1 /* obstack.h - object stack macros 2 Copyright (C) 1988-1994,1996-1999,2003,2004,2005 3 Free Software Foundation, Inc. 4 This file is part of the GNU C Library. 5 6 The GNU C Library is free software; you can redistribute it and/or 7 modify it under the terms of the GNU Lesser General Public 8 License as published by the Free Software Foundation; either 9 version 2.1 of the License, or (at your option) any later version. 10 11 The GNU C Library is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 Lesser General Public License for more details. 15 16 You should have received a copy of the GNU Lesser General Public 17 License along with the GNU C Library; if not, see 18 <http://www.gnu.org/licenses/>. */ 19 20 /* Summary: 21 22 All the apparent functions defined here are macros. The idea 23 is that you would use these pre-tested macros to solve a 24 very specific set of problems, and they would run fast. 25 Caution: no side-effects in arguments please!! They may be 26 evaluated MANY times!! 27 28 These macros operate a stack of objects. Each object starts life 29 small, and may grow to maturity. (Consider building a word syllable 30 by syllable.) An object can move while it is growing. Once it has 31 been "finished" it never changes address again. So the "top of the 32 stack" is typically an immature growing object, while the rest of the 33 stack is of mature, fixed size and fixed address objects. 34 35 These routines grab large chunks of memory, using a function you 36 supply, called `obstack_chunk_alloc'. On occasion, they free chunks, 37 by calling `obstack_chunk_free'. You must define them and declare 38 them before using any obstack macros. 39 40 Each independent stack is represented by a `struct obstack'. 41 Each of the obstack macros expects a pointer to such a structure 42 as the first argument. 43 44 One motivation for this package is the problem of growing char strings 45 in symbol tables. Unless you are "fascist pig with a read-only mind" 46 --Gosper's immortal quote from HAKMEM item 154, out of context--you 47 would not like to put any arbitrary upper limit on the length of your 48 symbols. 49 50 In practice this often means you will build many short symbols and a 51 few long symbols. At the time you are reading a symbol you don't know 52 how long it is. One traditional method is to read a symbol into a 53 buffer, realloc()ating the buffer every time you try to read a symbol 54 that is longer than the buffer. This is beaut, but you still will 55 want to copy the symbol from the buffer to a more permanent 56 symbol-table entry say about half the time. 57 58 With obstacks, you can work differently. Use one obstack for all symbol 59 names. As you read a symbol, grow the name in the obstack gradually. 60 When the name is complete, finalize it. Then, if the symbol exists already, 61 free the newly read name. 62 63 The way we do this is to take a large chunk, allocating memory from 64 low addresses. When you want to build a symbol in the chunk you just 65 add chars above the current "high water mark" in the chunk. When you 66 have finished adding chars, because you got to the end of the symbol, 67 you know how long the chars are, and you can create a new object. 68 Mostly the chars will not burst over the highest address of the chunk, 69 because you would typically expect a chunk to be (say) 100 times as 70 long as an average object. 71 72 In case that isn't clear, when we have enough chars to make up 73 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed) 74 so we just point to it where it lies. No moving of chars is 75 needed and this is the second win: potentially long strings need 76 never be explicitly shuffled. Once an object is formed, it does not 77 change its address during its lifetime. 78 79 When the chars burst over a chunk boundary, we allocate a larger 80 chunk, and then copy the partly formed object from the end of the old 81 chunk to the beginning of the new larger chunk. We then carry on 82 accreting characters to the end of the object as we normally would. 83 84 A special macro is provided to add a single char at a time to a 85 growing object. This allows the use of register variables, which 86 break the ordinary 'growth' macro. 87 88 Summary: 89 We allocate large chunks. 90 We carve out one object at a time from the current chunk. 91 Once carved, an object never moves. 92 We are free to append data of any size to the currently 93 growing object. 94 Exactly one object is growing in an obstack at any one time. 95 You can run one obstack per control block. 96 You may have as many control blocks as you dare. 97 Because of the way we do it, you can `unwind' an obstack 98 back to a previous state. (You may remove objects much 99 as you would with a stack.) 100 */ 101 102 103 /* Don't do the contents of this file more than once. */ 104 105 #ifndef _OBSTACK_H 106 #define _OBSTACK_H 1 107 108 #ifdef __cplusplus 109 extern "C" { 110 #endif 111 112 /* We need the type of a pointer subtraction. If __PTRDIFF_TYPE__ is 113 defined, as with GNU C, use that; that way we don't pollute the 114 namespace with <stddef.h>'s symbols. Otherwise, include <stddef.h> 115 and use ptrdiff_t. */ 116 117 #ifdef __PTRDIFF_TYPE__ 118 # define PTR_INT_TYPE __PTRDIFF_TYPE__ 119 #else 120 # include <stddef.h> 121 # define PTR_INT_TYPE ptrdiff_t 122 #endif 123 124 /* If B is the base of an object addressed by P, return the result of 125 aligning P to the next multiple of A + 1. B and P must be of type 126 char *. A + 1 must be a power of 2. */ 127 128 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A))) 129 130 /* Similiar to _BPTR_ALIGN (B, P, A), except optimize the common case 131 where pointers can be converted to integers, aligned as integers, 132 and converted back again. If PTR_INT_TYPE is narrower than a 133 pointer (e.g., the AS/400), play it safe and compute the alignment 134 relative to B. Otherwise, use the faster strategy of computing the 135 alignment relative to 0. */ 136 137 #define __PTR_ALIGN(B, P, A) \ 138 __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \ 139 P, A) 140 141 #include <string.h> 142 143 struct _obstack_chunk /* Lives at front of each chunk. */ 144 { 145 char *limit; /* 1 past end of this chunk */ 146 struct _obstack_chunk *prev; /* address of prior chunk or NULL */ 147 char contents[4]; /* objects begin here */ 148 }; 149 150 struct obstack /* control current object in current chunk */ 151 { 152 long chunk_size; /* preferred size to allocate chunks in */ 153 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */ 154 char *object_base; /* address of object we are building */ 155 char *next_free; /* where to add next char to current object */ 156 char *chunk_limit; /* address of char after current chunk */ 157 union 158 { 159 PTR_INT_TYPE tempint; 160 void *tempptr; 161 } temp; /* Temporary for some macros. */ 162 int alignment_mask; /* Mask of alignment for each object. */ 163 /* These prototypes vary based on `use_extra_arg', and we use 164 casts to the prototypeless function type in all assignments, 165 but having prototypes here quiets -Wstrict-prototypes. */ 166 struct _obstack_chunk *(*chunkfun) (void *, long); 167 void (*freefun) (void *, struct _obstack_chunk *); 168 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */ 169 unsigned use_extra_arg:1; /* chunk alloc/dealloc funcs take extra arg */ 170 unsigned maybe_empty_object:1;/* There is a possibility that the current 171 chunk contains a zero-length object. This 172 prevents freeing the chunk if we allocate 173 a bigger chunk to replace it. */ 174 unsigned alloc_failed:1; /* No longer used, as we now call the failed 175 handler on error, but retained for binary 176 compatibility. */ 177 }; 178 179 /* Declare the external functions we use; they are in obstack.c. */ 180 181 extern void _obstack_newchunk (struct obstack *, int); 182 libc_hidden_proto(_obstack_newchunk) 183 extern int _obstack_begin (struct obstack *, int, int, 184 void *(*) (long), void (*) (void *)); 185 extern int _obstack_begin_1 (struct obstack *, int, int, 186 void *(*) (void *, long), 187 void (*) (void *, void *), void *); 188 extern int _obstack_memory_used (struct obstack *); 189 190 void obstack_free (struct obstack *obstack, void *block); 191 192 193 /* Error handler called when `obstack_chunk_alloc' failed to allocate 194 more memory. This can be set to a user defined function which 195 should either abort gracefully or use longjump - but shouldn't 196 return. The default action is to print a message and abort. */ 197 extern void (*obstack_alloc_failed_handler) (void); 198 199 /* Exit value used when `print_and_abort' is used. */ 200 extern int obstack_exit_failure; 201 202 /* 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. */ 205 206 #define obstack_base(h) ((void *) (h)->object_base) 207 208 /* Size for allocating ordinary chunks. */ 209 210 #define obstack_chunk_size(h) ((h)->chunk_size) 211 212 /* Pointer to next byte not yet allocated in current chunk. */ 213 214 #define obstack_next_free(h) ((h)->next_free) 215 216 /* Mask specifying low bits that should be clear in address of an object. */ 217 218 #define obstack_alignment_mask(h) ((h)->alignment_mask) 219 220 /* To prevent prototype warnings provide complete argument list. */ 221 #define obstack_init(h) \ 222 _obstack_begin ((h), 0, 0, \ 223 (void *(*) (long)) obstack_chunk_alloc, \ 224 (void (*) (void *)) obstack_chunk_free) 225 226 #define obstack_begin(h, size) \ 227 _obstack_begin ((h), (size), 0, \ 228 (void *(*) (long)) obstack_chunk_alloc, \ 229 (void (*) (void *)) obstack_chunk_free) 230 231 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \ 232 _obstack_begin ((h), (size), (alignment), \ 233 (void *(*) (long)) (chunkfun), \ 234 (void (*) (void *)) (freefun)) 235 236 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \ 237 _obstack_begin_1 ((h), (size), (alignment), \ 238 (void *(*) (void *, long)) (chunkfun), \ 239 (void (*) (void *, void *)) (freefun), (arg)) 240 241 #define obstack_chunkfun(h, newchunkfun) \ 242 ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun)) 243 244 #define obstack_freefun(h, newfreefun) \ 245 ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun)) 246 247 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar)) 248 249 #define obstack_blank_fast(h,n) ((h)->next_free += (n)) 250 251 #define obstack_memory_used(h) _obstack_memory_used (h) 252 253 #if defined __GNUC__ && defined __STDC__ && __STDC__ 254 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and 255 does not implement __extension__. But that compiler doesn't define 256 __GNUC_MINOR__. */ 257 # if __GNUC__ < 2 || (defined __NeXT__ && __NeXT__ && !__GNUC_MINOR__) 258 # define __extension__ 259 # endif 260 261 /* For GNU C, if not -traditional, 262 we can define these macros to compute all args only once 263 without using a global variable. 264 Also, we can avoid using the `temp' slot, to make faster code. */ 265 266 # define obstack_object_size(OBSTACK) \ 267 __extension__ \ 268 ({ struct obstack const *__o = (OBSTACK); \ 269 (unsigned) (__o->next_free - __o->object_base); }) 270 271 # define obstack_room(OBSTACK) \ 272 __extension__ \ 273 ({ struct obstack const *__o = (OBSTACK); \ 274 (unsigned) (__o->chunk_limit - __o->next_free); }) 275 276 # define obstack_make_room(OBSTACK,length) \ 277 __extension__ \ 278 ({ struct obstack *__o = (OBSTACK); \ 279 int __len = (length); \ 280 if (__o->chunk_limit - __o->next_free < __len) \ 281 _obstack_newchunk (__o, __len); \ 282 (void) 0; }) 283 284 # define obstack_empty_p(OBSTACK) \ 285 __extension__ \ 286 ({ struct obstack const *__o = (OBSTACK); \ 287 (__o->chunk->prev == 0 \ 288 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \ 289 __o->chunk->contents, \ 290 __o->alignment_mask)); }) 291 292 # define obstack_grow(OBSTACK,where,length) \ 293 __extension__ \ 294 ({ struct obstack *__o = (OBSTACK); \ 295 int __len = (length); \ 296 if (__o->next_free + __len > __o->chunk_limit) \ 297 _obstack_newchunk (__o, __len); \ 298 memcpy (__o->next_free, where, __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 if (__o->next_free + __len + 1 > __o->chunk_limit) \ 307 _obstack_newchunk (__o, __len + 1); \ 308 memcpy (__o->next_free, where, __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 if (__o->next_free + 1 > __o->chunk_limit) \ 317 _obstack_newchunk (__o, 1); \ 318 obstack_1grow_fast (__o, datum); \ 319 (void) 0; }) 320 321 /* These assume that the obstack alignment is good enough for pointers 322 or ints, 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 if (__o->next_free + sizeof (void *) > __o->chunk_limit) \ 329 _obstack_newchunk (__o, sizeof (void *)); \ 330 obstack_ptr_grow_fast (__o, datum); }) \ 331 332 # define obstack_int_grow(OBSTACK,datum) \ 333 __extension__ \ 334 ({ struct obstack *__o = (OBSTACK); \ 335 if (__o->next_free + sizeof (int) > __o->chunk_limit) \ 336 _obstack_newchunk (__o, sizeof (int)); \ 337 obstack_int_grow_fast (__o, datum); }) 338 339 # define obstack_ptr_grow_fast(OBSTACK,aptr) \ 340 __extension__ \ 341 ({ struct obstack *__o1 = (OBSTACK); \ 342 *(const void **) __o1->next_free = (aptr); \ 343 __o1->next_free += sizeof (const void *); \ 344 (void) 0; }) 345 346 # define obstack_int_grow_fast(OBSTACK,aint) \ 347 __extension__ \ 348 ({ struct obstack *__o1 = (OBSTACK); \ 349 *(int *) __o1->next_free = (aint); \ 350 __o1->next_free += sizeof (int); \ 351 (void) 0; }) 352 353 # define obstack_blank(OBSTACK,length) \ 354 __extension__ \ 355 ({ struct obstack *__o = (OBSTACK); \ 356 int __len = (length); \ 357 if (__o->chunk_limit - __o->next_free < __len) \ 358 _obstack_newchunk (__o, __len); \ 359 obstack_blank_fast (__o, __len); \ 360 (void) 0; }) 361 362 # define obstack_alloc(OBSTACK,length) \ 363 __extension__ \ 364 ({ struct obstack *__h = (OBSTACK); \ 365 obstack_blank (__h, (length)); \ 366 obstack_finish (__h); }) 367 368 # define obstack_copy(OBSTACK,where,length) \ 369 __extension__ \ 370 ({ struct obstack *__h = (OBSTACK); \ 371 obstack_grow (__h, (where), (length)); \ 372 obstack_finish (__h); }) 373 374 # define obstack_copy0(OBSTACK,where,length) \ 375 __extension__ \ 376 ({ struct obstack *__h = (OBSTACK); \ 377 obstack_grow0 (__h, (where), (length)); \ 378 obstack_finish (__h); }) 379 380 /* The local variable is named __o1 to avoid a name conflict 381 when obstack_blank is called. */ 382 # define obstack_finish(OBSTACK) \ 383 __extension__ \ 384 ({ struct obstack *__o1 = (OBSTACK); \ 385 void *__value = (void *) __o1->object_base; \ 386 if (__o1->next_free == __value) \ 387 __o1->maybe_empty_object = 1; \ 388 __o1->next_free \ 389 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \ 390 __o1->alignment_mask); \ 391 if (__o1->next_free - (char *)__o1->chunk \ 392 > __o1->chunk_limit - (char *)__o1->chunk) \ 393 __o1->next_free = __o1->chunk_limit; \ 394 __o1->object_base = __o1->next_free; \ 395 __value; }) 396 397 # define obstack_free(OBSTACK, OBJ) \ 398 __extension__ \ 399 ({ struct obstack *__o = (OBSTACK); \ 400 void *__obj = (OBJ); \ 401 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \ 402 __o->next_free = __o->object_base = (char *)__obj; \ 403 else (obstack_free) (__o, __obj); }) 404 405 #else /* not __GNUC__ or not __STDC__ */ 406 407 # define obstack_object_size(h) \ 408 (unsigned) ((h)->next_free - (h)->object_base) 409 410 # define obstack_room(h) \ 411 (unsigned) ((h)->chunk_limit - (h)->next_free) 412 413 # define obstack_empty_p(h) \ 414 ((h)->chunk->prev == 0 \ 415 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \ 416 (h)->chunk->contents, \ 417 (h)->alignment_mask)) 418 419 /* Note that the call to _obstack_newchunk is enclosed in (..., 0) 420 so that we can avoid having void expressions 421 in the arms of the conditional expression. 422 Casting the third operand to void was tried before, 423 but some compilers won't accept it. */ 424 425 # define obstack_make_room(h,length) \ 426 ( (h)->temp.tempint = (length), \ 427 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 428 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0)) 429 430 # define obstack_grow(h,where,length) \ 431 ( (h)->temp.tempint = (length), \ 432 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 433 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 434 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 435 (h)->next_free += (h)->temp.tempint) 436 437 # define obstack_grow0(h,where,length) \ 438 ( (h)->temp.tempint = (length), \ 439 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \ 440 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \ 441 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 442 (h)->next_free += (h)->temp.tempint, \ 443 *((h)->next_free)++ = 0) 444 445 # define obstack_1grow(h,datum) \ 446 ( (((h)->next_free + 1 > (h)->chunk_limit) \ 447 ? (_obstack_newchunk ((h), 1), 0) : 0), \ 448 obstack_1grow_fast (h, datum)) 449 450 # define obstack_ptr_grow(h,datum) \ 451 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \ 452 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \ 453 obstack_ptr_grow_fast (h, datum)) 454 455 # define obstack_int_grow(h,datum) \ 456 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \ 457 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \ 458 obstack_int_grow_fast (h, datum)) 459 460 # define obstack_ptr_grow_fast(h,aptr) \ 461 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr)) 462 463 # define obstack_int_grow_fast(h,aint) \ 464 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint)) 465 466 # define obstack_blank(h,length) \ 467 ( (h)->temp.tempint = (length), \ 468 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \ 469 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 470 obstack_blank_fast (h, (h)->temp.tempint)) 471 472 # define obstack_alloc(h,length) \ 473 (obstack_blank ((h), (length)), obstack_finish ((h))) 474 475 # define obstack_copy(h,where,length) \ 476 (obstack_grow ((h), (where), (length)), obstack_finish ((h))) 477 478 # define obstack_copy0(h,where,length) \ 479 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h))) 480 481 # define obstack_finish(h) \ 482 ( ((h)->next_free == (h)->object_base \ 483 ? (((h)->maybe_empty_object = 1), 0) \ 484 : 0), \ 485 (h)->temp.tempptr = (h)->object_base, \ 486 (h)->next_free \ 487 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \ 488 (h)->alignment_mask), \ 489 (((h)->next_free - (char *) (h)->chunk \ 490 > (h)->chunk_limit - (char *) (h)->chunk) \ 491 ? ((h)->next_free = (h)->chunk_limit) : 0), \ 492 (h)->object_base = (h)->next_free, \ 493 (h)->temp.tempptr) 494 495 # define obstack_free(h,obj) \ 496 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \ 497 ((((h)->temp.tempint > 0 \ 498 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \ 499 ? (int) ((h)->next_free = (h)->object_base \ 500 = (h)->temp.tempint + (char *) (h)->chunk) \ 501 : (((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0))) 502 503 #endif /* not __GNUC__ or not __STDC__ */ 504 505 #ifdef __cplusplus 506 } /* C++ */ 507 #endif 508 509 #endif /* obstack.h */ 510