gdb/guile/scm-iterator.c

   1 /* Simple iterators for GDB/Scheme.
   2
   3    Copyright (C) 2014-2018 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 /* See README file in this directory for implementation notes, coding
  21    conventions, et.al.  */
  22
  23 /* These are *simple* iterators, used to implement iterating over a collection
  24    of objects.  They are implemented as a smob containing three objects:
  25
  26    1) the object being iterated over,
  27    2) an object to record the progress of the iteration,
  28    3) a procedure of one argument (the iterator object) that returns the next
  29       object in the iteration or a pre-determined end marker.
  30
  31    Simple example:
  32
  33    (define-public (make-list-iterator l end-marker)
  34      "Return a <gdb:iterator> object for a list."
  35      (let ((next! (lambda (iter)
  36                     (let ((l (iterator-progress iter)))
  37                       (if (eq? l '())
  38                           end-marker
  39                           (begin
  40                             (set-iterator-progress! iter (cdr l))
  41                             (car l)))))))
  42        (make-iterator l l next!)))
  43
  44    (define l '(1 2))
  45    (define i (make-list-iterator l #:eoi))
  46    (iterator-next! i) -> 1
  47    (iterator-next! i) -> 2
  48    (iterator-next! i) -> #:eoi
  49
  50    There is SRFI 41, Streams.  We might support that too eventually (not with
  51    this interface of course).  */
  52
  53 #include "defs.h"
  54 #include "guile-internal.h"
  55
  56 /* A smob for iterating over something.
  57    Typically this is used when computing a list of everything is
  58    too expensive.
  59    The typedef for this struct is in guile-internal.h.  */
  60
  61 struct _iterator_smob
  62 {
  63   /* This always appears first.  */
  64   gdb_smob base;
  65
  66   /* The object being iterated over.  */
  67   SCM object;
  68
  69   /* An arbitrary object describing the progress of the iteration.
  70      This is used by next_x to track progress.  */
  71   SCM progress;
  72
  73   /* A procedure of one argument, the iterator.
  74      It returns the next object in the iteration.
  75      How to signal "end of iteration" is up to next_x.  */
  76   SCM next_x;
  77 };
  78
  79 static const char iterator_smob_name[] = "gdb:iterator";
  80
  81 /* The tag Guile knows the iterator smob by.  */
  82 static scm_t_bits iterator_smob_tag;
  83
  84 /* A unique-enough marker to denote "end of iteration".  */
  85 static SCM end_of_iteration;
  86
  87 const char *
  88 itscm_iterator_smob_name (void)
  89 {
  90   return iterator_smob_name;
  91 }
  92
  93 SCM
  94 itscm_iterator_smob_object (iterator_smob *i_smob)
  95 {
  96   return i_smob->object;
  97 }
  98
  99 SCM
 100 itscm_iterator_smob_progress (iterator_smob *i_smob)
 101 {
 102   return i_smob->progress;
 103 }
 104
 105 void
 106 itscm_set_iterator_smob_progress_x (iterator_smob *i_smob, SCM progress)
 107 {
 108   i_smob->progress = progress;
 109 }
 110 \f
 111 /* Administrivia for iterator smobs.  */
 112
 113 /* The smob "print" function for <gdb:iterator>.  */
 114
 115 static int
 116 itscm_print_iterator_smob (SCM self, SCM port, scm_print_state *pstate)
 117 {
 118   iterator_smob *i_smob = (iterator_smob *) SCM_SMOB_DATA (self);
 119
 120   gdbscm_printf (port, "#<%s ", iterator_smob_name);
 121   scm_write (i_smob->object, port);
 122   scm_puts (" ", port);
 123   scm_write (i_smob->progress, port);
 124   scm_puts (" ", port);
 125   scm_write (i_smob->next_x, port);
 126   scm_puts (">", port);
 127
 128   scm_remember_upto_here_1 (self);
 129
 130   /* Non-zero means success.  */
 131   return 1;
 132 }
 133
 134 /* Low level routine to make a <gdb:iterator> object.
 135    Caller must verify correctness of arguments.
 136    No exceptions are thrown.  */
 137
 138 static SCM
 139 itscm_make_iterator_smob (SCM object, SCM progress, SCM next)
 140 {
 141   iterator_smob *i_smob = (iterator_smob *)
 142     scm_gc_malloc (sizeof (iterator_smob), iterator_smob_name);
 143   SCM i_scm;
 144
 145   i_smob->object = object;
 146   i_smob->progress = progress;
 147   i_smob->next_x = next;
 148   i_scm = scm_new_smob (iterator_smob_tag, (scm_t_bits) i_smob);
 149   gdbscm_init_gsmob (&i_smob->base);
 150
 151   return i_scm;
 152 }
 153
 154 /* (make-iterator object object procedure) -> <gdb:iterator> */
 155
 156 SCM
 157 gdbscm_make_iterator (SCM object, SCM progress, SCM next)
 158 {
 159   SCM i_scm;
 160
 161   SCM_ASSERT_TYPE (gdbscm_is_procedure (next), next, SCM_ARG3, FUNC_NAME,
 162                    _("procedure"));
 163
 164   i_scm = itscm_make_iterator_smob (object, progress, next);
 165
 166   return i_scm;
 167 }
 168
 169 /* Return non-zero if SCM is a <gdb:iterator> object.  */
 170
 171 int
 172 itscm_is_iterator (SCM scm)
 173 {
 174   return SCM_SMOB_PREDICATE (iterator_smob_tag, scm);
 175 }
 176
 177 /* (iterator? object) -> boolean */
 178
 179 static SCM
 180 gdbscm_iterator_p (SCM scm)
 181 {
 182   return scm_from_bool (itscm_is_iterator (scm));
 183 }
 184
 185 /* (end-of-iteration) -> an "end-of-iteration" marker
 186    We rely on this not being used as a data result of an iterator.  */
 187
 188 SCM
 189 gdbscm_end_of_iteration (void)
 190 {
 191   return end_of_iteration;
 192 }
 193
 194 /* Return non-zero if OBJ is the end-of-iteration marker.  */
 195
 196 int
 197 itscm_is_end_of_iteration (SCM obj)
 198 {
 199   return scm_is_eq (obj, end_of_iteration);
 200 }
 201
 202 /* (end-of-iteration? obj) -> boolean */
 203
 204 static SCM
 205 gdbscm_end_of_iteration_p (SCM obj)
 206 {
 207   return scm_from_bool (itscm_is_end_of_iteration (obj));
 208 }
 209
 210 /* Call the next! method on ITER, which must be a <gdb:iterator> object.
 211    Returns a <gdb:exception> object if an exception is thrown.
 212    OK_EXCPS is passed to gdbscm_safe_call_1.  */
 213
 214 SCM
 215 itscm_safe_call_next_x (SCM iter, excp_matcher_func *ok_excps)
 216 {
 217   iterator_smob *i_smob;
 218
 219   gdb_assert (itscm_is_iterator (iter));
 220
 221   i_smob = (iterator_smob *) SCM_SMOB_DATA (iter);
 222   return gdbscm_safe_call_1 (i_smob->next_x, iter, ok_excps);
 223 }
 224 \f
 225 /* Iterator methods.  */
 226
 227 /* Returns the <gdb:iterator> smob in SELF.
 228    Throws an exception if SELF is not an iterator smob.  */
 229
 230 SCM
 231 itscm_get_iterator_arg_unsafe (SCM self, int arg_pos, const char *func_name)
 232 {
 233   SCM_ASSERT_TYPE (itscm_is_iterator (self), self, arg_pos, func_name,
 234                    iterator_smob_name);
 235
 236   return self;
 237 }
 238
 239 /* (iterator-object <gdb:iterator>) -> object */
 240
 241 static SCM
 242 gdbscm_iterator_object (SCM self)
 243 {
 244   SCM i_scm;
 245   iterator_smob *i_smob;
 246
 247   i_scm = itscm_get_iterator_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
 248   i_smob = (iterator_smob *) SCM_SMOB_DATA (i_scm);
 249
 250   return i_smob->object;
 251 }
 252
 253 /* (iterator-progress <gdb:iterator>) -> object */
 254
 255 static SCM
 256 gdbscm_iterator_progress (SCM self)
 257 {
 258   SCM i_scm;
 259   iterator_smob *i_smob;
 260
 261   i_scm = itscm_get_iterator_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
 262   i_smob = (iterator_smob *) SCM_SMOB_DATA (i_scm);
 263
 264   return i_smob->progress;
 265 }
 266
 267 /* (set-iterator-progress! <gdb:iterator> object) -> unspecified */
 268
 269 static SCM
 270 gdbscm_set_iterator_progress_x (SCM self, SCM value)
 271 {
 272   SCM i_scm;
 273   iterator_smob *i_smob;
 274
 275   i_scm = itscm_get_iterator_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
 276   i_smob = (iterator_smob *) SCM_SMOB_DATA (i_scm);
 277
 278   i_smob->progress = value;
 279   return SCM_UNSPECIFIED;
 280 }
 281
 282 /* (iterator-next! <gdb:iterator>) -> object
 283    The result is the next value in the iteration or some "end" marker.
 284    It is up to each iterator's next! function to specify what its end
 285    marker is.  */
 286
 287 static SCM
 288 gdbscm_iterator_next_x (SCM self)
 289 {
 290   SCM i_scm;
 291   iterator_smob *i_smob;
 292
 293   i_scm = itscm_get_iterator_arg_unsafe (self, SCM_ARG1, FUNC_NAME);
 294   i_smob = (iterator_smob *) SCM_SMOB_DATA (i_scm);
 295   /* We leave type-checking of the procedure to gdbscm_safe_call_1.  */
 296
 297   return gdbscm_safe_call_1 (i_smob->next_x, self, NULL);
 298 }
 299 \f
 300 /* Initialize the Scheme iterator code.  */
 301
 302 static const scheme_function iterator_functions[] =
 303 {
 304   { "make-iterator", 3, 0, 0, as_a_scm_t_subr (gdbscm_make_iterator),
 305     "\
 306 Create a <gdb:iterator> object.\n\
 307 \n\
 308   Arguments: object progress next!\n\
 309     object:   The object to iterate over.\n\
 310     progress: An object to use to track progress of the iteration.\n\
 311     next!:    A procedure of one argument, the iterator.\n\
 312       Returns the next element in the iteration or an implementation-chosen\n\
 313       value to signify iteration is complete.\n\
 314       By convention end-of-iteration should be marked with (end-of-iteration)\n\
 315       from module (gdb iterator)." },
 316
 317   { "iterator?", 1, 0, 0, as_a_scm_t_subr (gdbscm_iterator_p),
 318     "\
 319 Return #t if the object is a <gdb:iterator> object." },
 320
 321   { "iterator-object", 1, 0, 0, as_a_scm_t_subr (gdbscm_iterator_object),
 322     "\
 323 Return the object being iterated over." },
 324
 325   { "iterator-progress", 1, 0, 0, as_a_scm_t_subr (gdbscm_iterator_progress),
 326     "\
 327 Return the progress object of the iterator." },
 328
 329   { "set-iterator-progress!", 2, 0, 0,
 330     as_a_scm_t_subr (gdbscm_set_iterator_progress_x),
 331     "\
 332 Set the progress object of the iterator." },
 333
 334   { "iterator-next!", 1, 0, 0, as_a_scm_t_subr (gdbscm_iterator_next_x),
 335     "\
 336 Invoke the next! procedure of the iterator and return its result." },
 337
 338   { "end-of-iteration", 0, 0, 0, as_a_scm_t_subr (gdbscm_end_of_iteration),
 339     "\
 340 Return the end-of-iteration marker." },
 341
 342   { "end-of-iteration?", 1, 0, 0, as_a_scm_t_subr (gdbscm_end_of_iteration_p),
 343     "\
 344 Return #t if the object is the end-of-iteration marker." },
 345
 346   END_FUNCTIONS
 347 };
 348
 349 void
 350 gdbscm_initialize_iterators (void)
 351 {
 352   iterator_smob_tag = gdbscm_make_smob_type (iterator_smob_name,
 353                                              sizeof (iterator_smob));
 354   scm_set_smob_print (iterator_smob_tag, itscm_print_iterator_smob);
 355
 356   gdbscm_define_functions (iterator_functions, 1);
 357
 358   /* We can make this more unique if it's necessary,
 359      but this is good enough for now.  */
 360   end_of_iteration = scm_from_latin1_keyword ("end-of-iteration");
 361 }