1 /* obstack.h - object stack macros 2 Copyright (C) 1988-2020 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__) || 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__ 287 # if !defined __GNUC_MINOR__ || __GNUC__ * 1000 + __GNUC_MINOR__ < 2008 288 # define __extension__ 289 # endif 290 291 /* For GNU C, if not -traditional, 292 we can define these macros to compute all args only once 293 without using a global variable. 294 Also, we can avoid using the 'temp' slot, to make faster code. */ 295 296 # define obstack_object_size(OBSTACK) \ 297 __extension__ \ 298 ({ struct obstack const *__o = (OBSTACK); \ 299 (_OBSTACK_SIZE_T) (__o->next_free - __o->object_base); }) 300 301 /* The local variable is named __o1 to avoid a shadowed variable 302 warning when invoked from other obstack macros. */ 303 # define obstack_room(OBSTACK) \ 304 __extension__ \ 305 ({ struct obstack const *__o1 = (OBSTACK); \ 306 (_OBSTACK_SIZE_T) (__o1->chunk_limit - __o1->next_free); }) 307 308 # define obstack_make_room(OBSTACK, length) \ 309 __extension__ \ 310 ({ struct obstack *__o = (OBSTACK); \ 311 _OBSTACK_SIZE_T __len = (length); \ 312 if (obstack_room (__o) < __len) \ 313 _obstack_newchunk (__o, __len); \ 314 (void) 0; }) 315 316 # define obstack_empty_p(OBSTACK) \ 317 __extension__ \ 318 ({ struct obstack const *__o = (OBSTACK); \ 319 (__o->chunk->prev == 0 \ 320 && __o->next_free == __PTR_ALIGN ((char *) __o->chunk, \ 321 __o->chunk->contents, \ 322 __o->alignment_mask)); }) 323 324 # define obstack_grow(OBSTACK, where, length) \ 325 __extension__ \ 326 ({ struct obstack *__o = (OBSTACK); \ 327 _OBSTACK_SIZE_T __len = (length); \ 328 if (obstack_room (__o) < __len) \ 329 _obstack_newchunk (__o, __len); \ 330 memcpy (__o->next_free, where, __len); \ 331 __o->next_free += __len; \ 332 (void) 0; }) 333 334 # define obstack_grow0(OBSTACK, where, length) \ 335 __extension__ \ 336 ({ struct obstack *__o = (OBSTACK); \ 337 _OBSTACK_SIZE_T __len = (length); \ 338 if (obstack_room (__o) < __len + 1) \ 339 _obstack_newchunk (__o, __len + 1); \ 340 memcpy (__o->next_free, where, __len); \ 341 __o->next_free += __len; \ 342 *(__o->next_free)++ = 0; \ 343 (void) 0; }) 344 345 # define obstack_1grow(OBSTACK, datum) \ 346 __extension__ \ 347 ({ struct obstack *__o = (OBSTACK); \ 348 if (obstack_room (__o) < 1) \ 349 _obstack_newchunk (__o, 1); \ 350 obstack_1grow_fast (__o, datum); }) 351 352 /* These assume that the obstack alignment is good enough for pointers 353 or ints, and that the data added so far to the current object 354 shares that much alignment. */ 355 356 # define obstack_ptr_grow(OBSTACK, datum) \ 357 __extension__ \ 358 ({ struct obstack *__o = (OBSTACK); \ 359 if (obstack_room (__o) < sizeof (void *)) \ 360 _obstack_newchunk (__o, sizeof (void *)); \ 361 obstack_ptr_grow_fast (__o, datum); }) 362 363 # define obstack_int_grow(OBSTACK, datum) \ 364 __extension__ \ 365 ({ struct obstack *__o = (OBSTACK); \ 366 if (obstack_room (__o) < sizeof (int)) \ 367 _obstack_newchunk (__o, sizeof (int)); \ 368 obstack_int_grow_fast (__o, datum); }) 369 370 # define obstack_ptr_grow_fast(OBSTACK, aptr) \ 371 __extension__ \ 372 ({ struct obstack *__o1 = (OBSTACK); \ 373 void *__p1 = __o1->next_free; \ 374 *(const void **) __p1 = (aptr); \ 375 __o1->next_free += sizeof (const void *); \ 376 (void) 0; }) 377 378 # define obstack_int_grow_fast(OBSTACK, aint) \ 379 __extension__ \ 380 ({ struct obstack *__o1 = (OBSTACK); \ 381 void *__p1 = __o1->next_free; \ 382 *(int *) __p1 = (aint); \ 383 __o1->next_free += sizeof (int); \ 384 (void) 0; }) 385 386 # define obstack_blank(OBSTACK, length) \ 387 __extension__ \ 388 ({ struct obstack *__o = (OBSTACK); \ 389 _OBSTACK_SIZE_T __len = (length); \ 390 if (obstack_room (__o) < __len) \ 391 _obstack_newchunk (__o, __len); \ 392 obstack_blank_fast (__o, __len); }) 393 394 # define obstack_alloc(OBSTACK, length) \ 395 __extension__ \ 396 ({ struct obstack *__h = (OBSTACK); \ 397 obstack_blank (__h, (length)); \ 398 obstack_finish (__h); }) 399 400 # define obstack_copy(OBSTACK, where, length) \ 401 __extension__ \ 402 ({ struct obstack *__h = (OBSTACK); \ 403 obstack_grow (__h, (where), (length)); \ 404 obstack_finish (__h); }) 405 406 # define obstack_copy0(OBSTACK, where, length) \ 407 __extension__ \ 408 ({ struct obstack *__h = (OBSTACK); \ 409 obstack_grow0 (__h, (where), (length)); \ 410 obstack_finish (__h); }) 411 412 /* The local variable is named __o1 to avoid a shadowed variable 413 warning when invoked from other obstack macros, typically obstack_free. */ 414 # define obstack_finish(OBSTACK) \ 415 __extension__ \ 416 ({ struct obstack *__o1 = (OBSTACK); \ 417 void *__value = (void *) __o1->object_base; \ 418 if (__o1->next_free == __value) \ 419 __o1->maybe_empty_object = 1; \ 420 __o1->next_free \ 421 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \ 422 __o1->alignment_mask); \ 423 if ((size_t) (__o1->next_free - (char *) __o1->chunk) \ 424 > (size_t) (__o1->chunk_limit - (char *) __o1->chunk)) \ 425 __o1->next_free = __o1->chunk_limit; \ 426 __o1->object_base = __o1->next_free; \ 427 __value; }) 428 429 # define obstack_free(OBSTACK, OBJ) \ 430 __extension__ \ 431 ({ struct obstack *__o = (OBSTACK); \ 432 void *__obj = (void *) (OBJ); \ 433 if (__obj > (void *) __o->chunk && __obj < (void *) __o->chunk_limit) \ 434 __o->next_free = __o->object_base = (char *) __obj; \ 435 else \ 436 _obstack_free (__o, __obj); }) 437 438 #else /* not __GNUC__ */ 439 440 # define obstack_object_size(h) \ 441 ((_OBSTACK_SIZE_T) ((h)->next_free - (h)->object_base)) 442 443 # define obstack_room(h) \ 444 ((_OBSTACK_SIZE_T) ((h)->chunk_limit - (h)->next_free)) 445 446 # define obstack_empty_p(h) \ 447 ((h)->chunk->prev == 0 \ 448 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \ 449 (h)->chunk->contents, \ 450 (h)->alignment_mask)) 451 452 /* Note that the call to _obstack_newchunk is enclosed in (..., 0) 453 so that we can avoid having void expressions 454 in the arms of the conditional expression. 455 Casting the third operand to void was tried before, 456 but some compilers won't accept it. */ 457 458 # define obstack_make_room(h, length) \ 459 ((h)->temp.i = (length), \ 460 ((obstack_room (h) < (h)->temp.i) \ 461 ? (_obstack_newchunk (h, (h)->temp.i), 0) : 0), \ 462 (void) 0) 463 464 # define obstack_grow(h, where, length) \ 465 ((h)->temp.i = (length), \ 466 ((obstack_room (h) < (h)->temp.i) \ 467 ? (_obstack_newchunk ((h), (h)->temp.i), 0) : 0), \ 468 memcpy ((h)->next_free, where, (h)->temp.i), \ 469 (h)->next_free += (h)->temp.i, \ 470 (void) 0) 471 472 # define obstack_grow0(h, where, length) \ 473 ((h)->temp.i = (length), \ 474 ((obstack_room (h) < (h)->temp.i + 1) \ 475 ? (_obstack_newchunk ((h), (h)->temp.i + 1), 0) : 0), \ 476 memcpy ((h)->next_free, where, (h)->temp.i), \ 477 (h)->next_free += (h)->temp.i, \ 478 *((h)->next_free)++ = 0, \ 479 (void) 0) 480 481 # define obstack_1grow(h, datum) \ 482 (((obstack_room (h) < 1) \ 483 ? (_obstack_newchunk ((h), 1), 0) : 0), \ 484 obstack_1grow_fast (h, datum)) 485 486 # define obstack_ptr_grow(h, datum) \ 487 (((obstack_room (h) < sizeof (char *)) \ 488 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \ 489 obstack_ptr_grow_fast (h, datum)) 490 491 # define obstack_int_grow(h, datum) \ 492 (((obstack_room (h) < sizeof (int)) \ 493 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \ 494 obstack_int_grow_fast (h, datum)) 495 496 # define obstack_ptr_grow_fast(h, aptr) \ 497 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr), \ 498 (void) 0) 499 500 # define obstack_int_grow_fast(h, aint) \ 501 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint), \ 502 (void) 0) 503 504 # define obstack_blank(h, length) \ 505 ((h)->temp.i = (length), \ 506 ((obstack_room (h) < (h)->temp.i) \ 507 ? (_obstack_newchunk ((h), (h)->temp.i), 0) : 0), \ 508 obstack_blank_fast (h, (h)->temp.i)) 509 510 # define obstack_alloc(h, length) \ 511 (obstack_blank ((h), (length)), obstack_finish ((h))) 512 513 # define obstack_copy(h, where, length) \ 514 (obstack_grow ((h), (where), (length)), obstack_finish ((h))) 515 516 # define obstack_copy0(h, where, length) \ 517 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h))) 518 519 # define obstack_finish(h) \ 520 (((h)->next_free == (h)->object_base \ 521 ? (((h)->maybe_empty_object = 1), 0) \ 522 : 0), \ 523 (h)->temp.p = (h)->object_base, \ 524 (h)->next_free \ 525 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \ 526 (h)->alignment_mask), \ 527 (((size_t) ((h)->next_free - (char *) (h)->chunk) \ 528 > (size_t) ((h)->chunk_limit - (char *) (h)->chunk)) \ 529 ? ((h)->next_free = (h)->chunk_limit) : 0), \ 530 (h)->object_base = (h)->next_free, \ 531 (h)->temp.p) 532 533 # define obstack_free(h, obj) \ 534 ((h)->temp.p = (void *) (obj), \ 535 (((h)->temp.p > (void *) (h)->chunk \ 536 && (h)->temp.p < (void *) (h)->chunk_limit) \ 537 ? (void) ((h)->next_free = (h)->object_base = (char *) (h)->temp.p) \ 538 : _obstack_free ((h), (h)->temp.p))) 539 540 #endif /* not __GNUC__ */ 541 542 #ifdef __cplusplus 543 } /* C++ */ 544 #endif 545 546 #endif /* _OBSTACK_H */ 547