1 /* Simple iterators for GDB/Scheme. 2 3 Copyright (C) 2014-2017 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 } 110 111 /* 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 } 224 225 /* 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 } 299 300 /* 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 } 362