summary refs log tree commit diff
path: root/malloc/obstack.h
blob: b09e9f4f65c1c2376956ce640e1ecdf24ae6ad68 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
/* obstack.h - object stack macros
   Copyright (C) 1988-2021 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

/* Summary:

   All the apparent functions defined here are macros. The idea
   is that you would use these pre-tested macros to solve a
   very specific set of problems, and they would run fast.
   Caution: no side-effects in arguments please!! They may be
   evaluated MANY times!!

   These macros operate a stack of objects.  Each object starts life
   small, and may grow to maturity.  (Consider building a word syllable
   by syllable.)  An object can move while it is growing.  Once it has
   been "finished" it never changes address again.  So the "top of the
   stack" is typically an immature growing object, while the rest of the
   stack is of mature, fixed size and fixed address objects.

   These routines grab large chunks of memory, using a function you
   supply, called 'obstack_chunk_alloc'.  On occasion, they free chunks,
   by calling 'obstack_chunk_free'.  You must define them and declare
   them before using any obstack macros.

   Each independent stack is represented by a 'struct obstack'.
   Each of the obstack macros expects a pointer to such a structure
   as the first argument.

   One motivation for this package is the problem of growing char strings
   in symbol tables.  Unless you are "fascist pig with a read-only mind"
   --Gosper's immortal quote from HAKMEM item 154, out of context--you
   would not like to put any arbitrary upper limit on the length of your
   symbols.

   In practice this often means you will build many short symbols and a
   few long symbols.  At the time you are reading a symbol you don't know
   how long it is.  One traditional method is to read a symbol into a
   buffer, realloc()ating the buffer every time you try to read a symbol
   that is longer than the buffer.  This is beaut, but you still will
   want to copy the symbol from the buffer to a more permanent
   symbol-table entry say about half the time.

   With obstacks, you can work differently.  Use one obstack for all symbol
   names.  As you read a symbol, grow the name in the obstack gradually.
   When the name is complete, finalize it.  Then, if the symbol exists already,
   free the newly read name.

   The way we do this is to take a large chunk, allocating memory from
   low addresses.  When you want to build a symbol in the chunk you just
   add chars above the current "high water mark" in the chunk.  When you
   have finished adding chars, because you got to the end of the symbol,
   you know how long the chars are, and you can create a new object.
   Mostly the chars will not burst over the highest address of the chunk,
   because you would typically expect a chunk to be (say) 100 times as
   long as an average object.

   In case that isn't clear, when we have enough chars to make up
   the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
   so we just point to it where it lies.  No moving of chars is
   needed and this is the second win: potentially long strings need
   never be explicitly shuffled. Once an object is formed, it does not
   change its address during its lifetime.

   When the chars burst over a chunk boundary, we allocate a larger
   chunk, and then copy the partly formed object from the end of the old
   chunk to the beginning of the new larger chunk.  We then carry on
   accreting characters to the end of the object as we normally would.

   A special macro is provided to add a single char at a time to a
   growing object.  This allows the use of register variables, which
   break the ordinary 'growth' macro.

   Summary:
	We allocate large chunks.
	We carve out one object at a time from the current chunk.
	Once carved, an object never moves.
	We are free to append data of any size to the currently
	  growing object.
	Exactly one object is growing in an obstack at any one time.
	You can run one obstack per control block.
	You may have as many control blocks as you dare.
	Because of the way we do it, you can "unwind" an obstack
	  back to a previous state. (You may remove objects much
	  as you would with a stack.)
 */


/* Don't do the contents of this file more than once.  */

#ifndef _OBSTACK_H
#define _OBSTACK_H 1

/* We need the type of a pointer subtraction.  If __PTRDIFF_TYPE__ is
   defined, as with GNU C, use that; that way we don't pollute the
   namespace with <stddef.h>'s symbols.  Otherwise, include <stddef.h>
   and use ptrdiff_t.  */

#ifdef __PTRDIFF_TYPE__
# define PTR_INT_TYPE __PTRDIFF_TYPE__
#else
# include <stddef.h>
# define PTR_INT_TYPE ptrdiff_t
#endif

/* If B is the base of an object addressed by P, return the result of
   aligning P to the next multiple of A + 1.  B and P must be of type
   char *.  A + 1 must be a power of 2.  */

#define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A)))

/* Similar to _BPTR_ALIGN (B, P, A), except optimize the common case
   where pointers can be converted to integers, aligned as integers,
   and converted back again.  If PTR_INT_TYPE is narrower than a
   pointer (e.g., the AS/400), play it safe and compute the alignment
   relative to B.  Otherwise, use the faster strategy of computing the
   alignment relative to 0.  */

#define __PTR_ALIGN(B, P, A)						      \
  __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \
		P, A)

#include <string.h>

#ifndef __attribute_pure__
# define __attribute_pure__ _GL_ATTRIBUTE_PURE
#endif

#ifdef __cplusplus
extern "C" {
#endif

struct _obstack_chunk           /* Lives at front of each chunk. */
{
  char *limit;                  /* 1 past end of this chunk */
  struct _obstack_chunk *prev;  /* address of prior chunk or NULL */
  char contents[4];             /* objects begin here */
};

struct obstack          /* control current object in current chunk */
{
  long chunk_size;              /* preferred size to allocate chunks in */
  struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
  char *object_base;            /* address of object we are building */
  char *next_free;              /* where to add next char to current object */
  char *chunk_limit;            /* address of char after current chunk */
  union
  {
    PTR_INT_TYPE tempint;
    void *tempptr;
  } temp;                       /* Temporary for some macros.  */
  int alignment_mask;           /* Mask of alignment for each object. */
  /* These prototypes vary based on 'use_extra_arg', and we use
     casts to the prototypeless function type in all assignments,
     but having prototypes here quiets -Wstrict-prototypes.  */
  struct _obstack_chunk *(*chunkfun) (void *, long);
  void (*freefun) (void *, struct _obstack_chunk *);
  void *extra_arg;              /* first arg for chunk alloc/dealloc funcs */
  unsigned use_extra_arg : 1;     /* chunk alloc/dealloc funcs take extra arg */
  unsigned maybe_empty_object : 1; /* There is a possibility that the current
				      chunk contains a zero-length object.  This
				      prevents freeing the chunk if we allocate
				      a bigger chunk to replace it. */
  unsigned alloc_failed : 1;      /* No longer used, as we now call the failed
				     handler on error, but retained for binary
				     compatibility.  */
};

/* Declare the external functions we use; they are in obstack.c.  */

extern void _obstack_newchunk (struct obstack *, int);
extern int _obstack_begin (struct obstack *, int, int,
			   void *(*)(long), void (*)(void *));
extern int _obstack_begin_1 (struct obstack *, int, int,
			     void *(*)(void *, long),
			     void (*)(void *, void *), void *);
extern int _obstack_memory_used (struct obstack *) __attribute_pure__;

/* The default name of the function for freeing a chunk is 'obstack_free',
   but gnulib users can override this by defining '__obstack_free'.  */
#ifndef __obstack_free
# define __obstack_free obstack_free
#endif
extern void __obstack_free (struct obstack *, void *);


/* Error handler called when 'obstack_chunk_alloc' failed to allocate
   more memory.  This can be set to a user defined function which
   should either abort gracefully or use longjump - but shouldn't
   return.  The default action is to print a message and abort.  */
extern void (*obstack_alloc_failed_handler) (void);

/* Exit value used when 'print_and_abort' is used.  */
extern int obstack_exit_failure;

/* Pointer to beginning of object being allocated or to be allocated next.
   Note that this might not be the final address of the object
   because a new chunk might be needed to hold the final size.  */

#define obstack_base(h) ((void *) (h)->object_base)

/* Size for allocating ordinary chunks.  */

#define obstack_chunk_size(h) ((h)->chunk_size)

/* Pointer to next byte not yet allocated in current chunk.  */

#define obstack_next_free(h)    ((h)->next_free)

/* Mask specifying low bits that should be clear in address of an object.  */

#define obstack_alignment_mask(h) ((h)->alignment_mask)

/* To prevent prototype warnings provide complete argument list.  */
#define obstack_init(h)							      \
  _obstack_begin ((h), 0, 0,						      \
		  (void *(*)(long))obstack_chunk_alloc,			      \
		  (void (*)(void *))obstack_chunk_free)

#define obstack_begin(h, size)						      \
  _obstack_begin ((h), (size), 0,					      \
		  (void *(*)(long))obstack_chunk_alloc,			      \
		  (void (*)(void *))obstack_chunk_free)

#define obstack_specify_allocation(h, size, alignment, chunkfun, freefun)  \
  _obstack_begin ((h), (size), (alignment),				      \
		  (void *(*)(long))(chunkfun),				      \
		  (void (*)(void *))(freefun))

#define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
  _obstack_begin_1 ((h), (size), (alignment),				      \
		    (void *(*)(void *, long))(chunkfun),		      \
		    (void (*)(void *, void *))(freefun), (arg))

#define obstack_chunkfun(h, newchunkfun) \
  ((h)->chunkfun = (struct _obstack_chunk *(*)(void *, long))(newchunkfun))

#define obstack_freefun(h, newfreefun) \
  ((h)->freefun = (void (*)(void *, struct _obstack_chunk *))(newfreefun))

#define obstack_1grow_fast(h, achar) (*((h)->next_free)++ = (achar))

#define obstack_blank_fast(h, n) ((h)->next_free += (n))

#define obstack_memory_used(h) _obstack_memory_used (h)

#if defined __GNUC__
# if ! (2 < __GNUC__ + (8 <= __GNUC_MINOR__))
#  define __extension__
# endif

/* For GNU C, if not -traditional,
   we can define these macros to compute all args only once
   without using a global variable.
   Also, we can avoid using the 'temp' slot, to make faster code.  */

# define obstack_object_size(OBSTACK)					      \
  __extension__								      \
    ({ struct obstack const *__o = (OBSTACK);				      \
       (unsigned) (__o->next_free - __o->object_base); })

# define obstack_room(OBSTACK)						      \
  __extension__								      \
    ({ struct obstack const *__o = (OBSTACK);				      \
       (unsigned) (__o->chunk_limit - __o->next_free); })

# define obstack_make_room(OBSTACK, length)				      \
  __extension__								      \
    ({ struct obstack *__o = (OBSTACK);					      \
       int __len = (length);						      \
       if (__o->chunk_limit - __o->next_free < __len)			      \
	 _obstack_newchunk (__o, __len);				      \
       (void) 0; })

# define obstack_empty_p(OBSTACK)					      \
  __extension__								      \
    ({ struct obstack const *__o = (OBSTACK);				      \
       (__o->chunk->prev == 0						      \
	&& __o->next_free == __PTR_ALIGN ((char *) __o->chunk,		      \
					  __o->chunk->contents,		      \
					  __o->alignment_mask)); })

# define obstack_grow(OBSTACK, where, length)				      \
  __extension__								      \
    ({ struct obstack *__o = (OBSTACK);					      \
       int __len = (length);						      \
       if (__o->next_free + __len > __o->chunk_limit)			      \
	 _obstack_newchunk (__o, __len);				      \
       memcpy (__o->next_free, where, __len);				      \
       __o->next_free += __len;						      \
       (void) 0; })

# define obstack_grow0(OBSTACK, where, length)				      \
  __extension__								      \
    ({ struct obstack *__o = (OBSTACK);					      \
       int __len = (length);						      \
       if (__o->next_free + __len + 1 > __o->chunk_limit)		      \
	 _obstack_newchunk (__o, __len + 1);				      \
       memcpy (__o->next_free, where, __len);				      \
       __o->next_free += __len;						      \
       *(__o->next_free)++ = 0;						      \
       (void) 0; })

# define obstack_1grow(OBSTACK, datum)					      \
  __extension__								      \
    ({ struct obstack *__o = (OBSTACK);					      \
       if (__o->next_free + 1 > __o->chunk_limit)			      \
	 _obstack_newchunk (__o, 1);					      \
       obstack_1grow_fast (__o, datum);					      \
       (void) 0; })

/* These assume that the obstack alignment is good enough for pointers
   or ints, and that the data added so far to the current object
   shares that much alignment.  */

# define obstack_ptr_grow(OBSTACK, datum)				      \
  __extension__								      \
    ({ struct obstack *__o = (OBSTACK);					      \
       if (__o->next_free + sizeof (void *) > __o->chunk_limit)		      \
	 _obstack_newchunk (__o, sizeof (void *));			      \
       obstack_ptr_grow_fast (__o, datum); })				      \

# define obstack_int_grow(OBSTACK, datum)				      \
  __extension__								      \
    ({ struct obstack *__o = (OBSTACK);					      \
       if (__o->next_free + sizeof (int) > __o->chunk_limit)		      \
	 _obstack_newchunk (__o, sizeof (int));				      \
       obstack_int_grow_fast (__o, datum); })

# define obstack_ptr_grow_fast(OBSTACK, aptr)				      \
  __extension__								      \
    ({ struct obstack *__o1 = (OBSTACK);				      \
       void *__p1 = __o1->next_free;					      \
       *(const void **) __p1 = (aptr);					      \
       __o1->next_free += sizeof (const void *);			      \
       (void) 0; })

# define obstack_int_grow_fast(OBSTACK, aint)				      \
  __extension__								      \
    ({ struct obstack *__o1 = (OBSTACK);				      \
       void *__p1 = __o1->next_free;					      \
       *(int *) __p1 = (aint);						      \
       __o1->next_free += sizeof (int);					      \
       (void) 0; })

# define obstack_blank(OBSTACK, length)					      \
  __extension__								      \
    ({ struct obstack *__o = (OBSTACK);					      \
       int __len = (length);						      \
       if (__o->chunk_limit - __o->next_free < __len)			      \
	 _obstack_newchunk (__o, __len);				      \
       obstack_blank_fast (__o, __len);					      \
       (void) 0; })

# define obstack_alloc(OBSTACK, length)					      \
  __extension__								      \
    ({ struct obstack *__h = (OBSTACK);					      \
       obstack_blank (__h, (length));					      \
       obstack_finish (__h); })

# define obstack_copy(OBSTACK, where, length)				      \
  __extension__								      \
    ({ struct obstack *__h = (OBSTACK);					      \
       obstack_grow (__h, (where), (length));				      \
       obstack_finish (__h); })

# define obstack_copy0(OBSTACK, where, length)				      \
  __extension__								      \
    ({ struct obstack *__h = (OBSTACK);					      \
       obstack_grow0 (__h, (where), (length));				      \
       obstack_finish (__h); })

/* The local variable is named __o1 to avoid a name conflict
   when obstack_blank is called.  */
# define obstack_finish(OBSTACK)					      \
  __extension__								      \
    ({ struct obstack *__o1 = (OBSTACK);				      \
       void *__value = (void *) __o1->object_base;			      \
       if (__o1->next_free == __value)					      \
	 __o1->maybe_empty_object = 1;					      \
       __o1->next_free							      \
	 = __PTR_ALIGN (__o1->object_base, __o1->next_free,		      \
			__o1->alignment_mask);				      \
       if (__o1->next_free - (char *) __o1->chunk			      \
	   > __o1->chunk_limit - (char *) __o1->chunk)			      \
	 __o1->next_free = __o1->chunk_limit;				      \
       __o1->object_base = __o1->next_free;				      \
       __value; })

# define obstack_free(OBSTACK, OBJ)					      \
  __extension__								      \
    ({ struct obstack *__o = (OBSTACK);					      \
       void *__obj = (OBJ);						      \
       if (__obj > (void *) __o->chunk && __obj < (void *) __o->chunk_limit)  \
	 __o->next_free = __o->object_base = (char *) __obj;		      \
       else (__obstack_free) (__o, __obj); })

#else /* not __GNUC__ */

# define obstack_object_size(h) \
  (unsigned) ((h)->next_free - (h)->object_base)

# define obstack_room(h)						      \
  (unsigned) ((h)->chunk_limit - (h)->next_free)

# define obstack_empty_p(h) \
  ((h)->chunk->prev == 0						      \
   && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk,		      \
				     (h)->chunk->contents,		      \
				     (h)->alignment_mask))

/* Note that the call to _obstack_newchunk is enclosed in (..., 0)
   so that we can avoid having void expressions
   in the arms of the conditional expression.
   Casting the third operand to void was tried before,
   but some compilers won't accept it.  */

# define obstack_make_room(h, length)					      \
  ((h)->temp.tempint = (length),					      \
   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)		      \
   ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))

# define obstack_grow(h, where, length)					      \
  ((h)->temp.tempint = (length),					      \
   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)		      \
   ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),		      \
   memcpy ((h)->next_free, where, (h)->temp.tempint),			      \
   (h)->next_free += (h)->temp.tempint)

# define obstack_grow0(h, where, length)				      \
  ((h)->temp.tempint = (length),					      \
   (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit)		      \
   ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0),		      \
   memcpy ((h)->next_free, where, (h)->temp.tempint),			      \
   (h)->next_free += (h)->temp.tempint,					      \
   *((h)->next_free)++ = 0)

# define obstack_1grow(h, datum)					      \
  ((((h)->next_free + 1 > (h)->chunk_limit)				      \
    ? (_obstack_newchunk ((h), 1), 0) : 0),				      \
   obstack_1grow_fast (h, datum))

# define obstack_ptr_grow(h, datum)					      \
  ((((h)->next_free + sizeof (char *) > (h)->chunk_limit)		      \
    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),		      \
   obstack_ptr_grow_fast (h, datum))

# define obstack_int_grow(h, datum)					      \
  ((((h)->next_free + sizeof (int) > (h)->chunk_limit)			      \
    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),			      \
   obstack_int_grow_fast (h, datum))

# define obstack_ptr_grow_fast(h, aptr)					      \
  (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))

# define obstack_int_grow_fast(h, aint)					      \
  (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))

# define obstack_blank(h, length)					      \
  ((h)->temp.tempint = (length),					      \
   (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint)		      \
   ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),		      \
   obstack_blank_fast (h, (h)->temp.tempint))

# define obstack_alloc(h, length)					      \
  (obstack_blank ((h), (length)), obstack_finish ((h)))

# define obstack_copy(h, where, length)					      \
  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))

# define obstack_copy0(h, where, length)				      \
  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))

# define obstack_finish(h)						      \
  (((h)->next_free == (h)->object_base					      \
    ? (((h)->maybe_empty_object = 1), 0)				      \
    : 0),								      \
   (h)->temp.tempptr = (h)->object_base,				      \
   (h)->next_free							      \
     = __PTR_ALIGN ((h)->object_base, (h)->next_free,			      \
		    (h)->alignment_mask),				      \
   (((h)->next_free - (char *) (h)->chunk				      \
     > (h)->chunk_limit - (char *) (h)->chunk)				      \
   ? ((h)->next_free = (h)->chunk_limit) : 0),				      \
   (h)->object_base = (h)->next_free,					      \
   (h)->temp.tempptr)

# define obstack_free(h, obj)						      \
  ((h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk,		      \
   ((((h)->temp.tempint > 0						      \
      && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk))	      \
    ? (void) ((h)->next_free = (h)->object_base				      \
	      = (h)->temp.tempint + (char *) (h)->chunk)		      \
    : (__obstack_free) (h, (h)->temp.tempint + (char *) (h)->chunk)))

#endif /* not __GNUC__ */

#ifdef __cplusplus
}       /* C++ */
#endif

#endif /* obstack.h */