tc7_vector:
 123       {
 124         size_t len = SCM_SIMPLE_VECTOR_LENGTH (obj);
 125         if (len > 5)
 126           {
 127             size_t i = d/2;
 128             unsigned long h = 1;
 129             while (i--)
 130               {
 131                 SCM elt = SCM_SIMPLE_VECTOR_REF (obj, h % len);
 132                 h = ((h << 8) + (scm_hasher (elt, n, 2))) % n;
 133               }
 134             return h;
 135           }
 136         else
 137           {
 138             size_t i = len;
 139             unsigned long h = (n)-1;
 140             while (i--)
 141               {
 142                 SCM elt = SCM_SIMPLE_VECTOR_REF (obj, h % len);
 143                 h = ((h << 8) + (scm_hasher (elt, n, d/len))) % n;
 144               }
 145             return h;
 146           }
 147       }
 148     case scm_tcs_cons_imcar:
 149     case scm_tcs_cons_nimcar:
 150       if (d) return (scm_hasher (SCM_CAR (obj), n, d/2)
 151                      + scm_hasher (SCM_CDR (obj), n, d/2)) % n;
 152       else return 1;
 153     case scm_tc7_port:
 154       return ((SCM_RDNG & SCM_CELL_WORD_0 (obj)) ? 260 : 261) % n;
 155     case scm_tcs_closures:
 156     case scm_tcs_subrs:
 157       return 262 % n;
 158     }
 159   }
 160 }
 161
 162
 163 \f
 164
 165
 166 unsigned long
 167 scm_ihashq (SCM obj, unsigned long n)
 168 {
 169   return (SCM_UNPACK (obj) >> 1) % n;
 170 }
 171
 172
 173 SCM_DEFINE (scm_hashq, "hashq", 2, 0, 0,
 174            (SCM key, SCM size),
 175             "Determine a hash value for @var{key} that is suitable for\n"
 176             "lookups in a hashtable of size @var{size}, where @code{eq?} is\n"
 177             "used as the equality predicate.  The function returns an\n"
 178             "integer in the range 0 to @var{size} - 1.  Note that\n"
 179             "@code{hashq} may use internal addresses.  Thus two calls to\n"
 180             "hashq where the keys are @code{eq?} are not guaranteed to\n"
 181             "deliver the same value if the key object gets garbage collected\n"
 182             "in between.  This can happen, for example with symbols:\n"
 183             "@code{(hashq 'foo n) (gc) (hashq 'foo n)} may produce two\n"
 184             "different values, since @code{foo} will be garbage collected.")
 185 #define FUNC_NAME s_scm_hashq
 186 {
 187   unsigned long sz = scm_to_unsigned_integer (size, 1, ULONG_MAX);
 188   return scm_from_ulong (scm_ihashq (key, sz));
 189 }
 190 #undef FUNC_NAME
 191
 192
 193 \f
 194
 195
 196 unsigned long
 197 scm_ihashv (SCM obj, unsigned long n)
 198 {
 199   if (SCM_CHARP(obj))
 200     return ((unsigned long) (scm_c_downcase (SCM_CHAR (obj)))) % n; /* downcase!?!! */
 201
 202   if (SCM_NUMP(obj))
 203     return (unsigned long) scm_hasher(obj, n, 10);
 204   else
 205     return SCM_UNPACK (obj) % n;
 206 }
 207
 208
 209 SCM_DEFINE (scm_hashv, "hashv", 2, 0, 0,
 210            (SCM key, SCM size),
 211             "Determine a hash value for @var{key} that is suitable for\n"
 212             "lookups in a hashtable of size @var{size}, where @code{eqv?} is\n"
 213             "used as the equality predicate.  The function returns an\n"
 214             "integer in the range 0 to @var{size} - 1.  Note that\n"
 215             "@code{(hashv key)} may use internal addresses.  Thus two calls\n"
 216             "to hashv where the keys are @code{eqv?} are not guaranteed to\n"
 217             "deliver the same value if the key object gets garbage collected\n"
 218             "in between.  This can happen, for example with symbols:\n"
 219             "@code{(hashv 'foo n) (gc) (hashv 'foo n)} may produce two\n"
 220             "different values, since @code{foo} will be garbage collected.")
 221 #define FUNC_NAME s_scm_hashv
 222 {
 223   unsigned long sz = scm_to_unsigned_integer (size, 1, ULONG_MAX);
 224   return scm_from_ulong (scm_ihashv (key, sz));
 225 }
 226 #undef FUNC_NAME
 227
 228
 229 \f
 230
 231
 232 unsigned long
 233 scm_ihash (SCM obj, unsigned long n)
 234 {
 235   return (unsigned long) scm_hasher (obj, n, 10);
 236 }
 237
 238 SCM_DEFINE (scm_hash, "hash", 2, 0, 0,
 239            (SCM key, SCM size),
 240             "Determine a hash value for @var{key} that is suitable for\n"
 241             "lookups in a hashtable of size @var{size}, where @code{equal?}\n"
 242             "is used as the equality predicate.  The function returns an\n"
 243             "integer in the range 0 to @var{size} - 1.")
 244 #define FUNC_NAME s_scm_hash
 245 {
 246   unsigned long sz = scm_to_unsigned_integer (size, 1, ULONG_MAX);
 247   return scm_from_ulong (scm_ihash (key, sz));
 248 }
 249 #undef FUNC_NAME
 250
 251
 252 \f
 253
 254
 255 void
 256 scm_init_hash ()
 257 {
 258 #include "libguile/hash.x"
 259 }
 260
 261
 262 /*
 263   Local Variables:
 264   c-file-style: "gnu"
 265   End:
 266 */