1 /* obstack.h - object stack macros
2 Copyright (C) 1988-1994, 1996-1999, 2003-2006, 2009-2011 Free Software
4 This file is part of the GNU C Library.
6 This program is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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!!
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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
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.)
102 /* Don't do the contents of this file more than once. */
107 /* We need the type of a pointer subtraction. If __PTRDIFF_TYPE__ is
108 defined, as with GNU C, use that; that way we don't pollute the
109 namespace with <stddef.h>'s symbols. Otherwise, include <stddef.h>
110 and use ptrdiff_t. */
112 #ifdef __PTRDIFF_TYPE__
113 # define PTR_INT_TYPE __PTRDIFF_TYPE__
116 # define PTR_INT_TYPE ptrdiff_t
119 /* If B is the base of an object addressed by P, return the result of
120 aligning P to the next multiple of A + 1. B and P must be of type
121 char *. A + 1 must be a power of 2. */
123 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A)))
125 /* Similiar to _BPTR_ALIGN (B, P, A), except optimize the common case
126 where pointers can be converted to integers, aligned as integers,
127 and converted back again. If PTR_INT_TYPE is narrower than a
128 pointer (e.g., the AS/400), play it safe and compute the alignment
129 relative to B. Otherwise, use the faster strategy of computing the
130 alignment relative to 0. */
132 #define __PTR_ALIGN(B, P, A) \
133 __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \
142 struct _obstack_chunk /* Lives at front of each chunk. */
144 char *limit; /* 1 past end of this chunk */
145 struct _obstack_chunk *prev; /* address of prior chunk or NULL */
146 char contents[4]; /* objects begin here */
149 struct obstack /* control current object in current chunk */
151 long chunk_size; /* preferred size to allocate chunks in */
152 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
153 char *object_base; /* address of object we are building */
154 char *next_free; /* where to add next char to current object */
155 char *chunk_limit; /* address of char after current chunk */
158 PTR_INT_TYPE tempint;
160 } temp; /* Temporary for some macros. */
161 int alignment_mask; /* Mask of alignment for each object. */
162 /* These prototypes vary based on `use_extra_arg', and we use
163 casts to the prototypeless function type in all assignments,
164 but having prototypes here quiets -Wstrict-prototypes. */
165 struct _obstack_chunk *(*chunkfun) (void *, long);
166 void (*freefun) (void *, struct _obstack_chunk *);
167 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */
168 unsigned use_extra_arg:1; /* chunk alloc/dealloc funcs take extra arg */
169 unsigned maybe_empty_object:1;/* There is a possibility that the current
170 chunk contains a zero-length object. This
171 prevents freeing the chunk if we allocate
172 a bigger chunk to replace it. */
173 unsigned alloc_failed:1; /* No longer used, as we now call the failed
174 handler on error, but retained for binary
178 /* Declare the external functions we use; they are in obstack.c. */
180 extern void _obstack_newchunk (struct obstack *, int);
181 extern int _obstack_begin (struct obstack *, int, int,
182 void *(*) (long), void (*) (void *));
183 extern int _obstack_begin_1 (struct obstack *, int, int,
184 void *(*) (void *, long),
185 void (*) (void *, void *), void *);
186 extern int _obstack_memory_used (struct obstack *);
188 /* The default name of the function for freeing a chunk is 'obstack_free',
189 but gnulib users can override this by defining '__obstack_free'. */
190 #ifndef __obstack_free
191 # define __obstack_free obstack_free
193 extern void __obstack_free (struct obstack *obstack, void *block);
196 /* Error handler called when `obstack_chunk_alloc' failed to allocate
197 more memory. This can be set to a user defined function which
198 should either abort gracefully or use longjump - but shouldn't
199 return. The default action is to print a message and abort. */
200 extern void (*obstack_alloc_failed_handler) (void);
202 /* Exit value used when `print_and_abort' is used. */
203 extern int obstack_exit_failure;
205 /* Pointer to beginning of object being allocated or to be allocated next.
206 Note that this might not be the final address of the object
207 because a new chunk might be needed to hold the final size. */
209 #define obstack_base(h) ((void *) (h)->object_base)
211 /* Size for allocating ordinary chunks. */
213 #define obstack_chunk_size(h) ((h)->chunk_size)
215 /* Pointer to next byte not yet allocated in current chunk. */
217 #define obstack_next_free(h) ((h)->next_free)
219 /* Mask specifying low bits that should be clear in address of an object. */
221 #define obstack_alignment_mask(h) ((h)->alignment_mask)
223 /* To prevent prototype warnings provide complete argument list. */
224 #define obstack_init(h) \
225 _obstack_begin ((h), 0, 0, \
226 (void *(*) (long)) obstack_chunk_alloc, \
227 (void (*) (void *)) obstack_chunk_free)
229 #define obstack_begin(h, size) \
230 _obstack_begin ((h), (size), 0, \
231 (void *(*) (long)) obstack_chunk_alloc, \
232 (void (*) (void *)) obstack_chunk_free)
234 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \
235 _obstack_begin ((h), (size), (alignment), \
236 (void *(*) (long)) (chunkfun), \
237 (void (*) (void *)) (freefun))
239 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
240 _obstack_begin_1 ((h), (size), (alignment), \
241 (void *(*) (void *, long)) (chunkfun), \
242 (void (*) (void *, void *)) (freefun), (arg))
244 #define obstack_chunkfun(h, newchunkfun) \
245 ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
247 #define obstack_freefun(h, newfreefun) \
248 ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
250 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
252 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
254 #define obstack_memory_used(h) _obstack_memory_used (h)
256 #if defined __GNUC__ && defined __STDC__ && __STDC__
257 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
258 does not implement __extension__. But that compiler doesn't define
260 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
261 # define __extension__
264 /* For GNU C, if not -traditional,
265 we can define these macros to compute all args only once
266 without using a global variable.
267 Also, we can avoid using the `temp' slot, to make faster code. */
269 # define obstack_object_size(OBSTACK) \
271 ({ struct obstack const *__o = (OBSTACK); \
272 (unsigned) (__o->next_free - __o->object_base); })
274 # define obstack_room(OBSTACK) \
276 ({ struct obstack const *__o = (OBSTACK); \
277 (unsigned) (__o->chunk_limit - __o->next_free); })
279 # define obstack_make_room(OBSTACK,length) \
281 ({ struct obstack *__o = (OBSTACK); \
282 int __len = (length); \
283 if (__o->chunk_limit - __o->next_free < __len) \
284 _obstack_newchunk (__o, __len); \
287 # define obstack_empty_p(OBSTACK) \
289 ({ struct obstack const *__o = (OBSTACK); \
290 (__o->chunk->prev == 0 \
291 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \
292 __o->chunk->contents, \
293 __o->alignment_mask)); })
295 # define obstack_grow(OBSTACK,where,length) \
297 ({ struct obstack *__o = (OBSTACK); \
298 int __len = (length); \
299 if (__o->next_free + __len > __o->chunk_limit) \
300 _obstack_newchunk (__o, __len); \
301 memcpy (__o->next_free, where, __len); \
302 __o->next_free += __len; \
305 # define obstack_grow0(OBSTACK,where,length) \
307 ({ struct obstack *__o = (OBSTACK); \
308 int __len = (length); \
309 if (__o->next_free + __len + 1 > __o->chunk_limit) \
310 _obstack_newchunk (__o, __len + 1); \
311 memcpy (__o->next_free, where, __len); \
312 __o->next_free += __len; \
313 *(__o->next_free)++ = 0; \
316 # define obstack_1grow(OBSTACK,datum) \
318 ({ struct obstack *__o = (OBSTACK); \
319 if (__o->next_free + 1 > __o->chunk_limit) \
320 _obstack_newchunk (__o, 1); \
321 obstack_1grow_fast (__o, datum); \
324 /* These assume that the obstack alignment is good enough for pointers
325 or ints, and that the data added so far to the current object
326 shares that much alignment. */
328 # define obstack_ptr_grow(OBSTACK,datum) \
330 ({ struct obstack *__o = (OBSTACK); \
331 if (__o->next_free + sizeof (void *) > __o->chunk_limit) \
332 _obstack_newchunk (__o, sizeof (void *)); \
333 obstack_ptr_grow_fast (__o, datum); }) \
335 # define obstack_int_grow(OBSTACK,datum) \
337 ({ struct obstack *__o = (OBSTACK); \
338 if (__o->next_free + sizeof (int) > __o->chunk_limit) \
339 _obstack_newchunk (__o, sizeof (int)); \
340 obstack_int_grow_fast (__o, datum); })
342 # define obstack_ptr_grow_fast(OBSTACK,aptr) \
344 ({ struct obstack *__o1 = (OBSTACK); \
345 *(const void **) __o1->next_free = (aptr); \
346 __o1->next_free += sizeof (const void *); \
349 # define obstack_int_grow_fast(OBSTACK,aint) \
351 ({ struct obstack *__o1 = (OBSTACK); \
352 *(int *) __o1->next_free = (aint); \
353 __o1->next_free += sizeof (int); \
356 # define obstack_blank(OBSTACK,length) \
358 ({ struct obstack *__o = (OBSTACK); \
359 int __len = (length); \
360 if (__o->chunk_limit - __o->next_free < __len) \
361 _obstack_newchunk (__o, __len); \
362 obstack_blank_fast (__o, __len); \
365 # define obstack_alloc(OBSTACK,length) \
367 ({ struct obstack *__h = (OBSTACK); \
368 obstack_blank (__h, (length)); \
369 obstack_finish (__h); })
371 # define obstack_copy(OBSTACK,where,length) \
373 ({ struct obstack *__h = (OBSTACK); \
374 obstack_grow (__h, (where), (length)); \
375 obstack_finish (__h); })
377 # define obstack_copy0(OBSTACK,where,length) \
379 ({ struct obstack *__h = (OBSTACK); \
380 obstack_grow0 (__h, (where), (length)); \
381 obstack_finish (__h); })
383 /* The local variable is named __o1 to avoid a name conflict
384 when obstack_blank is called. */
385 # define obstack_finish(OBSTACK) \
387 ({ struct obstack *__o1 = (OBSTACK); \
388 void *__value = (void *) __o1->object_base; \
389 if (__o1->next_free == __value) \
390 __o1->maybe_empty_object = 1; \
392 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \
393 __o1->alignment_mask); \
394 if (__o1->next_free - (char *)__o1->chunk \
395 > __o1->chunk_limit - (char *)__o1->chunk) \
396 __o1->next_free = __o1->chunk_limit; \
397 __o1->object_base = __o1->next_free; \
400 # define obstack_free(OBSTACK, OBJ) \
402 ({ struct obstack *__o = (OBSTACK); \
403 void *__obj = (OBJ); \
404 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \
405 __o->next_free = __o->object_base = (char *)__obj; \
406 else (__obstack_free) (__o, __obj); })
408 #else /* not __GNUC__ or not __STDC__ */
410 # define obstack_object_size(h) \
411 (unsigned) ((h)->next_free - (h)->object_base)
413 # define obstack_room(h) \
414 (unsigned) ((h)->chunk_limit - (h)->next_free)
416 # define obstack_empty_p(h) \
417 ((h)->chunk->prev == 0 \
418 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \
419 (h)->chunk->contents, \
420 (h)->alignment_mask))
422 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
423 so that we can avoid having void expressions
424 in the arms of the conditional expression.
425 Casting the third operand to void was tried before,
426 but some compilers won't accept it. */
428 # define obstack_make_room(h,length) \
429 ( (h)->temp.tempint = (length), \
430 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \
431 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
433 # define obstack_grow(h,where,length) \
434 ( (h)->temp.tempint = (length), \
435 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \
436 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \
437 memcpy ((h)->next_free, where, (h)->temp.tempint), \
438 (h)->next_free += (h)->temp.tempint)
440 # define obstack_grow0(h,where,length) \
441 ( (h)->temp.tempint = (length), \
442 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \
443 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \
444 memcpy ((h)->next_free, where, (h)->temp.tempint), \
445 (h)->next_free += (h)->temp.tempint, \
446 *((h)->next_free)++ = 0)
448 # define obstack_1grow(h,datum) \
449 ( (((h)->next_free + 1 > (h)->chunk_limit) \
450 ? (_obstack_newchunk ((h), 1), 0) : 0), \
451 obstack_1grow_fast (h, datum))
453 # define obstack_ptr_grow(h,datum) \
454 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \
455 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \
456 obstack_ptr_grow_fast (h, datum))
458 # define obstack_int_grow(h,datum) \
459 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \
460 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \
461 obstack_int_grow_fast (h, datum))
463 # define obstack_ptr_grow_fast(h,aptr) \
464 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
466 # define obstack_int_grow_fast(h,aint) \
467 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
469 # define obstack_blank(h,length) \
470 ( (h)->temp.tempint = (length), \
471 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \
472 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \
473 obstack_blank_fast (h, (h)->temp.tempint))
475 # define obstack_alloc(h,length) \
476 (obstack_blank ((h), (length)), obstack_finish ((h)))
478 # define obstack_copy(h,where,length) \
479 (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
481 # define obstack_copy0(h,where,length) \
482 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
484 # define obstack_finish(h) \
485 ( ((h)->next_free == (h)->object_base \
486 ? (((h)->maybe_empty_object = 1), 0) \
488 (h)->temp.tempptr = (h)->object_base, \
490 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \
491 (h)->alignment_mask), \
492 (((h)->next_free - (char *) (h)->chunk \
493 > (h)->chunk_limit - (char *) (h)->chunk) \
494 ? ((h)->next_free = (h)->chunk_limit) : 0), \
495 (h)->object_base = (h)->next_free, \
498 # define obstack_free(h,obj) \
499 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \
500 ((((h)->temp.tempint > 0 \
501 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \
502 ? (int) ((h)->next_free = (h)->object_base \
503 = (h)->temp.tempint + (char *) (h)->chunk) \
504 : (((__obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0)))
506 #endif /* not __GNUC__ or not __STDC__ */
512 #endif /* obstack.h */