libguile/dynstack.h

   1 /* classes: h_files */
   2
   3 #ifndef SCM_DYNSTACK_H
   4 #define SCM_DYNSTACK_H
   5
   6 /* Copyright (C) 2012, 2013 Free Software Foundation, Inc.
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public License
  10  * as published by the Free Software Foundation; either version 3 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This library is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  21  * 02110-1301 USA
  22  */
  23
  24 \f
  25
  26 #include "libguile/__scm.h"
  27 #include "libguile/control.h"
  28
  29 \f
  30
  31 typedef struct
  32 {
  33   scm_t_bits *base;
  34   scm_t_bits *top;
  35   scm_t_bits *limit;
  36 } scm_t_dynstack;
  37
  38 \f
  39
  40 /* Items on the dynstack are preceded by two-word headers, giving the
  41    offset of the preceding item (or 0 if there is none) and the type,
  42    flags, and length of the following dynstack entry, in words.  In
  43    addition, there is a "null header" at the top of the stack,
  44    indicating the length of the previous item, but with a tag of zero.
  45
  46    For example, consider an empty dynstack, with a capacity of 6 words:
  47
  48    +----------+----------+                                           +
  49    |prev=0    |tag=0     |                                           |
  50    +----------+----------+                                           +
  51    ^base                 ^top                                   limit^
  52
  53    Now we evaluate (dynamic-wind enter thunk leave).  That will result
  54    in a dynstack of:
  55
  56                          / the len=2 words     \
  57    +----------+----------+----------+----------+----------+----------+
  58    |prev=0    |tag:len=2 |enter     |leave     |prev=4    |tag=0     |
  59    +----------+----------+----------+----------+----------+----------+
  60    ^base                                                    top,limit^
  61
  62    The tag is a combination of the type of the dynstack item, some flags
  63    associated with the item, and the length of the item.  See
  64    SCM_MAKE_DYNSTACK_TAG below for the details.
  65
  66    This arrangement makes it possible to have variable-length dynstack
  67    items, and yet be able to traverse them forwards or backwards.  */
  68
  69 #define SCM_DYNSTACK_HEADER_LEN 2
  70
  71 #define SCM_DYNSTACK_PREV_OFFSET(top) ((top)[-2])
  72 #define SCM_DYNSTACK_SET_PREV_OFFSET(top, offset) (top)[-2] = (offset)
  73
  74 #define SCM_DYNSTACK_TAG(top) ((top)[-1])
  75 #define SCM_DYNSTACK_SET_TAG(top, tag) (top)[-1] = (tag)
  76
  77 typedef enum {
  78   SCM_DYNSTACK_TYPE_NONE = 0,
  79   SCM_DYNSTACK_TYPE_FRAME,
  80   SCM_DYNSTACK_TYPE_UNWINDER,
  81   SCM_DYNSTACK_TYPE_REWINDER,
  82   SCM_DYNSTACK_TYPE_WITH_FLUID,
  83   SCM_DYNSTACK_TYPE_PROMPT,
  84   SCM_DYNSTACK_TYPE_DYNWIND,
  85 } scm_t_dynstack_item_type;
  86
  87 #define SCM_DYNSTACK_TAG_TYPE_MASK 0xf
  88 #define SCM_DYNSTACK_TAG_FLAGS_MASK 0xf0
  89 #define SCM_DYNSTACK_TAG_FLAGS_SHIFT 4
  90 #define SCM_DYNSTACK_TAG_LEN_SHIFT 8
  91
  92 #define SCM_MAKE_DYNSTACK_TAG(type, flags, len)           \
  93   ((type) | (flags) | ((len) << SCM_DYNSTACK_TAG_LEN_SHIFT))
  94
  95 #define SCM_DYNSTACK_TAG_TYPE(tag)                     \
  96   ((tag) & SCM_DYNSTACK_TAG_TYPE_MASK)
  97 #define SCM_DYNSTACK_TAG_FLAGS(tag)                    \
  98   ((tag) & SCM_DYNSTACK_TAG_FLAGS_MASK)
  99 #define SCM_DYNSTACK_TAG_LEN(tag)                      \
 100   ((tag) >> SCM_DYNSTACK_TAG_LEN_SHIFT)
 101
 102 #define SCM_DYNSTACK_PREV(top)                                          \
 103   (SCM_DYNSTACK_PREV_OFFSET (top)                                       \
 104    ? ((top) - SCM_DYNSTACK_PREV_OFFSET (top)) : NULL)
 105 #define SCM_DYNSTACK_NEXT(top)                                          \
 106   (SCM_DYNSTACK_TAG (top)                                               \
 107    ? ((top) + SCM_DYNSTACK_TAG_LEN (SCM_DYNSTACK_TAG (top))             \
 108       + SCM_DYNSTACK_HEADER_LEN)                                        \
 109    : NULL)
 110
 111 #define SCM_DYNSTACK_FIRST(dynstack) \
 112   ((dynstack)->base + SCM_DYNSTACK_HEADER_LEN)
 113
 114 #define SCM_DYNSTACK_CAPACITY(dynstack) \
 115   ((dynstack)->limit - (dynstack)->base)
 116 #define SCM_DYNSTACK_SPACE(dynstack) \
 117   ((dynstack)->limit - (dynstack)->top)
 118 #define SCM_DYNSTACK_HEIGHT(dynstack) \
 119   ((dynstack)->top - (dynstack)->base)
 120
 121 #define SCM_DYNSTACK_HAS_SPACE(dynstack, n) \
 122   (SCM_DYNSTACK_SPACE (dynstack) >= n + SCM_DYNSTACK_HEADER_LEN)
 123
 124 typedef enum {
 125   SCM_F_DYNSTACK_FRAME_REWINDABLE = (1 << SCM_DYNSTACK_TAG_FLAGS_SHIFT)
 126 } scm_t_dynstack_frame_flags;
 127
 128 typedef enum {
 129   SCM_F_DYNSTACK_WINDER_EXPLICIT = (1 << SCM_DYNSTACK_TAG_FLAGS_SHIFT)
 130 } scm_t_dynstack_winder_flags;
 131
 132 typedef enum {
 133   SCM_F_DYNSTACK_PROMPT_ESCAPE_ONLY = (1 << SCM_DYNSTACK_TAG_FLAGS_SHIFT),
 134   SCM_F_DYNSTACK_PROMPT_PUSH_NARGS = (2 << SCM_DYNSTACK_TAG_FLAGS_SHIFT)
 135 } scm_t_dynstack_prompt_flags;
 136
 137 typedef void (*scm_t_guard) (void *);
 138
 139
 140 \f
 141
 142 /* Pushing and popping entries on the dynamic stack.  */
 143
 144 SCM_INTERNAL void scm_dynstack_push_frame (scm_t_dynstack *,
 145                                            scm_t_dynstack_frame_flags);
 146 SCM_INTERNAL void scm_dynstack_push_rewinder (scm_t_dynstack *,
 147                                               scm_t_dynstack_winder_flags,
 148                                               scm_t_guard, void *);
 149 SCM_INTERNAL void scm_dynstack_push_unwinder (scm_t_dynstack *,
 150                                               scm_t_dynstack_winder_flags,
 151                                               scm_t_guard, void *);
 152 SCM_INTERNAL void scm_dynstack_push_fluid (scm_t_dynstack *,
 153                                            SCM fluid, SCM value,
 154                                            SCM dynamic_state);
 155 SCM_INTERNAL void scm_dynstack_push_prompt (scm_t_dynstack *,
 156                                             scm_t_dynstack_prompt_flags,
 157                                             SCM key,
 158                                             SCM *fp, SCM *sp, scm_t_uint8 *ip,
 159                                             scm_i_jmp_buf *registers);
 160 SCM_INTERNAL void scm_dynstack_push_dynwind (scm_t_dynstack *,
 161                                              SCM enter, SCM leave);
 162
 163 SCM_INTERNAL void scm_dynstack_pop (scm_t_dynstack *);
 164
 165
 166 \f
 167
 168 /* Capturing, winding, and unwinding.  */
 169
 170 SCM_INTERNAL scm_t_dynstack* scm_dynstack_capture_all (scm_t_dynstack *dynstack);
 171 SCM_INTERNAL scm_t_dynstack* scm_dynstack_capture (scm_t_dynstack *dynstack,
 172                                                    scm_t_bits *item);
 173
 174 SCM_INTERNAL void scm_dynstack_wind_1 (scm_t_dynstack *, scm_t_bits *);
 175 SCM_INTERNAL scm_t_bits scm_dynstack_unwind_1 (scm_t_dynstack *);
 176
 177 SCM_INTERNAL void scm_dynstack_wind (scm_t_dynstack *, scm_t_bits *);
 178 SCM_INTERNAL void scm_dynstack_unwind (scm_t_dynstack *, scm_t_bits *);
 179
 180
 181 \f
 182
 183 /* Miscellany.  */
 184
 185 SCM_INTERNAL scm_t_bits* scm_dynstack_unwind_fork (scm_t_dynstack *,
 186                                                    scm_t_dynstack *);
 187
 188 SCM_INTERNAL void scm_dynstack_unwind_frame (scm_t_dynstack *);
 189 SCM_INTERNAL void scm_dynstack_unwind_fluid (scm_t_dynstack *dynstack,
 190                                              SCM dynamic_state);
 191
 192 SCM_INTERNAL scm_t_bits* scm_dynstack_find_prompt (scm_t_dynstack *, SCM,
 193                                                    scm_t_dynstack_prompt_flags *,
 194                                                    SCM **, SCM **, scm_t_uint8 **,
 195                                                    scm_i_jmp_buf **);
 196
 197 SCM_INTERNAL void scm_dynstack_wind_prompt (scm_t_dynstack *, scm_t_bits *,
 198                                             scm_t_ptrdiff, scm_i_jmp_buf *);
 199
 200
 201 #endif  /* SCM_DYNSTACK_H */
 202
 203 /*
 204   Local Variables:
 205   c-file-style: "gnu"
 206   End:
 207 */