libguile/fluids.c

   1 /* Copyright (C) 1996,1997,2000,2001 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 scm_bits_t scm_tc16_fluid;
  60
  61 SCM
  62 scm_make_initial_fluids ()
  63 {
  64   return scm_c_make_vector (INITIAL_FLUIDS, SCM_BOOL_F);
  65 }
  66
  67 static void
  68 grow_fluids (scm_root_state *root_state, int new_length)
  69 {
  70   SCM old_fluids, new_fluids;
  71   int old_length, i;
  72
  73   old_fluids = root_state->fluids;
  74   old_length = SCM_VECTOR_LENGTH (old_fluids);
  75   new_fluids = scm_c_make_vector (new_length, SCM_BOOL_F);
  76   i = 0;
  77   while (i < old_length)
  78     {
  79       SCM_VELTS(new_fluids)[i] = SCM_VELTS(old_fluids)[i];
  80       i++;
  81     }
  82   while (i < new_length)
  83     {
  84       SCM_VELTS(new_fluids)[i] = SCM_BOOL_F;
  85       i++;
  86     }
  87
  88   root_state->fluids = new_fluids;
  89 }
  90
  91 void
  92 scm_copy_fluids (scm_root_state *root_state)
  93 {
  94   grow_fluids (root_state, SCM_VECTOR_LENGTH (root_state->fluids));
  95 }
  96
  97 static int
  98 fluid_print (SCM exp, SCM port, scm_print_state *pstate)
  99 {
 100   scm_puts ("#<fluid ", port);
 101   scm_intprint ((int) SCM_FLUID_NUM (exp), 10, port);
 102   scm_putc ('>', port);
 103   return 1;
 104 }
 105
 106 static int
 107 next_fluid_num ()
 108 {
 109   int n;
 110 #ifdef USE_THREADS
 111   SCM_THREAD_CRITICAL_SECTION_START;
 112 #endif
 113   n = n_fluids++;
 114 #ifdef USE_THREADS
 115   SCM_THREAD_CRITICAL_SECTION_END;
 116 #endif
 117   return n;
 118 }
 119
 120 SCM_DEFINE (scm_make_fluid, "make-fluid", 0, 0, 0,
 121             (),
 122             "Return a newly created fluid.\n"
 123             "Fluids are objects of a certain type (a smob) that can hold one SCM\n"
 124             "value per dynamic root.  That is, modifications to this value are\n"
 125             "only visible to code that executes within the same dynamic root as\n"
 126             "the modifying code.  When a new dynamic root is constructed, it\n"
 127             "inherits the values from its parent.  Because each thread executes\n"
 128             "in its own dynamic root, you can use fluids for thread local storage.")
 129 #define FUNC_NAME s_scm_make_fluid
 130 {
 131   int n;
 132
 133   SCM_DEFER_INTS;
 134   n = next_fluid_num ();
 135   SCM_RETURN_NEWSMOB (scm_tc16_fluid, n);
 136 }
 137 #undef FUNC_NAME
 138
 139 SCM_DEFINE (scm_fluid_p, "fluid?", 1, 0, 0,
 140             (SCM obj),
 141             "Return @code{#t} iff @var{obj} is a fluid; otherwise, return\n"
 142             "@code{#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\n"
 152             "dynamic root.  If @var{fluid} has not been set, then return\n"
 153             "@code{#f}.")
 154 #define FUNC_NAME s_scm_fluid_ref
 155 {
 156   int n;
 157
 158   SCM_VALIDATE_FLUID (1, fluid);
 159
 160   n = SCM_FLUID_NUM (fluid);
 161
 162   if (SCM_VECTOR_LENGTH (scm_root->fluids) <= n)
 163     grow_fluids (scm_root, n+1);
 164   return SCM_VELTS (scm_root->fluids)[n];
 165 }
 166 #undef FUNC_NAME
 167
 168 SCM_DEFINE (scm_fluid_set_x, "fluid-set!", 2, 0, 0,
 169             (SCM fluid, SCM value),
 170             "Set the value associated with @var{fluid} in the current dynamic root.")
 171 #define FUNC_NAME s_scm_fluid_set_x
 172 {
 173   int n;
 174
 175   SCM_VALIDATE_FLUID (1, fluid);
 176   n = SCM_FLUID_NUM (fluid);
 177
 178   if (SCM_VECTOR_LENGTH (scm_root->fluids) <= n)
 179     grow_fluids (scm_root, n+1);
 180   SCM_VELTS (scm_root->fluids)[n] = value;
 181   return SCM_UNSPECIFIED;
 182 }
 183 #undef FUNC_NAME
 184
 185 void
 186 scm_swap_fluids (SCM fluids, SCM vals)
 187 {
 188   while (!SCM_NULLP (fluids))
 189     {
 190       SCM fl = SCM_CAR (fluids);
 191       SCM old_val = scm_fluid_ref (fl);
 192       scm_fluid_set_x (fl, SCM_CAR (vals));
 193       SCM_SETCAR (vals, old_val);
 194       fluids = SCM_CDR (fluids);
 195       vals = SCM_CDR (vals);
 196     }
 197 }
 198
 199 /* Swap the fluid values in reverse order.  This is important when the
 200 same fluid appears multiple times in the fluids list. */
 201
 202 void
 203 scm_swap_fluids_reverse (SCM fluids, SCM vals)
 204 {
 205   if (!SCM_NULLP (fluids))
 206     {
 207       SCM fl, old_val;
 208
 209       scm_swap_fluids_reverse (SCM_CDR (fluids), SCM_CDR (vals));
 210       fl = SCM_CAR (fluids);
 211       old_val = scm_fluid_ref (fl);
 212       scm_fluid_set_x (fl, SCM_CAR (vals));
 213       SCM_SETCAR (vals, old_val);
 214     }
 215 }
 216
 217
 218 static SCM
 219 apply_thunk (void *thunk)
 220 {
 221   return scm_apply (SCM_PACK (thunk), SCM_EOL, SCM_EOL);
 222 }
 223
 224 SCM_DEFINE (scm_with_fluids, "with-fluids*", 3, 0, 0,
 225             (SCM fluids, SCM values, SCM thunk),
 226             "Set @var{fluids} to @var{values} temporary, and call @var{thunk}.\n"
 227             "@var{fluids} must be a list of fluids and @var{values} must be the same\n"
 228             "number of their values to be applied.  Each substitution is done\n"
 229             "one after another.  @var{thunk} must be a procedure with no argument.")
 230 #define FUNC_NAME s_scm_with_fluids
 231 {
 232   return scm_internal_with_fluids (fluids, values, apply_thunk, (void *) SCM_UNPACK (thunk));
 233 }
 234 #undef FUNC_NAME
 235
 236 SCM
 237 scm_internal_with_fluids (SCM fluids, SCM values, SCM (*cproc) (), void *cdata)
 238 #define FUNC_NAME "scm_internal_with_fluids"
 239 {
 240   SCM ans;
 241   int flen, vlen;
 242
 243   SCM_VALIDATE_LIST_COPYLEN (1, fluids, flen);
 244   SCM_VALIDATE_LIST_COPYLEN (2, values, vlen);
 245   if (flen != vlen)
 246     scm_out_of_range (s_scm_with_fluids, values);
 247
 248   scm_swap_fluids (fluids, values);
 249   scm_dynwinds = scm_acons (fluids, values, scm_dynwinds);
 250   ans = cproc (cdata);
 251   scm_dynwinds = SCM_CDR (scm_dynwinds);
 252   scm_swap_fluids_reverse (fluids, values);
 253   return ans;
 254 }
 255 #undef FUNC_NAME
 256
 257
 258
 259 void
 260 scm_init_fluids ()
 261 {
 262   scm_tc16_fluid = scm_make_smob_type ("fluid", 0);
 263   scm_set_smob_print (scm_tc16_fluid, fluid_print);
 264 #ifndef SCM_MAGIC_SNARFER
 265 #include "libguile/fluids.x"
 266 #endif
 267 }
 268
 269 /*
 270   Local Variables:
 271   c-file-style: "gnu"
 272   End:
 273 */