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1 /* obstack.h - object stack macros
2    Copyright (C) 1988-1994,1996-1999,2003,2004,2005
3 	Free Software Foundation, Inc.
4    This file is part of the GNU C Library.
5 
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 2, or (at your option)
9    any later version.
10 
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.
15 
16    You should have received a copy of the GNU General Public License along
17    with this program; if not, write to the Free Software Foundation,
18    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
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 
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 /* Similiar 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 *obstack, void *block);
190 
191 
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 
198 /* Exit value used when `print_and_abort' is used.  */
199 extern int obstack_exit_failure;
200 
201 /* Pointer to beginning of object being allocated or to be allocated next.
202    Note that this might not be the final address of the object
203    because a new chunk might be needed to hold the final size.  */
204 
205 #define obstack_base(h) ((void *) (h)->object_base)
206 
207 /* Size for allocating ordinary chunks.  */
208 
209 #define obstack_chunk_size(h) ((h)->chunk_size)
210 
211 /* Pointer to next byte not yet allocated in current chunk.  */
212 
213 #define obstack_next_free(h)	((h)->next_free)
214 
215 /* Mask specifying low bits that should be clear in address of an object.  */
216 
217 #define obstack_alignment_mask(h) ((h)->alignment_mask)
218 
219 /* To prevent prototype warnings provide complete argument list.  */
220 #define obstack_init(h)						\
221   _obstack_begin ((h), 0, 0,					\
222 		  (void *(*) (long)) obstack_chunk_alloc,	\
223 		  (void (*) (void *)) obstack_chunk_free)
224 
225 #define obstack_begin(h, size)					\
226   _obstack_begin ((h), (size), 0,				\
227 		  (void *(*) (long)) obstack_chunk_alloc,	\
228 		  (void (*) (void *)) obstack_chunk_free)
229 
230 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun)  \
231   _obstack_begin ((h), (size), (alignment),				   \
232 		  (void *(*) (long)) (chunkfun),			   \
233 		  (void (*) (void *)) (freefun))
234 
235 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
236   _obstack_begin_1 ((h), (size), (alignment),				\
237 		    (void *(*) (void *, long)) (chunkfun),		\
238 		    (void (*) (void *, void *)) (freefun), (arg))
239 
240 #define obstack_chunkfun(h, newchunkfun) \
241   ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
242 
243 #define obstack_freefun(h, newfreefun) \
244   ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
245 
246 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
247 
248 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
249 
250 #define obstack_memory_used(h) _obstack_memory_used (h)
251 
252 #if defined __GNUC__ && defined __STDC__ && __STDC__
253 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
254    does not implement __extension__.  But that compiler doesn't define
255    __GNUC_MINOR__.  */
256 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
257 #  define __extension__
258 # endif
259 
260 /* For GNU C, if not -traditional,
261    we can define these macros to compute all args only once
262    without using a global variable.
263    Also, we can avoid using the `temp' slot, to make faster code.  */
264 
265 # define obstack_object_size(OBSTACK)					\
266   __extension__								\
267   ({ struct obstack const *__o = (OBSTACK);				\
268      (unsigned) (__o->next_free - __o->object_base); })
269 
270 # define obstack_room(OBSTACK)						\
271   __extension__								\
272   ({ struct obstack const *__o = (OBSTACK);				\
273      (unsigned) (__o->chunk_limit - __o->next_free); })
274 
275 # define obstack_make_room(OBSTACK,length)				\
276 __extension__								\
277 ({ struct obstack *__o = (OBSTACK);					\
278    int __len = (length);						\
279    if (__o->chunk_limit - __o->next_free < __len)			\
280      _obstack_newchunk (__o, __len);					\
281    (void) 0; })
282 
283 # define obstack_empty_p(OBSTACK)					\
284   __extension__								\
285   ({ struct obstack const *__o = (OBSTACK);				\
286      (__o->chunk->prev == 0						\
287       && __o->next_free == __PTR_ALIGN ((char *) __o->chunk,		\
288 					__o->chunk->contents,		\
289 					__o->alignment_mask)); })
290 
291 # define obstack_grow(OBSTACK,where,length)				\
292 __extension__								\
293 ({ struct obstack *__o = (OBSTACK);					\
294    int __len = (length);						\
295    if (__o->next_free + __len > __o->chunk_limit)			\
296      _obstack_newchunk (__o, __len);					\
297    memcpy (__o->next_free, where, __len);				\
298    __o->next_free += __len;						\
299    (void) 0; })
300 
301 # define obstack_grow0(OBSTACK,where,length)				\
302 __extension__								\
303 ({ struct obstack *__o = (OBSTACK);					\
304    int __len = (length);						\
305    if (__o->next_free + __len + 1 > __o->chunk_limit)			\
306      _obstack_newchunk (__o, __len + 1);				\
307    memcpy (__o->next_free, where, __len);				\
308    __o->next_free += __len;						\
309    *(__o->next_free)++ = 0;						\
310    (void) 0; })
311 
312 # define obstack_1grow(OBSTACK,datum)					\
313 __extension__								\
314 ({ struct obstack *__o = (OBSTACK);					\
315    if (__o->next_free + 1 > __o->chunk_limit)				\
316      _obstack_newchunk (__o, 1);					\
317    obstack_1grow_fast (__o, datum);					\
318    (void) 0; })
319 
320 /* These assume that the obstack alignment is good enough for pointers
321    or ints, and that the data added so far to the current object
322    shares that much alignment.  */
323 
324 # define obstack_ptr_grow(OBSTACK,datum)				\
325 __extension__								\
326 ({ struct obstack *__o = (OBSTACK);					\
327    if (__o->next_free + sizeof (void *) > __o->chunk_limit)		\
328      _obstack_newchunk (__o, sizeof (void *));				\
329    obstack_ptr_grow_fast (__o, datum); })				\
330 
331 # define obstack_int_grow(OBSTACK,datum)				\
332 __extension__								\
333 ({ struct obstack *__o = (OBSTACK);					\
334    if (__o->next_free + sizeof (int) > __o->chunk_limit)		\
335      _obstack_newchunk (__o, sizeof (int));				\
336    obstack_int_grow_fast (__o, datum); })
337 
338 # define obstack_ptr_grow_fast(OBSTACK,aptr)				\
339 __extension__								\
340 ({ struct obstack *__o1 = (OBSTACK);					\
341    *(const void **) __o1->next_free = (aptr);				\
342    __o1->next_free += sizeof (const void *);				\
343    (void) 0; })
344 
345 # define obstack_int_grow_fast(OBSTACK,aint)				\
346 __extension__								\
347 ({ struct obstack *__o1 = (OBSTACK);					\
348    *(int *) __o1->next_free = (aint);					\
349    __o1->next_free += sizeof (int);					\
350    (void) 0; })
351 
352 # define obstack_blank(OBSTACK,length)					\
353 __extension__								\
354 ({ struct obstack *__o = (OBSTACK);					\
355    int __len = (length);						\
356    if (__o->chunk_limit - __o->next_free < __len)			\
357      _obstack_newchunk (__o, __len);					\
358    obstack_blank_fast (__o, __len);					\
359    (void) 0; })
360 
361 # define obstack_alloc(OBSTACK,length)					\
362 __extension__								\
363 ({ struct obstack *__h = (OBSTACK);					\
364    obstack_blank (__h, (length));					\
365    obstack_finish (__h); })
366 
367 # define obstack_copy(OBSTACK,where,length)				\
368 __extension__								\
369 ({ struct obstack *__h = (OBSTACK);					\
370    obstack_grow (__h, (where), (length));				\
371    obstack_finish (__h); })
372 
373 # define obstack_copy0(OBSTACK,where,length)				\
374 __extension__								\
375 ({ struct obstack *__h = (OBSTACK);					\
376    obstack_grow0 (__h, (where), (length));				\
377    obstack_finish (__h); })
378 
379 /* The local variable is named __o1 to avoid a name conflict
380    when obstack_blank is called.  */
381 # define obstack_finish(OBSTACK)					\
382 __extension__								\
383 ({ struct obstack *__o1 = (OBSTACK);					\
384    void *__value = (void *) __o1->object_base;				\
385    if (__o1->next_free == __value)					\
386      __o1->maybe_empty_object = 1;					\
387    __o1->next_free							\
388      = __PTR_ALIGN (__o1->object_base, __o1->next_free,			\
389 		    __o1->alignment_mask);				\
390    if (__o1->next_free - (char *)__o1->chunk				\
391        > __o1->chunk_limit - (char *)__o1->chunk)			\
392      __o1->next_free = __o1->chunk_limit;				\
393    __o1->object_base = __o1->next_free;					\
394    __value; })
395 
396 # define obstack_free(OBSTACK, OBJ)					\
397 __extension__								\
398 ({ struct obstack *__o = (OBSTACK);					\
399    void *__obj = (OBJ);							\
400    if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit)  \
401      __o->next_free = __o->object_base = (char *)__obj;			\
402    else (obstack_free) (__o, __obj); })
403 
404 #else /* not __GNUC__ or not __STDC__ */
405 
406 # define obstack_object_size(h) \
407  (unsigned) ((h)->next_free - (h)->object_base)
408 
409 # define obstack_room(h)		\
410  (unsigned) ((h)->chunk_limit - (h)->next_free)
411 
412 # define obstack_empty_p(h) \
413  ((h)->chunk->prev == 0							\
414   && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk,		\
415 				    (h)->chunk->contents,		\
416 				    (h)->alignment_mask))
417 
418 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
419    so that we can avoid having void expressions
420    in the arms of the conditional expression.
421    Casting the third operand to void was tried before,
422    but some compilers won't accept it.  */
423 
424 # define obstack_make_room(h,length)					\
425 ( (h)->temp.tempint = (length),						\
426   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)		\
427    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
428 
429 # define obstack_grow(h,where,length)					\
430 ( (h)->temp.tempint = (length),						\
431   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)		\
432    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),		\
433   memcpy ((h)->next_free, where, (h)->temp.tempint),			\
434   (h)->next_free += (h)->temp.tempint)
435 
436 # define obstack_grow0(h,where,length)					\
437 ( (h)->temp.tempint = (length),						\
438   (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit)		\
439    ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0),		\
440   memcpy ((h)->next_free, where, (h)->temp.tempint),			\
441   (h)->next_free += (h)->temp.tempint,					\
442   *((h)->next_free)++ = 0)
443 
444 # define obstack_1grow(h,datum)						\
445 ( (((h)->next_free + 1 > (h)->chunk_limit)				\
446    ? (_obstack_newchunk ((h), 1), 0) : 0),				\
447   obstack_1grow_fast (h, datum))
448 
449 # define obstack_ptr_grow(h,datum)					\
450 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit)		\
451    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),		\
452   obstack_ptr_grow_fast (h, datum))
453 
454 # define obstack_int_grow(h,datum)					\
455 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit)			\
456    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),			\
457   obstack_int_grow_fast (h, datum))
458 
459 # define obstack_ptr_grow_fast(h,aptr)					\
460   (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
461 
462 # define obstack_int_grow_fast(h,aint)					\
463   (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
464 
465 # define obstack_blank(h,length)					\
466 ( (h)->temp.tempint = (length),						\
467   (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint)		\
468    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),		\
469   obstack_blank_fast (h, (h)->temp.tempint))
470 
471 # define obstack_alloc(h,length)					\
472  (obstack_blank ((h), (length)), obstack_finish ((h)))
473 
474 # define obstack_copy(h,where,length)					\
475  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
476 
477 # define obstack_copy0(h,where,length)					\
478  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
479 
480 # define obstack_finish(h)						\
481 ( ((h)->next_free == (h)->object_base					\
482    ? (((h)->maybe_empty_object = 1), 0)					\
483    : 0),								\
484   (h)->temp.tempptr = (h)->object_base,					\
485   (h)->next_free							\
486     = __PTR_ALIGN ((h)->object_base, (h)->next_free,			\
487 		   (h)->alignment_mask),				\
488   (((h)->next_free - (char *) (h)->chunk				\
489     > (h)->chunk_limit - (char *) (h)->chunk)				\
490    ? ((h)->next_free = (h)->chunk_limit) : 0),				\
491   (h)->object_base = (h)->next_free,					\
492   (h)->temp.tempptr)
493 
494 # define obstack_free(h,obj)						\
495 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk,		\
496   ((((h)->temp.tempint > 0						\
497     && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk))	\
498    ? (int) ((h)->next_free = (h)->object_base				\
499 	    = (h)->temp.tempint + (char *) (h)->chunk)			\
500    : (((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0)))
501 
502 #endif /* not __GNUC__ or not __STDC__ */
503 
504 #ifdef __cplusplus
505 }	/* C++ */
506 #endif
507 
508 #endif /* obstack.h */
509