Merge branch 'ds/midx-expire-repack'
[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'. */
164 union {
165 void *(*plain) (long);
166 struct _obstack_chunk *(*extra) (void *, long);
167 } chunkfun;
168 union {
169 void (*plain) (void *);
170 void (*extra) (void *, struct _obstack_chunk *);
171 } freefun;
172 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */
173 unsigned use_extra_arg:1; /* chunk alloc/dealloc funcs take extra arg */
174 unsigned maybe_empty_object:1;/* There is a possibility that the current
175 chunk contains a zero-length object. This
176 prevents freeing the chunk if we allocate
177 a bigger chunk to replace it. */
178 unsigned alloc_failed:1; /* No longer used, as we now call the failed
179 handler on error, but retained for binary
180 compatibility. */
181 };
182
183 /* Declare the external functions we use; they are in obstack.c. */
184
185 extern void _obstack_newchunk (struct obstack *, int);
186 extern int _obstack_begin (struct obstack *, int, int,
187 void *(*) (long), void (*) (void *));
188 extern int _obstack_begin_1 (struct obstack *, int, int,
189 void *(*) (void *, long),
190 void (*) (void *, void *), void *);
191 extern int _obstack_memory_used (struct obstack *);
192
193 void obstack_free (struct obstack *, void *);
194
195 \f
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);
201 \f
202 /* Pointer to beginning of object being allocated or to be allocated next.
203 Note that this might not be the final address of the object
204 because a new chunk might be needed to hold the final size. */
205
206 #define obstack_base(h) ((void *) (h)->object_base)
207
208 /* Size for allocating ordinary chunks. */
209
210 #define obstack_chunk_size(h) ((h)->chunk_size)
211
212 /* Pointer to next byte not yet allocated in current chunk. */
213
214 #define obstack_next_free(h) ((h)->next_free)
215
216 /* Mask specifying low bits that should be clear in address of an object. */
217
218 #define obstack_alignment_mask(h) ((h)->alignment_mask)
219
220 /* To prevent prototype warnings provide complete argument list. */
221 #define obstack_init(h) \
222 _obstack_begin ((h), 0, 0, \
223 (void *(*) (long)) obstack_chunk_alloc, \
224 (void (*) (void *)) obstack_chunk_free)
225
226 #define obstack_begin(h, size) \
227 _obstack_begin ((h), (size), 0, \
228 (void *(*) (long)) obstack_chunk_alloc, \
229 (void (*) (void *)) obstack_chunk_free)
230
231 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \
232 _obstack_begin ((h), (size), (alignment), \
233 (void *(*) (long)) (chunkfun), \
234 (void (*) (void *)) (freefun))
235
236 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
237 _obstack_begin_1 ((h), (size), (alignment), \
238 (void *(*) (void *, long)) (chunkfun), \
239 (void (*) (void *, void *)) (freefun), (arg))
240
241 #define obstack_chunkfun(h, newchunkfun) \
242 ((h)->chunkfun.extra = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
243
244 #define obstack_freefun(h, newfreefun) \
245 ((h)->freefun.extra = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
246
247 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
248
249 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
250
251 #define obstack_memory_used(h) _obstack_memory_used (h)
252 \f
253 #if defined __GNUC__ && defined __STDC__ && __STDC__
254 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
255 does not implement __extension__. But that compiler doesn't define
256 __GNUC_MINOR__. */
257 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
258 # define __extension__
259 # endif
260
261 /* For GNU C, if not -traditional,
262 we can define these macros to compute all args only once
263 without using a global variable.
264 Also, we can avoid using the `temp' slot, to make faster code. */
265
266 # define obstack_object_size(OBSTACK) \
267 __extension__ \
268 ({ struct obstack const *__o = (OBSTACK); \
269 (unsigned) (__o->next_free - __o->object_base); })
270
271 # define obstack_room(OBSTACK) \
272 __extension__ \
273 ({ struct obstack const *__o = (OBSTACK); \
274 (unsigned) (__o->chunk_limit - __o->next_free); })
275
276 # define obstack_make_room(OBSTACK,length) \
277 __extension__ \
278 ({ struct obstack *__o = (OBSTACK); \
279 int __len = (length); \
280 if (__o->chunk_limit - __o->next_free < __len) \
281 _obstack_newchunk (__o, __len); \
282 (void) 0; })
283
284 # define obstack_empty_p(OBSTACK) \
285 __extension__ \
286 ({ struct obstack const *__o = (OBSTACK); \
287 (__o->chunk->prev == 0 \
288 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \
289 __o->chunk->contents, \
290 __o->alignment_mask)); })
291
292 # define obstack_grow(OBSTACK,where,length) \
293 __extension__ \
294 ({ struct obstack *__o = (OBSTACK); \
295 int __len = (length); \
296 if (__o->next_free + __len > __o->chunk_limit) \
297 _obstack_newchunk (__o, __len); \
298 memcpy (__o->next_free, where, __len); \
299 __o->next_free += __len; \
300 (void) 0; })
301
302 # define obstack_grow0(OBSTACK,where,length) \
303 __extension__ \
304 ({ struct obstack *__o = (OBSTACK); \
305 int __len = (length); \
306 if (__o->next_free + __len + 1 > __o->chunk_limit) \
307 _obstack_newchunk (__o, __len + 1); \
308 memcpy (__o->next_free, where, __len); \
309 __o->next_free += __len; \
310 *(__o->next_free)++ = 0; \
311 (void) 0; })
312
313 # define obstack_1grow(OBSTACK,datum) \
314 __extension__ \
315 ({ struct obstack *__o = (OBSTACK); \
316 if (__o->next_free + 1 > __o->chunk_limit) \
317 _obstack_newchunk (__o, 1); \
318 obstack_1grow_fast (__o, datum); \
319 (void) 0; })
320
321 /* These assume that the obstack alignment is good enough for pointers
322 or ints, and that the data added so far to the current object
323 shares that much alignment. */
324
325 # define obstack_ptr_grow(OBSTACK,datum) \
326 __extension__ \
327 ({ struct obstack *__o = (OBSTACK); \
328 if (__o->next_free + sizeof (void *) > __o->chunk_limit) \
329 _obstack_newchunk (__o, sizeof (void *)); \
330 obstack_ptr_grow_fast (__o, datum); }) \
331
332 # define obstack_int_grow(OBSTACK,datum) \
333 __extension__ \
334 ({ struct obstack *__o = (OBSTACK); \
335 if (__o->next_free + sizeof (int) > __o->chunk_limit) \
336 _obstack_newchunk (__o, sizeof (int)); \
337 obstack_int_grow_fast (__o, datum); })
338
339 # define obstack_ptr_grow_fast(OBSTACK,aptr) \
340 __extension__ \
341 ({ struct obstack *__o1 = (OBSTACK); \
342 *(const void **) __o1->next_free = (aptr); \
343 __o1->next_free += sizeof (const void *); \
344 (void) 0; })
345
346 # define obstack_int_grow_fast(OBSTACK,aint) \
347 __extension__ \
348 ({ struct obstack *__o1 = (OBSTACK); \
349 *(int *) __o1->next_free = (aint); \
350 __o1->next_free += sizeof (int); \
351 (void) 0; })
352
353 # define obstack_blank(OBSTACK,length) \
354 __extension__ \
355 ({ struct obstack *__o = (OBSTACK); \
356 int __len = (length); \
357 if (__o->chunk_limit - __o->next_free < __len) \
358 _obstack_newchunk (__o, __len); \
359 obstack_blank_fast (__o, __len); \
360 (void) 0; })
361
362 # define obstack_alloc(OBSTACK,length) \
363 __extension__ \
364 ({ struct obstack *__h = (OBSTACK); \
365 obstack_blank (__h, (length)); \
366 obstack_finish (__h); })
367
368 # define obstack_copy(OBSTACK,where,length) \
369 __extension__ \
370 ({ struct obstack *__h = (OBSTACK); \
371 obstack_grow (__h, (where), (length)); \
372 obstack_finish (__h); })
373
374 # define obstack_copy0(OBSTACK,where,length) \
375 __extension__ \
376 ({ struct obstack *__h = (OBSTACK); \
377 obstack_grow0 (__h, (where), (length)); \
378 obstack_finish (__h); })
379
380 /* The local variable is named __o1 to avoid a name conflict
381 when obstack_blank is called. */
382 # define obstack_finish(OBSTACK) \
383 __extension__ \
384 ({ struct obstack *__o1 = (OBSTACK); \
385 void *__value = (void *) __o1->object_base; \
386 if (__o1->next_free == __value) \
387 __o1->maybe_empty_object = 1; \
388 __o1->next_free \
389 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \
390 __o1->alignment_mask); \
391 if (__o1->next_free - (char *)__o1->chunk \
392 > __o1->chunk_limit - (char *)__o1->chunk) \
393 __o1->next_free = __o1->chunk_limit; \
394 __o1->object_base = __o1->next_free; \
395 __value; })
396
397 # define obstack_free(OBSTACK, OBJ) \
398 __extension__ \
399 ({ struct obstack *__o = (OBSTACK); \
400 void *__obj = (OBJ); \
401 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \
402 __o->next_free = __o->object_base = (char *)__obj; \
403 else (obstack_free) (__o, __obj); })
404 \f
405 #else /* not __GNUC__ or not __STDC__ */
406
407 # define obstack_object_size(h) \
408 (unsigned) ((h)->next_free - (h)->object_base)
409
410 # define obstack_room(h) \
411 (unsigned) ((h)->chunk_limit - (h)->next_free)
412
413 # define obstack_empty_p(h) \
414 ((h)->chunk->prev == 0 \
415 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \
416 (h)->chunk->contents, \
417 (h)->alignment_mask))
418
419 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
420 so that we can avoid having void expressions
421 in the arms of the conditional expression.
422 Casting the third operand to void was tried before,
423 but some compilers won't accept it. */
424
425 # define obstack_make_room(h,length) \
426 ( (h)->temp.tempint = (length), \
427 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \
428 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
429
430 # define obstack_grow(h,where,length) \
431 ( (h)->temp.tempint = (length), \
432 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \
433 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \
434 memcpy ((h)->next_free, where, (h)->temp.tempint), \
435 (h)->next_free += (h)->temp.tempint)
436
437 # define obstack_grow0(h,where,length) \
438 ( (h)->temp.tempint = (length), \
439 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \
440 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \
441 memcpy ((h)->next_free, where, (h)->temp.tempint), \
442 (h)->next_free += (h)->temp.tempint, \
443 *((h)->next_free)++ = 0)
444
445 # define obstack_1grow(h,datum) \
446 ( (((h)->next_free + 1 > (h)->chunk_limit) \
447 ? (_obstack_newchunk ((h), 1), 0) : 0), \
448 obstack_1grow_fast (h, datum))
449
450 # define obstack_ptr_grow(h,datum) \
451 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \
452 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \
453 obstack_ptr_grow_fast (h, datum))
454
455 # define obstack_int_grow(h,datum) \
456 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \
457 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \
458 obstack_int_grow_fast (h, datum))
459
460 # define obstack_ptr_grow_fast(h,aptr) \
461 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
462
463 # define obstack_int_grow_fast(h,aint) \
464 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
465
466 # define obstack_blank(h,length) \
467 ( (h)->temp.tempint = (length), \
468 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \
469 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \
470 obstack_blank_fast (h, (h)->temp.tempint))
471
472 # define obstack_alloc(h,length) \
473 (obstack_blank ((h), (length)), obstack_finish ((h)))
474
475 # define obstack_copy(h,where,length) \
476 (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
477
478 # define obstack_copy0(h,where,length) \
479 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
480
481 # define obstack_finish(h) \
482 ( ((h)->next_free == (h)->object_base \
483 ? (((h)->maybe_empty_object = 1), 0) \
484 : 0), \
485 (h)->temp.tempptr = (h)->object_base, \
486 (h)->next_free \
487 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \
488 (h)->alignment_mask), \
489 (((h)->next_free - (char *) (h)->chunk \
490 > (h)->chunk_limit - (char *) (h)->chunk) \
491 ? ((h)->next_free = (h)->chunk_limit) : 0), \
492 (h)->object_base = (h)->next_free, \
493 (h)->temp.tempptr)
494
495 # define obstack_free(h,obj) \
496 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \
497 ((((h)->temp.tempint > 0 \
498 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \
499 ? (ptrdiff_t) ((h)->next_free = (h)->object_base \
500 = (h)->temp.tempint + (char *) (h)->chunk) \
501 : (((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0)))
502
503 #endif /* not __GNUC__ or not __STDC__ */
504
505 #ifdef __cplusplus
506 } /* C++ */
507 #endif
508
509 #endif /* obstack.h */