1 /* obstack.h - object stack macros 2 Copyright (C) 1988-2022 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 Lesser General Public 7 License as published by the Free Software Foundation; either 8 version 2.1 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 Lesser General Public License for more details. 14 15 You should have received a copy of the GNU Lesser 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 /* 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 #ifndef __attribute_pure__ 139 # define __attribute_pure__ _GL_ATTRIBUTE_PURE 140 #endif 141 142 #ifdef __cplusplus 143 extern "C" { 144 #endif 145 146 struct _obstack_chunk /* Lives at front of each chunk. */ 147 { 148 char *limit; /* 1 past end of this chunk */ 149 struct _obstack_chunk *prev; /* address of prior chunk or NULL */ 150 char contents[4]; /* objects begin here */ 151 }; 152 153 struct obstack /* control current object in current chunk */ 154 { 155 long chunk_size; /* preferred size to allocate chunks in */ 156 struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */ 157 char *object_base; /* address of object we are building */ 158 char *next_free; /* where to add next char to current object */ 159 char *chunk_limit; /* address of char after current chunk */ 160 union 161 { 162 PTR_INT_TYPE tempint; 163 void *tempptr; 164 } temp; /* Temporary for some macros. */ 165 int alignment_mask; /* Mask of alignment for each object. */ 166 /* These prototypes vary based on 'use_extra_arg', and we use 167 casts to the prototypeless function type in all assignments, 168 but having prototypes here quiets -Wstrict-prototypes. */ 169 struct _obstack_chunk *(*chunkfun) (void *, long); 170 void (*freefun) (void *, struct _obstack_chunk *); 171 void *extra_arg; /* first arg for chunk alloc/dealloc funcs */ 172 unsigned use_extra_arg : 1; /* chunk alloc/dealloc funcs take extra arg */ 173 unsigned maybe_empty_object : 1; /* There is a possibility that the current 174 chunk contains a zero-length object. This 175 prevents freeing the chunk if we allocate 176 a bigger chunk to replace it. */ 177 unsigned alloc_failed : 1; /* No longer used, as we now call the failed 178 handler on error, but retained for binary 179 compatibility. */ 180 }; 181 182 /* Declare the external functions we use; they are in obstack.c. */ 183 184 extern void _obstack_newchunk (struct obstack *, int); 185 extern int _obstack_begin (struct obstack *, int, int, 186 void *(*)(long), void (*)(void *)); 187 extern int _obstack_begin_1 (struct obstack *, int, int, 188 void *(*)(void *, long), 189 void (*)(void *, void *), void *); 190 extern int _obstack_memory_used (struct obstack *) __attribute_pure__; 191 192 /* The default name of the function for freeing a chunk is 'obstack_free', 193 but gnulib users can override this by defining '__obstack_free'. */ 194 #ifndef __obstack_free 195 # define __obstack_free obstack_free 196 #endif 197 extern void __obstack_free (struct obstack *, void *); 198 199 200 /* Error handler called when 'obstack_chunk_alloc' failed to allocate 201 more memory. This can be set to a user defined function which 202 should either abort gracefully or use longjump - but shouldn't 203 return. The default action is to print a message and abort. */ 204 extern void (*obstack_alloc_failed_handler) (void); 205 206 /* Exit value used when 'print_and_abort' is used. */ 207 extern int obstack_exit_failure; 208 209 /* Pointer to beginning of object being allocated or to be allocated next. 210 Note that this might not be the final address of the object 211 because a new chunk might be needed to hold the final size. */ 212 213 #define obstack_base(h) ((void *) (h)->object_base) 214 215 /* Size for allocating ordinary chunks. */ 216 217 #define obstack_chunk_size(h) ((h)->chunk_size) 218 219 /* Pointer to next byte not yet allocated in current chunk. */ 220 221 #define obstack_next_free(h) ((h)->next_free) 222 223 /* Mask specifying low bits that should be clear in address of an object. */ 224 225 #define obstack_alignment_mask(h) ((h)->alignment_mask) 226 227 /* To prevent prototype warnings provide complete argument list. */ 228 #define obstack_init(h) \ 229 _obstack_begin ((h), 0, 0, \ 230 (void *(*)(long))obstack_chunk_alloc, \ 231 (void (*)(void *))obstack_chunk_free) 232 233 #define obstack_begin(h, size) \ 234 _obstack_begin ((h), (size), 0, \ 235 (void *(*)(long))obstack_chunk_alloc, \ 236 (void (*)(void *))obstack_chunk_free) 237 238 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \ 239 _obstack_begin ((h), (size), (alignment), \ 240 (void *(*)(long))(chunkfun), \ 241 (void (*)(void *))(freefun)) 242 243 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \ 244 _obstack_begin_1 ((h), (size), (alignment), \ 245 (void *(*)(void *, long))(chunkfun), \ 246 (void (*)(void *, void *))(freefun), (arg)) 247 248 #define obstack_chunkfun(h, newchunkfun) \ 249 ((h)->chunkfun = (struct _obstack_chunk *(*)(void *, long))(newchunkfun)) 250 251 #define obstack_freefun(h, newfreefun) \ 252 ((h)->freefun = (void (*)(void *, struct _obstack_chunk *))(newfreefun)) 253 254 #define obstack_1grow_fast(h, achar) (*((h)->next_free)++ = (achar)) 255 256 #define obstack_blank_fast(h, n) ((h)->next_free += (n)) 257 258 #define obstack_memory_used(h) _obstack_memory_used (h) 259 260 #if defined __GNUC__ 261 # if ! (2 < __GNUC__ + (8 <= __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 void *__p1 = __o1->next_free; \ 347 *(const void **) __p1 = (aptr); \ 348 __o1->next_free += sizeof (const void *); \ 349 (void) 0; }) 350 351 # define obstack_int_grow_fast(OBSTACK, aint) \ 352 __extension__ \ 353 ({ struct obstack *__o1 = (OBSTACK); \ 354 void *__p1 = __o1->next_free; \ 355 *(int *) __p1 = (aint); \ 356 __o1->next_free += sizeof (int); \ 357 (void) 0; }) 358 359 # define obstack_blank(OBSTACK, length) \ 360 __extension__ \ 361 ({ struct obstack *__o = (OBSTACK); \ 362 int __len = (length); \ 363 if (__o->chunk_limit - __o->next_free < __len) \ 364 _obstack_newchunk (__o, __len); \ 365 obstack_blank_fast (__o, __len); \ 366 (void) 0; }) 367 368 # define obstack_alloc(OBSTACK, length) \ 369 __extension__ \ 370 ({ struct obstack *__h = (OBSTACK); \ 371 obstack_blank (__h, (length)); \ 372 obstack_finish (__h); }) 373 374 # define obstack_copy(OBSTACK, where, length) \ 375 __extension__ \ 376 ({ struct obstack *__h = (OBSTACK); \ 377 obstack_grow (__h, (where), (length)); \ 378 obstack_finish (__h); }) 379 380 # define obstack_copy0(OBSTACK, where, length) \ 381 __extension__ \ 382 ({ struct obstack *__h = (OBSTACK); \ 383 obstack_grow0 (__h, (where), (length)); \ 384 obstack_finish (__h); }) 385 386 /* The local variable is named __o1 to avoid a name conflict 387 when obstack_blank is called. */ 388 # define obstack_finish(OBSTACK) \ 389 __extension__ \ 390 ({ struct obstack *__o1 = (OBSTACK); \ 391 void *__value = (void *) __o1->object_base; \ 392 if (__o1->next_free == __value) \ 393 __o1->maybe_empty_object = 1; \ 394 __o1->next_free \ 395 = __PTR_ALIGN (__o1->object_base, __o1->next_free, \ 396 __o1->alignment_mask); \ 397 if (__o1->next_free - (char *) __o1->chunk \ 398 > __o1->chunk_limit - (char *) __o1->chunk) \ 399 __o1->next_free = __o1->chunk_limit; \ 400 __o1->object_base = __o1->next_free; \ 401 __value; }) 402 403 # define obstack_free(OBSTACK, OBJ) \ 404 __extension__ \ 405 ({ struct obstack *__o = (OBSTACK); \ 406 void *__obj = (OBJ); \ 407 if (__obj > (void *) __o->chunk && __obj < (void *) __o->chunk_limit) \ 408 __o->next_free = __o->object_base = (char *) __obj; \ 409 else (__obstack_free) (__o, __obj); }) 410 411 #else /* not __GNUC__ */ 412 413 # define obstack_object_size(h) \ 414 (unsigned) ((h)->next_free - (h)->object_base) 415 416 # define obstack_room(h) \ 417 (unsigned) ((h)->chunk_limit - (h)->next_free) 418 419 # define obstack_empty_p(h) \ 420 ((h)->chunk->prev == 0 \ 421 && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk, \ 422 (h)->chunk->contents, \ 423 (h)->alignment_mask)) 424 425 /* Note that the call to _obstack_newchunk is enclosed in (..., 0) 426 so that we can avoid having void expressions 427 in the arms of the conditional expression. 428 Casting the third operand to void was tried before, 429 but some compilers won't accept it. */ 430 431 # define obstack_make_room(h, length) \ 432 ((h)->temp.tempint = (length), \ 433 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 434 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0)) 435 436 # define obstack_grow(h, where, length) \ 437 ((h)->temp.tempint = (length), \ 438 (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit) \ 439 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 440 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 441 (h)->next_free += (h)->temp.tempint) 442 443 # define obstack_grow0(h, where, length) \ 444 ((h)->temp.tempint = (length), \ 445 (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit) \ 446 ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0), \ 447 memcpy ((h)->next_free, where, (h)->temp.tempint), \ 448 (h)->next_free += (h)->temp.tempint, \ 449 *((h)->next_free)++ = 0) 450 451 # define obstack_1grow(h, datum) \ 452 ((((h)->next_free + 1 > (h)->chunk_limit) \ 453 ? (_obstack_newchunk ((h), 1), 0) : 0), \ 454 obstack_1grow_fast (h, datum)) 455 456 # define obstack_ptr_grow(h, datum) \ 457 ((((h)->next_free + sizeof (char *) > (h)->chunk_limit) \ 458 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \ 459 obstack_ptr_grow_fast (h, datum)) 460 461 # define obstack_int_grow(h, datum) \ 462 ((((h)->next_free + sizeof (int) > (h)->chunk_limit) \ 463 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \ 464 obstack_int_grow_fast (h, datum)) 465 466 # define obstack_ptr_grow_fast(h, aptr) \ 467 (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr)) 468 469 # define obstack_int_grow_fast(h, aint) \ 470 (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint)) 471 472 # define obstack_blank(h, length) \ 473 ((h)->temp.tempint = (length), \ 474 (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint) \ 475 ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0), \ 476 obstack_blank_fast (h, (h)->temp.tempint)) 477 478 # define obstack_alloc(h, length) \ 479 (obstack_blank ((h), (length)), obstack_finish ((h))) 480 481 # define obstack_copy(h, where, length) \ 482 (obstack_grow ((h), (where), (length)), obstack_finish ((h))) 483 484 # define obstack_copy0(h, where, length) \ 485 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h))) 486 487 # define obstack_finish(h) \ 488 (((h)->next_free == (h)->object_base \ 489 ? (((h)->maybe_empty_object = 1), 0) \ 490 : 0), \ 491 (h)->temp.tempptr = (h)->object_base, \ 492 (h)->next_free \ 493 = __PTR_ALIGN ((h)->object_base, (h)->next_free, \ 494 (h)->alignment_mask), \ 495 (((h)->next_free - (char *) (h)->chunk \ 496 > (h)->chunk_limit - (char *) (h)->chunk) \ 497 ? ((h)->next_free = (h)->chunk_limit) : 0), \ 498 (h)->object_base = (h)->next_free, \ 499 (h)->temp.tempptr) 500 501 # define obstack_free(h, obj) \ 502 ((h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk, \ 503 ((((h)->temp.tempint > 0 \ 504 && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk)) \ 505 ? (void) ((h)->next_free = (h)->object_base \ 506 = (h)->temp.tempint + (char *) (h)->chunk) \ 507 : (__obstack_free) (h, (h)->temp.tempint + (char *) (h)->chunk))) 508 509 #endif /* not __GNUC__ */ 510 511 #ifdef __cplusplus 512 } /* C++ */ 513 #endif 514 515 #endif /* obstack.h */ 516