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1.1 root 1: /* obstack.h - object stack macros
2: Copyright (C) 1988 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' a 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: struct _obstack_chunk /* Lives at front of each chunk. */
119: {
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 */
123: };
124:
125: struct obstack /* control current object in current chunk */
126: {
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. */
134: struct _obstack_chunk *(*chunkfun) (); /* User's fcn to allocate a chunk. */
135: void (*freefun) (); /* User's function to free a chunk. */
136: /* Nonzero means there is a possibility the current chunk contains
137: a zero-length object. This prevents freeing the chunk
138: if we allocate a bigger chunk to replace it. */
139: char maybe_empty_object;
140: };
141:
142: /* Declare the external functions we use; they are in obstack.c. */
143:
144: #ifdef __STDC__
145: extern void _obstack_newchunk (struct obstack *, int);
146: extern void _obstack_free (struct obstack *, void *);
147: extern void _obstack_begin (struct obstack *, int, int,
148: void *(*) (), void (*) ());
149: #else
150: extern void _obstack_newchunk ();
151: extern void _obstack_free ();
152: extern void _obstack_begin ();
153: #endif
154:
155: #ifdef __STDC__
156:
157: /* Do the function-declarations after the structs
158: but before defining the macros. */
159:
160: void obstack_init (struct obstack *obstack);
161:
162: void * obstack_alloc (struct obstack *obstack, int size);
163:
164: void * obstack_copy (struct obstack *obstack, void *address, int size);
165: void * obstack_copy0 (struct obstack *obstack, void *address, int size);
166:
167: void obstack_free (struct obstack *obstack, void *block);
168:
169: void obstack_blank (struct obstack *obstack, int size);
170:
171: void obstack_grow (struct obstack *obstack, void *data, int size);
172: void obstack_grow0 (struct obstack *obstack, void *data, int size);
173:
174: void obstack_1grow (struct obstack *obstack, int data_char);
175: void obstack_ptr_grow (struct obstack *obstack, void *data);
176: void obstack_int_grow (struct obstack *obstack, int data);
177:
178: void * obstack_finish (struct obstack *obstack);
179:
180: int obstack_object_size (struct obstack *obstack);
181:
182: int obstack_room (struct obstack *obstack);
183: void obstack_1grow_fast (struct obstack *obstack, int data_char);
184: void obstack_ptr_grow_fast (struct obstack *obstack, void *data);
185: void obstack_int_grow_fast (struct obstack *obstack, int data);
186: void obstack_blank_fast (struct obstack *obstack, int size);
187:
188: void * obstack_base (struct obstack *obstack);
189: void * obstack_next_free (struct obstack *obstack);
190: int obstack_alignment_mask (struct obstack *obstack);
191: int obstack_chunk_size (struct obstack *obstack);
192:
193: #endif /* __STDC__ */
194:
195: /* Non-ANSI C cannot really support alternative functions for these macros,
196: so we do not declare them. */
197:
198: /* Pointer to beginning of object being allocated or to be allocated next.
199: Note that this might not be the final address of the object
200: because a new chunk might be needed to hold the final size. */
201:
202: #define obstack_base(h) ((h)->object_base)
203:
204: /* Size for allocating ordinary chunks. */
205:
206: #define obstack_chunk_size(h) ((h)->chunk_size)
207:
208: /* Pointer to next byte not yet allocated in current chunk. */
209:
210: #define obstack_next_free(h) ((h)->next_free)
211:
212: /* Mask specifying low bits that should be clear in address of an object. */
213:
214: #define obstack_alignment_mask(h) ((h)->alignment_mask)
215:
216: #define obstack_init(h) \
217: _obstack_begin ((h), 0, 0, \
218: (void *(*) ()) obstack_chunk_alloc, obstack_chunk_free)
219:
220: #define obstack_begin(h, size) \
221: _obstack_begin ((h), (size), 0, \
222: (void *(*) ()) obstack_chunk_alloc, obstack_chunk_free)
223:
224: #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = achar)
225:
226: #define obstack_blank_fast(h,n) ((h)->next_free += (n))
227:
228: #if defined (__GNUC__) && defined (__STDC__)
229: #if __GNUC__ < 2
230: #define __extension__
231: #endif
232:
233: /* For GNU C, if not -traditional,
234: we can define these macros to compute all args only once
235: without using a global variable.
236: Also, we can avoid using the `temp' slot, to make faster code. */
237:
238: #define obstack_object_size(OBSTACK) \
239: __extension__ \
240: ({ struct obstack *__o = (OBSTACK); \
241: (unsigned) (__o->next_free - __o->object_base); })
242:
243: #define obstack_room(OBSTACK) \
244: __extension__ \
245: ({ struct obstack *__o = (OBSTACK); \
246: (unsigned) (__o->chunk_limit - __o->next_free); })
247:
248: /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
249: so that we can avoid having void expressions
250: in the arms of the conditional expression.
251: Casting the third operand to void was tried before,
252: but some compilers won't accept it. */
253: #define obstack_grow(OBSTACK,where,length) \
254: __extension__ \
255: ({ struct obstack *__o = (OBSTACK); \
256: int __len = (length); \
257: ((__o->next_free + __len > __o->chunk_limit) \
258: ? (_obstack_newchunk (__o, __len), 0) : 0); \
259: bcopy (where, __o->next_free, __len); \
260: __o->next_free += __len; \
261: (void) 0; })
262:
263: #define obstack_grow0(OBSTACK,where,length) \
264: __extension__ \
265: ({ struct obstack *__o = (OBSTACK); \
266: int __len = (length); \
267: ((__o->next_free + __len + 1 > __o->chunk_limit) \
268: ? (_obstack_newchunk (__o, __len + 1), 0) : 0), \
269: bcopy (where, __o->next_free, __len), \
270: __o->next_free += __len, \
271: *(__o->next_free)++ = 0; \
272: (void) 0; })
273:
274: #define obstack_1grow(OBSTACK,datum) \
275: __extension__ \
276: ({ struct obstack *__o = (OBSTACK); \
277: ((__o->next_free + 1 > __o->chunk_limit) \
278: ? (_obstack_newchunk (__o, 1), 0) : 0), \
279: *(__o->next_free)++ = (datum); \
280: (void) 0; })
281:
282: /* These assume that the obstack alignment is good enough for pointers or ints,
283: and that the data added so far to the current object
284: shares that much alignment. */
285:
286: #define obstack_ptr_grow(OBSTACK,datum) \
287: __extension__ \
288: ({ struct obstack *__o = (OBSTACK); \
289: ((__o->next_free + sizeof (void *) > __o->chunk_limit) \
290: ? (_obstack_newchunk (__o, sizeof (void *)), 0) : 0), \
291: *((void **)__o->next_free)++ = ((void *)datum); \
292: (void) 0; })
293:
294: #define obstack_int_grow(OBSTACK,datum) \
295: __extension__ \
296: ({ struct obstack *__o = (OBSTACK); \
297: ((__o->next_free + sizeof (int) > __o->chunk_limit) \
298: ? (_obstack_newchunk (__o, sizeof (int)), 0) : 0), \
299: *((int *)__o->next_free)++ = ((int)datum); \
300: (void) 0; })
301:
302: #define obstack_ptr_grow_fast(h,aptr) (*((void **)(h)->next_free)++ = (void *)aptr)
303: #define obstack_int_grow_fast(h,aint) (*((int *)(h)->next_free)++ = (int)aint)
304:
305: #define obstack_blank(OBSTACK,length) \
306: __extension__ \
307: ({ struct obstack *__o = (OBSTACK); \
308: int __len = (length); \
309: ((__o->chunk_limit - __o->next_free < __len) \
310: ? (_obstack_newchunk (__o, __len), 0) : 0); \
311: __o->next_free += __len; \
312: (void) 0; })
313:
314: #define obstack_alloc(OBSTACK,length) \
315: __extension__ \
316: ({ struct obstack *__h = (OBSTACK); \
317: obstack_blank (__h, (length)); \
318: obstack_finish (__h); })
319:
320: #define obstack_copy(OBSTACK,where,length) \
321: __extension__ \
322: ({ struct obstack *__h = (OBSTACK); \
323: obstack_grow (__h, (where), (length)); \
324: obstack_finish (__h); })
325:
326: #define obstack_copy0(OBSTACK,where,length) \
327: __extension__ \
328: ({ struct obstack *__h = (OBSTACK); \
329: obstack_grow0 (__h, (where), (length)); \
330: obstack_finish (__h); })
331:
332: /* The local variable is named __o1 to avoid a name conflict
333: when obstack_blank is called. */
334: #define obstack_finish(OBSTACK) \
335: __extension__ \
336: ({ struct obstack *__o1 = (OBSTACK); \
337: void *value = (void *) __o1->object_base; \
338: if (__o1->next_free == value) \
339: __o1->maybe_empty_object = 1; \
340: __o1->next_free \
341: = __INT_TO_PTR ((__PTR_TO_INT (__o1->next_free)+__o1->alignment_mask)\
342: & ~ (__o1->alignment_mask)); \
343: ((__o1->next_free - (char *)__o1->chunk \
344: > __o1->chunk_limit - (char *)__o1->chunk) \
345: ? (__o1->next_free = __o1->chunk_limit) : 0); \
346: __o1->object_base = __o1->next_free; \
347: value; })
348:
349: #define obstack_free(OBSTACK, OBJ) \
350: __extension__ \
351: ({ struct obstack *__o = (OBSTACK); \
352: void *__obj = (OBJ); \
353: if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \
354: __o->next_free = __o->object_base = __obj; \
355: else (obstack_free) (__o, __obj); })
356:
357: #else /* not __GNUC__ or not __STDC__ */
358:
359: #define obstack_object_size(h) \
360: (unsigned) ((h)->next_free - (h)->object_base)
361:
362: #define obstack_room(h) \
363: (unsigned) ((h)->chunk_limit - (h)->next_free)
364:
365: #define obstack_grow(h,where,length) \
366: ( (h)->temp = (length), \
367: (((h)->next_free + (h)->temp > (h)->chunk_limit) \
368: ? (_obstack_newchunk ((h), (h)->temp), 0) : 0), \
369: bcopy (where, (h)->next_free, (h)->temp), \
370: (h)->next_free += (h)->temp)
371:
372: #define obstack_grow0(h,where,length) \
373: ( (h)->temp = (length), \
374: (((h)->next_free + (h)->temp + 1 > (h)->chunk_limit) \
375: ? (_obstack_newchunk ((h), (h)->temp + 1), 0) : 0), \
376: bcopy (where, (h)->next_free, (h)->temp), \
377: (h)->next_free += (h)->temp, \
378: *((h)->next_free)++ = 0)
379:
380: #define obstack_1grow(h,datum) \
381: ( (((h)->next_free + 1 > (h)->chunk_limit) \
382: ? (_obstack_newchunk ((h), 1), 0) : 0), \
383: *((h)->next_free)++ = (datum))
384:
385: #define obstack_ptr_grow(h,datum) \
386: ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \
387: ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \
388: *((char **)(((h)->next_free+=sizeof(char *))-sizeof(char *))) = ((char *)datum))
389:
390: #define obstack_int_grow(h,datum) \
391: ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \
392: ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \
393: *((int *)(((h)->next_free+=sizeof(int))-sizeof(int))) = ((int)datum))
394:
395: #define obstack_ptr_grow_fast(h,aptr) (*((char **)(h)->next_free)++ = (char *)aptr)
396: #define obstack_int_grow_fast(h,aint) (*((int *)(h)->next_free)++ = (int)aint)
397:
398: #define obstack_blank(h,length) \
399: ( (h)->temp = (length), \
400: (((h)->chunk_limit - (h)->next_free < (h)->temp) \
401: ? (_obstack_newchunk ((h), (h)->temp), 0) : 0), \
402: (h)->next_free += (h)->temp)
403:
404: #define obstack_alloc(h,length) \
405: (obstack_blank ((h), (length)), obstack_finish ((h)))
406:
407: #define obstack_copy(h,where,length) \
408: (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
409:
410: #define obstack_copy0(h,where,length) \
411: (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
412:
413: #define obstack_finish(h) \
414: ( ((h)->next_free == (h)->object_base \
415: ? (((h)->maybe_empty_object = 1), 0) \
416: : 0), \
417: (h)->temp = __PTR_TO_INT ((h)->object_base), \
418: (h)->next_free \
419: = __INT_TO_PTR ((__PTR_TO_INT ((h)->next_free)+(h)->alignment_mask) \
420: & ~ ((h)->alignment_mask)), \
421: (((h)->next_free - (char *)(h)->chunk \
422: > (h)->chunk_limit - (char *)(h)->chunk) \
423: ? ((h)->next_free = (h)->chunk_limit) : 0), \
424: (h)->object_base = (h)->next_free, \
425: __INT_TO_PTR ((h)->temp))
426:
427: #ifdef __STDC__
428: #define obstack_free(h,obj) \
429: ( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \
430: (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
431: ? (int) ((h)->next_free = (h)->object_base \
432: = (h)->temp + (char *) (h)->chunk) \
433: : (((obstack_free) ((h), (h)->temp + (char *) (h)->chunk), 0), 0)))
434: #else
435: #define obstack_free(h,obj) \
436: ( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \
437: (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
438: ? (int) ((h)->next_free = (h)->object_base \
439: = (h)->temp + (char *) (h)->chunk) \
440: : (_obstack_free ((h), (h)->temp + (char *) (h)->chunk), 0)))
441: #endif
442:
443: #endif /* not __GNUC__ or not __STDC__ */
444:
445: #endif /* not __OBSTACKS__ */
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