1 /* obstack.h - object stack macros 2 Copyright (C) 1988, 1992 Free Software Foundation, Inc. 3 4 This program is free software; you can redistribute it and/or modify it 5 under the terms of the GNU General Public License as published by the 6 Free Software Foundation; either version 2, or (at your option) any 7 later version. 8 9 This program is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 GNU General Public License for more details. 13 14 You should have received a copy of the GNU General Public License 15 along with this program; if not, write to the Free Software 16 Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ 17 18 /* Summary: 19 20 All the apparent functions defined here are macros. The idea 21 is that you would use these pre-tested macros to solve a 22 very specific set of problems, and they would run fast. 23 Caution: no side-effects in arguments please!! They may be 24 evaluated MANY times!! 25 26 These macros operate a stack of objects. Each object starts life 27 small, and may grow to maturity. (Consider building a word syllable 28 by syllable.) An object can move while it is growing. Once it has 29 been "finished" it never changes address again. So the "top of the 30 stack" is typically an immature growing object, while the rest of the 31 stack is of mature, fixed size and fixed address objects. 32 33 These routines grab large chunks of memory, using a function you 34 supply, called `obstack_chunk_alloc'. On occasion, they free chunks, 35 by calling `obstack_chunk_free'. You must define them and declare 36 them before using any obstack macros. 37 38 Each independent stack is represented by a `struct obstack'. 39 Each of the obstack macros expects a pointer to such a structure 40 as the first argument. 41 42 One motivation for this package is the problem of growing char strings 43 in symbol tables. Unless you are "fascist pig with a read-only mind" 44 --Gosper's immortal quote from HAKMEM item 154, out of context--you 45 would not like to put any arbitrary upper limit on the length of your 46 symbols. 47 48 In practice this often means you will build many short symbols and a 49 few long symbols. At the time you are reading a symbol you don't know 50 how long it is. One traditional method is to read a symbol into a 51 buffer, realloc()ating the buffer every time you try to read a symbol 52 that is longer than the buffer. This is beaut, but you still will 53 want to copy the symbol from the buffer to a more permanent 54 symbol-table entry say about half the time. 55 56 With obstacks, you can work differently. Use one obstack for all symbol 57 names. As you read a symbol, grow the name in the obstack gradually. 58 When the name is complete, finalize it. Then, if the symbol exists already, 59 free the newly read name. 60 61 The way we do this is to take a large chunk, allocating memory from 62 low addresses. When you want to build a symbol in the chunk you just 63 add chars above the current "high water mark" in the chunk. When you 64 have finished adding chars, because you got to the end of the symbol, 65 you know how long the chars are, and you can create a new object. 66 Mostly the chars will not burst over the highest address of the chunk, 67 because you would typically expect a chunk to be (say) 100 times as 68 long as an average object. 69 70 In case that isn't clear, when we have enough chars to make up 71 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed) 72 so we just point to it where it lies. No moving of chars is 73 needed and this is the second win: potentially long strings need 74 never be explicitly shuffled. Once an object is formed, it does not 75 change its address during its lifetime. 76 77 When the chars burst over a chunk boundary, we allocate a larger 78 chunk, and then copy the partly formed object from the end of the old 79 chunk to the beginning of the new larger chunk. We then carry on 80 accreting characters to the end of the object as we normally would. 81 82 A special macro is provided to add a single char at a time to a 83 growing object. This allows the use of register variables, which 84 break the ordinary 'growth' macro. 85 86 Summary: 87 We allocate large chunks. 88 We carve out one object at a time from the current chunk. 89 Once carved, an object never moves. 90 We are free to append data of any size to the currently 91 growing object. 92 Exactly one object is growing in an obstack at any one time. 93 You can run one obstack per control block. 94 You may have as many control blocks as you dare. 95 Because of the way we do it, you can `unwind' an obstack 96 back to a previous state. (You may remove objects much 97 as you would with a stack.) 98 */ 99 100 101 /* Don't do the contents of this file more than once. */ 102 103 #ifndef __OBSTACKS__ 104 #define __OBSTACKS__ 105 106 /* We use subtraction of (char *)0 instead of casting to int 107 because on word-addressable machines a simple cast to int 108 may ignore the byte-within-word field of the pointer. */ 109 110 #ifndef __PTR_TO_INT 111 #define __PTR_TO_INT(P) ((P) - (char *)0) 112 #endif 113 114 #ifndef __INT_TO_PTR 115 #define __INT_TO_PTR(P) ((P) + (char *)0) 116 #endif 117 118 /* We need the type of the resulting object. In ANSI C it is ptrdiff_t 119 but in traditional C it is usually long. If we are in ANSI C and 120 don't already have ptrdiff_t get it. */ 121 122 #if defined (__STDC__) && ! defined (offsetof) 123 #if defined (__GNUC__) && defined (IN_GCC) 124 /* On Next machine, the system's stddef.h screws up if included 125 after we have defined just ptrdiff_t, so include all of gstddef.h. 126 Otherwise, define just ptrdiff_t, which is all we need. */ 127 #ifndef __NeXT__ 128 #define __need_ptrdiff_t 129 #endif 130 131 /* While building GCC, the stddef.h that goes with GCC has this name. */ 132 #include "gstddef.h" 133 #else 134 #include <stddef.h> 135 #endif 136 #endif 137 138 #ifdef __STDC__ 139 140 141 #define PTR_INT_TYPE int 142 #else 143 #define PTR_INT_TYPE long 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 int temp; /* Temporary for some macros. */ 161 int alignment_mask; /* Mask of alignment for each object. */ 162 struct _obstack_chunk *(*chunkfun) (); /* User's fcn to allocate a chunk. */ 163 void (*freefun) (); /* User's function to free a chunk. */ 164 char *extra_arg; /* first arg for chunk alloc/dealloc funcs */ 165 unsigned use_extra_arg:1; /* chunk alloc/dealloc funcs take extra arg */ 166 unsigned maybe_empty_object:1;/* There is a possibility that the current 167 chunk contains a zero-length object. This 168 prevents freeing the chunk if we allocate 169 a bigger chunk to replace it. */ 170 }; 171 172 /* Declare the external functions we use; they are in obstack.c. */ 173 174 #ifdef __STDC__ 175 extern void _obstack_newchunk (struct obstack *, int); 176 extern void _obstack_free (struct obstack *, void *); 177 extern void _obstack_begin (struct obstack *, int, int, 178 void *(*) (), void (*) ()); 179 extern void _obstack_begin_1 (struct obstack *, int, int, 180 void *(*) (), void (*) (), void *); 181 #else 182 extern void _obstack_newchunk (); 183 extern void _obstack_free (); 184 extern void _obstack_begin (); 185 extern void _obstack_begin_1 (); 186 #endif 187 188 #ifdef __STDC__ 189 190 /* Do the function-declarations after the structs 191 but before defining the macros. */ 192 193 void obstack_init (struct obstack *obstack); 194 195 void * obstack_alloc (struct obstack *obstack, int size); 196 197 void * obstack_copy (struct obstack *obstack, void *address, int size); 198 void * obstack_copy0 (struct obstack *obstack, void *address, int size); 199 200 void obstack_free (struct obstack *obstack, void *block); 201 202 void obstack_blank (struct obstack *obstack, int size); 203 204 void obstack_grow (struct obstack *obstack, void *data, int size); 205 void obstack_grow0 (struct obstack *obstack, void *data, int size); 206 207 void obstack_1grow (struct obstack *obstack, int data_char); 208 void obstack_ptr_grow (struct obstack *obstack, void *data); 209 void obstack_int_grow (struct obstack *obstack, int data); 210 211 void * obstack_finish (struct obstack *obstack); 212 213 int obstack_object_size (struct obstack *obstack); 214 215 int obstack_room (struct obstack *obstack); 216 void obstack_1grow_fast (struct obstack *obstack, int data_char); 217 void obstack_ptr_grow_fast (struct obstack *obstack, void *data); 218 void obstack_int_grow_fast (struct obstack *obstack, int data); 219 void obstack_blank_fast (struct obstack *obstack, int size); 220 221 void * obstack_base (struct obstack *obstack); 222 void * obstack_next_free (struct obstack *obstack); 223 int obstack_alignment_mask (struct obstack *obstack); 224 int obstack_chunk_size (struct obstack *obstack); 225 226 #endif /* __STDC__ */ 227 228 /* Non-ANSI C cannot really support alternative functions for these macros, 229 so we do not declare them. */ 230 231 /* Pointer to beginning of object being allocated or to be allocated next. 232 Note that this might not be the final address of the object 233 because a new chunk might be needed to hold the final size. */ 234 235 #define obstack_base(h) ((h)->object_base) 236 237 /* Size for allocating ordinary chunks. */ 238 239 #define obstack_chunk_size(h) ((h)->chunk_size) 240 241 /* Pointer to next byte not yet allocated in current chunk. */ 242 243 #define obstack_next_free(h) ((h)->next_free) 244 245 /* Mask specifying low bits that should be clear in address of an object. */ 246 247 #define obstack_alignment_mask(h) ((h)->alignment_mask) 248 249 #define obstack_init(h) \ 250 _obstack_begin ((h), 0, 0, \ 251 (void *(*) ()) obstack_chunk_alloc, (void (*) ()) obstack_chunk_free) 252 253 #define obstack_begin(h, size) \ 254 _obstack_begin ((h), (size), 0, \ 255 (void *(*) ()) obstack_chunk_alloc, (void (*) ()) obstack_chunk_free) 256 257 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \ 258 _obstack_begin ((h), (size), (alignment), \ 259 (void *(*) ()) (chunkfun), (void (*) ()) (freefun)) 260 261 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \ 262 _obstack_begin_1 ((h), (size), (alignment), \ 263 (void *(*) ()) (chunkfun), (void (*) ()) (freefun), (arg)) 264 265 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = achar) 266 267 #define obstack_blank_fast(h,n) ((h)->next_free += (n)) 268 269 #if defined (__GNUC__) && defined (__STDC__) 270 #if __GNUC__ < 2 271 #define __extension__ 272 #endif 273 274 /* For GNU C, if not -traditional, 275 we can define these macros to compute all args only once 276 without using a global variable. 277 Also, we can avoid using the `temp' slot, to make faster code. */ 278 279 #define obstack_object_size(OBSTACK) \ 280 __extension__ \ 281 ({ struct obstack *__o = (OBSTACK); \ 282 (unsigned) (__o->next_free - __o->object_base); }) 283 284 #define obstack_room(OBSTACK) \ 285 __extension__ \ 286 ({ struct obstack *__o = (OBSTACK); \ 287 (unsigned) (__o->chunk_limit - __o->next_free); }) 288 289 /* Note that the call to _obstack_newchunk is enclosed in (..., 0) 290 so that we can avoid having void expressions 291 in the arms of the conditional expression. 292 Casting the third operand to void was tried before, 293 but some compilers won't accept it. */ 294 #define obstack_grow(OBSTACK,where,length) \ 295 __extension__ \ 296 ({ struct obstack *__o = (OBSTACK); \ 297 int __len = (length); \ 298 ((__o->next_free + __len > __o->chunk_limit) \ 299 ? (_obstack_newchunk (__o, __len), 0) : 0); \ 300 bcopy (where, __o->next_free, __len); \ 301 __o->next_free += __len; \ 302 (void) 0; }) 303 304 #define obstack_grow0(OBSTACK,where,length) \ 305 __extension__ \ 306 ({ struct obstack *__o = (OBSTACK); \ 307 int __len = (length); \ 308 ((__o->next_free + __len + 1 > __o->chunk_limit) \ 309 ? (_obstack_newchunk (__o, __len + 1), 0) : 0), \ 310 bcopy (where, __o->next_free, __len), \ 311 __o->next_free += __len, \ 312 *(__o->next_free)++ = 0; \ 313 (void) 0; }) 314 315 #define obstack_1grow(OBSTACK,datum) \ 316 __extension__ \ 317 ({ struct obstack *__o = (OBSTACK); \ 318 ((__o->next_free + 1 > __o->chunk_limit) \ 319 ? (_obstack_newchunk (__o, 1), 0) : 0), \ 320 *(__o->next_free)++ = (datum); \ 321 (void) 0; }) 322 323 /* These assume that the obstack alignment is good enough for pointers or ints, 324 and that the data added so far to the current object 325 shares that much alignment. */ 326 327 #define obstack_ptr_grow(OBSTACK,datum) \ 328 __extension__ \ 329 ({ struct obstack *__o = (OBSTACK); \ 330 ((__o->next_free + sizeof (void *) > __o->chunk_limit) \ 331 ? (_obstack_newchunk (__o, sizeof (void *)), 0) : 0), \ 332 *((void **)__o->next_free)++ = ((void *)datum); \ 333 (void) 0; }) 334 335 #define obstack_int_grow(OBSTACK,datum) \ 336 __extension__ \ 337 ({ struct obstack *__o = (OBSTACK); \ 338 ((__o->next_free + sizeof (int) > __o->chunk_limit) \ 339 ? (_obstack_newchunk (__o, sizeof (int)), 0) : 0), \ 340 *((int *)__o->next_free)++ = ((int)datum); \ 341 (void) 0; }) 342 343 #define obstack_ptr_grow_fast(h,aptr) (*((void **)(h)->next_free)++ = (void *)aptr) 344 #define obstack_int_grow_fast(h,aint) (*((int *)(h)->next_free)++ = (int)aint) 345 346 #define obstack_blank(OBSTACK,length) \ 347 __extension__ \ 348 ({ struct obstack *__o = (OBSTACK); \ 349 int __len = (length); \ 350 ((__o->chunk_limit - __o->next_free < __len) \ 351 ? (_obstack_newchunk (__o, __len), 0) : 0); \ 352 __o->next_free += __len; \ 353 (void) 0; }) 354 355 #define obstack_alloc(OBSTACK,length) \ 356 __extension__ \ 357 ({ struct obstack *__h = (OBSTACK); \ 358 obstack_blank (__h, (length)); \ 359 obstack_finish (__h); }) 360 361 #define obstack_copy(OBSTACK,where,length) \ 362 __extension__ \ 363 ({ struct obstack *__h = (OBSTACK); \ 364 obstack_grow (__h, (where), (length)); \ 365 obstack_finish (__h); }) 366 367 #define obstack_copy0(OBSTACK,where,length) \ 368 __extension__ \ 369 ({ struct obstack *__h = (OBSTACK); \ 370 obstack_grow0 (__h, (where), (length)); \ 371 obstack_finish (__h); }) 372 373 /* The local variable is named __o1 to avoid a name conflict 374 when obstack_blank is called. */ 375 #define obstack_finish(OBSTACK) \ 376 __extension__ \ 377 ({ struct obstack *__o1 = (OBSTACK); \ 378 void *value = (void *) __o1->object_base; \ 379 if (__o1->next_free == value) \ 380 __o1->maybe_empty_object = 1; \ 381 __o1->next_free \ 382 = __INT_TO_PTR ((__PTR_TO_INT (__o1->next_free)+__o1->alignment_mask)\ 383 & ~ (__o1->alignment_mask)); \ 384 ((__o1->next_free - (char *)__o1->chunk \ 385 > __o1->chunk_limit - (char *)__o1->chunk) \ 386 ? (__o1->next_free = __o1->chunk_limit) : 0); \ 387 __o1->object_base = __o1->next_free; \ 388 value; }) 389 390 #define obstack_free(OBSTACK, OBJ) \ 391 __extension__ \ 392 ({ struct obstack *__o = (OBSTACK); \ 393 void *__obj = (OBJ); \ 394 if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \ 395 __o->next_free = __o->object_base = __obj; \ 396 else (obstack_free) (__o, __obj); }) 397 398 #else /* not __GNUC__ or not __STDC__ */ 399 400 #define obstack_object_size(h) \ 401 (unsigned) ((h)->next_free - (h)->object_base) 402 403 #define obstack_room(h) \ 404 (unsigned) ((h)->chunk_limit - (h)->next_free) 405 406 #define obstack_grow(h,where,length) \ 407 ( (h)->temp = (length), \ 408 (((h)->next_free + (h)->temp > (h)->chunk_limit) \ 409 ? (_obstack_newchunk ((h), (h)->temp), 0) : 0), \ 410 bcopy (where, (h)->next_free, (h)->temp), \ 411 (h)->next_free += (h)->temp) 412 413 #define obstack_grow0(h,where,length) \ 414 ( (h)->temp = (length), \ 415 (((h)->next_free + (h)->temp + 1 > (h)->chunk_limit) \ 416 ? (_obstack_newchunk ((h), (h)->temp + 1), 0) : 0), \ 417 bcopy (where, (h)->next_free, (h)->temp), \ 418 (h)->next_free += (h)->temp, \ 419 *((h)->next_free)++ = 0) 420 421 #define obstack_1grow(h,datum) \ 422 ( (((h)->next_free + 1 > (h)->chunk_limit) \ 423 ? (_obstack_newchunk ((h), 1), 0) : 0), \ 424 *((h)->next_free)++ = (datum)) 425 426 #define obstack_ptr_grow(h,datum) \ 427 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \ 428 ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0), \ 429 *((char **)(((h)->next_free+=sizeof(char *))-sizeof(char *))) = ((char *)datum)) 430 431 #define obstack_int_grow(h,datum) \ 432 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \ 433 ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0), \ 434 *((int *)(((h)->next_free+=sizeof(int))-sizeof(int))) = ((int)datum)) 435 436 #define obstack_ptr_grow_fast(h,aptr) (*((char **)(h)->next_free)++ = (char *)aptr) 437 #define obstack_int_grow_fast(h,aint) (*((int *)(h)->next_free)++ = (int)aint) 438 439 #define obstack_blank(h,length) \ 440 ( (h)->temp = (length), \ 441 (((h)->chunk_limit - (h)->next_free < (h)->temp) \ 442 ? (_obstack_newchunk ((h), (h)->temp), 0) : 0), \ 443 (h)->next_free += (h)->temp) 444 445 #define obstack_alloc(h,length) \ 446 (obstack_blank ((h), (length)), obstack_finish ((h))) 447 448 #define obstack_copy(h,where,length) \ 449 (obstack_grow ((h), (where), (length)), obstack_finish ((h))) 450 451 #define obstack_copy0(h,where,length) \ 452 (obstack_grow0 ((h), (where), (length)), obstack_finish ((h))) 453 454 #define obstack_finish(h) \ 455 ( ((h)->next_free == (h)->object_base \ 456 ? (((h)->maybe_empty_object = 1), 0) \ 457 : 0), \ 458 (h)->temp = __PTR_TO_INT ((h)->object_base), \ 459 (h)->next_free \ 460 = __INT_TO_PTR ((__PTR_TO_INT ((h)->next_free)+(h)->alignment_mask) \ 461 & ~ ((h)->alignment_mask)), \ 462 (((h)->next_free - (char *)(h)->chunk \ 463 > (h)->chunk_limit - (char *)(h)->chunk) \ 464 ? ((h)->next_free = (h)->chunk_limit) : 0), \ 465 (h)->object_base = (h)->next_free, \ 466 __INT_TO_PTR ((h)->temp)) 467 468 #ifdef __STDC__ 469 #define obstack_free(h,obj) \ 470 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \ 471 (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\ 472 ? (int) ((h)->next_free = (h)->object_base \ 473 = (h)->temp + (char *) (h)->chunk) \ 474 : (((obstack_free) ((h), (h)->temp + (char *) (h)->chunk), 0), 0))) 475 #else 476 #define obstack_free(h,obj) \ 477 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \ 478 (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\ 479 ? (int) ((h)->next_free = (h)->object_base \ 480 = (h)->temp + (char *) (h)->chunk) \ 481 : (_obstack_free ((h), (h)->temp + (char *) (h)->chunk), 0))) 482 #endif 483 484 #endif /* not __GNUC__ or not __STDC__ */ 485 486 #endif /* not __OBSTACKS__ */ 487