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 108 defined, as with GNU C, use that; that way we don't pollute the 109 namespace with <stddef.h>'s symbols. Otherwise, include <stddef.h> 110 and use ptrdiff_t. */ 111 112 #ifdef __PTRDIFF_TYPE__ 113 # define PTR_INT_TYPE __PTRDIFF_TYPE__ 114 #else 115 # include <stddef.h> 116 # define PTR_INT_TYPE ptrdiff_t 117 #endif 118 119 /* If B is the base of an object addressed by P, return the result of 120 aligning P to the next multiple of A + 1. B and P must be of type 121 char *. A + 1 must be a power of 2. */ 122 123 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A))) 124 125 /* Similar to _BPTR_ALIGN (B, P, A), except optimize the common case 126 where pointers can be converted to integers, aligned as integers, 127 and converted back again. If PTR_INT_TYPE is narrower than a 128 pointer (e.g., the AS/400), play it safe and compute the alignment 129 relative to B. Otherwise, use the faster strategy of computing the 130 alignment relative to 0. */ 131 132 #define __PTR_ALIGN(B, P, A) \ 133 __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \ 134 P, A) 135 136 #include <string.h> 137 138 #ifdef __cplusplus 139 extern "C" { 140 #endif 141 142 struct _obstack_chunk /* Lives at front of each chunk. */ 143 { 144 char *limit; /* 1 past end of this chunk */ 145 struct _obstack_chunk *prev; /* address of prior chunk or NULL */ 146 char contents[4]; /* objects begin here */ 147 }; 148 149 struct obstack /* control current object in current chunk */ 150 { 151 long chunk_size; /* preferred size to allocate chunks in */ 152 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */ 153 char *object_base; /* address of object we are building */ 154 char *next_free; /* where to add next char to current object */ 155 char *chunk_limit; /* address of char after current chunk */ 156 union 157 { 158 PTR_INT_TYPE tempint; 159 void *tempptr; 160 } temp; /* Temporary for some macros. */ 161 int alignment_mask; /* Mask of alignment for each object. */ 162 /* These prototypes vary based on 'use_extra_arg', and we use 163 casts to the prototypeless function type in all assignments, 164 but having prototypes here quiets -Wstrict-prototypes. */ 165 struct _obstack_chunk *(*chunkfun) (void *, long); 166 void (*freefun) (void *, struct _obstack_chunk *); 167 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */ 168 unsigned use_extra_arg:1; /* chunk alloc/dealloc funcs take extra arg */ 169 unsigned maybe_empty_object:1;/* There is a possibility that the current 170 chunk contains a zero-length object. This 171 prevents freeing the chunk if we allocate 172 a bigger chunk to replace it. */ 173 unsigned alloc_failed:1; /* No longer used, as we now call the failed 174 handler on error, but retained for binary 175 compatibility. */ 176 }; 177 178 /* Declare the external functions we use; they are in obstack.c. */ 179 180 extern void _obstack_newchunk (struct obstack *, int); 181 extern int _obstack_begin (struct obstack *, int, int, 182 void *(*) (long), void (*) (void *)); 183 extern int _obstack_begin_1 (struct obstack *, int, int, 184 void *(*) (void *, long), 185 void (*) (void *, void *), void *); 186 extern int _obstack_memory_used (struct obstack *); 187 188 /* The default name of the function for freeing a chunk is 'obstack_free', 189 but gnulib users can override this by defining '__obstack_free'. */ 190 #ifndef __obstack_free 191 # define __obstack_free obstack_free 192 #endif 193 extern void __obstack_free (struct obstack *obstack, void *block); 194 195 196 /* Error handler called when 'obstack_chunk_alloc' failed to allocate 197 more memory. This can be set to a user defined function which 198 should either abort gracefully or use longjump - but shouldn't 199 return. The default action is to print a message and abort. */ 200 extern void (*obstack_alloc_failed_handler) (void); 201 202 /* Exit value used when 'print_and_abort' is used. */ 203 extern int obstack_exit_failure; 204 205 /* Pointer to beginning of object being allocated or to be allocated next. 206 Note that this might not be the final address of the object 207 because a new chunk might be needed to hold the final size. */ 208 209 #define obstack_base(h) ((void *) (h)->object_base) 210 211 /* Size for allocating ordinary chunks. */ 212 213 #define obstack_chunk_size(h) ((h)->chunk_size) 214 215 /* Pointer to next byte not yet allocated in current chunk. */ 216 217 #define obstack_next_free(h) ((h)->next_free) 218 219 /* Mask specifying low bits that should be clear in address of an object. */ 220 221 #define obstack_alignment_mask(h) ((h)->alignment_mask) 222 223 /* To prevent prototype warnings provide complete argument list. */ 224 #define obstack_init(h) \ 225 _obstack_begin ((h), 0, 0, \ 226 (void *(*) (long)) obstack_chunk_alloc, \ 227 (void (*) (void *)) obstack_chunk_free) 228 229 #define obstack_begin(h, size) \ 230 _obstack_begin ((h), (size), 0, \ 231 (void *(*) (long)) obstack_chunk_alloc, \ 232 (void (*) (void *)) obstack_chunk_free) 233 234 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \ 235 _obstack_begin ((h), (size), (alignment), \ 236 (void *(*) (long)) (chunkfun), \ 237 (void (*) (void *)) (freefun)) 238 239 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \ 240 _obstack_begin_1 ((h), (size), (alignment), \ 241 (void *(*) (void *, long)) (chunkfun), \ 242 (void (*) (void *, void *)) (freefun), (arg)) 243 244 #define obstack_chunkfun(h, newchunkfun) \ 245 ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun)) 246 247 #define obstack_freefun(h, newfreefun) \ 248 ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun)) 249 250 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar)) 251 252 #define obstack_blank_fast(h,n) ((h)->next_free += (n)) 253 254 #define obstack_memory_used(h) _obstack_memory_used (h) 255 256 #if defined __GNUC__ 257 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and 258 does not implement __extension__. But that compiler doesn't define 259 __GNUC_MINOR__. */ 260 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__) 261 # define __extension__ 262 # endif 263 264 /* For GNU C, if not -traditional, 265 we can define these macros to compute all args only once 266 without using a global variable. 267 Also, we can avoid using the 'temp' slot, to make faster code. */ 268 269 # define obstack_object_size(OBSTACK) \ 270 __extension__ \ 271 ({ struct obstack const *__o = (OBSTACK); \ 272 (unsigned) (__o->next_free - __o->object_base); }) 273 274 # define obstack_room(OBSTACK) \ 275 __extension__ \ 276 ({ struct obstack const *__o = (OBSTACK); \ 277 (unsigned) (__o->chunk_limit - __o->next_free); }) 278 279 # define obstack_make_room(OBSTACK,length) \ 280 __extension__ \ 281 ({ struct obstack *__o = (OBSTACK); \ 282 int __len = (length); \ 283 if (__o->chunk_limit - __o->next_free < __len) \ 284 _obstack_newchunk (__o, __len); \ 285 (void) 0; }) 286 287 # define obstack_empty_p(OBSTACK) \ 288 __extension__ \ 289 ({ struct obstack const *__o = (OBSTACK); \ 290 (__o->chunk->prev == 0 \ 291 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \ 292 __o->chunk->contents, \ 293 __o->alignment_mask)); }) 294 295 # define obstack_grow(OBSTACK,where,length) \ 296 __extension__ \ 297 ({ struct obstack *__o = (OBSTACK); \ 298 int __len = (length); \ 299 if (__o->next_free + __len > __o->chunk_limit) \ 300 _obstack_newchunk (__o, __len); \ 301 memcpy (__o->next_free, where, __len); \ 302 __o->next_free += __len; \ 303 (void) 0; }) 304 305 # define obstack_grow0(OBSTACK,where,length) \ 306 __extension__ \ 307 ({ struct obstack *__o = (OBSTACK); \ 308 int __len = (length); \ 309 if (__o->next_free + __len + 1 > __o->chunk_limit) \ 310 _obstack_newchunk (__o, __len + 1); \ 311 memcpy (__o->next_free, where, __len); \ 312 __o->next_free += __len; \ 313 *(__o->next_free)++ = 0; \ 314 (void) 0; }) 315 316 # define obstack_1grow(OBSTACK,datum) \ 317 __extension__ \ 318 ({ struct obstack *__o = (OBSTACK); \ 319 if (__o->next_free + 1 > __o->chunk_limit) \ 320 _obstack_newchunk (__o, 1); \ 321 obstack_1grow_fast (__o, datum); \ 322 (void) 0; }) 323 324 /* These assume that the obstack alignment is good enough for pointers 325 or ints, and that the data added so far to the current object 326 shares that much alignment. */ 327 328 # define obstack_ptr_grow(OBSTACK,datum) \ 329 __extension__ \ 330 ({ struct obstack *__o = (OBSTACK); \ 331 if (__o->next_free + sizeof (void *) > __o->chunk_limit) \ 332 _obstack_newchunk (__o, sizeof (void *)); \ 333 obstack_ptr_grow_fast (__o, datum); }) \ 334 335 # define obstack_int_grow(OBSTACK,datum) \ 336 __extension__ \ 337 ({ struct obstack *__o = (OBSTACK); \ 338 if (__o->next_free + sizeof (int) > __o->chunk_limit) \ 339 _obstack_newchunk (__o, sizeof (int)); \ 340 obstack_int_grow_fast (__o, datum); }) 341 342 # define obstack_ptr_grow_fast(OBSTACK,aptr) \ 343 __extension__ \ 344 ({ struct obstack *__o1 = (OBSTACK); \ 345 *(const void **) __o1->next_free = (aptr); \ 346 __o1->next_free += sizeof (const void *); \ 347 (void) 0; }) 348 349 # define obstack_int_grow_fast(OBSTACK,aint) \ 350 __extension__ \ 351 ({ struct obstack *__o1 = (OBSTACK); \ 352 *(int *) __o1->next_free = (aint); \ 353 __o1->next_free += sizeof (int); \ 354 (void) 0; }) 355 356 # define obstack_blank(OBSTACK,length) \ 357 __extension__ \ 358 ({ struct obstack *__o = (OBSTACK); \ 359 int __len = (length); \ 360 if (__o->chunk_limit - __o->next_free < __len) \ 361 _obstack_newchunk (__o, __len); \ 362 obstack_blank_fast (__o, __len); \ 363 (void) 0; }) 364 365 # define obstack_alloc(OBSTACK,length) \ 366 __extension__ \ 367 ({ struct obstack *__h = (OBSTACK); \ 368 obstack_blank (__h, (length)); \ 369 obstack_finish (__h); }) 370 371 # define obstack_copy(OBSTACK,where,length) \ 372 __extension__ \ 373 ({ struct obstack *__h = (OBSTACK); \ 374 obstack_grow (__h, (where), (length)); \ 375 obstack_finish (__h); }) 376 377 # define obstack_copy0(OBSTACK,where,length) \ 378 __extension__ \ 379 ({ struct obstack *__h = (OBSTACK); \ 380 obstack_grow0 (__h, (where), (length)); \ 381 obstack_finish (__h); }) 382 383 /* The local variable is named __o1 to avoid a name conflict 384 when obstack_blank is called. */ 385 # define obstack_finish(OBSTACK) \ 386 __extension__ \ 387 ({ struct obstack *__o1 = (OBSTACK); \ 388 void *__value = (void *) __o1->object_base; \ 389 if (__o1->next_free == __value) \ 390 __o1->maybe_empty_object = 1; \ 391 __o1->next_free \ 392 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \ 393 __o1->alignment_mask); \ 394 if (__o1->next_free - (char *)__o1->chunk \ 395 > __o1->chunk_limit - (char *)__o1->chunk) \ 396 __o1->next_free = __o1->chunk_limit; \ 397 __o1->object_base = __o1->next_free; \ 398 __value; }) 399 400 # define obstack_free(OBSTACK, OBJ) \ 401 __extension__ \ 402 ({ struct obstack *__o = (OBSTACK); \ 403 void *__obj = (OBJ); \ 404 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \ 405 __o->next_free = __o->object_base = (char *)__obj; \ 406 else (__obstack_free) (__o, __obj); }) 407 408 #else /* not __GNUC__ */ 409 410 # define obstack_object_size(h) \ 411 (unsigned) ((h)->next_free - (h)->object_base) 412 413 # define obstack_room(h) \ 414 (unsigned) ((h)->chunk_limit - (h)->next_free) 415 416 # define obstack_empty_p(h) \ 417 ((h)->chunk->prev == 0 \ 418 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \ 419 (h)->chunk->contents, \ 420 (h)->alignment_mask)) 421 422 /* Note that the call to _obstack_newchunk is enclosed in (..., 0) 423 so that we can avoid having void expressions 424 in the arms of the conditional expression. 425 Casting the third operand to void was tried before, 426 but some compilers won't accept it. */ 427 428 # define obstack_make_room(h,length) \ 429 ( (h)->temp.tempint = (length), \ 430 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 431 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0)) 432 433 # define obstack_grow(h,where,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 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 438 (h)->next_free += (h)->temp.tempint) 439 440 # define obstack_grow0(h,where,length) \ 441 ( (h)->temp.tempint = (length), \ 442 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \ 443 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \ 444 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 445 (h)->next_free += (h)->temp.tempint, \ 446 *((h)->next_free)++ = 0) 447 448 # define obstack_1grow(h,datum) \ 449 ( (((h)->next_free + 1 > (h)->chunk_limit) \ 450 ? (_obstack_newchunk ((h), 1), 0) : 0), \ 451 obstack_1grow_fast (h, datum)) 452 453 # define obstack_ptr_grow(h,datum) \ 454 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \ 455 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \ 456 obstack_ptr_grow_fast (h, datum)) 457 458 # define obstack_int_grow(h,datum) \ 459 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \ 460 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \ 461 obstack_int_grow_fast (h, datum)) 462 463 # define obstack_ptr_grow_fast(h,aptr) \ 464 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr)) 465 466 # define obstack_int_grow_fast(h,aint) \ 467 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint)) 468 469 # define obstack_blank(h,length) \ 470 ( (h)->temp.tempint = (length), \ 471 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \ 472 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 473 obstack_blank_fast (h, (h)->temp.tempint)) 474 475 # define obstack_alloc(h,length) \ 476 (obstack_blank ((h), (length)), obstack_finish ((h))) 477 478 # define obstack_copy(h,where,length) \ 479 (obstack_grow ((h), (where), (length)), obstack_finish ((h))) 480 481 # define obstack_copy0(h,where,length) \ 482 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h))) 483 484 # define obstack_finish(h) \ 485 ( ((h)->next_free == (h)->object_base \ 486 ? (((h)->maybe_empty_object = 1), 0) \ 487 : 0), \ 488 (h)->temp.tempptr = (h)->object_base, \ 489 (h)->next_free \ 490 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \ 491 (h)->alignment_mask), \ 492 (((h)->next_free - (char *) (h)->chunk \ 493 > (h)->chunk_limit - (char *) (h)->chunk) \ 494 ? ((h)->next_free = (h)->chunk_limit) : 0), \ 495 (h)->object_base = (h)->next_free, \ 496 (h)->temp.tempptr) 497 498 # define obstack_free(h,obj) \ 499 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \ 500 ((((h)->temp.tempint > 0 \ 501 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \ 502 ? (int) ((h)->next_free = (h)->object_base \ 503 = (h)->temp.tempint + (char *) (h)->chunk) \ 504 : (((__obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0))) 505 506 #endif /* not __GNUC__ */ 507 508 #ifdef __cplusplus 509 } /* C++ */ 510 #endif 511 512 #endif /* obstack.h */ 513