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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
22All the apparent functions defined here are macros. The idea
23is that you would use these pre-tested macros to solve a
24very specific set of problems, and they would run fast.
25Caution: no side-effects in arguments please!! They may be
26evaluated MANY times!!
27
28These macros operate a stack of objects. Each object starts life
29small, and may grow to maturity. (Consider building a word syllable
30by syllable.) An object can move while it is growing. Once it has
31been "finished" it never changes address again. So the "top of the
32stack" is typically an immature growing object, while the rest of the
33stack is of mature, fixed size and fixed address objects.
34
35These routines grab large chunks of memory, using a function you
36supply, called `obstack_chunk_alloc'. On occasion, they free chunks,
37by calling `obstack_chunk_free'. You must define them and declare
38them before using any obstack macros.
39
40Each independent stack is represented by a `struct obstack'.
41Each of the obstack macros expects a pointer to such a structure
42as the first argument.
43
44One motivation for this package is the problem of growing char strings
45in 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
47would not like to put any arbitrary upper limit on the length of your
48symbols.
49
50In practice this often means you will build many short symbols and a
51few long symbols. At the time you are reading a symbol you don't know
52how long it is. One traditional method is to read a symbol into a
53buffer, realloc()ating the buffer every time you try to read a symbol
54that is longer than the buffer. This is beaut, but you still will
55want to copy the symbol from the buffer to a more permanent
56symbol-table entry say about half the time.
57
58With obstacks, you can work differently. Use one obstack for all symbol
59names. As you read a symbol, grow the name in the obstack gradually.
60When the name is complete, finalize it. Then, if the symbol exists already,
61free the newly read name.
62
63The way we do this is to take a large chunk, allocating memory from
64low addresses. When you want to build a symbol in the chunk you just
65add chars above the current "high water mark" in the chunk. When you
66have finished adding chars, because you got to the end of the symbol,
67you know how long the chars are, and you can create a new object.
68Mostly the chars will not burst over the highest address of the chunk,
69because you would typically expect a chunk to be (say) 100 times as
70long as an average object.
71
72In case that isn't clear, when we have enough chars to make up
73the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
74so we just point to it where it lies. No moving of chars is
75needed and this is the second win: potentially long strings need
76never be explicitly shuffled. Once an object is formed, it does not
77change its address during its lifetime.
78
79When the chars burst over a chunk boundary, we allocate a larger
80chunk, and then copy the partly formed object from the end of the old
81chunk to the beginning of the new larger chunk. We then carry on
82accrediting characters to the end of the object as we normally would.
83
84A special macro is provided to add a single char at a time to a
85growing object. This allows the use of register variables, which
86break the ordinary 'growth' macro.
87
88Summary:
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
109extern "C" {
110#endif
111
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 (sizeof (PTR_INT_TYPE) < sizeof(void *) ? \
139 __BPTR_ALIGN((B), (P), (A)) : \
140 (void *)__BPTR_ALIGN((PTR_INT_TYPE)(void *)0, (PTR_INT_TYPE)(P), (A)) \
141 )
142
143#include <string.h>
144
145struct _obstack_chunk /* Lives at front of each chunk. */
146{
147 char *limit; /* 1 past end of this chunk */
148 struct _obstack_chunk *prev; /* address of prior chunk or NULL */
149 char contents[4]; /* objects begin here */
150};
151
152struct obstack /* control current object in current chunk */
153{
154 long chunk_size; /* preferred size to allocate chunks in */
155 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
156 char *object_base; /* address of object we are building */
157 char *next_free; /* where to add next char to current object */
158 char *chunk_limit; /* address of char after current chunk */
159 union
160 {
161 PTR_INT_TYPE tempint;
162 void *tempptr;
163 } temp; /* Temporary for some macros. */
164 int alignment_mask; /* Mask of alignment for each object. */
165 /* These prototypes vary based on `use_extra_arg'. */
166 union {
167 void *(*plain) (long);
168 struct _obstack_chunk *(*extra) (void *, long);
169 } chunkfun;
170 union {
171 void (*plain) (void *);
172 void (*extra) (void *, struct _obstack_chunk *);
173 } freefun;
174 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */
175 unsigned use_extra_arg:1; /* chunk alloc/dealloc funcs take extra arg */
176 unsigned maybe_empty_object:1;/* There is a possibility that the current
177 chunk contains a zero-length object. This
178 prevents freeing the chunk if we allocate
179 a bigger chunk to replace it. */
180 unsigned alloc_failed:1; /* No longer used, as we now call the failed
181 handler on error, but retained for binary
182 compatibility. */
183};
184
185/* Declare the external functions we use; they are in obstack.c. */
186
187extern void _obstack_newchunk (struct obstack *, int);
188extern int _obstack_begin (struct obstack *, int, int,
189 void *(*) (long), void (*) (void *));
190extern int _obstack_begin_1 (struct obstack *, int, int,
191 void *(*) (void *, long),
192 void (*) (void *, void *), void *);
193extern int _obstack_memory_used (struct obstack *);
194
195void obstack_free (struct obstack *, void *);
196
197
198/* Error handler called when `obstack_chunk_alloc' failed to allocate
199 more memory. This can be set to a user defined function which
200 should either abort gracefully or use longjump - but shouldn't
201 return. The default action is to print a message and abort. */
202extern void (*obstack_alloc_failed_handler) (void);
203
204/* Pointer to beginning of object being allocated or to be allocated next.
205 Note that this might not be the final address of the object
206 because a new chunk might be needed to hold the final size. */
207
208#define obstack_base(h) ((void *) (h)->object_base)
209
210/* Size for allocating ordinary chunks. */
211
212#define obstack_chunk_size(h) ((h)->chunk_size)
213
214/* Pointer to next byte not yet allocated in current chunk. */
215
216#define obstack_next_free(h) ((h)->next_free)
217
218/* Mask specifying low bits that should be clear in address of an object. */
219
220#define obstack_alignment_mask(h) ((h)->alignment_mask)
221
222/* To prevent prototype warnings provide complete argument list. */
223#define obstack_init(h) \
224 _obstack_begin ((h), 0, 0, \
225 (void *(*) (long)) obstack_chunk_alloc, \
226 (void (*) (void *)) obstack_chunk_free)
227
228#define obstack_begin(h, size) \
229 _obstack_begin ((h), (size), 0, \
230 (void *(*) (long)) obstack_chunk_alloc, \
231 (void (*) (void *)) obstack_chunk_free)
232
233#define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \
234 _obstack_begin ((h), (size), (alignment), \
235 (void *(*) (long)) (chunkfun), \
236 (void (*) (void *)) (freefun))
237
238#define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
239 _obstack_begin_1 ((h), (size), (alignment), \
240 (void *(*) (void *, long)) (chunkfun), \
241 (void (*) (void *, void *)) (freefun), (arg))
242
243#define obstack_chunkfun(h, newchunkfun) \
244 ((h)->chunkfun.extra = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
245
246#define obstack_freefun(h, newfreefun) \
247 ((h)->freefun.extra = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
248
249#define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
250
251#define obstack_blank_fast(h,n) ((h)->next_free += (n))
252
253#define obstack_memory_used(h) _obstack_memory_used (h)
254
255#if defined __GNUC__ && defined __STDC__ && __STDC__
256/* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
257 does not implement __extension__. But that compiler doesn't define
258 __GNUC_MINOR__. */
259# if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
260# define __extension__
261# endif
262
263/* For GNU C, if not -traditional,
264 we can define these macros to compute all args only once
265 without using a global variable.
266 Also, we can avoid using the `temp' slot, to make faster code. */
267
268# define obstack_object_size(OBSTACK) \
269 __extension__ \
270 ({ struct obstack const *__o = (OBSTACK); \
271 (unsigned) (__o->next_free - __o->object_base); })
272
273# define obstack_room(OBSTACK) \
274 __extension__ \
275 ({ struct obstack const *__o = (OBSTACK); \
276 (unsigned) (__o->chunk_limit - __o->next_free); })
277
278# define obstack_make_room(OBSTACK,length) \
279__extension__ \
280({ struct obstack *__o = (OBSTACK); \
281 int __len = (length); \
282 if (__o->chunk_limit - __o->next_free < __len) \
283 _obstack_newchunk (__o, __len); \
284 (void) 0; })
285
286# define obstack_empty_p(OBSTACK) \
287 __extension__ \
288 ({ struct obstack const *__o = (OBSTACK); \
289 (__o->chunk->prev == 0 \
290 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \
291 __o->chunk->contents, \
292 __o->alignment_mask)); })
293
294# define obstack_grow(OBSTACK,where,length) \
295__extension__ \
296({ struct obstack *__o = (OBSTACK); \
297 int __len = (length); \
298 if (__o->next_free + __len > __o->chunk_limit) \
299 _obstack_newchunk (__o, __len); \
300 memcpy (__o->next_free, where, __len); \
301 __o->next_free += __len; \
302 (void) 0; })
303
304# define obstack_grow0(OBSTACK,where,length) \
305__extension__ \
306({ struct obstack *__o = (OBSTACK); \
307 int __len = (length); \
308 if (__o->next_free + __len + 1 > __o->chunk_limit) \
309 _obstack_newchunk (__o, __len + 1); \
310 memcpy (__o->next_free, where, __len); \
311 __o->next_free += __len; \
312 *(__o->next_free)++ = 0; \
313 (void) 0; })
314
315# define obstack_1grow(OBSTACK,datum) \
316__extension__ \
317({ struct obstack *__o = (OBSTACK); \
318 if (__o->next_free + 1 > __o->chunk_limit) \
319 _obstack_newchunk (__o, 1); \
320 obstack_1grow_fast (__o, datum); \
321 (void) 0; })
322
323/* These assume that the obstack alignment is good enough for pointers
324 or ints, and that the data added so far to the current object
325 shares that much alignment. */
326
327# define obstack_ptr_grow(OBSTACK,datum) \
328__extension__ \
329({ struct obstack *__o = (OBSTACK); \
330 if (__o->next_free + sizeof (void *) > __o->chunk_limit) \
331 _obstack_newchunk (__o, sizeof (void *)); \
332 obstack_ptr_grow_fast (__o, datum); }) \
333
334# define obstack_int_grow(OBSTACK,datum) \
335__extension__ \
336({ struct obstack *__o = (OBSTACK); \
337 if (__o->next_free + sizeof (int) > __o->chunk_limit) \
338 _obstack_newchunk (__o, sizeof (int)); \
339 obstack_int_grow_fast (__o, datum); })
340
341# define obstack_ptr_grow_fast(OBSTACK,aptr) \
342__extension__ \
343({ struct obstack *__o1 = (OBSTACK); \
344 *(const void **) __o1->next_free = (aptr); \
345 __o1->next_free += sizeof (const void *); \
346 (void) 0; })
347
348# define obstack_int_grow_fast(OBSTACK,aint) \
349__extension__ \
350({ struct obstack *__o1 = (OBSTACK); \
351 *(int *) __o1->next_free = (aint); \
352 __o1->next_free += sizeof (int); \
353 (void) 0; })
354
355# define obstack_blank(OBSTACK,length) \
356__extension__ \
357({ struct obstack *__o = (OBSTACK); \
358 int __len = (length); \
359 if (__o->chunk_limit - __o->next_free < __len) \
360 _obstack_newchunk (__o, __len); \
361 obstack_blank_fast (__o, __len); \
362 (void) 0; })
363
364# define obstack_alloc(OBSTACK,length) \
365__extension__ \
366({ struct obstack *__h = (OBSTACK); \
367 obstack_blank (__h, (length)); \
368 obstack_finish (__h); })
369
370# define obstack_copy(OBSTACK,where,length) \
371__extension__ \
372({ struct obstack *__h = (OBSTACK); \
373 obstack_grow (__h, (where), (length)); \
374 obstack_finish (__h); })
375
376# define obstack_copy0(OBSTACK,where,length) \
377__extension__ \
378({ struct obstack *__h = (OBSTACK); \
379 obstack_grow0 (__h, (where), (length)); \
380 obstack_finish (__h); })
381
382/* The local variable is named __o1 to avoid a name conflict
383 when obstack_blank is called. */
384# define obstack_finish(OBSTACK) \
385__extension__ \
386({ struct obstack *__o1 = (OBSTACK); \
387 void *__value = (void *) __o1->object_base; \
388 if (__o1->next_free == __value) \
389 __o1->maybe_empty_object = 1; \
390 __o1->next_free \
391 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \
392 __o1->alignment_mask); \
393 if (__o1->next_free - (char *)__o1->chunk \
394 > __o1->chunk_limit - (char *)__o1->chunk) \
395 __o1->next_free = __o1->chunk_limit; \
396 __o1->object_base = __o1->next_free; \
397 __value; })
398
399# define obstack_free(OBSTACK, OBJ) \
400__extension__ \
401({ struct obstack *__o = (OBSTACK); \
402 void *__obj = (OBJ); \
403 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \
404 __o->next_free = __o->object_base = (char *)__obj; \
405 else (obstack_free) (__o, __obj); })
406
407#else /* not __GNUC__ or not __STDC__ */
408
409# define obstack_object_size(h) \
410 (unsigned) ((h)->next_free - (h)->object_base)
411
412# define obstack_room(h) \
413 (unsigned) ((h)->chunk_limit - (h)->next_free)
414
415# define obstack_empty_p(h) \
416 ((h)->chunk->prev == 0 \
417 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \
418 (h)->chunk->contents, \
419 (h)->alignment_mask))
420
421/* Note that the call to _obstack_newchunk is enclosed in (..., 0)
422 so that we can avoid having void expressions
423 in the arms of the conditional expression.
424 Casting the third operand to void was tried before,
425 but some compilers won't accept it. */
426
427# define obstack_make_room(h,length) \
428( (h)->temp.tempint = (length), \
429 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \
430 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
431
432# define obstack_grow(h,where,length) \
433( (h)->temp.tempint = (length), \
434 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \
435 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \
436 memcpy ((h)->next_free, where, (h)->temp.tempint), \
437 (h)->next_free += (h)->temp.tempint)
438
439# define obstack_grow0(h,where,length) \
440( (h)->temp.tempint = (length), \
441 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \
442 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \
443 memcpy ((h)->next_free, where, (h)->temp.tempint), \
444 (h)->next_free += (h)->temp.tempint, \
445 *((h)->next_free)++ = 0)
446
447# define obstack_1grow(h,datum) \
448( (((h)->next_free + 1 > (h)->chunk_limit) \
449 ? (_obstack_newchunk ((h), 1), 0) : 0), \
450 obstack_1grow_fast (h, datum))
451
452# define obstack_ptr_grow(h,datum) \
453( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \
454 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \
455 obstack_ptr_grow_fast (h, datum))
456
457# define obstack_int_grow(h,datum) \
458( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \
459 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \
460 obstack_int_grow_fast (h, datum))
461
462# define obstack_ptr_grow_fast(h,aptr) \
463 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
464
465# define obstack_int_grow_fast(h,aint) \
466 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
467
468# define obstack_blank(h,length) \
469( (h)->temp.tempint = (length), \
470 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \
471 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \
472 obstack_blank_fast (h, (h)->temp.tempint))
473
474# define obstack_alloc(h,length) \
475 (obstack_blank ((h), (length)), obstack_finish ((h)))
476
477# define obstack_copy(h,where,length) \
478 (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
479
480# define obstack_copy0(h,where,length) \
481 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
482
483# define obstack_finish(h) \
484( ((h)->next_free == (h)->object_base \
485 ? (((h)->maybe_empty_object = 1), 0) \
486 : 0), \
487 (h)->temp.tempptr = (h)->object_base, \
488 (h)->next_free \
489 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \
490 (h)->alignment_mask), \
491 (((h)->next_free - (char *) (h)->chunk \
492 > (h)->chunk_limit - (char *) (h)->chunk) \
493 ? ((h)->next_free = (h)->chunk_limit) : 0), \
494 (h)->object_base = (h)->next_free, \
495 (h)->temp.tempptr)
496
497# define obstack_free(h,obj) \
498( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \
499 ((((h)->temp.tempint > 0 \
500 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \
501 ? (ptrdiff_t) ((h)->next_free = (h)->object_base \
502 = (h)->temp.tempint + (char *) (h)->chunk) \
503 : (((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0)))
504
505#endif /* not __GNUC__ or not __STDC__ */
506
507#ifdef __cplusplus
508} /* C++ */
509#endif
510
511#endif /* obstack.h */