1 /* obstack.h - object stack macros 2 Copyright (C) 1988-1994,1996-1999,2003,2004,2005,2009 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 accrediting 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 /* Similar 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 (sizeof (PTR_INT_TYPE) < sizeof(void *) ? \ 139 __BPTR_ALIGN((B), (P), (A)) : \ 140 (void *)__BPTR_ALIGN((PTR_INT_TYPE)(void *)0, (PTR_INT_TYPE)(P), (A)) \ 141 ) 142 143 #include <string.h> 144 145 struct _obstack_chunk /* Lives at front of each chunk. */ 146 { 147 char *limit; /* 1 past end of this chunk */ 148 struct _obstack_chunk *prev; /* address of prior chunk or NULL */ 149 char contents[4]; /* objects begin here */ 150 }; 151 152 struct obstack /* control current object in current chunk */ 153 { 154 long chunk_size; /* preferred size to allocate chunks in */ 155 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */ 156 char *object_base; /* address of object we are building */ 157 char *next_free; /* where to add next char to current object */ 158 char *chunk_limit; /* address of char after current chunk */ 159 union 160 { 161 PTR_INT_TYPE tempint; 162 void *tempptr; 163 } temp; /* Temporary for some macros. */ 164 int alignment_mask; /* Mask of alignment for each object. */ 165 /* These prototypes vary based on `use_extra_arg'. */ 166 union { 167 void *(*plain) (long); 168 struct _obstack_chunk *(*extra) (void *, long); 169 } chunkfun; 170 union { 171 void (*plain) (void *); 172 void (*extra) (void *, struct _obstack_chunk *); 173 } freefun; 174 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */ 175 unsigned use_extra_arg:1; /* chunk alloc/dealloc funcs take extra arg */ 176 unsigned maybe_empty_object:1;/* There is a possibility that the current 177 chunk contains a zero-length object. This 178 prevents freeing the chunk if we allocate 179 a bigger chunk to replace it. */ 180 unsigned alloc_failed:1; /* No longer used, as we now call the failed 181 handler on error, but retained for binary 182 compatibility. */ 183 }; 184 185 /* Declare the external functions we use; they are in obstack.c. */ 186 187 extern void _obstack_newchunk (struct obstack *, int); 188 extern int _obstack_begin (struct obstack *, int, int, 189 void *(*) (long), void (*) (void *)); 190 extern int _obstack_begin_1 (struct obstack *, int, int, 191 void *(*) (void *, long), 192 void (*) (void *, void *), void *); 193 extern int _obstack_memory_used (struct obstack *); 194 195 void obstack_free (struct obstack *, void *); 196 197 198 /* Error handler called when `obstack_chunk_alloc' failed to allocate 199 more memory. This can be set to a user defined function which 200 should either abort gracefully or use longjump - but shouldn't 201 return. The default action is to print a message and abort. */ 202 extern void (*obstack_alloc_failed_handler) (void); 203 204 /* Pointer to beginning of object being allocated or to be allocated next. 205 Note that this might not be the final address of the object 206 because a new chunk might be needed to hold the final size. */ 207 208 #define obstack_base(h) ((void *) (h)->object_base) 209 210 /* Size for allocating ordinary chunks. */ 211 212 #define obstack_chunk_size(h) ((h)->chunk_size) 213 214 /* Pointer to next byte not yet allocated in current chunk. */ 215 216 #define obstack_next_free(h) ((h)->next_free) 217 218 /* Mask specifying low bits that should be clear in address of an object. */ 219 220 #define obstack_alignment_mask(h) ((h)->alignment_mask) 221 222 /* To prevent prototype warnings provide complete argument list. */ 223 #define obstack_init(h) \ 224 _obstack_begin ((h), 0, 0, \ 225 (void *(*) (long)) obstack_chunk_alloc, \ 226 (void (*) (void *)) obstack_chunk_free) 227 228 #define obstack_begin(h, size) \ 229 _obstack_begin ((h), (size), 0, \ 230 (void *(*) (long)) obstack_chunk_alloc, \ 231 (void (*) (void *)) obstack_chunk_free) 232 233 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \ 234 _obstack_begin ((h), (size), (alignment), \ 235 (void *(*) (long)) (chunkfun), \ 236 (void (*) (void *)) (freefun)) 237 238 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \ 239 _obstack_begin_1 ((h), (size), (alignment), \ 240 (void *(*) (void *, long)) (chunkfun), \ 241 (void (*) (void *, void *)) (freefun), (arg)) 242 243 #define obstack_chunkfun(h, newchunkfun) \ 244 ((h)->chunkfun.extra = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun)) 245 246 #define obstack_freefun(h, newfreefun) \ 247 ((h)->freefun.extra = (void (*)(void *, struct _obstack_chunk *)) (newfreefun)) 248 249 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar)) 250 251 #define obstack_blank_fast(h,n) ((h)->next_free += (n)) 252 253 #define obstack_memory_used(h) _obstack_memory_used (h) 254 255 #if defined __GNUC__ && defined __STDC__ && __STDC__ 256 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and 257 does not implement __extension__. But that compiler doesn't define 258 __GNUC_MINOR__. */ 259 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__) 260 # define __extension__ 261 # endif 262 263 /* For GNU C, if not -traditional, 264 we can define these macros to compute all args only once 265 without using a global variable. 266 Also, we can avoid using the `temp' slot, to make faster code. */ 267 268 # define obstack_object_size(OBSTACK) \ 269 __extension__ \ 270 ({ struct obstack const *__o = (OBSTACK); \ 271 (unsigned) (__o->next_free - __o->object_base); }) 272 273 # define obstack_room(OBSTACK) \ 274 __extension__ \ 275 ({ struct obstack const *__o = (OBSTACK); \ 276 (unsigned) (__o->chunk_limit - __o->next_free); }) 277 278 # define obstack_make_room(OBSTACK,length) \ 279 __extension__ \ 280 ({ struct obstack *__o = (OBSTACK); \ 281 int __len = (length); \ 282 if (__o->chunk_limit - __o->next_free < __len) \ 283 _obstack_newchunk (__o, __len); \ 284 (void) 0; }) 285 286 # define obstack_empty_p(OBSTACK) \ 287 __extension__ \ 288 ({ struct obstack const *__o = (OBSTACK); \ 289 (__o->chunk->prev == 0 \ 290 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \ 291 __o->chunk->contents, \ 292 __o->alignment_mask)); }) 293 294 # define obstack_grow(OBSTACK,where,length) \ 295 __extension__ \ 296 ({ struct obstack *__o = (OBSTACK); \ 297 int __len = (length); \ 298 if (__o->next_free + __len > __o->chunk_limit) \ 299 _obstack_newchunk (__o, __len); \ 300 memcpy (__o->next_free, where, __len); \ 301 __o->next_free += __len; \ 302 (void) 0; }) 303 304 # define obstack_grow0(OBSTACK,where,length) \ 305 __extension__ \ 306 ({ struct obstack *__o = (OBSTACK); \ 307 int __len = (length); \ 308 if (__o->next_free + __len + 1 > __o->chunk_limit) \ 309 _obstack_newchunk (__o, __len + 1); \ 310 memcpy (__o->next_free, where, __len); \ 311 __o->next_free += __len; \ 312 *(__o->next_free)++ = 0; \ 313 (void) 0; }) 314 315 # define obstack_1grow(OBSTACK,datum) \ 316 __extension__ \ 317 ({ struct obstack *__o = (OBSTACK); \ 318 if (__o->next_free + 1 > __o->chunk_limit) \ 319 _obstack_newchunk (__o, 1); \ 320 obstack_1grow_fast (__o, datum); \ 321 (void) 0; }) 322 323 /* These assume that the obstack alignment is good enough for pointers 324 or ints, and that the data added so far to the current object 325 shares that much alignment. */ 326 327 # define obstack_ptr_grow(OBSTACK,datum) \ 328 __extension__ \ 329 ({ struct obstack *__o = (OBSTACK); \ 330 if (__o->next_free + sizeof (void *) > __o->chunk_limit) \ 331 _obstack_newchunk (__o, sizeof (void *)); \ 332 obstack_ptr_grow_fast (__o, datum); }) \ 333 334 # define obstack_int_grow(OBSTACK,datum) \ 335 __extension__ \ 336 ({ struct obstack *__o = (OBSTACK); \ 337 if (__o->next_free + sizeof (int) > __o->chunk_limit) \ 338 _obstack_newchunk (__o, sizeof (int)); \ 339 obstack_int_grow_fast (__o, datum); }) 340 341 # define obstack_ptr_grow_fast(OBSTACK,aptr) \ 342 __extension__ \ 343 ({ struct obstack *__o1 = (OBSTACK); \ 344 *(const void **) __o1->next_free = (aptr); \ 345 __o1->next_free += sizeof (const void *); \ 346 (void) 0; }) 347 348 # define obstack_int_grow_fast(OBSTACK,aint) \ 349 __extension__ \ 350 ({ struct obstack *__o1 = (OBSTACK); \ 351 *(int *) __o1->next_free = (aint); \ 352 __o1->next_free += sizeof (int); \ 353 (void) 0; }) 354 355 # define obstack_blank(OBSTACK,length) \ 356 __extension__ \ 357 ({ struct obstack *__o = (OBSTACK); \ 358 int __len = (length); \ 359 if (__o->chunk_limit - __o->next_free < __len) \ 360 _obstack_newchunk (__o, __len); \ 361 obstack_blank_fast (__o, __len); \ 362 (void) 0; }) 363 364 # define obstack_alloc(OBSTACK,length) \ 365 __extension__ \ 366 ({ struct obstack *__h = (OBSTACK); \ 367 obstack_blank (__h, (length)); \ 368 obstack_finish (__h); }) 369 370 # define obstack_copy(OBSTACK,where,length) \ 371 __extension__ \ 372 ({ struct obstack *__h = (OBSTACK); \ 373 obstack_grow (__h, (where), (length)); \ 374 obstack_finish (__h); }) 375 376 # define obstack_copy0(OBSTACK,where,length) \ 377 __extension__ \ 378 ({ struct obstack *__h = (OBSTACK); \ 379 obstack_grow0 (__h, (where), (length)); \ 380 obstack_finish (__h); }) 381 382 /* The local variable is named __o1 to avoid a name conflict 383 when obstack_blank is called. */ 384 # define obstack_finish(OBSTACK) \ 385 __extension__ \ 386 ({ struct obstack *__o1 = (OBSTACK); \ 387 void *__value = (void *) __o1->object_base; \ 388 if (__o1->next_free == __value) \ 389 __o1->maybe_empty_object = 1; \ 390 __o1->next_free \ 391 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \ 392 __o1->alignment_mask); \ 393 if (__o1->next_free - (char *)__o1->chunk \ 394 > __o1->chunk_limit - (char *)__o1->chunk) \ 395 __o1->next_free = __o1->chunk_limit; \ 396 __o1->object_base = __o1->next_free; \ 397 __value; }) 398 399 # define obstack_free(OBSTACK, OBJ) \ 400 __extension__ \ 401 ({ struct obstack *__o = (OBSTACK); \ 402 void *__obj = (OBJ); \ 403 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \ 404 __o->next_free = __o->object_base = (char *)__obj; \ 405 else (obstack_free) (__o, __obj); }) 406 407 #else /* not __GNUC__ or not __STDC__ */ 408 409 # define obstack_object_size(h) \ 410 (unsigned) ((h)->next_free - (h)->object_base) 411 412 # define obstack_room(h) \ 413 (unsigned) ((h)->chunk_limit - (h)->next_free) 414 415 # define obstack_empty_p(h) \ 416 ((h)->chunk->prev == 0 \ 417 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \ 418 (h)->chunk->contents, \ 419 (h)->alignment_mask)) 420 421 /* Note that the call to _obstack_newchunk is enclosed in (..., 0) 422 so that we can avoid having void expressions 423 in the arms of the conditional expression. 424 Casting the third operand to void was tried before, 425 but some compilers won't accept it. */ 426 427 # define obstack_make_room(h,length) \ 428 ( (h)->temp.tempint = (length), \ 429 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 430 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0)) 431 432 # define obstack_grow(h,where,length) \ 433 ( (h)->temp.tempint = (length), \ 434 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 435 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 436 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 437 (h)->next_free += (h)->temp.tempint) 438 439 # define obstack_grow0(h,where,length) \ 440 ( (h)->temp.tempint = (length), \ 441 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \ 442 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \ 443 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 444 (h)->next_free += (h)->temp.tempint, \ 445 *((h)->next_free)++ = 0) 446 447 # define obstack_1grow(h,datum) \ 448 ( (((h)->next_free + 1 > (h)->chunk_limit) \ 449 ? (_obstack_newchunk ((h), 1), 0) : 0), \ 450 obstack_1grow_fast (h, datum)) 451 452 # define obstack_ptr_grow(h,datum) \ 453 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \ 454 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \ 455 obstack_ptr_grow_fast (h, datum)) 456 457 # define obstack_int_grow(h,datum) \ 458 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \ 459 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \ 460 obstack_int_grow_fast (h, datum)) 461 462 # define obstack_ptr_grow_fast(h,aptr) \ 463 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr)) 464 465 # define obstack_int_grow_fast(h,aint) \ 466 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint)) 467 468 # define obstack_blank(h,length) \ 469 ( (h)->temp.tempint = (length), \ 470 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \ 471 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 472 obstack_blank_fast (h, (h)->temp.tempint)) 473 474 # define obstack_alloc(h,length) \ 475 (obstack_blank ((h), (length)), obstack_finish ((h))) 476 477 # define obstack_copy(h,where,length) \ 478 (obstack_grow ((h), (where), (length)), obstack_finish ((h))) 479 480 # define obstack_copy0(h,where,length) \ 481 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h))) 482 483 # define obstack_finish(h) \ 484 ( ((h)->next_free == (h)->object_base \ 485 ? (((h)->maybe_empty_object = 1), 0) \ 486 : 0), \ 487 (h)->temp.tempptr = (h)->object_base, \ 488 (h)->next_free \ 489 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \ 490 (h)->alignment_mask), \ 491 (((h)->next_free - (char *) (h)->chunk \ 492 > (h)->chunk_limit - (char *) (h)->chunk) \ 493 ? ((h)->next_free = (h)->chunk_limit) : 0), \ 494 (h)->object_base = (h)->next_free, \ 495 (h)->temp.tempptr) 496 497 # define obstack_free(h,obj) \ 498 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \ 499 ((((h)->temp.tempint > 0 \ 500 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \ 501 ? (ptrdiff_t) ((h)->next_free = (h)->object_base \ 502 = (h)->temp.tempint + (char *) (h)->chunk) \ 503 : (((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0))) 504 505 #endif /* not __GNUC__ or not __STDC__ */ 506 507 #ifdef __cplusplus 508 } /* C++ */ 509 #endif 510 511 #endif /* obstack.h */ 512