1 /* obstack.h - object stack macros
2 Copyright (C) 1988 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify it
5 under the terms of the GNU General Public License as published by the
6 Free Software Foundation; either version 2, or (at your option) any
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
18 * $FreeBSD: src/gnu/usr.bin/as/obstack.h,v 1.6 1999/08/27 23:34:20 peter Exp $
24 All the apparent functions defined here are macros. The idea
25 is that you would use these pre-tested macros to solve a
26 very specific set of problems, and they would run fast.
27 Caution: no side-effects in arguments please!! They may be
28 evaluated MANY times!!
30 These macros operate a stack of objects. Each object starts life
31 small, and may grow to maturity. (Consider building a word syllable
32 by syllable.) An object can move while it is growing. Once it has
33 been "finished" it never changes address again. So the "top of the
34 stack" is typically an immature growing object, while the rest of the
35 stack is of mature, fixed size and fixed address objects.
37 These routines grab large chunks of memory, using a function you
38 supply, called `obstack_chunk_alloc'. On occasion, they free chunks,
39 by calling `obstack_chunk_free'. You must define them and declare
40 them before using any obstack macros.
42 Each independent stack is represented by a `struct obstack'.
43 Each of the obstack macros expects a pointer to such a structure
44 as the first argument.
46 One motivation for this package is the problem of growing char strings
47 in symbol tables. Unless you are "fascist pig with a read-only mind"
48 [Gosper's immortal quote from HAKMEM item 154, out of context] you
49 would not like to put any arbitrary upper limit on the length of your
52 In practice this often means you will build many short symbols and a
53 few long symbols. At the time you are reading a symbol you don't know
54 how long it is. One traditional method is to read a symbol into a
55 buffer, realloc()ating the buffer every time you try to read a symbol
56 that is longer than the buffer. This is beaut, but you still will
57 want to copy the symbol from the buffer to a more permanent
58 symbol-table entry say about half the time.
60 With obstacks, you can work differently. Use one obstack for all symbol
61 names. As you read a symbol, grow the name in the obstack gradually.
62 When the name is complete, finalize it. Then, if the symbol exists already,
63 free the newly read name.
65 The way we do this is to take a large chunk, allocating memory from
66 low addresses. When you want to build a symbol in the chunk you just
67 add chars above the current "high water mark" in the chunk. When you
68 have finished adding chars, because you got to the end of the symbol,
69 you know how long the chars are, and you can create a new object.
70 Mostly the chars will not burst over the highest address of the chunk,
71 because you would typically expect a chunk to be (say) 100 times as
72 long as an average object.
74 In case that isn't clear, when we have enough chars to make up
75 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
76 so we just point to it where it lies. No moving of chars is
77 needed and this is the second win: potentially long strings need
78 never be explicitly shuffled. Once an object is formed, it does not
79 change its address during its lifetime.
81 When the chars burst over a chunk boundary, we allocate a larger
82 chunk, and then copy the partly formed object from the end of the old
83 chunk to the beginning of the new larger chunk. We then carry on
84 accreting characters to the end of the object as we normally would.
86 A special macro is provided to add a single char at a time to a
87 growing object. This allows the use of register variables, which
88 break the ordinary 'growth' macro.
91 We allocate large chunks.
92 We carve out one object at a time from the current chunk.
93 Once carved, an object never moves.
94 We are free to append data of any size to the currently
96 Exactly one object is growing in an obstack at any one time.
97 You can run one obstack per control block.
98 You may have as many control blocks as you dare.
99 Because of the way we do it, you can `unwind' a obstack
100 back to a previous state. (You may remove objects much
101 as you would with a stack.)
105 /* Don't do the contents of this file more than once. */
110 /* We use subtraction of (char *)0 instead of casting to int
111 because on word-addressable machines a simple cast to int
112 may ignore the byte-within-word field of the pointer. */
115 #define __PTR_TO_INT(P) ((P) - (char *)0)
119 #define __INT_TO_PTR(P) ((P) + (char *)0)
122 struct _obstack_chunk /* Lives at front of each chunk. */
124 char *limit; /* 1 past end of this chunk */
125 struct _obstack_chunk *prev; /* address of prior chunk or NULL */
126 char contents[4]; /* objects begin here */
129 struct obstack /* control current object in current chunk */
131 long chunk_size; /* preferred size to allocate chunks in */
132 struct _obstack_chunk* chunk; /* address of current struct obstack_chunk */
133 char *object_base; /* address of object we are building */
134 char *next_free; /* where to add next char to current object */
135 char *chunk_limit; /* address of char after current chunk */
136 int temp; /* Temporary for some macros. */
137 int alignment_mask; /* Mask of alignment for each object. */
138 struct _obstack_chunk *(*chunkfun) (); /* User's fcn to allocate a chunk. */
139 void (*freefun) (); /* User's function to free a chunk. */
140 /* Nonzero means there is a possibility the current chunk contains
141 a zero-length object. This prevents freeing the chunk
142 if we allocate a bigger chunk to replace it. */
143 char maybe_empty_object;
146 /* Declare the external functions we use; they are in obstack.c. */
149 extern void _obstack_newchunk (struct obstack *, int);
150 extern void _obstack_free (struct obstack *, void *);
151 extern void _obstack_begin (struct obstack *, int, int,
152 void *(*) (), void (*) ());
154 extern void _obstack_newchunk ();
155 extern void _obstack_free ();
156 extern void _obstack_begin ();
161 /* Do the function-declarations after the structs
162 but before defining the macros. */
164 void obstack_init (struct obstack *obstack);
166 void * obstack_alloc (struct obstack *obstack, int size);
168 void * obstack_copy (struct obstack *obstack, void *address, int size);
169 void * obstack_copy0 (struct obstack *obstack, void *address, int size);
171 void obstack_free (struct obstack *obstack, void *block);
173 void obstack_blank (struct obstack *obstack, int size);
175 void obstack_grow (struct obstack *obstack, void *data, int size);
176 void obstack_grow0 (struct obstack *obstack, void *data, int size);
178 void obstack_1grow (struct obstack *obstack, int data_char);
179 void obstack_ptr_grow (struct obstack *obstack, void *data);
180 void obstack_int_grow (struct obstack *obstack, int data);
182 void * obstack_finish (struct obstack *obstack);
184 int obstack_object_size (struct obstack *obstack);
186 int obstack_room (struct obstack *obstack);
187 void obstack_1grow_fast (struct obstack *obstack, int data_char);
188 void obstack_ptr_grow_fast (struct obstack *obstack, void *data);
189 void obstack_int_grow_fast (struct obstack *obstack, int data);
190 void obstack_blank_fast (struct obstack *obstack, int size);
192 void * obstack_base (struct obstack *obstack);
193 void * obstack_next_free (struct obstack *obstack);
194 int obstack_alignment_mask (struct obstack *obstack);
195 int obstack_chunk_size (struct obstack *obstack);
197 #endif /* __STDC__ */
199 /* Non-ANSI C cannot really support alternative functions for these macros,
200 so we do not declare them. */
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. */
206 #define obstack_base(h) ((h)->object_base)
208 /* Size for allocating ordinary chunks. */
210 #define obstack_chunk_size(h) ((h)->chunk_size)
212 /* Pointer to next byte not yet allocated in current chunk. */
214 #define obstack_next_free(h) ((h)->next_free)
216 /* Mask specifying low bits that should be clear in address of an object. */
218 #define obstack_alignment_mask(h) ((h)->alignment_mask)
220 #define obstack_init(h) \
221 _obstack_begin ((h), 0, 0, \
222 (void *(*) ()) obstack_chunk_alloc, (void (*) ())obstack_chunk_free)
224 #define obstack_begin(h, size) \
225 _obstack_begin ((h), (size), 0, \
226 (void *(*) ()) obstack_chunk_alloc, (void (*) ())obstack_chunk_free)
228 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = achar)
230 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
232 #if defined (__GNUC__) && defined (__STDC__)
234 #define __extension__
237 /* For GNU C, if not -traditional,
238 we can define these macros to compute all args only once
239 without using a global variable.
240 Also, we can avoid using the `temp' slot, to make faster code. */
242 #define obstack_object_size(OBSTACK) \
244 ({ struct obstack *__o = (OBSTACK); \
245 (unsigned) (__o->next_free - __o->object_base); })
247 #define obstack_room(OBSTACK) \
249 ({ struct obstack *__o = (OBSTACK); \
250 (unsigned) (__o->chunk_limit - __o->next_free); })
252 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
253 so that we can avoid having void expressions
254 in the arms of the conditional expression.
255 Casting the third operand to void was tried before,
256 but some compilers won't accept it. */
257 #define obstack_grow(OBSTACK,where,length) \
259 ({ struct obstack *__o = (OBSTACK); \
260 int __len = (length); \
261 ((__o->next_free + __len > __o->chunk_limit) \
262 ? (_obstack_newchunk (__o, __len), 0) : 0); \
263 memcpy (__o->next_free, where, __len); \
264 __o->next_free += __len; \
267 #define obstack_grow0(OBSTACK,where,length) \
269 ({ struct obstack *__o = (OBSTACK); \
270 int __len = (length); \
271 ((__o->next_free + __len + 1 > __o->chunk_limit) \
272 ? (_obstack_newchunk (__o, __len + 1), 0) : 0), \
273 memcpy (__o->next_free, where, __len), \
274 __o->next_free += __len, \
275 *(__o->next_free)++ = 0; \
278 #define obstack_1grow(OBSTACK,datum) \
280 ({ struct obstack *__o = (OBSTACK); \
281 ((__o->next_free + 1 > __o->chunk_limit) \
282 ? (_obstack_newchunk (__o, 1), 0) : 0), \
283 *(__o->next_free)++ = (datum); \
286 /* These assume that the obstack alignment is good enough for pointers or ints,
287 and that the data added so far to the current object
288 shares that much alignment. */
290 #define obstack_ptr_grow(OBSTACK,datum) \
292 ({ struct obstack *__o = (OBSTACK); \
293 ((__o->next_free + sizeof (void *) > __o->chunk_limit) \
294 ? (_obstack_newchunk (__o, sizeof (void *)), 0) : 0), \
295 *(*(void ***)&__o->next_free)++ = ((void *)datum); \
298 #define obstack_int_grow(OBSTACK,datum) \
300 ({ struct obstack *__o = (OBSTACK); \
301 ((__o->next_free + sizeof (int) > __o->chunk_limit) \
302 ? (_obstack_newchunk (__o, sizeof (int)), 0) : 0), \
303 *(*(int **)&__o->next_free)++ = ((int)datum); \
306 #define obstack_ptr_grow_fast(h,aptr) (*(*(void ***)&(h)->next_free)++ = (void *)aptr)
307 #define obstack_int_grow_fast(h,aint) (*(*(int **)&(h)->next_free)++ = (int)aint)
309 #define obstack_blank(OBSTACK,length) \
311 ({ struct obstack *__o = (OBSTACK); \
312 int __len = (length); \
313 ((__o->chunk_limit - __o->next_free < __len) \
314 ? (_obstack_newchunk (__o, __len), 0) : 0); \
315 __o->next_free += __len; \
318 #define obstack_alloc(OBSTACK,length) \
320 ({ struct obstack *__h = (OBSTACK); \
321 obstack_blank (__h, (length)); \
322 obstack_finish (__h); })
324 #define obstack_copy(OBSTACK,where,length) \
326 ({ struct obstack *__h = (OBSTACK); \
327 obstack_grow (__h, (where), (length)); \
328 obstack_finish (__h); })
330 #define obstack_copy0(OBSTACK,where,length) \
332 ({ struct obstack *__h = (OBSTACK); \
333 obstack_grow0 (__h, (where), (length)); \
334 obstack_finish (__h); })
336 /* The local variable is named __o1 to avoid a name conflict
337 when obstack_blank is called. */
338 #define obstack_finish(OBSTACK) \
340 ({ struct obstack *__o1 = (OBSTACK); \
341 void *value = (void *) __o1->object_base; \
342 if (__o1->next_free == value) \
343 __o1->maybe_empty_object = 1; \
345 = __INT_TO_PTR ((__PTR_TO_INT (__o1->next_free)+__o1->alignment_mask)\
346 & ~ (__o1->alignment_mask)); \
347 ((__o1->next_free - (char *)__o1->chunk \
348 > __o1->chunk_limit - (char *)__o1->chunk) \
349 ? (__o1->next_free = __o1->chunk_limit) : 0); \
350 __o1->object_base = __o1->next_free; \
353 #define obstack_free(OBSTACK, OBJ) \
355 ({ struct obstack *__o = (OBSTACK); \
356 void *__obj = (OBJ); \
357 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \
358 __o->next_free = __o->object_base = __obj; \
359 else (obstack_free) (__o, __obj); })
361 #else /* not __GNUC__ or not __STDC__ */
363 #define obstack_object_size(h) \
364 (unsigned) ((h)->next_free - (h)->object_base)
366 #define obstack_room(h) \
367 (unsigned) ((h)->chunk_limit - (h)->next_free)
369 #define obstack_grow(h,where,length) \
370 ( (h)->temp = (length), \
371 (((h)->next_free + (h)->temp > (h)->chunk_limit) \
372 ? (_obstack_newchunk ((h), (h)->temp), 0) : 0), \
373 memcpy ((h)->next_free, where, (h)->temp), \
374 (h)->next_free += (h)->temp)
376 #define obstack_grow0(h,where,length) \
377 ( (h)->temp = (length), \
378 (((h)->next_free + (h)->temp + 1 > (h)->chunk_limit) \
379 ? (_obstack_newchunk ((h), (h)->temp + 1), 0) : 0), \
380 memcpy ((h)->next_free, where, (h)->temp), \
381 (h)->next_free += (h)->temp, \
382 *((h)->next_free)++ = 0)
384 #define obstack_1grow(h,datum) \
385 ( (((h)->next_free + 1 > (h)->chunk_limit) \
386 ? (_obstack_newchunk ((h), 1), 0) : 0), \
387 *((h)->next_free)++ = (datum))
389 #define obstack_ptr_grow(h,datum) \
390 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \
391 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \
392 *(*(char ***)&(h)->next_free)++ = ((char *)datum))
394 #define obstack_int_grow(h,datum) \
395 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \
396 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \
397 *(*(int **)&(h)->next_free)++ = ((int)datum))
399 #define obstack_ptr_grow_fast(h,aptr) (*(*(char ***)&(h)->next_free)++ = (char *)aptr)
400 #define obstack_int_grow_fast(h,aint) (*(*(int **)&(h)->next_free)++ = (int)aint)
401 #define obstack_blank(h,length) \
402 ( (h)->temp = (length), \
403 (((h)->chunk_limit - (h)->next_free < (h)->temp) \
404 ? (_obstack_newchunk ((h), (h)->temp), 0) : 0), \
405 (h)->next_free += (h)->temp)
407 #define obstack_alloc(h,length) \
408 (obstack_blank ((h), (length)), obstack_finish ((h)))
410 #define obstack_copy(h,where,length) \
411 (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
413 #define obstack_copy0(h,where,length) \
414 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
416 #define obstack_finish(h) \
417 ( ((h)->next_free == (h)->object_base \
418 ? (((h)->maybe_empty_object = 1), 0) \
420 (h)->temp = __PTR_TO_INT ((h)->object_base), \
422 = __INT_TO_PTR ((__PTR_TO_INT ((h)->next_free)+(h)->alignment_mask) \
423 & ~ ((h)->alignment_mask)), \
424 (((h)->next_free - (char *)(h)->chunk \
425 > (h)->chunk_limit - (char *)(h)->chunk) \
426 ? ((h)->next_free = (h)->chunk_limit) : 0), \
427 (h)->object_base = (h)->next_free, \
428 __INT_TO_PTR ((h)->temp))
431 #define obstack_free(h,obj) \
432 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \
433 (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
434 ? (int) ((h)->next_free = (h)->object_base \
435 = (h)->temp + (char *) (h)->chunk) \
436 : (((obstack_free) ((h), (h)->temp + (char *) (h)->chunk), 0), 0)))
438 #define obstack_free(h,obj) \
439 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \
440 (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
441 ? (int) ((h)->next_free = (h)->object_base \
442 = (h)->temp + (char *) (h)->chunk) \
443 : (_obstack_free ((h), (h)->temp + (char *) (h)->chunk), 0)))
446 #endif /* not __GNUC__ or not __STDC__ */
448 #endif /* not __OBSTACKS__ */