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1.1 root 1: /* obstack.h - object stack macros
2: Copyright (C) 1988, 1992 Free Software Foundation, Inc.
3:
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
7: later version.
8:
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.
13:
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. */
17:
18: /* Summary:
19:
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!!
25:
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.
32:
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.
37:
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.
41:
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
46: symbols.
47:
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.
55:
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.
60:
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.
69:
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.
76:
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.
81:
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.
85:
86: Summary:
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
91: growing object.
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' an obstack
96: back to a previous state. (You may remove objects much
97: as you would with a stack.)
98: */
99:
100:
101: /* Don't do the contents of this file more than once. */
102:
103: #ifndef __OBSTACKS__
104: #define __OBSTACKS__
105:
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. */
109:
110: #ifndef __PTR_TO_INT
111: #define __PTR_TO_INT(P) ((P) - (char *)0)
112: #endif
113:
114: #ifndef __INT_TO_PTR
115: #define __INT_TO_PTR(P) ((P) + (char *)0)
116: #endif
117:
118: /* We need the type of the resulting object. In ANSI C it is ptrdiff_t
119: but in traditional C it is usually long. If we are in ANSI C and
120: don't already have ptrdiff_t get it. */
121:
122: #if defined (__STDC__) && ! defined (offsetof)
123: #if defined (__GNUC__) && defined (IN_GCC)
124: /* On Next machine, the system's stddef.h screws up if included
125: after we have defined just ptrdiff_t, so include all of gstddef.h.
126: Otherwise, define just ptrdiff_t, which is all we need. */
127: #ifndef __NeXT__
128: #define __need_ptrdiff_t
129: #endif
130:
131: /* While building GCC, the stddef.h that goes with GCC has this name. */
132: #include "gstddef.h"
133: #else
134: #include <stddef.h>
135: #endif
136: #endif
137:
138: #ifdef __STDC__
139: #define PTR_INT_TYPE ptrdiff_t
140: #else
141: #define PTR_INT_TYPE long
142: #endif
143:
144: struct _obstack_chunk /* Lives at front of each chunk. */
145: {
146: char *limit; /* 1 past end of this chunk */
147: struct _obstack_chunk *prev; /* address of prior chunk or NULL */
148: char contents[4]; /* objects begin here */
149: };
150:
151: struct obstack /* control current object in current chunk */
152: {
153: long chunk_size; /* preferred size to allocate chunks in */
154: struct _obstack_chunk* chunk; /* address of current struct obstack_chunk */
155: char *object_base; /* address of object we are building */
156: char *next_free; /* where to add next char to current object */
157: char *chunk_limit; /* address of char after current chunk */
158: PTR_INT_TYPE temp; /* Temporary for some macros. */
159: int alignment_mask; /* Mask of alignment for each object. */
160: struct _obstack_chunk *(*chunkfun) (); /* User's fcn to allocate a chunk. */
161: void (*freefun) (); /* User's function to free a chunk. */
162: char *extra_arg; /* first arg for chunk alloc/dealloc funcs */
163: unsigned use_extra_arg:1; /* chunk alloc/dealloc funcs take extra arg */
164: unsigned maybe_empty_object:1;/* There is a possibility that the current
165: chunk contains a zero-length object. This
166: prevents freeing the chunk if we allocate
167: a bigger chunk to replace it. */
168: };
169:
170: /* Declare the external functions we use; they are in obstack.c. */
171:
172: #ifdef __STDC__
173: extern void _obstack_newchunk (struct obstack *, int);
174: extern void _obstack_free (struct obstack *, void *);
175: extern void _obstack_begin (struct obstack *, int, int,
176: void *(*) (), void (*) ());
177: extern void _obstack_begin_1 (struct obstack *, int, int,
178: void *(*) (), void (*) (), void *);
179: #else
180: extern void _obstack_newchunk ();
181: extern void _obstack_free ();
182: extern void _obstack_begin ();
183: extern void _obstack_begin_1 ();
184: #endif
185:
186: #ifdef __STDC__
187:
188: /* Do the function-declarations after the structs
189: but before defining the macros. */
190:
191: void obstack_init (struct obstack *obstack);
192:
193: void * obstack_alloc (struct obstack *obstack, int size);
194:
195: void * obstack_copy (struct obstack *obstack, void *address, int size);
196: void * obstack_copy0 (struct obstack *obstack, void *address, int size);
197:
198: void obstack_free (struct obstack *obstack, void *block);
199:
200: void obstack_blank (struct obstack *obstack, int size);
201:
202: void obstack_grow (struct obstack *obstack, void *data, int size);
203: void obstack_grow0 (struct obstack *obstack, void *data, int size);
204:
205: void obstack_1grow (struct obstack *obstack, int data_char);
206: void obstack_ptr_grow (struct obstack *obstack, void *data);
207: void obstack_int_grow (struct obstack *obstack, int data);
208:
209: void * obstack_finish (struct obstack *obstack);
210:
211: int obstack_object_size (struct obstack *obstack);
212:
213: int obstack_room (struct obstack *obstack);
214: void obstack_1grow_fast (struct obstack *obstack, int data_char);
215: void obstack_ptr_grow_fast (struct obstack *obstack, void *data);
216: void obstack_int_grow_fast (struct obstack *obstack, int data);
217: void obstack_blank_fast (struct obstack *obstack, int size);
218:
219: void * obstack_base (struct obstack *obstack);
220: void * obstack_next_free (struct obstack *obstack);
221: int obstack_alignment_mask (struct obstack *obstack);
222: int obstack_chunk_size (struct obstack *obstack);
223:
224: #endif /* __STDC__ */
225:
226: /* Non-ANSI C cannot really support alternative functions for these macros,
227: so we do not declare them. */
228:
229: /* Pointer to beginning of object being allocated or to be allocated next.
230: Note that this might not be the final address of the object
231: because a new chunk might be needed to hold the final size. */
232:
233: #define obstack_base(h) ((h)->object_base)
234:
235: /* Size for allocating ordinary chunks. */
236:
237: #define obstack_chunk_size(h) ((h)->chunk_size)
238:
239: /* Pointer to next byte not yet allocated in current chunk. */
240:
241: #define obstack_next_free(h) ((h)->next_free)
242:
243: /* Mask specifying low bits that should be clear in address of an object. */
244:
245: #define obstack_alignment_mask(h) ((h)->alignment_mask)
246:
247: #define obstack_init(h) \
248: _obstack_begin ((h), 0, 0, \
249: (void *(*) ()) obstack_chunk_alloc, (void (*) ()) obstack_chunk_free)
250:
251: #define obstack_begin(h, size) \
252: _obstack_begin ((h), (size), 0, \
253: (void *(*) ()) obstack_chunk_alloc, (void (*) ()) obstack_chunk_free)
254:
255: #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \
256: _obstack_begin ((h), (size), (alignment), \
257: (void *(*) ()) (chunkfun), (void (*) ()) (freefun))
258:
259: #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
260: _obstack_begin_1 ((h), (size), (alignment), \
261: (void *(*) ()) (chunkfun), (void (*) ()) (freefun), (arg))
262:
263: #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = achar)
264:
265: #define obstack_blank_fast(h,n) ((h)->next_free += (n))
266:
267: #if defined (__GNUC__) && defined (__STDC__)
268: #if __GNUC__ < 2
269: #define __extension__
270: #endif
271:
272: /* For GNU C, if not -traditional,
273: we can define these macros to compute all args only once
274: without using a global variable.
275: Also, we can avoid using the `temp' slot, to make faster code. */
276:
277: #define obstack_object_size(OBSTACK) \
278: __extension__ \
279: ({ struct obstack *__o = (OBSTACK); \
280: (unsigned) (__o->next_free - __o->object_base); })
281:
282: #define obstack_room(OBSTACK) \
283: __extension__ \
284: ({ struct obstack *__o = (OBSTACK); \
285: (unsigned) (__o->chunk_limit - __o->next_free); })
286:
287: /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
288: so that we can avoid having void expressions
289: in the arms of the conditional expression.
290: Casting the third operand to void was tried before,
291: but some compilers won't accept it. */
292: #define obstack_grow(OBSTACK,where,length) \
293: __extension__ \
294: ({ struct obstack *__o = (OBSTACK); \
295: int __len = (length); \
296: ((__o->next_free + __len > __o->chunk_limit) \
297: ? (_obstack_newchunk (__o, __len), 0) : 0); \
298: bcopy (where, __o->next_free, __len); \
299: __o->next_free += __len; \
300: (void) 0; })
301:
302: #define obstack_grow0(OBSTACK,where,length) \
303: __extension__ \
304: ({ struct obstack *__o = (OBSTACK); \
305: int __len = (length); \
306: ((__o->next_free + __len + 1 > __o->chunk_limit) \
307: ? (_obstack_newchunk (__o, __len + 1), 0) : 0), \
308: bcopy (where, __o->next_free, __len), \
309: __o->next_free += __len, \
310: *(__o->next_free)++ = 0; \
311: (void) 0; })
312:
313: #define obstack_1grow(OBSTACK,datum) \
314: __extension__ \
315: ({ struct obstack *__o = (OBSTACK); \
316: ((__o->next_free + 1 > __o->chunk_limit) \
317: ? (_obstack_newchunk (__o, 1), 0) : 0), \
318: *(__o->next_free)++ = (datum); \
319: (void) 0; })
320:
321: /* These assume that the obstack alignment is good enough for pointers or ints,
322: and that the data added so far to the current object
323: shares that much alignment. */
324:
325: #define obstack_ptr_grow(OBSTACK,datum) \
326: __extension__ \
327: ({ struct obstack *__o = (OBSTACK); \
328: ((__o->next_free + sizeof (void *) > __o->chunk_limit) \
329: ? (_obstack_newchunk (__o, sizeof (void *)), 0) : 0), \
330: *((void **)__o->next_free)++ = ((void *)datum); \
331: (void) 0; })
332:
333: #define obstack_int_grow(OBSTACK,datum) \
334: __extension__ \
335: ({ struct obstack *__o = (OBSTACK); \
336: ((__o->next_free + sizeof (int) > __o->chunk_limit) \
337: ? (_obstack_newchunk (__o, sizeof (int)), 0) : 0), \
338: *((int *)__o->next_free)++ = ((int)datum); \
339: (void) 0; })
340:
341: #define obstack_ptr_grow_fast(h,aptr) (*((void **)(h)->next_free)++ = (void *)aptr)
342: #define obstack_int_grow_fast(h,aint) (*((int *)(h)->next_free)++ = (int)aint)
343:
344: #define obstack_blank(OBSTACK,length) \
345: __extension__ \
346: ({ struct obstack *__o = (OBSTACK); \
347: int __len = (length); \
348: ((__o->chunk_limit - __o->next_free < __len) \
349: ? (_obstack_newchunk (__o, __len), 0) : 0); \
350: __o->next_free += __len; \
351: (void) 0; })
352:
353: #define obstack_alloc(OBSTACK,length) \
354: __extension__ \
355: ({ struct obstack *__h = (OBSTACK); \
356: obstack_blank (__h, (length)); \
357: obstack_finish (__h); })
358:
359: #define obstack_copy(OBSTACK,where,length) \
360: __extension__ \
361: ({ struct obstack *__h = (OBSTACK); \
362: obstack_grow (__h, (where), (length)); \
363: obstack_finish (__h); })
364:
365: #define obstack_copy0(OBSTACK,where,length) \
366: __extension__ \
367: ({ struct obstack *__h = (OBSTACK); \
368: obstack_grow0 (__h, (where), (length)); \
369: obstack_finish (__h); })
370:
371: /* The local variable is named __o1 to avoid a name conflict
372: when obstack_blank is called. */
373: #define obstack_finish(OBSTACK) \
374: __extension__ \
375: ({ struct obstack *__o1 = (OBSTACK); \
376: void *value = (void *) __o1->object_base; \
377: if (__o1->next_free == value) \
378: __o1->maybe_empty_object = 1; \
379: __o1->next_free \
380: = __INT_TO_PTR ((__PTR_TO_INT (__o1->next_free)+__o1->alignment_mask)\
381: & ~ (__o1->alignment_mask)); \
382: ((__o1->next_free - (char *)__o1->chunk \
383: > __o1->chunk_limit - (char *)__o1->chunk) \
384: ? (__o1->next_free = __o1->chunk_limit) : 0); \
385: __o1->object_base = __o1->next_free; \
386: value; })
387:
388: #define obstack_free(OBSTACK, OBJ) \
389: __extension__ \
390: ({ struct obstack *__o = (OBSTACK); \
391: void *__obj = (OBJ); \
392: if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \
393: __o->next_free = __o->object_base = __obj; \
394: else (obstack_free) (__o, __obj); })
395:
396: #else /* not __GNUC__ or not __STDC__ */
397:
398: #define obstack_object_size(h) \
399: (unsigned) ((h)->next_free - (h)->object_base)
400:
401: #define obstack_room(h) \
402: (unsigned) ((h)->chunk_limit - (h)->next_free)
403:
404: #define obstack_grow(h,where,length) \
405: ( (h)->temp = (length), \
406: (((h)->next_free + (h)->temp > (h)->chunk_limit) \
407: ? (_obstack_newchunk ((h), (h)->temp), 0) : 0), \
408: bcopy (where, (h)->next_free, (h)->temp), \
409: (h)->next_free += (h)->temp)
410:
411: #define obstack_grow0(h,where,length) \
412: ( (h)->temp = (length), \
413: (((h)->next_free + (h)->temp + 1 > (h)->chunk_limit) \
414: ? (_obstack_newchunk ((h), (h)->temp + 1), 0) : 0), \
415: bcopy (where, (h)->next_free, (h)->temp), \
416: (h)->next_free += (h)->temp, \
417: *((h)->next_free)++ = 0)
418:
419: #define obstack_1grow(h,datum) \
420: ( (((h)->next_free + 1 > (h)->chunk_limit) \
421: ? (_obstack_newchunk ((h), 1), 0) : 0), \
422: *((h)->next_free)++ = (datum))
423:
424: #define obstack_ptr_grow(h,datum) \
425: ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \
426: ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \
427: *((char **)(((h)->next_free+=sizeof(char *))-sizeof(char *))) = ((char *)datum))
428:
429: #define obstack_int_grow(h,datum) \
430: ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \
431: ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \
432: *((int *)(((h)->next_free+=sizeof(int))-sizeof(int))) = ((int)datum))
433:
434: #define obstack_ptr_grow_fast(h,aptr) (*((char **)(h)->next_free)++ = (char *)aptr)
435: #define obstack_int_grow_fast(h,aint) (*((int *)(h)->next_free)++ = (int)aint)
436:
437: #define obstack_blank(h,length) \
438: ( (h)->temp = (length), \
439: (((h)->chunk_limit - (h)->next_free < (h)->temp) \
440: ? (_obstack_newchunk ((h), (h)->temp), 0) : 0), \
441: (h)->next_free += (h)->temp)
442:
443: #define obstack_alloc(h,length) \
444: (obstack_blank ((h), (length)), obstack_finish ((h)))
445:
446: #define obstack_copy(h,where,length) \
447: (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
448:
449: #define obstack_copy0(h,where,length) \
450: (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
451:
452: #define obstack_finish(h) \
453: ( ((h)->next_free == (h)->object_base \
454: ? (((h)->maybe_empty_object = 1), 0) \
455: : 0), \
456: (h)->temp = __PTR_TO_INT ((h)->object_base), \
457: (h)->next_free \
458: = __INT_TO_PTR ((__PTR_TO_INT ((h)->next_free)+(h)->alignment_mask) \
459: & ~ ((h)->alignment_mask)), \
460: (((h)->next_free - (char *)(h)->chunk \
461: > (h)->chunk_limit - (char *)(h)->chunk) \
462: ? ((h)->next_free = (h)->chunk_limit) : 0), \
463: (h)->object_base = (h)->next_free, \
464: __INT_TO_PTR ((h)->temp))
465:
466: #ifdef __STDC__
467: #define obstack_free(h,obj) \
468: ( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \
469: (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
470: ? (int) ((h)->next_free = (h)->object_base \
471: = (h)->temp + (char *) (h)->chunk) \
472: : (((obstack_free) ((h), (h)->temp + (char *) (h)->chunk), 0), 0)))
473: #else
474: #define obstack_free(h,obj) \
475: ( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \
476: (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
477: ? (int) ((h)->next_free = (h)->object_base \
478: = (h)->temp + (char *) (h)->chunk) \
479: : (_obstack_free ((h), (h)->temp + (char *) (h)->chunk), 0)))
480: #endif
481:
482: #endif /* not __GNUC__ or not __STDC__ */
483:
484: #endif /* not __OBSTACKS__ */
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