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__ */ 485