1 /* obstack.h - object stack macros 2 Copyright (C) 1988-1994,1996-1999,2003,2004,2005,2006 3 Free Software Foundation, Inc. 4 This file is part of the GNU C Library. 5 6 This program is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2, or (at your option) 9 any later version. 10 11 This program 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 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License along 17 with this program; if not, write to the Free Software Foundation, 18 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ 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 extern int _obstack_begin (struct obstack *, int, int, 183 void *(*) (long), void (*) (void *)); 184 extern int _obstack_begin_1 (struct obstack *, int, int, 185 void *(*) (void *, long), 186 void (*) (void *, void *), void *); 187 extern int _obstack_memory_used (struct obstack *); 188 189 /* The default name of the function for freeing a chunk is 'obstack_free', 190 but gnulib users can override this by defining '__obstack_free'. */ 191 #ifndef __obstack_free 192 # define __obstack_free obstack_free 193 #endif 194 extern void __obstack_free (struct obstack *obstack, void *block); 195 196 197 /* Error handler called when `obstack_chunk_alloc' failed to allocate 198 more memory. This can be set to a user defined function which 199 should either abort gracefully or use longjump - but shouldn't 200 return. The default action is to print a message and abort. */ 201 extern void (*obstack_alloc_failed_handler) (void); 202 203 /* Exit value used when `print_and_abort' is used. */ 204 extern int obstack_exit_failure; 205 206 /* Pointer to beginning of object being allocated or to be allocated next. 207 Note that this might not be the final address of the object 208 because a new chunk might be needed to hold the final size. */ 209 210 #define obstack_base(h) ((void *) (h)->object_base) 211 212 /* Size for allocating ordinary chunks. */ 213 214 #define obstack_chunk_size(h) ((h)->chunk_size) 215 216 /* Pointer to next byte not yet allocated in current chunk. */ 217 218 #define obstack_next_free(h) ((h)->next_free) 219 220 /* Mask specifying low bits that should be clear in address of an object. */ 221 222 #define obstack_alignment_mask(h) ((h)->alignment_mask) 223 224 /* To prevent prototype warnings provide complete argument list. */ 225 #define obstack_init(h) \ 226 _obstack_begin ((h), 0, 0, \ 227 (void *(*) (long)) obstack_chunk_alloc, \ 228 (void (*) (void *)) obstack_chunk_free) 229 230 #define obstack_begin(h, size) \ 231 _obstack_begin ((h), (size), 0, \ 232 (void *(*) (long)) obstack_chunk_alloc, \ 233 (void (*) (void *)) obstack_chunk_free) 234 235 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \ 236 _obstack_begin ((h), (size), (alignment), \ 237 (void *(*) (long)) (chunkfun), \ 238 (void (*) (void *)) (freefun)) 239 240 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \ 241 _obstack_begin_1 ((h), (size), (alignment), \ 242 (void *(*) (void *, long)) (chunkfun), \ 243 (void (*) (void *, void *)) (freefun), (arg)) 244 245 #define obstack_chunkfun(h, newchunkfun) \ 246 ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun)) 247 248 #define obstack_freefun(h, newfreefun) \ 249 ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun)) 250 251 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar)) 252 253 #define obstack_blank_fast(h,n) ((h)->next_free += (n)) 254 255 #define obstack_memory_used(h) _obstack_memory_used (h) 256 257 #if defined __GNUC__ && defined __STDC__ && __STDC__ 258 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and 259 does not implement __extension__. But that compiler doesn't define 260 __GNUC_MINOR__. */ 261 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__) 262 # define __extension__ 263 # endif 264 265 /* For GNU C, if not -traditional, 266 we can define these macros to compute all args only once 267 without using a global variable. 268 Also, we can avoid using the `temp' slot, to make faster code. */ 269 270 # define obstack_object_size(OBSTACK) \ 271 __extension__ \ 272 ({ struct obstack const *__o = (OBSTACK); \ 273 (unsigned) (__o->next_free - __o->object_base); }) 274 275 # define obstack_room(OBSTACK) \ 276 __extension__ \ 277 ({ struct obstack const *__o = (OBSTACK); \ 278 (unsigned) (__o->chunk_limit - __o->next_free); }) 279 280 # define obstack_make_room(OBSTACK,length) \ 281 __extension__ \ 282 ({ struct obstack *__o = (OBSTACK); \ 283 int __len = (length); \ 284 if (__o->chunk_limit - __o->next_free < __len) \ 285 _obstack_newchunk (__o, __len); \ 286 (void) 0; }) 287 288 # define obstack_empty_p(OBSTACK) \ 289 __extension__ \ 290 ({ struct obstack const *__o = (OBSTACK); \ 291 (__o->chunk->prev == 0 \ 292 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \ 293 __o->chunk->contents, \ 294 __o->alignment_mask)); }) 295 296 # define obstack_grow(OBSTACK,where,length) \ 297 __extension__ \ 298 ({ struct obstack *__o = (OBSTACK); \ 299 int __len = (length); \ 300 if (__o->next_free + __len > __o->chunk_limit) \ 301 _obstack_newchunk (__o, __len); \ 302 memcpy (__o->next_free, where, __len); \ 303 __o->next_free += __len; \ 304 (void) 0; }) 305 306 # define obstack_grow0(OBSTACK,where,length) \ 307 __extension__ \ 308 ({ struct obstack *__o = (OBSTACK); \ 309 int __len = (length); \ 310 if (__o->next_free + __len + 1 > __o->chunk_limit) \ 311 _obstack_newchunk (__o, __len + 1); \ 312 memcpy (__o->next_free, where, __len); \ 313 __o->next_free += __len; \ 314 *(__o->next_free)++ = 0; \ 315 (void) 0; }) 316 317 # define obstack_1grow(OBSTACK,datum) \ 318 __extension__ \ 319 ({ struct obstack *__o = (OBSTACK); \ 320 if (__o->next_free + 1 > __o->chunk_limit) \ 321 _obstack_newchunk (__o, 1); \ 322 obstack_1grow_fast (__o, datum); \ 323 (void) 0; }) 324 325 /* These assume that the obstack alignment is good enough for pointers 326 or ints, and that the data added so far to the current object 327 shares that much alignment. */ 328 329 # define obstack_ptr_grow(OBSTACK,datum) \ 330 __extension__ \ 331 ({ struct obstack *__o = (OBSTACK); \ 332 if (__o->next_free + sizeof (void *) > __o->chunk_limit) \ 333 _obstack_newchunk (__o, sizeof (void *)); \ 334 obstack_ptr_grow_fast (__o, datum); }) \ 335 336 # define obstack_int_grow(OBSTACK,datum) \ 337 __extension__ \ 338 ({ struct obstack *__o = (OBSTACK); \ 339 if (__o->next_free + sizeof (int) > __o->chunk_limit) \ 340 _obstack_newchunk (__o, sizeof (int)); \ 341 obstack_int_grow_fast (__o, datum); }) 342 343 # define obstack_ptr_grow_fast(OBSTACK,aptr) \ 344 __extension__ \ 345 ({ struct obstack *__o1 = (OBSTACK); \ 346 *(const void **) __o1->next_free = (aptr); \ 347 __o1->next_free += sizeof (const void *); \ 348 (void) 0; }) 349 350 # define obstack_int_grow_fast(OBSTACK,aint) \ 351 __extension__ \ 352 ({ struct obstack *__o1 = (OBSTACK); \ 353 *(int *) __o1->next_free = (aint); \ 354 __o1->next_free += sizeof (int); \ 355 (void) 0; }) 356 357 # define obstack_blank(OBSTACK,length) \ 358 __extension__ \ 359 ({ struct obstack *__o = (OBSTACK); \ 360 int __len = (length); \ 361 if (__o->chunk_limit - __o->next_free < __len) \ 362 _obstack_newchunk (__o, __len); \ 363 obstack_blank_fast (__o, __len); \ 364 (void) 0; }) 365 366 # define obstack_alloc(OBSTACK,length) \ 367 __extension__ \ 368 ({ struct obstack *__h = (OBSTACK); \ 369 obstack_blank (__h, (length)); \ 370 obstack_finish (__h); }) 371 372 # define obstack_copy(OBSTACK,where,length) \ 373 __extension__ \ 374 ({ struct obstack *__h = (OBSTACK); \ 375 obstack_grow (__h, (where), (length)); \ 376 obstack_finish (__h); }) 377 378 # define obstack_copy0(OBSTACK,where,length) \ 379 __extension__ \ 380 ({ struct obstack *__h = (OBSTACK); \ 381 obstack_grow0 (__h, (where), (length)); \ 382 obstack_finish (__h); }) 383 384 /* The local variable is named __o1 to avoid a name conflict 385 when obstack_blank is called. */ 386 # define obstack_finish(OBSTACK) \ 387 __extension__ \ 388 ({ struct obstack *__o1 = (OBSTACK); \ 389 void *__value = (void *) __o1->object_base; \ 390 if (__o1->next_free == __value) \ 391 __o1->maybe_empty_object = 1; \ 392 __o1->next_free \ 393 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \ 394 __o1->alignment_mask); \ 395 if (__o1->next_free - (char *)__o1->chunk \ 396 > __o1->chunk_limit - (char *)__o1->chunk) \ 397 __o1->next_free = __o1->chunk_limit; \ 398 __o1->object_base = __o1->next_free; \ 399 __value; }) 400 401 # define obstack_free(OBSTACK, OBJ) \ 402 __extension__ \ 403 ({ struct obstack *__o = (OBSTACK); \ 404 void *__obj = (OBJ); \ 405 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \ 406 __o->next_free = __o->object_base = (char *)__obj; \ 407 else (__obstack_free) (__o, __obj); }) 408 409 #else /* not __GNUC__ or not __STDC__ */ 410 411 # define obstack_object_size(h) \ 412 (unsigned) ((h)->next_free - (h)->object_base) 413 414 # define obstack_room(h) \ 415 (unsigned) ((h)->chunk_limit - (h)->next_free) 416 417 # define obstack_empty_p(h) \ 418 ((h)->chunk->prev == 0 \ 419 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \ 420 (h)->chunk->contents, \ 421 (h)->alignment_mask)) 422 423 /* Note that the call to _obstack_newchunk is enclosed in (..., 0) 424 so that we can avoid having void expressions 425 in the arms of the conditional expression. 426 Casting the third operand to void was tried before, 427 but some compilers won't accept it. */ 428 429 # define obstack_make_room(h,length) \ 430 ( (h)->temp.tempint = (length), \ 431 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 432 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0)) 433 434 # define obstack_grow(h,where,length) \ 435 ( (h)->temp.tempint = (length), \ 436 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 437 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 438 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 439 (h)->next_free += (h)->temp.tempint) 440 441 # define obstack_grow0(h,where,length) \ 442 ( (h)->temp.tempint = (length), \ 443 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \ 444 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \ 445 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 446 (h)->next_free += (h)->temp.tempint, \ 447 *((h)->next_free)++ = 0) 448 449 # define obstack_1grow(h,datum) \ 450 ( (((h)->next_free + 1 > (h)->chunk_limit) \ 451 ? (_obstack_newchunk ((h), 1), 0) : 0), \ 452 obstack_1grow_fast (h, datum)) 453 454 # define obstack_ptr_grow(h,datum) \ 455 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \ 456 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \ 457 obstack_ptr_grow_fast (h, datum)) 458 459 # define obstack_int_grow(h,datum) \ 460 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \ 461 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \ 462 obstack_int_grow_fast (h, datum)) 463 464 # define obstack_ptr_grow_fast(h,aptr) \ 465 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr)) 466 467 # define obstack_int_grow_fast(h,aint) \ 468 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint)) 469 470 # define obstack_blank(h,length) \ 471 ( (h)->temp.tempint = (length), \ 472 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \ 473 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 474 obstack_blank_fast (h, (h)->temp.tempint)) 475 476 # define obstack_alloc(h,length) \ 477 (obstack_blank ((h), (length)), obstack_finish ((h))) 478 479 # define obstack_copy(h,where,length) \ 480 (obstack_grow ((h), (where), (length)), obstack_finish ((h))) 481 482 # define obstack_copy0(h,where,length) \ 483 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h))) 484 485 # define obstack_finish(h) \ 486 ( ((h)->next_free == (h)->object_base \ 487 ? (((h)->maybe_empty_object = 1), 0) \ 488 : 0), \ 489 (h)->temp.tempptr = (h)->object_base, \ 490 (h)->next_free \ 491 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \ 492 (h)->alignment_mask), \ 493 (((h)->next_free - (char *) (h)->chunk \ 494 > (h)->chunk_limit - (char *) (h)->chunk) \ 495 ? ((h)->next_free = (h)->chunk_limit) : 0), \ 496 (h)->object_base = (h)->next_free, \ 497 (h)->temp.tempptr) 498 499 # define obstack_free(h,obj) \ 500 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \ 501 ((((h)->temp.tempint > 0 \ 502 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \ 503 ? (int) ((h)->next_free = (h)->object_base \ 504 = (h)->temp.tempint + (char *) (h)->chunk) \ 505 : (((__obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0))) 506 507 #endif /* not __GNUC__ or not __STDC__ */ 508 509 #ifdef __cplusplus 510 } /* C++ */ 511 #endif 512 513 #endif /* obstack.h */ 514