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1 /* obstack.h - object stack macros
2    Copyright (C) 1988-1994, 1996-1999, 2003-2006, 2009-2012 Free Software
3    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 3 of the License, or
9    (at your option) 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
17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
18 
19 /* Summary:
20 
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!!
26 
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.
33 
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.
38 
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.
42 
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
47 symbols.
48 
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.
56 
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.
61 
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.
70 
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.
77 
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.
82 
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.
86 
87 Summary:
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
92           growing object.
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.)
99 */
100 
101 
102 /* Don't do the contents of this file more than once.  */
103 
104 #ifndef _OBSTACK_H
105 #define _OBSTACK_H 1
106 
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.  */
111 
112 #ifdef __PTRDIFF_TYPE__
113 # define PTR_INT_TYPE __PTRDIFF_TYPE__
114 #else
115 # include <stddef.h>
116 # define PTR_INT_TYPE ptrdiff_t
117 #endif
118 
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.  */
122 
123 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A)))
124 
125 /* Similar 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.  */
131 
132 #define __PTR_ALIGN(B, P, A)                                                \
133   __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \
134                 P, A)
135 
136 #include <string.h>
137 
138 #ifdef __cplusplus
139 extern "C" {
140 #endif
141 
142 struct _obstack_chunk           /* Lives at front of each chunk. */
143 {
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 */
147 };
148 
149 struct obstack          /* control current object in current chunk */
150 {
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 */
156   union
157   {
158     PTR_INT_TYPE tempint;
159     void *tempptr;
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
175                                    compatibility.  */
176 };
177 
178 /* Declare the external functions we use; they are in obstack.c.  */
179 
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 *);
187 
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
192 #endif
193 extern void __obstack_free (struct obstack *obstack, void *block);
194 
195 
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 
202 /* Exit value used when 'print_and_abort' is used.  */
203 extern int obstack_exit_failure;
204 
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.  */
208 
209 #define obstack_base(h) ((void *) (h)->object_base)
210 
211 /* Size for allocating ordinary chunks.  */
212 
213 #define obstack_chunk_size(h) ((h)->chunk_size)
214 
215 /* Pointer to next byte not yet allocated in current chunk.  */
216 
217 #define obstack_next_free(h)    ((h)->next_free)
218 
219 /* Mask specifying low bits that should be clear in address of an object.  */
220 
221 #define obstack_alignment_mask(h) ((h)->alignment_mask)
222 
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)
228 
229 #define obstack_begin(h, size)                                  \
230   _obstack_begin ((h), (size), 0,                               \
231                   (void *(*) (long)) obstack_chunk_alloc,       \
232                   (void (*) (void *)) obstack_chunk_free)
233 
234 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun)  \
235   _obstack_begin ((h), (size), (alignment),                                \
236                   (void *(*) (long)) (chunkfun),                           \
237                   (void (*) (void *)) (freefun))
238 
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))
243 
244 #define obstack_chunkfun(h, newchunkfun) \
245   ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
246 
247 #define obstack_freefun(h, newfreefun) \
248   ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
249 
250 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
251 
252 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
253 
254 #define obstack_memory_used(h) _obstack_memory_used (h)
255 
256 #if defined __GNUC__
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
259    __GNUC_MINOR__.  */
260 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
261 #  define __extension__
262 # endif
263 
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.  */
268 
269 # define obstack_object_size(OBSTACK)                                   \
270   __extension__                                                         \
271   ({ struct obstack const *__o = (OBSTACK);                             \
272      (unsigned) (__o->next_free - __o->object_base); })
273 
274 # define obstack_room(OBSTACK)                                          \
275   __extension__                                                         \
276   ({ struct obstack const *__o = (OBSTACK);                             \
277      (unsigned) (__o->chunk_limit - __o->next_free); })
278 
279 # define obstack_make_room(OBSTACK,length)                              \
280 __extension__                                                           \
281 ({ struct obstack *__o = (OBSTACK);                                     \
282    int __len = (length);                                                \
283    if (__o->chunk_limit - __o->next_free < __len)                       \
284      _obstack_newchunk (__o, __len);                                    \
285    (void) 0; })
286 
287 # define obstack_empty_p(OBSTACK)                                       \
288   __extension__                                                         \
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)); })
294 
295 # define obstack_grow(OBSTACK,where,length)                             \
296 __extension__                                                           \
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;                                             \
303    (void) 0; })
304 
305 # define obstack_grow0(OBSTACK,where,length)                            \
306 __extension__                                                           \
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;                                             \
314    (void) 0; })
315 
316 # define obstack_1grow(OBSTACK,datum)                                   \
317 __extension__                                                           \
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);                                     \
322    (void) 0; })
323 
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.  */
327 
328 # define obstack_ptr_grow(OBSTACK,datum)                                \
329 __extension__                                                           \
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); })                               \
334 
335 # define obstack_int_grow(OBSTACK,datum)                                \
336 __extension__                                                           \
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); })
341 
342 # define obstack_ptr_grow_fast(OBSTACK,aptr)                            \
343 __extension__                                                           \
344 ({ struct obstack *__o1 = (OBSTACK);                                    \
345    *(const void **) __o1->next_free = (aptr);                           \
346    __o1->next_free += sizeof (const void *);                            \
347    (void) 0; })
348 
349 # define obstack_int_grow_fast(OBSTACK,aint)                            \
350 __extension__                                                           \
351 ({ struct obstack *__o1 = (OBSTACK);                                    \
352    *(int *) __o1->next_free = (aint);                                   \
353    __o1->next_free += sizeof (int);                                     \
354    (void) 0; })
355 
356 # define obstack_blank(OBSTACK,length)                                  \
357 __extension__                                                           \
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);                                     \
363    (void) 0; })
364 
365 # define obstack_alloc(OBSTACK,length)                                  \
366 __extension__                                                           \
367 ({ struct obstack *__h = (OBSTACK);                                     \
368    obstack_blank (__h, (length));                                       \
369    obstack_finish (__h); })
370 
371 # define obstack_copy(OBSTACK,where,length)                             \
372 __extension__                                                           \
373 ({ struct obstack *__h = (OBSTACK);                                     \
374    obstack_grow (__h, (where), (length));                               \
375    obstack_finish (__h); })
376 
377 # define obstack_copy0(OBSTACK,where,length)                            \
378 __extension__                                                           \
379 ({ struct obstack *__h = (OBSTACK);                                     \
380    obstack_grow0 (__h, (where), (length));                              \
381    obstack_finish (__h); })
382 
383 /* The local variable is named __o1 to avoid a name conflict
384    when obstack_blank is called.  */
385 # define obstack_finish(OBSTACK)                                        \
386 __extension__                                                           \
387 ({ struct obstack *__o1 = (OBSTACK);                                    \
388    void *__value = (void *) __o1->object_base;                          \
389    if (__o1->next_free == __value)                                      \
390      __o1->maybe_empty_object = 1;                                      \
391    __o1->next_free                                                      \
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;                                 \
398    __value; })
399 
400 # define obstack_free(OBSTACK, OBJ)                                     \
401 __extension__                                                           \
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); })
407 
408 #else /* not __GNUC__ */
409 
410 # define obstack_object_size(h) \
411  (unsigned) ((h)->next_free - (h)->object_base)
412 
413 # define obstack_room(h)                \
414  (unsigned) ((h)->chunk_limit - (h)->next_free)
415 
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))
421 
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.  */
427 
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))
432 
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)
439 
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)
447 
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))
452 
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))
457 
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))
462 
463 # define obstack_ptr_grow_fast(h,aptr)                                  \
464   (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
465 
466 # define obstack_int_grow_fast(h,aint)                                  \
467   (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
468 
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))
474 
475 # define obstack_alloc(h,length)                                        \
476  (obstack_blank ((h), (length)), obstack_finish ((h)))
477 
478 # define obstack_copy(h,where,length)                                   \
479  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
480 
481 # define obstack_copy0(h,where,length)                                  \
482  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
483 
484 # define obstack_finish(h)                                              \
485 ( ((h)->next_free == (h)->object_base                                   \
486    ? (((h)->maybe_empty_object = 1), 0)                                 \
487    : 0),                                                                \
488   (h)->temp.tempptr = (h)->object_base,                                 \
489   (h)->next_free                                                        \
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,                                    \
496   (h)->temp.tempptr)
497 
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)))
505 
506 #endif /* not __GNUC__ */
507 
508 #ifdef __cplusplus
509 }       /* C++ */
510 #endif
511 
512 #endif /* obstack.h */
513