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[git/git.git] / compat / obstack.h
1 /* obstack.h - object stack macros
2 Copyright (C) 1988-1994,1996-1999,2003,2004,2005,2009
3 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library 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 GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
19
20 /* Summary:
21
22 All the apparent functions defined here are macros. The idea
23 is that you would use these pre-tested macros to solve a
24 very specific set of problems, and they would run fast.
25 Caution: no side-effects in arguments please!! They may be
26 evaluated MANY times!!
27
28 These macros operate a stack of objects. Each object starts life
29 small, and may grow to maturity. (Consider building a word syllable
30 by syllable.) An object can move while it is growing. Once it has
31 been "finished" it never changes address again. So the "top of the
32 stack" is typically an immature growing object, while the rest of the
33 stack is of mature, fixed size and fixed address objects.
34
35 These routines grab large chunks of memory, using a function you
36 supply, called `obstack_chunk_alloc'. On occasion, they free chunks,
37 by calling `obstack_chunk_free'. You must define them and declare
38 them before using any obstack macros.
39
40 Each independent stack is represented by a `struct obstack'.
41 Each of the obstack macros expects a pointer to such a structure
42 as the first argument.
43
44 One motivation for this package is the problem of growing char strings
45 in symbol tables. Unless you are "fascist pig with a read-only mind"
46 --Gosper's immortal quote from HAKMEM item 154, out of context--you
47 would not like to put any arbitrary upper limit on the length of your
48 symbols.
49
50 In practice this often means you will build many short symbols and a
51 few long symbols. At the time you are reading a symbol you don't know
52 how long it is. One traditional method is to read a symbol into a
53 buffer, realloc()ating the buffer every time you try to read a symbol
54 that is longer than the buffer. This is beaut, but you still will
55 want to copy the symbol from the buffer to a more permanent
56 symbol-table entry say about half the time.
57
58 With obstacks, you can work differently. Use one obstack for all symbol
59 names. As you read a symbol, grow the name in the obstack gradually.
60 When the name is complete, finalize it. Then, if the symbol exists already,
61 free the newly read name.
62
63 The way we do this is to take a large chunk, allocating memory from
64 low addresses. When you want to build a symbol in the chunk you just
65 add chars above the current "high water mark" in the chunk. When you
66 have finished adding chars, because you got to the end of the symbol,
67 you know how long the chars are, and you can create a new object.
68 Mostly the chars will not burst over the highest address of the chunk,
69 because you would typically expect a chunk to be (say) 100 times as
70 long as an average object.
71
72 In case that isn't clear, when we have enough chars to make up
73 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
74 so we just point to it where it lies. No moving of chars is
75 needed and this is the second win: potentially long strings need
76 never be explicitly shuffled. Once an object is formed, it does not
77 change its address during its lifetime.
78
79 When the chars burst over a chunk boundary, we allocate a larger
80 chunk, and then copy the partly formed object from the end of the old
81 chunk to the beginning of the new larger chunk. We then carry on
82 accreting characters to the end of the object as we normally would.
83
84 A special macro is provided to add a single char at a time to a
85 growing object. This allows the use of register variables, which
86 break the ordinary 'growth' macro.
87
88 Summary:
89 We allocate large chunks.
90 We carve out one object at a time from the current chunk.
91 Once carved, an object never moves.
92 We are free to append data of any size to the currently
93 growing object.
94 Exactly one object is growing in an obstack at any one time.
95 You can run one obstack per control block.
96 You may have as many control blocks as you dare.
97 Because of the way we do it, you can `unwind' an obstack
98 back to a previous state. (You may remove objects much
99 as you would with a stack.)
100 */
101
102
103 /* Don't do the contents of this file more than once. */
104
105 #ifndef _OBSTACK_H
106 #define _OBSTACK_H 1
107
108 #ifdef __cplusplus
109 extern "C" {
110 #endif
111 \f
112 /* We need the type of a pointer subtraction. If __PTRDIFF_TYPE__ is
113 defined, as with GNU C, use that; that way we don't pollute the
114 namespace with <stddef.h>'s symbols. Otherwise, include <stddef.h>
115 and use ptrdiff_t. */
116
117 #ifdef __PTRDIFF_TYPE__
118 # define PTR_INT_TYPE __PTRDIFF_TYPE__
119 #else
120 # include <stddef.h>
121 # define PTR_INT_TYPE ptrdiff_t
122 #endif
123
124 /* If B is the base of an object addressed by P, return the result of
125 aligning P to the next multiple of A + 1. B and P must be of type
126 char *. A + 1 must be a power of 2. */
127
128 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A)))
129
130 /* Similar to _BPTR_ALIGN (B, P, A), except optimize the common case
131 where pointers can be converted to integers, aligned as integers,
132 and converted back again. If PTR_INT_TYPE is narrower than a
133 pointer (e.g., the AS/400), play it safe and compute the alignment
134 relative to B. Otherwise, use the faster strategy of computing the
135 alignment relative to 0. */
136
137 #define __PTR_ALIGN(B, P, A) \
138 __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \
139 P, A)
140
141 #include <string.h>
142
143 struct _obstack_chunk /* Lives at front of each chunk. */
144 {
145 char *limit; /* 1 past end of this chunk */
146 struct _obstack_chunk *prev; /* address of prior chunk or NULL */
147 char contents[4]; /* objects begin here */
148 };
149
150 struct obstack /* control current object in current chunk */
151 {
152 long chunk_size; /* preferred size to allocate chunks in */
153 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
154 char *object_base; /* address of object we are building */
155 char *next_free; /* where to add next char to current object */
156 char *chunk_limit; /* address of char after current chunk */
157 union
158 {
159 PTR_INT_TYPE tempint;
160 void *tempptr;
161 } temp; /* Temporary for some macros. */
162 int alignment_mask; /* Mask of alignment for each object. */
163 /* These prototypes vary based on `use_extra_arg', and we use
164 casts to the prototypeless function type in all assignments,
165 but having prototypes here quiets -Wstrict-prototypes. */
166 struct _obstack_chunk *(*chunkfun) (void *, long);
167 void (*freefun) (void *, struct _obstack_chunk *);
168 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */
169 unsigned use_extra_arg:1; /* chunk alloc/dealloc funcs take extra arg */
170 unsigned maybe_empty_object:1;/* There is a possibility that the current
171 chunk contains a zero-length object. This
172 prevents freeing the chunk if we allocate
173 a bigger chunk to replace it. */
174 unsigned alloc_failed:1; /* No longer used, as we now call the failed
175 handler on error, but retained for binary
176 compatibility. */
177 };
178
179 /* Declare the external functions we use; they are in obstack.c. */
180
181 extern void _obstack_newchunk (struct obstack *, int);
182 extern int _obstack_begin (struct obstack *, int, int,
183 void *(*) (long), void (*) (void *));
184 extern int _obstack_begin_1 (struct obstack *, int, int,
185 void *(*) (void *, long),
186 void (*) (void *, void *), void *);
187 extern int _obstack_memory_used (struct obstack *);
188
189 void obstack_free (struct obstack *, void *);
190
191 \f
192 /* Error handler called when `obstack_chunk_alloc' failed to allocate
193 more memory. This can be set to a user defined function which
194 should either abort gracefully or use longjump - but shouldn't
195 return. The default action is to print a message and abort. */
196 extern void (*obstack_alloc_failed_handler) (void);
197 \f
198 /* Pointer to beginning of object being allocated or to be allocated next.
199 Note that this might not be the final address of the object
200 because a new chunk might be needed to hold the final size. */
201
202 #define obstack_base(h) ((void *) (h)->object_base)
203
204 /* Size for allocating ordinary chunks. */
205
206 #define obstack_chunk_size(h) ((h)->chunk_size)
207
208 /* Pointer to next byte not yet allocated in current chunk. */
209
210 #define obstack_next_free(h) ((h)->next_free)
211
212 /* Mask specifying low bits that should be clear in address of an object. */
213
214 #define obstack_alignment_mask(h) ((h)->alignment_mask)
215
216 /* To prevent prototype warnings provide complete argument list. */
217 #define obstack_init(h) \
218 _obstack_begin ((h), 0, 0, \
219 (void *(*) (long)) obstack_chunk_alloc, \
220 (void (*) (void *)) obstack_chunk_free)
221
222 #define obstack_begin(h, size) \
223 _obstack_begin ((h), (size), 0, \
224 (void *(*) (long)) obstack_chunk_alloc, \
225 (void (*) (void *)) obstack_chunk_free)
226
227 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \
228 _obstack_begin ((h), (size), (alignment), \
229 (void *(*) (long)) (chunkfun), \
230 (void (*) (void *)) (freefun))
231
232 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
233 _obstack_begin_1 ((h), (size), (alignment), \
234 (void *(*) (void *, long)) (chunkfun), \
235 (void (*) (void *, void *)) (freefun), (arg))
236
237 #define obstack_chunkfun(h, newchunkfun) \
238 ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
239
240 #define obstack_freefun(h, newfreefun) \
241 ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
242
243 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
244
245 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
246
247 #define obstack_memory_used(h) _obstack_memory_used (h)
248 \f
249 #if defined __GNUC__ && defined __STDC__ && __STDC__
250 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
251 does not implement __extension__. But that compiler doesn't define
252 __GNUC_MINOR__. */
253 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
254 # define __extension__
255 # endif
256
257 /* For GNU C, if not -traditional,
258 we can define these macros to compute all args only once
259 without using a global variable.
260 Also, we can avoid using the `temp' slot, to make faster code. */
261
262 # define obstack_object_size(OBSTACK) \
263 __extension__ \
264 ({ struct obstack const *__o = (OBSTACK); \
265 (unsigned) (__o->next_free - __o->object_base); })
266
267 # define obstack_room(OBSTACK) \
268 __extension__ \
269 ({ struct obstack const *__o = (OBSTACK); \
270 (unsigned) (__o->chunk_limit - __o->next_free); })
271
272 # define obstack_make_room(OBSTACK,length) \
273 __extension__ \
274 ({ struct obstack *__o = (OBSTACK); \
275 int __len = (length); \
276 if (__o->chunk_limit - __o->next_free < __len) \
277 _obstack_newchunk (__o, __len); \
278 (void) 0; })
279
280 # define obstack_empty_p(OBSTACK) \
281 __extension__ \
282 ({ struct obstack const *__o = (OBSTACK); \
283 (__o->chunk->prev == 0 \
284 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \
285 __o->chunk->contents, \
286 __o->alignment_mask)); })
287
288 # define obstack_grow(OBSTACK,where,length) \
289 __extension__ \
290 ({ struct obstack *__o = (OBSTACK); \
291 int __len = (length); \
292 if (__o->next_free + __len > __o->chunk_limit) \
293 _obstack_newchunk (__o, __len); \
294 memcpy (__o->next_free, where, __len); \
295 __o->next_free += __len; \
296 (void) 0; })
297
298 # define obstack_grow0(OBSTACK,where,length) \
299 __extension__ \
300 ({ struct obstack *__o = (OBSTACK); \
301 int __len = (length); \
302 if (__o->next_free + __len + 1 > __o->chunk_limit) \
303 _obstack_newchunk (__o, __len + 1); \
304 memcpy (__o->next_free, where, __len); \
305 __o->next_free += __len; \
306 *(__o->next_free)++ = 0; \
307 (void) 0; })
308
309 # define obstack_1grow(OBSTACK,datum) \
310 __extension__ \
311 ({ struct obstack *__o = (OBSTACK); \
312 if (__o->next_free + 1 > __o->chunk_limit) \
313 _obstack_newchunk (__o, 1); \
314 obstack_1grow_fast (__o, datum); \
315 (void) 0; })
316
317 /* These assume that the obstack alignment is good enough for pointers
318 or ints, and that the data added so far to the current object
319 shares that much alignment. */
320
321 # define obstack_ptr_grow(OBSTACK,datum) \
322 __extension__ \
323 ({ struct obstack *__o = (OBSTACK); \
324 if (__o->next_free + sizeof (void *) > __o->chunk_limit) \
325 _obstack_newchunk (__o, sizeof (void *)); \
326 obstack_ptr_grow_fast (__o, datum); }) \
327
328 # define obstack_int_grow(OBSTACK,datum) \
329 __extension__ \
330 ({ struct obstack *__o = (OBSTACK); \
331 if (__o->next_free + sizeof (int) > __o->chunk_limit) \
332 _obstack_newchunk (__o, sizeof (int)); \
333 obstack_int_grow_fast (__o, datum); })
334
335 # define obstack_ptr_grow_fast(OBSTACK,aptr) \
336 __extension__ \
337 ({ struct obstack *__o1 = (OBSTACK); \
338 *(const void **) __o1->next_free = (aptr); \
339 __o1->next_free += sizeof (const void *); \
340 (void) 0; })
341
342 # define obstack_int_grow_fast(OBSTACK,aint) \
343 __extension__ \
344 ({ struct obstack *__o1 = (OBSTACK); \
345 *(int *) __o1->next_free = (aint); \
346 __o1->next_free += sizeof (int); \
347 (void) 0; })
348
349 # define obstack_blank(OBSTACK,length) \
350 __extension__ \
351 ({ struct obstack *__o = (OBSTACK); \
352 int __len = (length); \
353 if (__o->chunk_limit - __o->next_free < __len) \
354 _obstack_newchunk (__o, __len); \
355 obstack_blank_fast (__o, __len); \
356 (void) 0; })
357
358 # define obstack_alloc(OBSTACK,length) \
359 __extension__ \
360 ({ struct obstack *__h = (OBSTACK); \
361 obstack_blank (__h, (length)); \
362 obstack_finish (__h); })
363
364 # define obstack_copy(OBSTACK,where,length) \
365 __extension__ \
366 ({ struct obstack *__h = (OBSTACK); \
367 obstack_grow (__h, (where), (length)); \
368 obstack_finish (__h); })
369
370 # define obstack_copy0(OBSTACK,where,length) \
371 __extension__ \
372 ({ struct obstack *__h = (OBSTACK); \
373 obstack_grow0 (__h, (where), (length)); \
374 obstack_finish (__h); })
375
376 /* The local variable is named __o1 to avoid a name conflict
377 when obstack_blank is called. */
378 # define obstack_finish(OBSTACK) \
379 __extension__ \
380 ({ struct obstack *__o1 = (OBSTACK); \
381 void *__value = (void *) __o1->object_base; \
382 if (__o1->next_free == __value) \
383 __o1->maybe_empty_object = 1; \
384 __o1->next_free \
385 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \
386 __o1->alignment_mask); \
387 if (__o1->next_free - (char *)__o1->chunk \
388 > __o1->chunk_limit - (char *)__o1->chunk) \
389 __o1->next_free = __o1->chunk_limit; \
390 __o1->object_base = __o1->next_free; \
391 __value; })
392
393 # define obstack_free(OBSTACK, OBJ) \
394 __extension__ \
395 ({ struct obstack *__o = (OBSTACK); \
396 void *__obj = (OBJ); \
397 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \
398 __o->next_free = __o->object_base = (char *)__obj; \
399 else (obstack_free) (__o, __obj); })
400 \f
401 #else /* not __GNUC__ or not __STDC__ */
402
403 # define obstack_object_size(h) \
404 (unsigned) ((h)->next_free - (h)->object_base)
405
406 # define obstack_room(h) \
407 (unsigned) ((h)->chunk_limit - (h)->next_free)
408
409 # define obstack_empty_p(h) \
410 ((h)->chunk->prev == 0 \
411 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \
412 (h)->chunk->contents, \
413 (h)->alignment_mask))
414
415 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
416 so that we can avoid having void expressions
417 in the arms of the conditional expression.
418 Casting the third operand to void was tried before,
419 but some compilers won't accept it. */
420
421 # define obstack_make_room(h,length) \
422 ( (h)->temp.tempint = (length), \
423 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \
424 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
425
426 # define obstack_grow(h,where,length) \
427 ( (h)->temp.tempint = (length), \
428 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \
429 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \
430 memcpy ((h)->next_free, where, (h)->temp.tempint), \
431 (h)->next_free += (h)->temp.tempint)
432
433 # define obstack_grow0(h,where,length) \
434 ( (h)->temp.tempint = (length), \
435 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \
436 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \
437 memcpy ((h)->next_free, where, (h)->temp.tempint), \
438 (h)->next_free += (h)->temp.tempint, \
439 *((h)->next_free)++ = 0)
440
441 # define obstack_1grow(h,datum) \
442 ( (((h)->next_free + 1 > (h)->chunk_limit) \
443 ? (_obstack_newchunk ((h), 1), 0) : 0), \
444 obstack_1grow_fast (h, datum))
445
446 # define obstack_ptr_grow(h,datum) \
447 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \
448 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \
449 obstack_ptr_grow_fast (h, datum))
450
451 # define obstack_int_grow(h,datum) \
452 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \
453 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \
454 obstack_int_grow_fast (h, datum))
455
456 # define obstack_ptr_grow_fast(h,aptr) \
457 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
458
459 # define obstack_int_grow_fast(h,aint) \
460 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
461
462 # define obstack_blank(h,length) \
463 ( (h)->temp.tempint = (length), \
464 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \
465 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \
466 obstack_blank_fast (h, (h)->temp.tempint))
467
468 # define obstack_alloc(h,length) \
469 (obstack_blank ((h), (length)), obstack_finish ((h)))
470
471 # define obstack_copy(h,where,length) \
472 (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
473
474 # define obstack_copy0(h,where,length) \
475 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
476
477 # define obstack_finish(h) \
478 ( ((h)->next_free == (h)->object_base \
479 ? (((h)->maybe_empty_object = 1), 0) \
480 : 0), \
481 (h)->temp.tempptr = (h)->object_base, \
482 (h)->next_free \
483 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \
484 (h)->alignment_mask), \
485 (((h)->next_free - (char *) (h)->chunk \
486 > (h)->chunk_limit - (char *) (h)->chunk) \
487 ? ((h)->next_free = (h)->chunk_limit) : 0), \
488 (h)->object_base = (h)->next_free, \
489 (h)->temp.tempptr)
490
491 # define obstack_free(h,obj) \
492 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \
493 ((((h)->temp.tempint > 0 \
494 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \
495 ? (int) ((h)->next_free = (h)->object_base \
496 = (h)->temp.tempint + (char *) (h)->chunk) \
497 : (((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0)))
498
499 #endif /* not __GNUC__ or not __STDC__ */
500
501 #ifdef __cplusplus
502 } /* C++ */
503 #endif
504
505 #endif /* obstack.h */