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 1, 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. */
20 All the apparent functions defined here are macros. The idea
21 is that you would use these pre-tested macros to solve a
22 very specific set of problems, and they would run fast.
23 Caution: no side-effects in arguments please!! They may be
24 evaluated MANY times!!
26 These macros operate a stack of objects. Each object starts life
27 small, and may grow to maturity. (Consider building a word syllable
28 by syllable.) An object can move while it is growing. Once it has
29 been "finished" it never changes address again. So the "top of the
30 stack" is typically an immature growing object, while the rest of the
31 stack is of mature, fixed size and fixed address objects.
33 These routines grab large chunks of memory, using a function you
34 supply, called `obstack_chunk_alloc'. On occasion, they free chunks,
35 by calling `obstack_chunk_free'. You must define them and declare
36 them before using any obstack macros.
38 Each independent stack is represented by a `struct obstack'.
39 Each of the obstack macros expects a pointer to such a structure
40 as the first argument.
42 One motivation for this package is the problem of growing char strings
43 in symbol tables. Unless you are "fascist pig with a read-only mind"
44 [Gosper's immortal quote from HAKMEM item 154, out of context] you
45 would not like to put any arbitrary upper limit on the length of your
48 In practice this often means you will build many short symbols and a
49 few long symbols. At the time you are reading a symbol you don't know
50 how long it is. One traditional method is to read a symbol into a
51 buffer, realloc()ating the buffer every time you try to read a symbol
52 that is longer than the buffer. This is beaut, but you still will
53 want to copy the symbol from the buffer to a more permanent
54 symbol-table entry say about half the time.
56 With obstacks, you can work differently. Use one obstack for all symbol
57 names. As you read a symbol, grow the name in the obstack gradually.
58 When the name is complete, finalize it. Then, if the symbol exists already,
59 free the newly read name.
61 The way we do this is to take a large chunk, allocating memory from
62 low addresses. When you want to build a symbol in the chunk you just
63 add chars above the current "high water mark" in the chunk. When you
64 have finished adding chars, because you got to the end of the symbol,
65 you know how long the chars are, and you can create a new object.
66 Mostly the chars will not burst over the highest address of the chunk,
67 because you would typically expect a chunk to be (say) 100 times as
68 long as an average object.
70 In case that isn't clear, when we have enough chars to make up
71 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
72 so we just point to it where it lies. No moving of chars is
73 needed and this is the second win: potentially long strings need
74 never be explicitly shuffled. Once an object is formed, it does not
75 change its address during its lifetime.
77 When the chars burst over a chunk boundary, we allocate a larger
78 chunk, and then copy the partly formed object from the end of the old
79 chunk to the beginning of the new larger chunk. We then carry on
80 accreting characters to the end of the object as we normally would.
82 A special macro is provided to add a single char at a time to a
83 growing object. This allows the use of register variables, which
84 break the ordinary 'growth' macro.
87 We allocate large chunks.
88 We carve out one object at a time from the current chunk.
89 Once carved, an object never moves.
90 We are free to append data of any size to the currently
92 Exactly one object is growing in an obstack at any one time.
93 You can run one obstack per control block.
94 You may have as many control blocks as you dare.
95 Because of the way we do it, you can `unwind' a obstack
96 back to a previous state. (You may remove objects much
97 as you would with a stack.)
101 /* Don't do the contents of this file more than once. */
106 /* We use subtraction of (char *)0 instead of casting to int
107 because on word-addressable machines a simple cast to int
108 may ignore the byte-within-word field of the pointer. */
111 #define __PTR_TO_INT(P) ((P) - (char *)0)
115 #define __INT_TO_PTR(P) ((P) + (char *)0)
118 struct _obstack_chunk
/* Lives at front of each chunk. */
120 char *limit
; /* 1 past end of this chunk */
121 struct _obstack_chunk
*prev
; /* address of prior chunk or NULL */
122 char contents
[4]; /* objects begin here */
125 struct obstack
/* control current object in current chunk */
127 long chunk_size
; /* preferred size to allocate chunks in */
128 struct _obstack_chunk
* chunk
; /* address of current struct obstack_chunk */
129 char *object_base
; /* address of object we are building */
130 char *next_free
; /* where to add next char to current object */
131 char *chunk_limit
; /* address of char after current chunk */
132 int temp
; /* Temporary for some macros. */
133 int alignment_mask
; /* Mask of alignment for each object. */
135 void *(*chunkfun
) (); /* User's fcn to allocate a chunk. */
137 char *(*chunkfun
) (); /* User's fcn to allocate a chunk. */
139 void (*freefun
) (); /* User's function to free a chunk. */
144 /* Do the function-declarations after the structs
145 but before defining the macros. */
147 void obstack_init (struct obstack
*obstack
);
149 void * obstack_alloc (struct obstack
*obstack
, int size
);
151 void * obstack_copy (struct obstack
*obstack
, void *address
, int size
);
152 void * obstack_copy0 (struct obstack
*obstack
, void *address
, int size
);
154 void obstack_free (struct obstack
*obstack
, void *block
);
156 void obstack_blank (struct obstack
*obstack
, int size
);
158 void obstack_grow (struct obstack
*obstack
, void *data
, int size
);
159 void obstack_grow0 (struct obstack
*obstack
, void *data
, int size
);
161 void obstack_1grow (struct obstack
*obstack
, int data_char
);
162 void obstack_ptr_grow (struct obstack
*obstack
, void *data
);
163 void obstack_int_grow (struct obstack
*obstack
, int data
);
165 void * obstack_finish (struct obstack
*obstack
);
167 int obstack_object_size (struct obstack
*obstack
);
169 int obstack_room (struct obstack
*obstack
);
170 void obstack_1grow_fast (struct obstack
*obstack
, int data_char
);
171 void obstack_ptr_grow_fast (struct obstack
*obstack
, void *data
);
172 void obstack_int_grow_fast (struct obstack
*obstack
, int data
);
173 void obstack_blank_fast (struct obstack
*obstack
, int size
);
175 void * obstack_base (struct obstack
*obstack
);
176 void * obstack_next_free (struct obstack
*obstack
);
177 int obstack_alignment_mask (struct obstack
*obstack
);
178 int obstack_chunk_size (struct obstack
*obstack
);
180 #endif /* __STDC__ */
182 /* Non-ANSI C cannot really support alternative functions for these macros,
183 so we do not declare them. */
185 /* Pointer to beginning of object being allocated or to be allocated next.
186 Note that this might not be the final address of the object
187 because a new chunk might be needed to hold the final size. */
189 #define obstack_base(h) ((h)->object_base)
191 /* Size for allocating ordinary chunks. */
193 #define obstack_chunk_size(h) ((h)->chunk_size)
195 /* Pointer to next byte not yet allocated in current chunk. */
197 #define obstack_next_free(h) ((h)->next_free)
199 /* Mask specifying low bits that should be clear in address of an object. */
201 #define obstack_alignment_mask(h) ((h)->alignment_mask)
203 #define obstack_init(h) \
204 _obstack_begin ((h), 0, 0, obstack_chunk_alloc, obstack_chunk_free)
206 #define obstack_begin(h, size) \
207 _obstack_begin ((h), (size), 0, obstack_chunk_alloc, obstack_chunk_free)
209 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = achar)
211 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
213 #if defined (__GNUC__) && defined (__STDC__)
215 /* For GNU C, if not -traditional,
216 we can define these macros to compute all args only once
217 without using a global variable.
218 Also, we can avoid using the `temp' slot, to make faster code. */
220 #define obstack_object_size(OBSTACK) \
221 ({ struct obstack *__o = (OBSTACK); \
222 (unsigned) (__o->next_free - __o->object_base); })
224 #define obstack_room(OBSTACK) \
225 ({ struct obstack *__o = (OBSTACK); \
226 (unsigned) (__o->chunk_limit - __o->next_free); })
228 #define obstack_grow(OBSTACK,where,length) \
229 ({ struct obstack *__o = (OBSTACK); \
230 int __len = (length); \
231 ((__o->next_free + __len > __o->chunk_limit) \
232 ? _obstack_newchunk (__o, __len) : 0); \
233 bcopy (where, __o->next_free, __len); \
234 __o->next_free += __len; \
237 #define obstack_grow0(OBSTACK,where,length) \
238 ({ struct obstack *__o = (OBSTACK); \
239 int __len = (length); \
240 ((__o->next_free + __len + 1 > __o->chunk_limit) \
241 ? _obstack_newchunk (__o, __len + 1) : 0), \
242 bcopy (where, __o->next_free, __len), \
243 __o->next_free += __len, \
244 *(__o->next_free)++ = 0; \
247 #define obstack_1grow(OBSTACK,datum) \
248 ({ struct obstack *__o = (OBSTACK); \
249 ((__o->next_free + 1 > __o->chunk_limit) \
250 ? _obstack_newchunk (__o, 1) : 0), \
251 *(__o->next_free)++ = (datum); \
254 /* These assume that the obstack alignment is good enough for pointers or ints,
255 and that the data added so far to the current object
256 shares that much alignment. */
258 #define obstack_ptr_grow(OBSTACK,datum) \
259 ({ struct obstack *__o = (OBSTACK); \
260 ((__o->next_free + sizeof (void *) > __o->chunk_limit) \
261 ? _obstack_newchunk (__o, sizeof (void *)) : 0), \
262 *(*(void ***)&__o->next_free)++ = ((void *)datum); \
265 #define obstack_int_grow(OBSTACK,datum) \
266 ({ struct obstack *__o = (OBSTACK); \
267 ((__o->next_free + sizeof (int) > __o->chunk_limit) \
268 ? _obstack_newchunk (__o, sizeof (int)) : 0), \
269 *(*(int **)&__o->next_free)++ = ((int)datum); \
272 #define obstack_ptr_grow_fast(h,aptr) (*(*(void ***)&(h)->next_free)++ = (void *)aptr)
273 #define obstack_int_grow_fast(h,aint) (*(*(int **)&(h)->next_free)++ = (int)aint)
275 #define obstack_blank(OBSTACK,length) \
276 ({ struct obstack *__o = (OBSTACK); \
277 int __len = (length); \
278 ((__o->chunk_limit - __o->next_free < __len) \
279 ? _obstack_newchunk (__o, __len) : 0); \
280 __o->next_free += __len; \
283 #define obstack_alloc(OBSTACK,length) \
284 ({ struct obstack *__h = (OBSTACK); \
285 obstack_blank (__h, (length)); \
286 obstack_finish (__h); })
288 #define obstack_copy(OBSTACK,where,length) \
289 ({ struct obstack *__h = (OBSTACK); \
290 obstack_grow (__h, (where), (length)); \
291 obstack_finish (__h); })
293 #define obstack_copy0(OBSTACK,where,length) \
294 ({ struct obstack *__h = (OBSTACK); \
295 obstack_grow0 (__h, (where), (length)); \
296 obstack_finish (__h); })
298 #define obstack_finish(OBSTACK) \
299 ({ struct obstack *__o = (OBSTACK); \
300 void *value = (void *) __o->object_base; \
302 = __INT_TO_PTR ((__PTR_TO_INT (__o->next_free)+__o->alignment_mask)\
303 & ~ (__o->alignment_mask)); \
304 ((__o->next_free - (char *)__o->chunk \
305 > __o->chunk_limit - (char *)__o->chunk) \
306 ? (__o->next_free = __o->chunk_limit) : 0); \
307 __o->object_base = __o->next_free; \
310 #define obstack_free(OBSTACK, OBJ) \
311 ({ struct obstack *__o = (OBSTACK); \
312 void *__obj = (OBJ); \
313 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \
314 __o->next_free = __o->object_base = __obj; \
315 else (obstack_free) (__o, __obj); })
317 #else /* not __GNUC__ or not __STDC__ */
319 #define obstack_object_size(h) \
320 (unsigned) ((h)->next_free - (h)->object_base)
322 #define obstack_room(h) \
323 (unsigned) ((h)->chunk_limit - (h)->next_free)
325 #define obstack_grow(h,where,length) \
326 ( (h)->temp = (length), \
327 (((h)->next_free + (h)->temp > (h)->chunk_limit) \
328 ? _obstack_newchunk ((h), (h)->temp) : 0), \
329 bcopy (where, (h)->next_free, (h)->temp), \
330 (h)->next_free += (h)->temp)
332 #define obstack_grow0(h,where,length) \
333 ( (h)->temp = (length), \
334 (((h)->next_free + (h)->temp + 1 > (h)->chunk_limit) \
335 ? _obstack_newchunk ((h), (h)->temp + 1) : 0), \
336 bcopy (where, (h)->next_free, (h)->temp), \
337 (h)->next_free += (h)->temp, \
338 *((h)->next_free)++ = 0)
340 #define obstack_1grow(h,datum) \
341 ( (((h)->next_free + 1 > (h)->chunk_limit) \
342 ? _obstack_newchunk ((h), 1) : 0), \
343 *((h)->next_free)++ = (datum))
345 #define obstack_ptr_grow(h,datum) \
346 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \
347 ? _obstack_newchunk ((h), sizeof (char *)) : 0), \
348 *(*(char ***)&(h)->next_free)++ = ((char *)datum))
350 #define obstack_int_grow(h,datum) \
351 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \
352 ? _obstack_newchunk ((h), sizeof (int)) : 0), \
353 *(*(int **)&(h)->next_free)++ = ((int)datum))
355 #define obstack_ptr_grow_fast(h,aptr) (*(*(char ***)&(h)->next_free)++ = (char *)aptr)
356 #define obstack_int_grow_fast(h,aint) (*(*(int **)&(h)->next_free)++ = (int)aint)
358 #define obstack_blank(h,length) \
359 ( (h)->temp = (length), \
360 (((h)->chunk_limit - (h)->next_free < (h)->temp) \
361 ? _obstack_newchunk ((h), (h)->temp) : 0), \
362 (h)->next_free += (h)->temp)
364 #define obstack_alloc(h,length) \
365 (obstack_blank ((h), (length)), obstack_finish ((h)))
367 #define obstack_copy(h,where,length) \
368 (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
370 #define obstack_copy0(h,where,length) \
371 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
373 #define obstack_finish(h) \
374 ( (h)->temp = __PTR_TO_INT ((h)->object_base), \
376 = __INT_TO_PTR ((__PTR_TO_INT ((h)->next_free)+(h)->alignment_mask) \
377 & ~ ((h)->alignment_mask)), \
378 (((h)->next_free - (char *)(h)->chunk \
379 > (h)->chunk_limit - (char *)(h)->chunk) \
380 ? ((h)->next_free = (h)->chunk_limit) : 0), \
381 (h)->object_base = (h)->next_free, \
382 __INT_TO_PTR ((h)->temp))
385 #define obstack_free(h,obj) \
386 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \
387 (((h)->temp >= 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
388 ? (int) ((h)->next_free = (h)->object_base \
389 = (h)->temp + (char *) (h)->chunk) \
390 : ((obstack_free) ((h), (h)->temp + (char *) (h)->chunk), 0)))
392 #define obstack_free(h,obj) \
393 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \
394 (((h)->temp >= 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
395 ? (int) ((h)->next_free = (h)->object_base \
396 = (h)->temp + (char *) (h)->chunk) \
397 : (int) _obstack_free ((h), (h)->temp + (char *) (h)->chunk)))
400 #endif /* not __GNUC__ or not __STDC__ */
402 /* Declare the external functions we use; they are in obstack.c. */
405 extern int _obstack_newchunk (struct obstack
*h
, int length
);
406 extern int _obstack_free (struct obstack
*h
, void *obj
);
407 extern void _obstack_begin (struct obstack
*h
, int size
, int alignment
,
408 void *(*chunkfun
) (), void (*freefun
) ());
410 extern int _obstack_newchunk ();
411 extern int _obstack_free ();
412 extern void _obstack_begin ();
415 #endif /* not __OBSTACKS__ */
This page took 0.038002 seconds and 4 git commands to generate.