1 /* obstack.h - object stack macros
2 Copyright (C) 1988-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19 /* Summary:
20
21 All the apparent functions defined here are macros. The idea
22 is that you would use these pre-tested macros to solve a
23 very specific set of problems, and they would run fast.
24 Caution: no side-effects in arguments please!! They may be
25 evaluated MANY times!!
26
27 These macros operate a stack of objects. Each object starts life
28 small, and may grow to maturity. (Consider building a word syllable
29 by syllable.) An object can move while it is growing. Once it has
30 been "finished" it never changes address again. So the "top of the
31 stack" is typically an immature growing object, while the rest of the
32 stack is of mature, fixed size and fixed address objects.
33
34 These routines grab large chunks of memory, using a function you
35 supply, called 'obstack_chunk_alloc'. On occasion, they free chunks,
36 by calling 'obstack_chunk_free'. You must define them and declare
37 them before using any obstack macros.
38
39 Each independent stack is represented by a 'struct obstack'.
40 Each of the obstack macros expects a pointer to such a structure
41 as the first argument.
42
43 One motivation for this package is the problem of growing char strings
44 in symbol tables. Unless you are "fascist pig with a read-only mind"
45 --Gosper's immortal quote from HAKMEM item 154, out of context--you
46 would not like to put any arbitrary upper limit on the length of your
47 symbols.
48
49 In practice this often means you will build many short symbols and a
50 few long symbols. At the time you are reading a symbol you don't know
51 how long it is. One traditional method is to read a symbol into a
52 buffer, realloc()ating the buffer every time you try to read a symbol
53 that is longer than the buffer. This is beaut, but you still will
54 want to copy the symbol from the buffer to a more permanent
55 symbol-table entry say about half the time.
56
57 With obstacks, you can work differently. Use one obstack for all symbol
58 names. As you read a symbol, grow the name in the obstack gradually.
59 When the name is complete, finalize it. Then, if the symbol exists already,
60 free the newly read name.
61
62 The way we do this is to take a large chunk, allocating memory from
63 low addresses. When you want to build a symbol in the chunk you just
64 add chars above the current "high water mark" in the chunk. When you
65 have finished adding chars, because you got to the end of the symbol,
66 you know how long the chars are, and you can create a new object.
67 Mostly the chars will not burst over the highest address of the chunk,
68 because you would typically expect a chunk to be (say) 100 times as
69 long as an average object.
70
71 In case that isn't clear, when we have enough chars to make up
72 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
73 so we just point to it where it lies. No moving of chars is
74 needed and this is the second win: potentially long strings need
75 never be explicitly shuffled. Once an object is formed, it does not
76 change its address during its lifetime.
77
78 When the chars burst over a chunk boundary, we allocate a larger
79 chunk, and then copy the partly formed object from the end of the old
80 chunk to the beginning of the new larger chunk. We then carry on
81 accreting characters to the end of the object as we normally would.
82
83 A special macro is provided to add a single char at a time to a
84 growing object. This allows the use of register variables, which
85 break the ordinary 'growth' macro.
86
87 Summary:
88 We allocate large chunks.
89 We carve out one object at a time from the current chunk.
90 Once carved, an object never moves.
91 We are free to append data of any size to the currently
92 growing object.
93 Exactly one object is growing in an obstack at any one time.
94 You can run one obstack per control block.
95 You may have as many control blocks as you dare.
96 Because of the way we do it, you can "unwind" an obstack
97 back to a previous state. (You may remove objects much
98 as you would with a stack.)
99 */
100
101
102 /* Don't do the contents of this file more than once. */
103
104 #ifndef _OBSTACK_H
105 #define _OBSTACK_H 1
106
107 #ifndef _OBSTACK_INTERFACE_VERSION
108 # define _OBSTACK_INTERFACE_VERSION 2
109 #endif
110
111 #include <stddef.h> /* For size_t and ptrdiff_t. */
112 #include <string.h> /* For __GNU_LIBRARY__, and memcpy. */
113
114 #if _OBSTACK_INTERFACE_VERSION == 1
115 /* For binary compatibility with obstack version 1, which used "int"
116 and "long" for these two types. */
117 # define _OBSTACK_SIZE_T unsigned int
118 # define _CHUNK_SIZE_T unsigned long
119 # define _OBSTACK_CAST(type, expr) ((type) (expr))
120 #else
121 /* Version 2 with sane types, especially for 64-bit hosts. */
122 # define _OBSTACK_SIZE_T size_t
123 # define _CHUNK_SIZE_T size_t
124 # define _OBSTACK_CAST(type, expr) (expr)
125 #endif
126
127 /* If B is the base of an object addressed by P, return the result of
128 aligning P to the next multiple of A + 1. B and P must be of type
129 char *. A + 1 must be a power of 2. */
130
131 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A)))
132
133 /* Similar to __BPTR_ALIGN (B, P, A), except optimize the common case
134 where pointers can be converted to integers, aligned as integers,
135 and converted back again. If ptrdiff_t is narrower than a
136 pointer (e.g., the AS/400), play it safe and compute the alignment
137 relative to B. Otherwise, use the faster strategy of computing the
138 alignment relative to 0. */
139
140 #define __PTR_ALIGN(B, P, A) \
141 (sizeof (ptrdiff_t) < sizeof (void *) ? __BPTR_ALIGN (B, P, A) \
142 : (char *) (((ptrdiff_t) (P) + (A)) & ~(A)))
143
144 #ifndef __attribute_pure__
145 # if defined __GNUC_MINOR__ && __GNUC__ * 1000 + __GNUC_MINOR__ >= 2096
146 # define __attribute_pure__ __attribute__ ((__pure__))
147 # else
148 # define __attribute_pure__
149 # endif
150 #endif
151
152 #ifdef __cplusplus
153 extern "C" {
154 #endif
155
156 struct _obstack_chunk /* Lives at front of each chunk. */
157 {
158 char *limit; /* 1 past end of this chunk */
159 struct _obstack_chunk *prev; /* address of prior chunk or NULL */
160 char contents[4]; /* objects begin here */
161 };
162
163 struct obstack /* control current object in current chunk */
164 {
165 _CHUNK_SIZE_T chunk_size; /* preferred size to allocate chunks in */
166 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
167 char *object_base; /* address of object we are building */
168 char *next_free; /* where to add next char to current object */
169 char *chunk_limit; /* address of char after current chunk */
170 union
171 {
172 _OBSTACK_SIZE_T i;
173 void *p;
174 } temp; /* Temporary for some macros. */
175 _OBSTACK_SIZE_T alignment_mask; /* Mask of alignment for each object. */
176
177 /* These prototypes vary based on 'use_extra_arg'. */
178 union
179 {
180 void *(*plain) (size_t);
181 void *(*extra) (void *, size_t);
182 } chunkfun;
183 union
184 {
185 void (*plain) (void *);
186 void (*extra) (void *, void *);
187 } freefun;
188
189 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */
190 unsigned use_extra_arg : 1; /* chunk alloc/dealloc funcs take extra arg */
191 unsigned maybe_empty_object : 1; /* There is a possibility that the current
192 chunk contains a zero-length object. This
193 prevents freeing the chunk if we allocate
194 a bigger chunk to replace it. */
195 unsigned alloc_failed : 1; /* No longer used, as we now call the failed
196 handler on error, but retained for binary
197 compatibility. */
198 };
199
200 /* Declare the external functions we use; they are in obstack.c. */
201
202 extern void _obstack_newchunk (struct obstack *, _OBSTACK_SIZE_T);
203 extern void _obstack_free (struct obstack *, void *);
204 extern int _obstack_begin (struct obstack *,
205 _OBSTACK_SIZE_T, _OBSTACK_SIZE_T,
206 void *(*) (size_t), void (*) (void *));
207 extern int _obstack_begin_1 (struct obstack *,
208 _OBSTACK_SIZE_T, _OBSTACK_SIZE_T,
209 void *(*) (void *, size_t),
210 void (*) (void *, void *), void *);
211 extern _OBSTACK_SIZE_T _obstack_memory_used (struct obstack *)
212 __attribute_pure__;
213
214
215 /* Error handler called when 'obstack_chunk_alloc' failed to allocate
216 more memory. This can be set to a user defined function which
217 should either abort gracefully or use longjump - but shouldn't
218 return. The default action is to print a message and abort. */
219 extern void (*obstack_alloc_failed_handler) (void);
220
221 /* Exit value used when 'print_and_abort' is used. */
222 extern int obstack_exit_failure;
223
224 /* Pointer to beginning of object being allocated or to be allocated next.
225 Note that this might not be the final address of the object
226 because a new chunk might be needed to hold the final size. */
227
228 #define obstack_base(h) ((void *) (h)->object_base)
229
230 /* Size for allocating ordinary chunks. */
231
232 #define obstack_chunk_size(h) ((h)->chunk_size)
233
234 /* Pointer to next byte not yet allocated in current chunk. */
235
236 #define obstack_next_free(h) ((void *) (h)->next_free)
237
238 /* Mask specifying low bits that should be clear in address of an object. */
239
240 #define obstack_alignment_mask(h) ((h)->alignment_mask)
241
242 /* To prevent prototype warnings provide complete argument list. */
243 #define obstack_init(h) \
244 _obstack_begin ((h), 0, 0, \
245 _OBSTACK_CAST (void *(*) (size_t), obstack_chunk_alloc), \
246 _OBSTACK_CAST (void (*) (void *), obstack_chunk_free))
247
248 #define obstack_begin(h, size) \
249 _obstack_begin ((h), (size), 0, \
250 _OBSTACK_CAST (void *(*) (size_t), obstack_chunk_alloc), \
251 _OBSTACK_CAST (void (*) (void *), obstack_chunk_free))
252
253 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \
254 _obstack_begin ((h), (size), (alignment), \
255 _OBSTACK_CAST (void *(*) (size_t), chunkfun), \
256 _OBSTACK_CAST (void (*) (void *), freefun))
257
258 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
259 _obstack_begin_1 ((h), (size), (alignment), \
260 _OBSTACK_CAST (void *(*) (void *, size_t), chunkfun), \
261 _OBSTACK_CAST (void (*) (void *, void *), freefun), arg)
262
263 #define obstack_chunkfun(h, newchunkfun) \
264 ((void) ((h)->chunkfun.extra = (void *(*) (void *, size_t)) (newchunkfun)))
265
266 #define obstack_freefun(h, newfreefun) \
267 ((void) ((h)->freefun.extra = (void *(*) (void *, void *)) (newfreefun)))
268
269 #define obstack_1grow_fast(h, achar) ((void) (*((h)->next_free)++ = (achar)))
270
271 #define obstack_blank_fast(h, n) ((void) ((h)->next_free += (n)))
272
273 #define obstack_memory_used(h) _obstack_memory_used (h)
274
275 #if defined __GNUC__
276 # if !defined __GNUC_MINOR__ || __GNUC__ * 1000 + __GNUC_MINOR__ < 2008
277 # define __extension__
278 # endif
279
280 /* For GNU C, if not -traditional,
281 we can define these macros to compute all args only once
282 without using a global variable.
283 Also, we can avoid using the 'temp' slot, to make faster code. */
284
285 # define obstack_object_size(OBSTACK) \
286 __extension__ \
287 ({ struct obstack const *__o = (OBSTACK); \
288 (_OBSTACK_SIZE_T) (__o->next_free - __o->object_base); })
289
290 /* The local variable is named __o1 to avoid a shadowed variable
291 warning when invoked from other obstack macros. */
292 # define obstack_room(OBSTACK) \
293 __extension__ \
294 ({ struct obstack const *__o1 = (OBSTACK); \
295 (_OBSTACK_SIZE_T) (__o1->chunk_limit - __o1->next_free); })
296
297 # define obstack_make_room(OBSTACK, length) \
298 __extension__ \
299 ({ struct obstack *__o = (OBSTACK); \
300 _OBSTACK_SIZE_T __len = (length); \
301 if (obstack_room (__o) < __len) \
302 _obstack_newchunk (__o, __len); \
303 (void) 0; })
304
305 # define obstack_empty_p(OBSTACK) \
306 __extension__ \
307 ({ struct obstack const *__o = (OBSTACK); \
308 (__o->chunk->prev == 0 \
309 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \
310 __o->chunk->contents, \
311 __o->alignment_mask)); })
312
313 # define obstack_grow(OBSTACK, where, length) \
314 __extension__ \
315 ({ struct obstack *__o = (OBSTACK); \
316 _OBSTACK_SIZE_T __len = (length); \
317 if (obstack_room (__o) < __len) \
318 _obstack_newchunk (__o, __len); \
319 memcpy (__o->next_free, where, __len); \
320 __o->next_free += __len; \
321 (void) 0; })
322
323 # define obstack_grow0(OBSTACK, where, length) \
324 __extension__ \
325 ({ struct obstack *__o = (OBSTACK); \
326 _OBSTACK_SIZE_T __len = (length); \
327 if (obstack_room (__o) < __len + 1) \
328 _obstack_newchunk (__o, __len + 1); \
329 memcpy (__o->next_free, where, __len); \
330 __o->next_free += __len; \
331 *(__o->next_free)++ = 0; \
332 (void) 0; })
333
334 # define obstack_1grow(OBSTACK, datum) \
335 __extension__ \
336 ({ struct obstack *__o = (OBSTACK); \
337 if (obstack_room (__o) < 1) \
338 _obstack_newchunk (__o, 1); \
339 obstack_1grow_fast (__o, datum); })
340
341 /* These assume that the obstack alignment is good enough for pointers
342 or ints, and that the data added so far to the current object
343 shares that much alignment. */
344
345 # define obstack_ptr_grow(OBSTACK, datum) \
346 __extension__ \
347 ({ struct obstack *__o = (OBSTACK); \
348 if (obstack_room (__o) < sizeof (void *)) \
349 _obstack_newchunk (__o, sizeof (void *)); \
350 obstack_ptr_grow_fast (__o, datum); })
351
352 # define obstack_int_grow(OBSTACK, datum) \
353 __extension__ \
354 ({ struct obstack *__o = (OBSTACK); \
355 if (obstack_room (__o) < sizeof (int)) \
356 _obstack_newchunk (__o, sizeof (int)); \
357 obstack_int_grow_fast (__o, datum); })
358
359 # define obstack_ptr_grow_fast(OBSTACK, aptr) \
360 __extension__ \
361 ({ struct obstack *__o1 = (OBSTACK); \
362 void *__p1 = __o1->next_free; \
363 *(const void **) __p1 = (aptr); \
364 __o1->next_free += sizeof (const void *); \
365 (void) 0; })
366
367 # define obstack_int_grow_fast(OBSTACK, aint) \
368 __extension__ \
369 ({ struct obstack *__o1 = (OBSTACK); \
370 void *__p1 = __o1->next_free; \
371 *(int *) __p1 = (aint); \
372 __o1->next_free += sizeof (int); \
373 (void) 0; })
374
375 # define obstack_blank(OBSTACK, length) \
376 __extension__ \
377 ({ struct obstack *__o = (OBSTACK); \
378 _OBSTACK_SIZE_T __len = (length); \
379 if (obstack_room (__o) < __len) \
380 _obstack_newchunk (__o, __len); \
381 obstack_blank_fast (__o, __len); })
382
383 # define obstack_alloc(OBSTACK, length) \
384 __extension__ \
385 ({ struct obstack *__h = (OBSTACK); \
386 obstack_blank (__h, (length)); \
387 obstack_finish (__h); })
388
389 # define obstack_copy(OBSTACK, where, length) \
390 __extension__ \
391 ({ struct obstack *__h = (OBSTACK); \
392 obstack_grow (__h, (where), (length)); \
393 obstack_finish (__h); })
394
395 # define obstack_copy0(OBSTACK, where, length) \
396 __extension__ \
397 ({ struct obstack *__h = (OBSTACK); \
398 obstack_grow0 (__h, (where), (length)); \
399 obstack_finish (__h); })
400
401 /* The local variable is named __o1 to avoid a shadowed variable
402 warning when invoked from other obstack macros, typically obstack_free. */
403 # define obstack_finish(OBSTACK) \
404 __extension__ \
405 ({ struct obstack *__o1 = (OBSTACK); \
406 void *__value = (void *) __o1->object_base; \
407 if (__o1->next_free == __value) \
408 __o1->maybe_empty_object = 1; \
409 __o1->next_free \
410 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \
411 __o1->alignment_mask); \
412 if ((size_t) (__o1->next_free - (char *) __o1->chunk) \
413 > (size_t) (__o1->chunk_limit - (char *) __o1->chunk)) \
414 __o1->next_free = __o1->chunk_limit; \
415 __o1->object_base = __o1->next_free; \
416 __value; })
417
418 # define obstack_free(OBSTACK, OBJ) \
419 __extension__ \
420 ({ struct obstack *__o = (OBSTACK); \
421 void *__obj = (void *) (OBJ); \
422 if (__obj > (void *) __o->chunk && __obj < (void *) __o->chunk_limit) \
423 __o->next_free = __o->object_base = (char *) __obj; \
424 else \
425 _obstack_free (__o, __obj); })
426
427 #else /* not __GNUC__ */
428
429 # define obstack_object_size(h) \
430 ((_OBSTACK_SIZE_T) ((h)->next_free - (h)->object_base))
431
432 # define obstack_room(h) \
433 ((_OBSTACK_SIZE_T) ((h)->chunk_limit - (h)->next_free))
434
435 # define obstack_empty_p(h) \
436 ((h)->chunk->prev == 0 \
437 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \
438 (h)->chunk->contents, \
439 (h)->alignment_mask))
440
441 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
442 so that we can avoid having void expressions
443 in the arms of the conditional expression.
444 Casting the third operand to void was tried before,
445 but some compilers won't accept it. */
446
447 # define obstack_make_room(h, length) \
448 ((h)->temp.i = (length), \
449 ((obstack_room (h) < (h)->temp.i) \
450 ? (_obstack_newchunk (h, (h)->temp.i), 0) : 0), \
451 (void) 0)
452
453 # define obstack_grow(h, where, length) \
454 ((h)->temp.i = (length), \
455 ((obstack_room (h) < (h)->temp.i) \
456 ? (_obstack_newchunk ((h), (h)->temp.i), 0) : 0), \
457 memcpy ((h)->next_free, where, (h)->temp.i), \
458 (h)->next_free += (h)->temp.i, \
459 (void) 0)
460
461 # define obstack_grow0(h, where, length) \
462 ((h)->temp.i = (length), \
463 ((obstack_room (h) < (h)->temp.i + 1) \
464 ? (_obstack_newchunk ((h), (h)->temp.i + 1), 0) : 0), \
465 memcpy ((h)->next_free, where, (h)->temp.i), \
466 (h)->next_free += (h)->temp.i, \
467 *((h)->next_free)++ = 0, \
468 (void) 0)
469
470 # define obstack_1grow(h, datum) \
471 (((obstack_room (h) < 1) \
472 ? (_obstack_newchunk ((h), 1), 0) : 0), \
473 obstack_1grow_fast (h, datum))
474
475 # define obstack_ptr_grow(h, datum) \
476 (((obstack_room (h) < sizeof (char *)) \
477 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \
478 obstack_ptr_grow_fast (h, datum))
479
480 # define obstack_int_grow(h, datum) \
481 (((obstack_room (h) < sizeof (int)) \
482 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \
483 obstack_int_grow_fast (h, datum))
484
485 # define obstack_ptr_grow_fast(h, aptr) \
486 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr), \
487 (void) 0)
488
489 # define obstack_int_grow_fast(h, aint) \
490 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint), \
491 (void) 0)
492
493 # define obstack_blank(h, length) \
494 ((h)->temp.i = (length), \
495 ((obstack_room (h) < (h)->temp.i) \
496 ? (_obstack_newchunk ((h), (h)->temp.i), 0) : 0), \
497 obstack_blank_fast (h, (h)->temp.i))
498
499 # define obstack_alloc(h, length) \
500 (obstack_blank ((h), (length)), obstack_finish ((h)))
501
502 # define obstack_copy(h, where, length) \
503 (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
504
505 # define obstack_copy0(h, where, length) \
506 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
507
508 # define obstack_finish(h) \
509 (((h)->next_free == (h)->object_base \
510 ? (((h)->maybe_empty_object = 1), 0) \
511 : 0), \
512 (h)->temp.p = (h)->object_base, \
513 (h)->next_free \
514 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \
515 (h)->alignment_mask), \
516 (((size_t) ((h)->next_free - (char *) (h)->chunk) \
517 > (size_t) ((h)->chunk_limit - (char *) (h)->chunk)) \
518 ? ((h)->next_free = (h)->chunk_limit) : 0), \
519 (h)->object_base = (h)->next_free, \
520 (h)->temp.p)
521
522 # define obstack_free(h, obj) \
523 ((h)->temp.p = (void *) (obj), \
524 (((h)->temp.p > (void *) (h)->chunk \
525 && (h)->temp.p < (void *) (h)->chunk_limit) \
526 ? (void) ((h)->next_free = (h)->object_base = (char *) (h)->temp.p) \
527 : _obstack_free ((h), (h)->temp.p)))
528
529 #endif /* not __GNUC__ */
530
531 #ifdef __cplusplus
532 } /* C++ */
533 #endif
534
535 #endif /* _OBSTACK_H */