libguile/fluids.c

   1 /*      Copyright (C) 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
  46 #include "libguile/_scm.h"
  47 #include "libguile/print.h"
  48 #include "libguile/smob.h"
  49 #include "libguile/dynwind.h"
  50 #include "libguile/fluids.h"
  51 #include "libguile/alist.h"
  52 #include "libguile/eval.h"
  53 #include "libguile/ports.h"
  54
  55 #define INITIAL_FLUIDS 10
  56 #include "libguile/validate.h"
  57
  58 static volatile int n_fluids;
  59 long scm_tc16_fluid;
  60
  61 SCM
  62 scm_make_initial_fluids ()
  63 {
  64   return scm_make_vector (SCM_MAKINUM (INITIAL_FLUIDS),
  65                           SCM_BOOL_F);
  66 }
  67
  68 static void
  69 grow_fluids (scm_root_state *root_state, int new_length)
  70 {
  71   SCM old_fluids, new_fluids;
  72   int old_length, i;
  73
  74   old_fluids = root_state->fluids;
  75   old_length = SCM_LENGTH (old_fluids);
  76   new_fluids = scm_make_vector (SCM_MAKINUM (new_length), SCM_BOOL_F);
  77   i = 0;
  78   while (i < old_length)
  79     {
  80       SCM_VELTS(new_fluids)[i] = SCM_VELTS(old_fluids)[i];
  81       i++;
  82     }
  83   while (i < new_length)
  84     {
  85       SCM_VELTS(new_fluids)[i] = SCM_BOOL_F;
  86       i++;
  87     }
  88
  89   root_state->fluids = new_fluids;
  90 }
  91
  92 void
  93 scm_copy_fluids (scm_root_state *root_state)
  94 {
  95   grow_fluids (root_state, SCM_LENGTH(root_state->fluids));
  96 }
  97
  98 static int
  99 print_fluid (SCM exp, SCM port, scm_print_state *pstate)
 100 {
 101   scm_puts ("#<fluid ", port);
 102   scm_intprint ((int) SCM_FLUID_NUM (exp), 10, port);
 103   scm_putc ('>', port);
 104   return 1;
 105 }
 106
 107 static int
 108 next_fluid_num ()
 109 {
 110   int n;
 111 #ifdef USE_THREADS
 112   SCM_THREAD_CRITICAL_SECTION_START;
 113 #endif
 114   n = n_fluids++;
 115 #ifdef USE_THREADS
 116   SCM_THREAD_CRITICAL_SECTION_END;
 117 #endif
 118   return n;
 119 }
 120
 121 SCM_DEFINE (scm_make_fluid, "make-fluid", 0, 0, 0,
 122             (),
 123             "Return a newly created fluid.\n"
 124             "Fluids are objects of a certain type (a smob) that can hold one SCM\n"
 125             "value per dynamic root.  That is, modifications to this value are\n"
 126             "only visible to code that executes within the same dynamic root as\n"
 127             "the modifying code.  When a new dynamic root is constructed, it\n"
 128             "inherits the values from its parent.  Because each thread executes\n"
 129             "in its own dynamic root, you can use fluids for thread local storage.")
 130 #define FUNC_NAME s_scm_make_fluid
 131 {
 132   int n;
 133
 134   SCM_DEFER_INTS;
 135   n = next_fluid_num ();
 136   SCM_RETURN_NEWSMOB (scm_tc16_fluid, n);
 137 }
 138 #undef FUNC_NAME
 139
 140 SCM_DEFINE (scm_fluid_p, "fluid?", 1, 0, 0,
 141             (SCM obj),
 142             "Return #t iff @var{obj} is a fluid; otherwise, return #f.")
 143 #define FUNC_NAME s_scm_fluid_p
 144 {
 145   return SCM_BOOL(SCM_FLUIDP (obj));
 146 }
 147 #undef FUNC_NAME
 148
 149 SCM_DEFINE (scm_fluid_ref, "fluid-ref", 1, 0, 0,
 150             (SCM fluid),
 151             "Return the value associated with @var{fluid} in the current dynamic root.\n"
 152             "If @var{fluid} has not been set, then this returns #f.")
 153 #define FUNC_NAME s_scm_fluid_ref
 154 {
 155   int n;
 156
 157   SCM_VALIDATE_FLUID (1, fluid);
 158
 159   n = SCM_FLUID_NUM (fluid);
 160
 161   if (SCM_LENGTH (scm_root->fluids) <= n)
 162     grow_fluids (scm_root, n+1);
 163   return SCM_VELTS(scm_root->fluids)[n];
 164 }
 165 #undef FUNC_NAME
 166
 167 SCM_DEFINE (scm_fluid_set_x, "fluid-set!", 2, 0, 0,
 168             (SCM fluid, SCM value),
 169             "Set the value associated with @var{fluid} in the current dynamic root.")
 170 #define FUNC_NAME s_scm_fluid_set_x
 171 {
 172   int n;
 173
 174   SCM_VALIDATE_FLUID (1, fluid);
 175   n = SCM_FLUID_NUM (fluid);
 176
 177   if (SCM_LENGTH (scm_root->fluids) <= n)
 178     grow_fluids (scm_root, n+1);
 179   SCM_VELTS(scm_root->fluids)[n] = value;
 180   return value;
 181 }
 182 #undef FUNC_NAME
 183
 184 void
 185 scm_swap_fluids (SCM fluids, SCM vals)
 186 {
 187   while (SCM_NIMP (fluids))
 188     {
 189       SCM fl = SCM_CAR (fluids);
 190       SCM old_val = scm_fluid_ref (fl);
 191       scm_fluid_set_x (fl, SCM_CAR (vals));
 192       SCM_SETCAR (vals, old_val);
 193       fluids = SCM_CDR (fluids);
 194       vals = SCM_CDR (vals);
 195     }
 196 }
 197
 198 /* Swap the fluid values in reverse order.  This is important when the
 199 same fluid appears multiple times in the fluids list. */
 200
 201 void
 202 scm_swap_fluids_reverse (SCM fluids, SCM vals)
 203 {
 204   if (SCM_NIMP (fluids))
 205     {
 206       SCM fl, old_val;
 207
 208       scm_swap_fluids_reverse (SCM_CDR (fluids), SCM_CDR (vals));
 209       fl = SCM_CAR (fluids);
 210       old_val = scm_fluid_ref (fl);
 211       scm_fluid_set_x (fl, SCM_CAR (vals));
 212       SCM_SETCAR (vals, old_val);
 213     }
 214 }
 215
 216
 217 static SCM
 218 apply_thunk (void *thunk)
 219 {
 220   return scm_apply (SCM_PACK (thunk), SCM_EOL, SCM_EOL);
 221 }
 222
 223 SCM_DEFINE (scm_with_fluids, "with-fluids*", 3, 0, 0,
 224             (SCM fluids, SCM values, SCM thunk),
 225             "Set @var{fluids} to @var{values} temporary, and call @var{thunk}.\n"
 226             "@var{fluids} must be a list of fluids and @var{values} must be the same\n"
 227             "number of their values to be applied.  Each substitution is done\n"
 228             "one after another.  @var{thunk} must be a procedure with no argument.")
 229 #define FUNC_NAME s_scm_with_fluids
 230 {
 231   return scm_internal_with_fluids (fluids, values, apply_thunk, (void *) SCM_UNPACK (thunk));
 232 }
 233 #undef FUNC_NAME
 234
 235 SCM
 236 scm_internal_with_fluids (SCM fluids, SCM values, SCM (*cproc) (), void *cdata)
 237 #define FUNC_NAME "scm_internal_with_fluids"
 238 {
 239   SCM ans;
 240   int flen, vlen;
 241
 242   SCM_VALIDATE_LIST_COPYLEN (1, fluids, flen);
 243   SCM_VALIDATE_LIST_COPYLEN (2, values, vlen);
 244   if (flen != vlen)
 245     scm_out_of_range (s_scm_with_fluids, values);
 246
 247   scm_swap_fluids (fluids, values);
 248   scm_dynwinds = scm_acons (fluids, values, scm_dynwinds);
 249   ans = cproc (cdata);
 250   scm_dynwinds = SCM_CDR (scm_dynwinds);
 251   scm_swap_fluids_reverse (fluids, values);
 252   return ans;
 253 }
 254 #undef FUNC_NAME
 255
 256
 257
 258 void
 259 scm_init_fluids ()
 260 {
 261   scm_tc16_fluid = scm_make_smob_type_mfpe ("fluid", 0,
 262                                            NULL, NULL, print_fluid, NULL);
 263 #include "libguile/fluids.x"
 264 }
 265
 266 /*
 267   Local Variables:
 268   c-file-style: "gnu"
 269   End:
 270 */