libguile/fluids.c

   1 /*      Copyright (C) 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
  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 #t iff @var{obj} is a fluid; otherwise, return #f.")
 142 #define FUNC_NAME s_scm_fluid_p
 143 {
 144   return SCM_BOOL(SCM_FLUIDP (obj));
 145 }
 146 #undef FUNC_NAME
 147
 148 SCM_DEFINE (scm_fluid_ref, "fluid-ref", 1, 0, 0,
 149             (SCM fluid),
 150             "Return the value associated with @var{fluid} in the current dynamic root.\n"
 151             "If @var{fluid} has not been set, then this returns #f.")
 152 #define FUNC_NAME s_scm_fluid_ref
 153 {
 154   int n;
 155
 156   SCM_VALIDATE_FLUID (1, fluid);
 157
 158   n = SCM_FLUID_NUM (fluid);
 159
 160   if (SCM_VECTOR_LENGTH (scm_root->fluids) <= n)
 161     grow_fluids (scm_root, n+1);
 162   return SCM_VELTS (scm_root->fluids)[n];
 163 }
 164 #undef FUNC_NAME
 165
 166 SCM_DEFINE (scm_fluid_set_x, "fluid-set!", 2, 0, 0,
 167             (SCM fluid, SCM value),
 168             "Set the value associated with @var{fluid} in the current dynamic root.")
 169 #define FUNC_NAME s_scm_fluid_set_x
 170 {
 171   int n;
 172
 173   SCM_VALIDATE_FLUID (1, fluid);
 174   n = SCM_FLUID_NUM (fluid);
 175
 176   if (SCM_VECTOR_LENGTH (scm_root->fluids) <= n)
 177     grow_fluids (scm_root, n+1);
 178   SCM_VELTS (scm_root->fluids)[n] = value;
 179   return SCM_UNSPECIFIED;
 180 }
 181 #undef FUNC_NAME
 182
 183 void
 184 scm_swap_fluids (SCM fluids, SCM vals)
 185 {
 186   while (SCM_NIMP (fluids))
 187     {
 188       SCM fl = SCM_CAR (fluids);
 189       SCM old_val = scm_fluid_ref (fl);
 190       scm_fluid_set_x (fl, SCM_CAR (vals));
 191       SCM_SETCAR (vals, old_val);
 192       fluids = SCM_CDR (fluids);
 193       vals = SCM_CDR (vals);
 194     }
 195 }
 196
 197 /* Swap the fluid values in reverse order.  This is important when the
 198 same fluid appears multiple times in the fluids list. */
 199
 200 void
 201 scm_swap_fluids_reverse (SCM fluids, SCM vals)
 202 {
 203   if (SCM_NIMP (fluids))
 204     {
 205       SCM fl, old_val;
 206
 207       scm_swap_fluids_reverse (SCM_CDR (fluids), SCM_CDR (vals));
 208       fl = SCM_CAR (fluids);
 209       old_val = scm_fluid_ref (fl);
 210       scm_fluid_set_x (fl, SCM_CAR (vals));
 211       SCM_SETCAR (vals, old_val);
 212     }
 213 }
 214
 215
 216 static SCM
 217 apply_thunk (void *thunk)
 218 {
 219   return scm_apply (SCM_PACK (thunk), SCM_EOL, SCM_EOL);
 220 }
 221
 222 SCM_DEFINE (scm_with_fluids, "with-fluids*", 3, 0, 0,
 223             (SCM fluids, SCM values, SCM thunk),
 224             "Set @var{fluids} to @var{values} temporary, and call @var{thunk}.\n"
 225             "@var{fluids} must be a list of fluids and @var{values} must be the same\n"
 226             "number of their values to be applied.  Each substitution is done\n"
 227             "one after another.  @var{thunk} must be a procedure with no argument.")
 228 #define FUNC_NAME s_scm_with_fluids
 229 {
 230   return scm_internal_with_fluids (fluids, values, apply_thunk, (void *) SCM_UNPACK (thunk));
 231 }
 232 #undef FUNC_NAME
 233
 234 SCM
 235 scm_internal_with_fluids (SCM fluids, SCM values, SCM (*cproc) (), void *cdata)
 236 #define FUNC_NAME "scm_internal_with_fluids"
 237 {
 238   SCM ans;
 239   int flen, vlen;
 240
 241   SCM_VALIDATE_LIST_COPYLEN (1, fluids, flen);
 242   SCM_VALIDATE_LIST_COPYLEN (2, values, vlen);
 243   if (flen != vlen)
 244     scm_out_of_range (s_scm_with_fluids, values);
 245
 246   scm_swap_fluids (fluids, values);
 247   scm_dynwinds = scm_acons (fluids, values, scm_dynwinds);
 248   ans = cproc (cdata);
 249   scm_dynwinds = SCM_CDR (scm_dynwinds);
 250   scm_swap_fluids_reverse (fluids, values);
 251   return ans;
 252 }
 253 #undef FUNC_NAME
 254
 255
 256
 257 void
 258 scm_init_fluids ()
 259 {
 260   scm_tc16_fluid = scm_make_smob_type ("fluid", 0);
 261   scm_set_smob_print (scm_tc16_fluid, fluid_print);
 262 #ifndef SCM_MAGIC_SNARFER
 263 #include "libguile/fluids.x"
 264 #endif
 265 }
 266
 267 /*
 268   Local Variables:
 269   c-file-style: "gnu"
 270   End:
 271 */