libguile/fluids.h

   1 /* classes: h_files */
   2
   3 #ifndef SCM_FLUIDS_H
   4 #define SCM_FLUIDS_H
   5
   6 /* Copyright (C) 1996,2000,2001 Free Software Foundation, Inc.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2, or (at your option)
  11  * any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this software; see the file COPYING.  If not, write to
  20  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  21  * Boston, MA 02111-1307 USA
  22  *
  23  * As a special exception, the Free Software Foundation gives permission
  24  * for additional uses of the text contained in its release of GUILE.
  25  *
  26  * The exception is that, if you link the GUILE library with other files
  27  * to produce an executable, this does not by itself cause the
  28  * resulting executable to be covered by the GNU General Public License.
  29  * Your use of that executable is in no way restricted on account of
  30  * linking the GUILE library code into it.
  31  *
  32  * This exception does not however invalidate any other reasons why
  33  * the executable file might be covered by the GNU General Public License.
  34  *
  35  * This exception applies only to the code released by the
  36  * Free Software Foundation under the name GUILE.  If you copy
  37  * code from other Free Software Foundation releases into a copy of
  38  * GUILE, as the General Public License permits, the exception does
  39  * not apply to the code that you add in this way.  To avoid misleading
  40  * anyone as to the status of such modified files, you must delete
  41  * this exception notice from them.
  42  *
  43  * If you write modifications of your own for GUILE, it is your choice
  44  * whether to permit this exception to apply to your modifications.
  45  * If you do not wish that, delete this exception notice.  */
  46
  47 \f
  48
  49 #include "libguile/__scm.h"
  50 #include "libguile/root.h"
  51 #include "libguile/vectors.h"
  52
  53 /* Fluids.
  54
  55    Fluids are objects of a certain type (a smob) that can hold one SCM
  56    value per dynamic root.  That is, modifications to this value are
  57    only visible to code that executes within the same dynamic root as
  58    the modifying code.  When a new dynamic root is constructed, it
  59    inherits the values from its parent.  Because each thread executes
  60    in its own dynamic root, you can use fluids for thread local
  61    storage.
  62
  63    Each fluid is identified by a small integer.  This integer is used
  64    to index a vector that holds the values of all fluids.  Each root
  65    has its own vector.
  66
  67    Currently, you can't get rid a certain fluid if you don't use it
  68    any longer.  The slot that has been allocated for it in the fluid
  69    vector will not be reused for other fluids.  Therefore, only use
  70    SCM_MAKE_FLUID or its Scheme variant `make-fluid' in initialization
  71    code that is only run once.  Nevertheless, it should be possible to
  72    implement a more lightweight version of fluids on top of this basic
  73    mechanism. */
  74
  75 SCM_API scm_t_bits scm_tc16_fluid;
  76
  77 #define SCM_FLUIDP(x)    (!SCM_IMP (x) && (SCM_CELL_TYPE (x) == scm_tc16_fluid))
  78 #define SCM_FLUID_NUM(x) (SCM_CELL_WORD_1 (x))
  79
  80 /* The fastest way to acces/modify the value of a fluid.  These macros
  81 do no error checking at all.  You should only use them when you know
  82 that the relevant fluid already exists in the current dynamic root.
  83 The easiest way to ensure this is to execute a SCM_FLUID_SET_X in the
  84 topmost root, for example right after SCM_MAKE_FLUID in your
  85 SCM_INIT_MUMBLE routine that gets called from SCM_BOOT_GUILE_1.  The
  86 first argument is the index number of the fluid, obtained via
  87 SCM_FLUID_NUM, not the fluid itself. */
  88
  89 #define SCM_FAST_FLUID_REF(n) (SCM_VELTS(scm_root->fluids)[n])
  90 #define SCM_FAST_FLUID_SET_X(n, val) (SCM_VELTS(scm_root->fluids)[n] = val)
  91
  92 SCM_API SCM scm_make_fluid (void);
  93 SCM_API SCM scm_fluid_p (SCM fl);
  94 SCM_API SCM scm_fluid_ref (SCM fluid);
  95 SCM_API SCM scm_fluid_set_x (SCM fluid, SCM value);
  96
  97 SCM_API SCM scm_c_with_fluids (SCM fluids, SCM vals,
  98                                SCM (*cproc)(void *), void *cdata);
  99 SCM_API SCM scm_c_with_fluid (SCM fluid, SCM val,
 100                               SCM (*cproc)(void *), void *cdata);
 101 SCM_API SCM scm_with_fluids (SCM fluids, SCM vals, SCM thunk);
 102
 103 SCM_API SCM scm_make_initial_fluids (void);
 104 SCM_API void scm_copy_fluids (scm_root_state *);
 105 SCM_API void scm_swap_fluids (SCM fluids, SCM vals);
 106 SCM_API void scm_swap_fluids_reverse (SCM fluids, SCM vals);
 107
 108 SCM_API void scm_init_fluids (void);
 109
 110 #endif  /* SCM_FLUIDS_H */
 111
 112 /*
 113   Local Variables:
 114   c-file-style: "gnu"
 115   End:
 116 */