compat/obstack.h

   1 /* obstack.h - object stack macros
   2    Copyright (C) 1988-1994,1996-1999,2003,2004,2005,2009
   3         Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library 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 GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 /* Summary:
  21
  22 All the apparent functions defined here are macros. The idea
  23 is that you would use these pre-tested macros to solve a
  24 very specific set of problems, and they would run fast.
  25 Caution: no side-effects in arguments please!! They may be
  26 evaluated MANY times!!
  27
  28 These macros operate a stack of objects.  Each object starts life
  29 small, and may grow to maturity.  (Consider building a word syllable
  30 by syllable.)  An object can move while it is growing.  Once it has
  31 been "finished" it never changes address again.  So the "top of the
  32 stack" is typically an immature growing object, while the rest of the
  33 stack is of mature, fixed size and fixed address objects.
  34
  35 These routines grab large chunks of memory, using a function you
  36 supply, called `obstack_chunk_alloc'.  On occasion, they free chunks,
  37 by calling `obstack_chunk_free'.  You must define them and declare
  38 them before using any obstack macros.
  39
  40 Each independent stack is represented by a `struct obstack'.
  41 Each of the obstack macros expects a pointer to such a structure
  42 as the first argument.
  43
  44 One motivation for this package is the problem of growing char strings
  45 in symbol tables.  Unless you are "fascist pig with a read-only mind"
  46 --Gosper's immortal quote from HAKMEM item 154, out of context--you
  47 would not like to put any arbitrary upper limit on the length of your
  48 symbols.
  49
  50 In practice this often means you will build many short symbols and a
  51 few long symbols.  At the time you are reading a symbol you don't know
  52 how long it is.  One traditional method is to read a symbol into a
  53 buffer, realloc()ating the buffer every time you try to read a symbol
  54 that is longer than the buffer.  This is beaut, but you still will
  55 want to copy the symbol from the buffer to a more permanent
  56 symbol-table entry say about half the time.
  57
  58 With obstacks, you can work differently.  Use one obstack for all symbol
  59 names.  As you read a symbol, grow the name in the obstack gradually.
  60 When the name is complete, finalize it.  Then, if the symbol exists already,
  61 free the newly read name.
  62
  63 The way we do this is to take a large chunk, allocating memory from
  64 low addresses.  When you want to build a symbol in the chunk you just
  65 add chars above the current "high water mark" in the chunk.  When you
  66 have finished adding chars, because you got to the end of the symbol,
  67 you know how long the chars are, and you can create a new object.
  68 Mostly the chars will not burst over the highest address of the chunk,
  69 because you would typically expect a chunk to be (say) 100 times as
  70 long as an average object.
  71
  72 In case that isn't clear, when we have enough chars to make up
  73 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
  74 so we just point to it where it lies.  No moving of chars is
  75 needed and this is the second win: potentially long strings need
  76 never be explicitly shuffled. Once an object is formed, it does not
  77 change its address during its lifetime.
  78
  79 When the chars burst over a chunk boundary, we allocate a larger
  80 chunk, and then copy the partly formed object from the end of the old
  81 chunk to the beginning of the new larger chunk.  We then carry on
  82 accrediting characters to the end of the object as we normally would.
  83
  84 A special macro is provided to add a single char at a time to a
  85 growing object.  This allows the use of register variables, which
  86 break the ordinary 'growth' macro.
  87
  88 Summary:
  89         We allocate large chunks.
  90         We carve out one object at a time from the current chunk.
  91         Once carved, an object never moves.
  92         We are free to append data of any size to the currently
  93           growing object.
  94         Exactly one object is growing in an obstack at any one time.
  95         You can run one obstack per control block.
  96         You may have as many control blocks as you dare.
  97         Because of the way we do it, you can `unwind' an obstack
  98           back to a previous state. (You may remove objects much
  99           as you would with a stack.)
 100 */
 101
 102
 103 /* Don't do the contents of this file more than once.  */
 104
 105 #ifndef _OBSTACK_H
 106 #define _OBSTACK_H 1
 107
 108 #ifdef __cplusplus
 109 extern "C" {
 110 #endif
 111 \f
 112 /* We need the type of a pointer subtraction.  If __PTRDIFF_TYPE__ is
 113    defined, as with GNU C, use that; that way we don't pollute the
 114    namespace with <stddef.h>'s symbols.  Otherwise, include <stddef.h>
 115    and use ptrdiff_t.  */
 116
 117 #ifdef __PTRDIFF_TYPE__
 118 # define PTR_INT_TYPE __PTRDIFF_TYPE__
 119 #else
 120 # include <stddef.h>
 121 # define PTR_INT_TYPE ptrdiff_t
 122 #endif
 123
 124 /* If B is the base of an object addressed by P, return the result of
 125    aligning P to the next multiple of A + 1.  B and P must be of type
 126    char *.  A + 1 must be a power of 2.  */
 127
 128 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A)))
 129
 130 /* Similar to _BPTR_ALIGN (B, P, A), except optimize the common case
 131    where pointers can be converted to integers, aligned as integers,
 132    and converted back again.  If PTR_INT_TYPE is narrower than a
 133    pointer (e.g., the AS/400), play it safe and compute the alignment
 134    relative to B.  Otherwise, use the faster strategy of computing the
 135    alignment relative to 0.  */
 136
 137 #define __PTR_ALIGN(B, P, A)                                                \
 138   (sizeof (PTR_INT_TYPE) < sizeof(void *) ?                                 \
 139    __BPTR_ALIGN((B), (P), (A)) :                                            \
 140    (void *)__BPTR_ALIGN((PTR_INT_TYPE)(void *)0, (PTR_INT_TYPE)(P), (A))            \
 141   )
 142
 143 #include <string.h>
 144
 145 struct _obstack_chunk           /* Lives at front of each chunk. */
 146 {
 147   char  *limit;                 /* 1 past end of this chunk */
 148   struct _obstack_chunk *prev;  /* address of prior chunk or NULL */
 149   char  contents[4];            /* objects begin here */
 150 };
 151
 152 struct obstack          /* control current object in current chunk */
 153 {
 154   long  chunk_size;             /* preferred size to allocate chunks in */
 155   struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
 156   char  *object_base;           /* address of object we are building */
 157   char  *next_free;             /* where to add next char to current object */
 158   char  *chunk_limit;           /* address of char after current chunk */
 159   union
 160   {
 161     PTR_INT_TYPE tempint;
 162     void *tempptr;
 163   } temp;                       /* Temporary for some macros.  */
 164   int   alignment_mask;         /* Mask of alignment for each object. */
 165   /* These prototypes vary based on `use_extra_arg'. */
 166   union {
 167     void *(*plain) (long);
 168     struct _obstack_chunk *(*extra) (void *, long);
 169   } chunkfun;
 170   union {
 171     void (*plain) (void *);
 172     void (*extra) (void *, struct _obstack_chunk *);
 173   } freefun;
 174   void *extra_arg;              /* first arg for chunk alloc/dealloc funcs */
 175   unsigned use_extra_arg:1;     /* chunk alloc/dealloc funcs take extra arg */
 176   unsigned maybe_empty_object:1;/* There is a possibility that the current
 177                                    chunk contains a zero-length object.  This
 178                                    prevents freeing the chunk if we allocate
 179                                    a bigger chunk to replace it. */
 180   unsigned alloc_failed:1;      /* No longer used, as we now call the failed
 181                                    handler on error, but retained for binary
 182                                    compatibility.  */
 183 };
 184
 185 /* Declare the external functions we use; they are in obstack.c.  */
 186
 187 extern void _obstack_newchunk (struct obstack *, int);
 188 extern int _obstack_begin (struct obstack *, int, int,
 189                             void *(*) (long), void (*) (void *));
 190 extern int _obstack_begin_1 (struct obstack *, int, int,
 191                              void *(*) (void *, long),
 192                              void (*) (void *, void *), void *);
 193 extern int _obstack_memory_used (struct obstack *);
 194
 195 void obstack_free (struct obstack *, void *);
 196
 197 \f
 198 /* Error handler called when `obstack_chunk_alloc' failed to allocate
 199    more memory.  This can be set to a user defined function which
 200    should either abort gracefully or use longjump - but shouldn't
 201    return.  The default action is to print a message and abort.  */
 202 extern void (*obstack_alloc_failed_handler) (void);
 203 \f
 204 /* Pointer to beginning of object being allocated or to be allocated next.
 205    Note that this might not be the final address of the object
 206    because a new chunk might be needed to hold the final size.  */
 207
 208 #define obstack_base(h) ((void *) (h)->object_base)
 209
 210 /* Size for allocating ordinary chunks.  */
 211
 212 #define obstack_chunk_size(h) ((h)->chunk_size)
 213
 214 /* Pointer to next byte not yet allocated in current chunk.  */
 215
 216 #define obstack_next_free(h)    ((h)->next_free)
 217
 218 /* Mask specifying low bits that should be clear in address of an object.  */
 219
 220 #define obstack_alignment_mask(h) ((h)->alignment_mask)
 221
 222 /* To prevent prototype warnings provide complete argument list.  */
 223 #define obstack_init(h)                                         \
 224   _obstack_begin ((h), 0, 0,                                    \
 225                   (void *(*) (long)) obstack_chunk_alloc,       \
 226                   (void (*) (void *)) obstack_chunk_free)
 227
 228 #define obstack_begin(h, size)                                  \
 229   _obstack_begin ((h), (size), 0,                               \
 230                   (void *(*) (long)) obstack_chunk_alloc,       \
 231                   (void (*) (void *)) obstack_chunk_free)
 232
 233 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun)  \
 234   _obstack_begin ((h), (size), (alignment),                                \
 235                   (void *(*) (long)) (chunkfun),                           \
 236                   (void (*) (void *)) (freefun))
 237
 238 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
 239   _obstack_begin_1 ((h), (size), (alignment),                           \
 240                     (void *(*) (void *, long)) (chunkfun),              \
 241                     (void (*) (void *, void *)) (freefun), (arg))
 242
 243 #define obstack_chunkfun(h, newchunkfun) \
 244   ((h)->chunkfun.extra = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
 245
 246 #define obstack_freefun(h, newfreefun) \
 247   ((h)->freefun.extra = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
 248
 249 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
 250
 251 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
 252
 253 #define obstack_memory_used(h) _obstack_memory_used (h)
 254 \f
 255 #if defined __GNUC__ && defined __STDC__ && __STDC__
 256 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
 257    does not implement __extension__.  But that compiler doesn't define
 258    __GNUC_MINOR__.  */
 259 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
 260 #  define __extension__
 261 # endif
 262
 263 /* For GNU C, if not -traditional,
 264    we can define these macros to compute all args only once
 265    without using a global variable.
 266    Also, we can avoid using the `temp' slot, to make faster code.  */
 267
 268 # define obstack_object_size(OBSTACK)                                   \
 269   __extension__                                                         \
 270   ({ struct obstack const *__o = (OBSTACK);                             \
 271      (unsigned) (__o->next_free - __o->object_base); })
 272
 273 # define obstack_room(OBSTACK)                                          \
 274   __extension__                                                         \
 275   ({ struct obstack const *__o = (OBSTACK);                             \
 276      (unsigned) (__o->chunk_limit - __o->next_free); })
 277
 278 # define obstack_make_room(OBSTACK,length)                              \
 279 __extension__                                                           \
 280 ({ struct obstack *__o = (OBSTACK);                                     \
 281    int __len = (length);                                                \
 282    if (__o->chunk_limit - __o->next_free < __len)                       \
 283      _obstack_newchunk (__o, __len);                                    \
 284    (void) 0; })
 285
 286 # define obstack_empty_p(OBSTACK)                                       \
 287   __extension__                                                         \
 288   ({ struct obstack const *__o = (OBSTACK);                             \
 289      (__o->chunk->prev == 0                                             \
 290       && __o->next_free == __PTR_ALIGN ((char *) __o->chunk,            \
 291                                         __o->chunk->contents,           \
 292                                         __o->alignment_mask)); })
 293
 294 # define obstack_grow(OBSTACK,where,length)                             \
 295 __extension__                                                           \
 296 ({ struct obstack *__o = (OBSTACK);                                     \
 297    int __len = (length);                                                \
 298    if (__o->next_free + __len > __o->chunk_limit)                       \
 299      _obstack_newchunk (__o, __len);                                    \
 300    memcpy (__o->next_free, where, __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    if (__o->next_free + __len + 1 > __o->chunk_limit)                   \
 309      _obstack_newchunk (__o, __len + 1);                                \
 310    memcpy (__o->next_free, where, __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    if (__o->next_free + 1 > __o->chunk_limit)                           \
 319      _obstack_newchunk (__o, 1);                                        \
 320    obstack_1grow_fast (__o, datum);                                     \
 321    (void) 0; })
 322
 323 /* These assume that the obstack alignment is good enough for pointers
 324    or ints, 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    if (__o->next_free + sizeof (void *) > __o->chunk_limit)             \
 331      _obstack_newchunk (__o, sizeof (void *));                          \
 332    obstack_ptr_grow_fast (__o, datum); })                               \
 333
 334 # define obstack_int_grow(OBSTACK,datum)                                \
 335 __extension__                                                           \
 336 ({ struct obstack *__o = (OBSTACK);                                     \
 337    if (__o->next_free + sizeof (int) > __o->chunk_limit)                \
 338      _obstack_newchunk (__o, sizeof (int));                             \
 339    obstack_int_grow_fast (__o, datum); })
 340
 341 # define obstack_ptr_grow_fast(OBSTACK,aptr)                            \
 342 __extension__                                                           \
 343 ({ struct obstack *__o1 = (OBSTACK);                                    \
 344    *(const void **) __o1->next_free = (aptr);                           \
 345    __o1->next_free += sizeof (const void *);                            \
 346    (void) 0; })
 347
 348 # define obstack_int_grow_fast(OBSTACK,aint)                            \
 349 __extension__                                                           \
 350 ({ struct obstack *__o1 = (OBSTACK);                                    \
 351    *(int *) __o1->next_free = (aint);                                   \
 352    __o1->next_free += sizeof (int);                                     \
 353    (void) 0; })
 354
 355 # define obstack_blank(OBSTACK,length)                                  \
 356 __extension__                                                           \
 357 ({ struct obstack *__o = (OBSTACK);                                     \
 358    int __len = (length);                                                \
 359    if (__o->chunk_limit - __o->next_free < __len)                       \
 360      _obstack_newchunk (__o, __len);                                    \
 361    obstack_blank_fast (__o, __len);                                     \
 362    (void) 0; })
 363
 364 # define obstack_alloc(OBSTACK,length)                                  \
 365 __extension__                                                           \
 366 ({ struct obstack *__h = (OBSTACK);                                     \
 367    obstack_blank (__h, (length));                                       \
 368    obstack_finish (__h); })
 369
 370 # define obstack_copy(OBSTACK,where,length)                             \
 371 __extension__                                                           \
 372 ({ struct obstack *__h = (OBSTACK);                                     \
 373    obstack_grow (__h, (where), (length));                               \
 374    obstack_finish (__h); })
 375
 376 # define obstack_copy0(OBSTACK,where,length)                            \
 377 __extension__                                                           \
 378 ({ struct obstack *__h = (OBSTACK);                                     \
 379    obstack_grow0 (__h, (where), (length));                              \
 380    obstack_finish (__h); })
 381
 382 /* The local variable is named __o1 to avoid a name conflict
 383    when obstack_blank is called.  */
 384 # define obstack_finish(OBSTACK)                                        \
 385 __extension__                                                           \
 386 ({ struct obstack *__o1 = (OBSTACK);                                    \
 387    void *__value = (void *) __o1->object_base;                          \
 388    if (__o1->next_free == __value)                                      \
 389      __o1->maybe_empty_object = 1;                                      \
 390    __o1->next_free                                                      \
 391      = __PTR_ALIGN (__o1->object_base, __o1->next_free,                 \
 392                     __o1->alignment_mask);                              \
 393    if (__o1->next_free - (char *)__o1->chunk                            \
 394        > __o1->chunk_limit - (char *)__o1->chunk)                       \
 395      __o1->next_free = __o1->chunk_limit;                               \
 396    __o1->object_base = __o1->next_free;                                 \
 397    __value; })
 398
 399 # define obstack_free(OBSTACK, OBJ)                                     \
 400 __extension__                                                           \
 401 ({ struct obstack *__o = (OBSTACK);                                     \
 402    void *__obj = (OBJ);                                                 \
 403    if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit)  \
 404      __o->next_free = __o->object_base = (char *)__obj;                 \
 405    else (obstack_free) (__o, __obj); })
 406 \f
 407 #else /* not __GNUC__ or not __STDC__ */
 408
 409 # define obstack_object_size(h) \
 410  (unsigned) ((h)->next_free - (h)->object_base)
 411
 412 # define obstack_room(h)                \
 413  (unsigned) ((h)->chunk_limit - (h)->next_free)
 414
 415 # define obstack_empty_p(h) \
 416  ((h)->chunk->prev == 0                                                 \
 417   && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk,                \
 418                                     (h)->chunk->contents,               \
 419                                     (h)->alignment_mask))
 420
 421 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
 422    so that we can avoid having void expressions
 423    in the arms of the conditional expression.
 424    Casting the third operand to void was tried before,
 425    but some compilers won't accept it.  */
 426
 427 # define obstack_make_room(h,length)                                    \
 428 ( (h)->temp.tempint = (length),                                         \
 429   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)              \
 430    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
 431
 432 # define obstack_grow(h,where,length)                                   \
 433 ( (h)->temp.tempint = (length),                                         \
 434   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)              \
 435    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),              \
 436   memcpy ((h)->next_free, where, (h)->temp.tempint),                    \
 437   (h)->next_free += (h)->temp.tempint)
 438
 439 # define obstack_grow0(h,where,length)                                  \
 440 ( (h)->temp.tempint = (length),                                         \
 441   (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit)          \
 442    ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0),          \
 443   memcpy ((h)->next_free, where, (h)->temp.tempint),                    \
 444   (h)->next_free += (h)->temp.tempint,                                  \
 445   *((h)->next_free)++ = 0)
 446
 447 # define obstack_1grow(h,datum)                                         \
 448 ( (((h)->next_free + 1 > (h)->chunk_limit)                              \
 449    ? (_obstack_newchunk ((h), 1), 0) : 0),                              \
 450   obstack_1grow_fast (h, datum))
 451
 452 # define obstack_ptr_grow(h,datum)                                      \
 453 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit)                \
 454    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),                \
 455   obstack_ptr_grow_fast (h, datum))
 456
 457 # define obstack_int_grow(h,datum)                                      \
 458 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit)                   \
 459    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),                   \
 460   obstack_int_grow_fast (h, datum))
 461
 462 # define obstack_ptr_grow_fast(h,aptr)                                  \
 463   (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
 464
 465 # define obstack_int_grow_fast(h,aint)                                  \
 466   (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
 467
 468 # define obstack_blank(h,length)                                        \
 469 ( (h)->temp.tempint = (length),                                         \
 470   (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint)              \
 471    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),              \
 472   obstack_blank_fast (h, (h)->temp.tempint))
 473
 474 # define obstack_alloc(h,length)                                        \
 475  (obstack_blank ((h), (length)), obstack_finish ((h)))
 476
 477 # define obstack_copy(h,where,length)                                   \
 478  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
 479
 480 # define obstack_copy0(h,where,length)                                  \
 481  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
 482
 483 # define obstack_finish(h)                                              \
 484 ( ((h)->next_free == (h)->object_base                                   \
 485    ? (((h)->maybe_empty_object = 1), 0)                                 \
 486    : 0),                                                                \
 487   (h)->temp.tempptr = (h)->object_base,                                 \
 488   (h)->next_free                                                        \
 489     = __PTR_ALIGN ((h)->object_base, (h)->next_free,                    \
 490                    (h)->alignment_mask),                                \
 491   (((h)->next_free - (char *) (h)->chunk                                \
 492     > (h)->chunk_limit - (char *) (h)->chunk)                           \
 493    ? ((h)->next_free = (h)->chunk_limit) : 0),                          \
 494   (h)->object_base = (h)->next_free,                                    \
 495   (h)->temp.tempptr)
 496
 497 # define obstack_free(h,obj)                                            \
 498 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk,             \
 499   ((((h)->temp.tempint > 0                                              \
 500     && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk))     \
 501    ? (ptrdiff_t) ((h)->next_free = (h)->object_base                             \
 502             = (h)->temp.tempint + (char *) (h)->chunk)                  \
 503    : (((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0)))
 504
 505 #endif /* not __GNUC__ or not __STDC__ */
 506
 507 #ifdef __cplusplus
 508 }       /* C++ */
 509 #endif
 510
 511 #endif /* obstack.h */