1 /* obstack.h - object stack macros 2 Copyright (C) 1988-1994, 1996-1999, 2003-2006, 2009-2012 Free Software 3 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 3 of the License, or 9 (at your option) 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 17 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 18 19 /* Summary: 20 21 All the apparent functions defined here are macros. The idea 22 is that you would use these pre-tested macros to solve a 23 very specific set of problems, and they would run fast. 24 Caution: no side-effects in arguments please!! They may be 25 evaluated MANY times!! 26 27 These macros operate a stack of objects. Each object starts life 28 small, and may grow to maturity. (Consider building a word syllable 29 by syllable.) An object can move while it is growing. Once it has 30 been "finished" it never changes address again. So the "top of the 31 stack" is typically an immature growing object, while the rest of the 32 stack is of mature, fixed size and fixed address objects. 33 34 These routines grab large chunks of memory, using a function you 35 supply, called 'obstack_chunk_alloc'. On occasion, they free chunks, 36 by calling 'obstack_chunk_free'. You must define them and declare 37 them before using any obstack macros. 38 39 Each independent stack is represented by a 'struct obstack'. 40 Each of the obstack macros expects a pointer to such a structure 41 as the first argument. 42 43 One motivation for this package is the problem of growing char strings 44 in symbol tables. Unless you are "fascist pig with a read-only mind" 45 --Gosper's immortal quote from HAKMEM item 154, out of context--you 46 would not like to put any arbitrary upper limit on the length of your 47 symbols. 48 49 In practice this often means you will build many short symbols and a 50 few long symbols. At the time you are reading a symbol you don't know 51 how long it is. One traditional method is to read a symbol into a 52 buffer, realloc()ating the buffer every time you try to read a symbol 53 that is longer than the buffer. This is beaut, but you still will 54 want to copy the symbol from the buffer to a more permanent 55 symbol-table entry say about half the time. 56 57 With obstacks, you can work differently. Use one obstack for all symbol 58 names. As you read a symbol, grow the name in the obstack gradually. 59 When the name is complete, finalize it. Then, if the symbol exists already, 60 free the newly read name. 61 62 The way we do this is to take a large chunk, allocating memory from 63 low addresses. When you want to build a symbol in the chunk you just 64 add chars above the current "high water mark" in the chunk. When you 65 have finished adding chars, because you got to the end of the symbol, 66 you know how long the chars are, and you can create a new object. 67 Mostly the chars will not burst over the highest address of the chunk, 68 because you would typically expect a chunk to be (say) 100 times as 69 long as an average object. 70 71 In case that isn't clear, when we have enough chars to make up 72 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed) 73 so we just point to it where it lies. No moving of chars is 74 needed and this is the second win: potentially long strings need 75 never be explicitly shuffled. Once an object is formed, it does not 76 change its address during its lifetime. 77 78 When the chars burst over a chunk boundary, we allocate a larger 79 chunk, and then copy the partly formed object from the end of the old 80 chunk to the beginning of the new larger chunk. We then carry on 81 accreting characters to the end of the object as we normally would. 82 83 A special macro is provided to add a single char at a time to a 84 growing object. This allows the use of register variables, which 85 break the ordinary 'growth' macro. 86 87 Summary: 88 We allocate large chunks. 89 We carve out one object at a time from the current chunk. 90 Once carved, an object never moves. 91 We are free to append data of any size to the currently 92 growing object. 93 Exactly one object is growing in an obstack at any one time. 94 You can run one obstack per control block. 95 You may have as many control blocks as you dare. 96 Because of the way we do it, you can "unwind" an obstack 97 back to a previous state. (You may remove objects much 98 as you would with a stack.) 99 */ 100 101 102 /* Don't do the contents of this file more than once. */ 103 104 #ifndef _OBSTACK_H 105 #define _OBSTACK_H 1 106 107 /* We need the type of a pointer subtraction. If __PTRDIFF_TYPE__ is 109 defined, as with GNU C, use that; that way we don't pollute the 110 namespace with <stddef.h>'s symbols. Otherwise, include <stddef.h> 111 and use ptrdiff_t. */ 112 113 #ifdef __PTRDIFF_TYPE__ 114 # define PTR_INT_TYPE __PTRDIFF_TYPE__ 115 #else 116 # include <stddef.h> 117 # define PTR_INT_TYPE ptrdiff_t 118 #endif 119 120 /* If B is the base of an object addressed by P, return the result of 121 aligning P to the next multiple of A + 1. B and P must be of type 122 char *. A + 1 must be a power of 2. */ 123 124 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A))) 125 126 /* Similar to _BPTR_ALIGN (B, P, A), except optimize the common case 127 where pointers can be converted to integers, aligned as integers, 128 and converted back again. If PTR_INT_TYPE is narrower than a 129 pointer (e.g., the AS/400), play it safe and compute the alignment 130 relative to B. Otherwise, use the faster strategy of computing the 131 alignment relative to 0. */ 132 133 #define __PTR_ALIGN(B, P, A) \ 134 __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \ 135 P, A) 136 137 #include <string.h> 138 139 #ifdef __cplusplus 140 extern "C" { 141 #endif 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 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 /* Exit value used when 'print_and_abort' is used. */ 205 extern int obstack_exit_failure; 206 207 /* Pointer to beginning of object being allocated or to be allocated next. 209 Note that this might not be the final address of the object 210 because a new chunk might be needed to hold the final size. */ 211 212 #define obstack_base(h) ((void *) (h)->object_base) 213 214 /* Size for allocating ordinary chunks. */ 215 216 #define obstack_chunk_size(h) ((h)->chunk_size) 217 218 /* Pointer to next byte not yet allocated in current chunk. */ 219 220 #define obstack_next_free(h) ((h)->next_free) 221 222 /* Mask specifying low bits that should be clear in address of an object. */ 223 224 #define obstack_alignment_mask(h) ((h)->alignment_mask) 225 226 /* To prevent prototype warnings provide complete argument list. */ 227 #define obstack_init(h) \ 228 _obstack_begin ((h), 0, 0, \ 229 (void *(*) (long)) obstack_chunk_alloc, \ 230 (void (*) (void *)) obstack_chunk_free) 231 232 #define obstack_begin(h, size) \ 233 _obstack_begin ((h), (size), 0, \ 234 (void *(*) (long)) obstack_chunk_alloc, \ 235 (void (*) (void *)) obstack_chunk_free) 236 237 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \ 238 _obstack_begin ((h), (size), (alignment), \ 239 (void *(*) (long)) (chunkfun), \ 240 (void (*) (void *)) (freefun)) 241 242 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \ 243 _obstack_begin_1 ((h), (size), (alignment), \ 244 (void *(*) (void *, long)) (chunkfun), \ 245 (void (*) (void *, void *)) (freefun), (arg)) 246 247 #define obstack_chunkfun(h, newchunkfun) \ 248 ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun)) 249 250 #define obstack_freefun(h, newfreefun) \ 251 ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun)) 252 253 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar)) 254 255 #define obstack_blank_fast(h,n) ((h)->next_free += (n)) 256 257 #define obstack_memory_used(h) _obstack_memory_used (h) 258 259 #if defined __GNUC__ 261 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and 262 does not implement __extension__. But that compiler doesn't define 263 __GNUC_MINOR__. */ 264 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__) 265 # define __extension__ 266 # endif 267 268 /* For GNU C, if not -traditional, 269 we can define these macros to compute all args only once 270 without using a global variable. 271 Also, we can avoid using the 'temp' slot, to make faster code. */ 272 273 # define obstack_object_size(OBSTACK) \ 274 __extension__ \ 275 ({ struct obstack const *__o = (OBSTACK); \ 276 (unsigned) (__o->next_free - __o->object_base); }) 277 278 # define obstack_room(OBSTACK) \ 279 __extension__ \ 280 ({ struct obstack const *__o = (OBSTACK); \ 281 (unsigned) (__o->chunk_limit - __o->next_free); }) 282 283 # define obstack_make_room(OBSTACK,length) \ 284 __extension__ \ 285 ({ struct obstack *__o = (OBSTACK); \ 286 int __len = (length); \ 287 if (__o->chunk_limit - __o->next_free < __len) \ 288 _obstack_newchunk (__o, __len); \ 289 (void) 0; }) 290 291 # define obstack_empty_p(OBSTACK) \ 292 __extension__ \ 293 ({ struct obstack const *__o = (OBSTACK); \ 294 (__o->chunk->prev == 0 \ 295 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \ 296 __o->chunk->contents, \ 297 __o->alignment_mask)); }) 298 299 # define obstack_grow(OBSTACK,where,length) \ 300 __extension__ \ 301 ({ struct obstack *__o = (OBSTACK); \ 302 int __len = (length); \ 303 if (__o->next_free + __len > __o->chunk_limit) \ 304 _obstack_newchunk (__o, __len); \ 305 memcpy (__o->next_free, where, __len); \ 306 __o->next_free += __len; \ 307 (void) 0; }) 308 309 # define obstack_grow0(OBSTACK,where,length) \ 310 __extension__ \ 311 ({ struct obstack *__o = (OBSTACK); \ 312 int __len = (length); \ 313 if (__o->next_free + __len + 1 > __o->chunk_limit) \ 314 _obstack_newchunk (__o, __len + 1); \ 315 memcpy (__o->next_free, where, __len); \ 316 __o->next_free += __len; \ 317 *(__o->next_free)++ = 0; \ 318 (void) 0; }) 319 320 # define obstack_1grow(OBSTACK,datum) \ 321 __extension__ \ 322 ({ struct obstack *__o = (OBSTACK); \ 323 if (__o->next_free + 1 > __o->chunk_limit) \ 324 _obstack_newchunk (__o, 1); \ 325 obstack_1grow_fast (__o, datum); \ 326 (void) 0; }) 327 328 /* These assume that the obstack alignment is good enough for pointers 329 or ints, and that the data added so far to the current object 330 shares that much alignment. */ 331 332 # define obstack_ptr_grow(OBSTACK,datum) \ 333 __extension__ \ 334 ({ struct obstack *__o = (OBSTACK); \ 335 if (__o->next_free + sizeof (void *) > __o->chunk_limit) \ 336 _obstack_newchunk (__o, sizeof (void *)); \ 337 obstack_ptr_grow_fast (__o, datum); }) \ 338 339 # define obstack_int_grow(OBSTACK,datum) \ 340 __extension__ \ 341 ({ struct obstack *__o = (OBSTACK); \ 342 if (__o->next_free + sizeof (int) > __o->chunk_limit) \ 343 _obstack_newchunk (__o, sizeof (int)); \ 344 obstack_int_grow_fast (__o, datum); }) 345 346 # define obstack_ptr_grow_fast(OBSTACK,aptr) \ 347 __extension__ \ 348 ({ struct obstack *__o1 = (OBSTACK); \ 349 *(const void **) __o1->next_free = (aptr); \ 350 __o1->next_free += sizeof (const void *); \ 351 (void) 0; }) 352 353 # define obstack_int_grow_fast(OBSTACK,aint) \ 354 __extension__ \ 355 ({ struct obstack *__o1 = (OBSTACK); \ 356 *(int *) __o1->next_free = (aint); \ 357 __o1->next_free += sizeof (int); \ 358 (void) 0; }) 359 360 # define obstack_blank(OBSTACK,length) \ 361 __extension__ \ 362 ({ struct obstack *__o = (OBSTACK); \ 363 int __len = (length); \ 364 if (__o->chunk_limit - __o->next_free < __len) \ 365 _obstack_newchunk (__o, __len); \ 366 obstack_blank_fast (__o, __len); \ 367 (void) 0; }) 368 369 # define obstack_alloc(OBSTACK,length) \ 370 __extension__ \ 371 ({ struct obstack *__h = (OBSTACK); \ 372 obstack_blank (__h, (length)); \ 373 obstack_finish (__h); }) 374 375 # define obstack_copy(OBSTACK,where,length) \ 376 __extension__ \ 377 ({ struct obstack *__h = (OBSTACK); \ 378 obstack_grow (__h, (where), (length)); \ 379 obstack_finish (__h); }) 380 381 # define obstack_copy0(OBSTACK,where,length) \ 382 __extension__ \ 383 ({ struct obstack *__h = (OBSTACK); \ 384 obstack_grow0 (__h, (where), (length)); \ 385 obstack_finish (__h); }) 386 387 /* The local variable is named __o1 to avoid a name conflict 388 when obstack_blank is called. */ 389 # define obstack_finish(OBSTACK) \ 390 __extension__ \ 391 ({ struct obstack *__o1 = (OBSTACK); \ 392 void *__value = (void *) __o1->object_base; \ 393 if (__o1->next_free == __value) \ 394 __o1->maybe_empty_object = 1; \ 395 __o1->next_free \ 396 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \ 397 __o1->alignment_mask); \ 398 if (__o1->next_free - (char *)__o1->chunk \ 399 > __o1->chunk_limit - (char *)__o1->chunk) \ 400 __o1->next_free = __o1->chunk_limit; \ 401 __o1->object_base = __o1->next_free; \ 402 __value; }) 403 404 # define obstack_free(OBSTACK, OBJ) \ 405 __extension__ \ 406 ({ struct obstack *__o = (OBSTACK); \ 407 void *__obj = (OBJ); \ 408 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \ 409 __o->next_free = __o->object_base = (char *)__obj; \ 410 else (__obstack_free) (__o, __obj); }) 411 412 #else /* not __GNUC__ */ 414 415 # define obstack_object_size(h) \ 416 (unsigned) ((h)->next_free - (h)->object_base) 417 418 # define obstack_room(h) \ 419 (unsigned) ((h)->chunk_limit - (h)->next_free) 420 421 # define obstack_empty_p(h) \ 422 ((h)->chunk->prev == 0 \ 423 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \ 424 (h)->chunk->contents, \ 425 (h)->alignment_mask)) 426 427 /* Note that the call to _obstack_newchunk is enclosed in (..., 0) 428 so that we can avoid having void expressions 429 in the arms of the conditional expression. 430 Casting the third operand to void was tried before, 431 but some compilers won't accept it. */ 432 433 # define obstack_make_room(h,length) \ 434 ( (h)->temp.tempint = (length), \ 435 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 436 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0)) 437 438 # define obstack_grow(h,where,length) \ 439 ( (h)->temp.tempint = (length), \ 440 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 441 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 442 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 443 (h)->next_free += (h)->temp.tempint) 444 445 # define obstack_grow0(h,where,length) \ 446 ( (h)->temp.tempint = (length), \ 447 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \ 448 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \ 449 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 450 (h)->next_free += (h)->temp.tempint, \ 451 *((h)->next_free)++ = 0) 452 453 # define obstack_1grow(h,datum) \ 454 ( (((h)->next_free + 1 > (h)->chunk_limit) \ 455 ? (_obstack_newchunk ((h), 1), 0) : 0), \ 456 obstack_1grow_fast (h, datum)) 457 458 # define obstack_ptr_grow(h,datum) \ 459 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \ 460 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \ 461 obstack_ptr_grow_fast (h, datum)) 462 463 # define obstack_int_grow(h,datum) \ 464 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \ 465 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \ 466 obstack_int_grow_fast (h, datum)) 467 468 # define obstack_ptr_grow_fast(h,aptr) \ 469 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr)) 470 471 # define obstack_int_grow_fast(h,aint) \ 472 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint)) 473 474 # define obstack_blank(h,length) \ 475 ( (h)->temp.tempint = (length), \ 476 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \ 477 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 478 obstack_blank_fast (h, (h)->temp.tempint)) 479 480 # define obstack_alloc(h,length) \ 481 (obstack_blank ((h), (length)), obstack_finish ((h))) 482 483 # define obstack_copy(h,where,length) \ 484 (obstack_grow ((h), (where), (length)), obstack_finish ((h))) 485 486 # define obstack_copy0(h,where,length) \ 487 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h))) 488 489 # define obstack_finish(h) \ 490 ( ((h)->next_free == (h)->object_base \ 491 ? (((h)->maybe_empty_object = 1), 0) \ 492 : 0), \ 493 (h)->temp.tempptr = (h)->object_base, \ 494 (h)->next_free \ 495 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \ 496 (h)->alignment_mask), \ 497 (((h)->next_free - (char *) (h)->chunk \ 498 > (h)->chunk_limit - (char *) (h)->chunk) \ 499 ? ((h)->next_free = (h)->chunk_limit) : 0), \ 500 (h)->object_base = (h)->next_free, \ 501 (h)->temp.tempptr) 502 503 # define obstack_free(h,obj) \ 504 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \ 505 ((((h)->temp.tempint > 0 \ 506 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \ 507 ? (int) ((h)->next_free = (h)->object_base \ 508 = (h)->temp.tempint + (char *) (h)->chunk) \ 509 : (((__obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0))) 510 511 #endif /* not __GNUC__ */ 512 513 #ifdef __cplusplus 514 } /* C++ */ 515 #endif 516 517 #endif /* obstack.h */ 518
