1 /* obstack.h - object stack macros 2 Copyright (C) 1988-2021 Free Software Foundation, Inc. 3 This file is part of the GNU C Library. 4 5 The GNU C Library is free software; you can redistribute it and/or 6 modify it under the terms of the GNU General Public 7 License as published by the Free Software Foundation; either 8 version 3 of the License, or (at your option) any later version. 9 10 The GNU C Library is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 General Public License for more details. 14 15 You should have received a copy of the GNU General Public 16 License along with the GNU C Library; if not, see 17 <https://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 #ifndef _OBSTACK_INTERFACE_VERSION 108 # define _OBSTACK_INTERFACE_VERSION 2 109 #endif 110 111 #include <stddef.h> /* For size_t and ptrdiff_t. */ 112 #include <string.h> /* For __GNU_LIBRARY__, and memcpy. */ 113 114 #if __STDC_VERSION__ < 199901L || defined __HP_cc 115 # define __FLEXIBLE_ARRAY_MEMBER 1 116 #else 117 # define __FLEXIBLE_ARRAY_MEMBER 118 #endif 119 120 #if _OBSTACK_INTERFACE_VERSION == 1 121 /* For binary compatibility with obstack version 1, which used "int" 122 and "long" for these two types. */ 123 # define _OBSTACK_SIZE_T unsigned int 124 # define _CHUNK_SIZE_T unsigned long 125 # define _OBSTACK_CAST(type, expr) ((type) (expr)) 126 #else 127 /* Version 2 with sane types, especially for 64-bit hosts. */ 128 # define _OBSTACK_SIZE_T size_t 129 # define _CHUNK_SIZE_T size_t 130 # define _OBSTACK_CAST(type, expr) (expr) 131 #endif 132 133 /* If B is the base of an object addressed by P, return the result of 134 aligning P to the next multiple of A + 1. B and P must be of type 135 char *. A + 1 must be a power of 2. */ 136 137 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A))) 138 139 /* Similar to __BPTR_ALIGN (B, P, A), except optimize the common case 140 where pointers can be converted to integers, aligned as integers, 141 and converted back again. If ptrdiff_t is narrower than a 142 pointer (e.g., the AS/400), play it safe and compute the alignment 143 relative to B. Otherwise, use the faster strategy of computing the 144 alignment relative to 0. */ 145 146 #define __PTR_ALIGN(B, P, A) \ 147 __BPTR_ALIGN (sizeof (ptrdiff_t) < sizeof (void *) ? (B) : (char *) 0, \ 148 P, A) 149 150 #ifndef __attribute_pure__ 151 # define __attribute_pure__ _GL_ATTRIBUTE_PURE 152 #endif 153 154 /* Not the same as _Noreturn, since it also works with function pointers. */ 155 #ifndef __attribute_noreturn__ 156 # if 2 < __GNUC__ + (8 <= __GNUC_MINOR__) || defined __clang__ || 0x5110 <= __SUNPRO_C 157 # define __attribute_noreturn__ __attribute__ ((__noreturn__)) 158 # else 159 # define __attribute_noreturn__ 160 # endif 161 #endif 162 163 #ifdef __cplusplus 164 extern "C" { 165 #endif 166 167 struct _obstack_chunk /* Lives at front of each chunk. */ 168 { 169 char *limit; /* 1 past end of this chunk */ 170 struct _obstack_chunk *prev; /* address of prior chunk or NULL */ 171 char contents[__FLEXIBLE_ARRAY_MEMBER]; /* objects begin here */ 172 }; 173 174 struct obstack /* control current object in current chunk */ 175 { 176 _CHUNK_SIZE_T chunk_size; /* preferred size to allocate chunks in */ 177 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */ 178 char *object_base; /* address of object we are building */ 179 char *next_free; /* where to add next char to current object */ 180 char *chunk_limit; /* address of char after current chunk */ 181 union 182 { 183 _OBSTACK_SIZE_T i; 184 void *p; 185 } temp; /* Temporary for some macros. */ 186 _OBSTACK_SIZE_T alignment_mask; /* Mask of alignment for each object. */ 187 188 /* These prototypes vary based on 'use_extra_arg'. */ 189 union 190 { 191 void *(*plain) (size_t); 192 void *(*extra) (void *, size_t); 193 } chunkfun; 194 union 195 { 196 void (*plain) (void *); 197 void (*extra) (void *, void *); 198 } freefun; 199 200 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */ 201 unsigned use_extra_arg : 1; /* chunk alloc/dealloc funcs take extra arg */ 202 unsigned maybe_empty_object : 1; /* There is a possibility that the current 203 chunk contains a zero-length object. This 204 prevents freeing the chunk if we allocate 205 a bigger chunk to replace it. */ 206 unsigned alloc_failed : 1; /* No longer used, as we now call the failed 207 handler on error, but retained for binary 208 compatibility. */ 209 }; 210 211 /* Declare the external functions we use; they are in obstack.c. */ 212 213 extern void _obstack_newchunk (struct obstack *, _OBSTACK_SIZE_T); 214 extern void _obstack_free (struct obstack *, void *); 215 extern int _obstack_begin (struct obstack *, 216 _OBSTACK_SIZE_T, _OBSTACK_SIZE_T, 217 void *(*) (size_t), void (*) (void *)); 218 extern int _obstack_begin_1 (struct obstack *, 219 _OBSTACK_SIZE_T, _OBSTACK_SIZE_T, 220 void *(*) (void *, size_t), 221 void (*) (void *, void *), void *); 222 extern _OBSTACK_SIZE_T _obstack_memory_used (struct obstack *) 223 __attribute_pure__; 224 225 226 /* Error handler called when 'obstack_chunk_alloc' failed to allocate 227 more memory. This can be set to a user defined function which 228 should either abort gracefully or use longjump - but shouldn't 229 return. The default action is to print a message and abort. */ 230 extern __attribute_noreturn__ void (*obstack_alloc_failed_handler) (void); 231 232 /* Exit value used when 'print_and_abort' is used. */ 233 extern int obstack_exit_failure; 234 235 /* Pointer to beginning of object being allocated or to be allocated next. 236 Note that this might not be the final address of the object 237 because a new chunk might be needed to hold the final size. */ 238 239 #define obstack_base(h) ((void *) (h)->object_base) 240 241 /* Size for allocating ordinary chunks. */ 242 243 #define obstack_chunk_size(h) ((h)->chunk_size) 244 245 /* Pointer to next byte not yet allocated in current chunk. */ 246 247 #define obstack_next_free(h) ((void *) (h)->next_free) 248 249 /* Mask specifying low bits that should be clear in address of an object. */ 250 251 #define obstack_alignment_mask(h) ((h)->alignment_mask) 252 253 /* To prevent prototype warnings provide complete argument list. */ 254 #define obstack_init(h) \ 255 _obstack_begin ((h), 0, 0, \ 256 _OBSTACK_CAST (void *(*) (size_t), obstack_chunk_alloc), \ 257 _OBSTACK_CAST (void (*) (void *), obstack_chunk_free)) 258 259 #define obstack_begin(h, size) \ 260 _obstack_begin ((h), (size), 0, \ 261 _OBSTACK_CAST (void *(*) (size_t), obstack_chunk_alloc), \ 262 _OBSTACK_CAST (void (*) (void *), obstack_chunk_free)) 263 264 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \ 265 _obstack_begin ((h), (size), (alignment), \ 266 _OBSTACK_CAST (void *(*) (size_t), chunkfun), \ 267 _OBSTACK_CAST (void (*) (void *), freefun)) 268 269 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \ 270 _obstack_begin_1 ((h), (size), (alignment), \ 271 _OBSTACK_CAST (void *(*) (void *, size_t), chunkfun), \ 272 _OBSTACK_CAST (void (*) (void *, void *), freefun), arg) 273 274 #define obstack_chunkfun(h, newchunkfun) \ 275 ((void) ((h)->chunkfun.extra = (void *(*) (void *, size_t)) (newchunkfun))) 276 277 #define obstack_freefun(h, newfreefun) \ 278 ((void) ((h)->freefun.extra = (void *(*) (void *, void *)) (newfreefun))) 279 280 #define obstack_1grow_fast(h, achar) ((void) (*((h)->next_free)++ = (achar))) 281 282 #define obstack_blank_fast(h, n) ((void) ((h)->next_free += (n))) 283 284 #define obstack_memory_used(h) _obstack_memory_used (h) 285 286 #if defined __GNUC__ || defined __clang__ 287 # if !(defined __GNUC_MINOR__ && __GNUC__ * 1000 + __GNUC_MINOR__ >= 2008 \ 288 || defined __clang__) 289 # define __extension__ 290 # endif 291 292 /* For GNU C, if not -traditional, 293 we can define these macros to compute all args only once 294 without using a global variable. 295 Also, we can avoid using the 'temp' slot, to make faster code. */ 296 297 # define obstack_object_size(OBSTACK) \ 298 __extension__ \ 299 ({ struct obstack const *__o = (OBSTACK); \ 300 (_OBSTACK_SIZE_T) (__o->next_free - __o->object_base); }) 301 302 /* The local variable is named __o1 to avoid a shadowed variable 303 warning when invoked from other obstack macros. */ 304 # define obstack_room(OBSTACK) \ 305 __extension__ \ 306 ({ struct obstack const *__o1 = (OBSTACK); \ 307 (_OBSTACK_SIZE_T) (__o1->chunk_limit - __o1->next_free); }) 308 309 # define obstack_make_room(OBSTACK, length) \ 310 __extension__ \ 311 ({ struct obstack *__o = (OBSTACK); \ 312 _OBSTACK_SIZE_T __len = (length); \ 313 if (obstack_room (__o) < __len) \ 314 _obstack_newchunk (__o, __len); \ 315 (void) 0; }) 316 317 # define obstack_empty_p(OBSTACK) \ 318 __extension__ \ 319 ({ struct obstack const *__o = (OBSTACK); \ 320 (__o->chunk->prev == 0 \ 321 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \ 322 __o->chunk->contents, \ 323 __o->alignment_mask)); }) 324 325 # define obstack_grow(OBSTACK, where, length) \ 326 __extension__ \ 327 ({ struct obstack *__o = (OBSTACK); \ 328 _OBSTACK_SIZE_T __len = (length); \ 329 if (obstack_room (__o) < __len) \ 330 _obstack_newchunk (__o, __len); \ 331 memcpy (__o->next_free, where, __len); \ 332 __o->next_free += __len; \ 333 (void) 0; }) 334 335 # define obstack_grow0(OBSTACK, where, length) \ 336 __extension__ \ 337 ({ struct obstack *__o = (OBSTACK); \ 338 _OBSTACK_SIZE_T __len = (length); \ 339 if (obstack_room (__o) < __len + 1) \ 340 _obstack_newchunk (__o, __len + 1); \ 341 memcpy (__o->next_free, where, __len); \ 342 __o->next_free += __len; \ 343 *(__o->next_free)++ = 0; \ 344 (void) 0; }) 345 346 # define obstack_1grow(OBSTACK, datum) \ 347 __extension__ \ 348 ({ struct obstack *__o = (OBSTACK); \ 349 if (obstack_room (__o) < 1) \ 350 _obstack_newchunk (__o, 1); \ 351 obstack_1grow_fast (__o, datum); }) 352 353 /* These assume that the obstack alignment is good enough for pointers 354 or ints, and that the data added so far to the current object 355 shares that much alignment. */ 356 357 # define obstack_ptr_grow(OBSTACK, datum) \ 358 __extension__ \ 359 ({ struct obstack *__o = (OBSTACK); \ 360 if (obstack_room (__o) < sizeof (void *)) \ 361 _obstack_newchunk (__o, sizeof (void *)); \ 362 obstack_ptr_grow_fast (__o, datum); }) 363 364 # define obstack_int_grow(OBSTACK, datum) \ 365 __extension__ \ 366 ({ struct obstack *__o = (OBSTACK); \ 367 if (obstack_room (__o) < sizeof (int)) \ 368 _obstack_newchunk (__o, sizeof (int)); \ 369 obstack_int_grow_fast (__o, datum); }) 370 371 # define obstack_ptr_grow_fast(OBSTACK, aptr) \ 372 __extension__ \ 373 ({ struct obstack *__o1 = (OBSTACK); \ 374 void *__p1 = __o1->next_free; \ 375 *(const void **) __p1 = (aptr); \ 376 __o1->next_free += sizeof (const void *); \ 377 (void) 0; }) 378 379 # define obstack_int_grow_fast(OBSTACK, aint) \ 380 __extension__ \ 381 ({ struct obstack *__o1 = (OBSTACK); \ 382 void *__p1 = __o1->next_free; \ 383 *(int *) __p1 = (aint); \ 384 __o1->next_free += sizeof (int); \ 385 (void) 0; }) 386 387 # define obstack_blank(OBSTACK, length) \ 388 __extension__ \ 389 ({ struct obstack *__o = (OBSTACK); \ 390 _OBSTACK_SIZE_T __len = (length); \ 391 if (obstack_room (__o) < __len) \ 392 _obstack_newchunk (__o, __len); \ 393 obstack_blank_fast (__o, __len); }) 394 395 # define obstack_alloc(OBSTACK, length) \ 396 __extension__ \ 397 ({ struct obstack *__h = (OBSTACK); \ 398 obstack_blank (__h, (length)); \ 399 obstack_finish (__h); }) 400 401 # define obstack_copy(OBSTACK, where, length) \ 402 __extension__ \ 403 ({ struct obstack *__h = (OBSTACK); \ 404 obstack_grow (__h, (where), (length)); \ 405 obstack_finish (__h); }) 406 407 # define obstack_copy0(OBSTACK, where, length) \ 408 __extension__ \ 409 ({ struct obstack *__h = (OBSTACK); \ 410 obstack_grow0 (__h, (where), (length)); \ 411 obstack_finish (__h); }) 412 413 /* The local variable is named __o1 to avoid a shadowed variable 414 warning when invoked from other obstack macros, typically obstack_free. */ 415 # define obstack_finish(OBSTACK) \ 416 __extension__ \ 417 ({ struct obstack *__o1 = (OBSTACK); \ 418 void *__value = (void *) __o1->object_base; \ 419 if (__o1->next_free == __value) \ 420 __o1->maybe_empty_object = 1; \ 421 __o1->next_free \ 422 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \ 423 __o1->alignment_mask); \ 424 if ((size_t) (__o1->next_free - (char *) __o1->chunk) \ 425 > (size_t) (__o1->chunk_limit - (char *) __o1->chunk)) \ 426 __o1->next_free = __o1->chunk_limit; \ 427 __o1->object_base = __o1->next_free; \ 428 __value; }) 429 430 # define obstack_free(OBSTACK, OBJ) \ 431 __extension__ \ 432 ({ struct obstack *__o = (OBSTACK); \ 433 void *__obj = (void *) (OBJ); \ 434 if (__obj > (void *) __o->chunk && __obj < (void *) __o->chunk_limit) \ 435 __o->next_free = __o->object_base = (char *) __obj; \ 436 else \ 437 _obstack_free (__o, __obj); }) 438 439 #else /* not __GNUC__ */ 440 441 # define obstack_object_size(h) \ 442 ((_OBSTACK_SIZE_T) ((h)->next_free - (h)->object_base)) 443 444 # define obstack_room(h) \ 445 ((_OBSTACK_SIZE_T) ((h)->chunk_limit - (h)->next_free)) 446 447 # define obstack_empty_p(h) \ 448 ((h)->chunk->prev == 0 \ 449 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \ 450 (h)->chunk->contents, \ 451 (h)->alignment_mask)) 452 453 /* Note that the call to _obstack_newchunk is enclosed in (..., 0) 454 so that we can avoid having void expressions 455 in the arms of the conditional expression. 456 Casting the third operand to void was tried before, 457 but some compilers won't accept it. */ 458 459 # define obstack_make_room(h, length) \ 460 ((h)->temp.i = (length), \ 461 ((obstack_room (h) < (h)->temp.i) \ 462 ? (_obstack_newchunk (h, (h)->temp.i), 0) : 0), \ 463 (void) 0) 464 465 # define obstack_grow(h, where, length) \ 466 ((h)->temp.i = (length), \ 467 ((obstack_room (h) < (h)->temp.i) \ 468 ? (_obstack_newchunk ((h), (h)->temp.i), 0) : 0), \ 469 memcpy ((h)->next_free, where, (h)->temp.i), \ 470 (h)->next_free += (h)->temp.i, \ 471 (void) 0) 472 473 # define obstack_grow0(h, where, length) \ 474 ((h)->temp.i = (length), \ 475 ((obstack_room (h) < (h)->temp.i + 1) \ 476 ? (_obstack_newchunk ((h), (h)->temp.i + 1), 0) : 0), \ 477 memcpy ((h)->next_free, where, (h)->temp.i), \ 478 (h)->next_free += (h)->temp.i, \ 479 *((h)->next_free)++ = 0, \ 480 (void) 0) 481 482 # define obstack_1grow(h, datum) \ 483 (((obstack_room (h) < 1) \ 484 ? (_obstack_newchunk ((h), 1), 0) : 0), \ 485 obstack_1grow_fast (h, datum)) 486 487 # define obstack_ptr_grow(h, datum) \ 488 (((obstack_room (h) < sizeof (char *)) \ 489 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \ 490 obstack_ptr_grow_fast (h, datum)) 491 492 # define obstack_int_grow(h, datum) \ 493 (((obstack_room (h) < sizeof (int)) \ 494 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \ 495 obstack_int_grow_fast (h, datum)) 496 497 # define obstack_ptr_grow_fast(h, aptr) \ 498 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr), \ 499 (void) 0) 500 501 # define obstack_int_grow_fast(h, aint) \ 502 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint), \ 503 (void) 0) 504 505 # define obstack_blank(h, length) \ 506 ((h)->temp.i = (length), \ 507 ((obstack_room (h) < (h)->temp.i) \ 508 ? (_obstack_newchunk ((h), (h)->temp.i), 0) : 0), \ 509 obstack_blank_fast (h, (h)->temp.i)) 510 511 # define obstack_alloc(h, length) \ 512 (obstack_blank ((h), (length)), obstack_finish ((h))) 513 514 # define obstack_copy(h, where, length) \ 515 (obstack_grow ((h), (where), (length)), obstack_finish ((h))) 516 517 # define obstack_copy0(h, where, length) \ 518 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h))) 519 520 # define obstack_finish(h) \ 521 (((h)->next_free == (h)->object_base \ 522 ? (((h)->maybe_empty_object = 1), 0) \ 523 : 0), \ 524 (h)->temp.p = (h)->object_base, \ 525 (h)->next_free \ 526 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \ 527 (h)->alignment_mask), \ 528 (((size_t) ((h)->next_free - (char *) (h)->chunk) \ 529 > (size_t) ((h)->chunk_limit - (char *) (h)->chunk)) \ 530 ? ((h)->next_free = (h)->chunk_limit) : 0), \ 531 (h)->object_base = (h)->next_free, \ 532 (h)->temp.p) 533 534 # define obstack_free(h, obj) \ 535 ((h)->temp.p = (void *) (obj), \ 536 (((h)->temp.p > (void *) (h)->chunk \ 537 && (h)->temp.p < (void *) (h)->chunk_limit) \ 538 ? (void) ((h)->next_free = (h)->object_base = (char *) (h)->temp.p) \ 539 : _obstack_free ((h), (h)->temp.p))) 540 541 #endif /* not __GNUC__ */ 542 543 #ifdef __cplusplus 544 } /* C++ */ 545 #endif 546 547 #endif /* _OBSTACK_H */ 548