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, write to the Free
  18    Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  19    Boston, MA 02110-1301, USA.  */
  20
  21 /* Summary:
  22
  23 All the apparent functions defined here are macros. The idea
  24 is that you would use these pre-tested macros to solve a
  25 very specific set of problems, and they would run fast.
  26 Caution: no side-effects in arguments please!! They may be
  27 evaluated MANY times!!
  28
  29 These macros operate a stack of objects.  Each object starts life
  30 small, and may grow to maturity.  (Consider building a word syllable
  31 by syllable.)  An object can move while it is growing.  Once it has
  32 been "finished" it never changes address again.  So the "top of the
  33 stack" is typically an immature growing object, while the rest of the
  34 stack is of mature, fixed size and fixed address objects.
  35
  36 These routines grab large chunks of memory, using a function you
  37 supply, called `obstack_chunk_alloc'.  On occasion, they free chunks,
  38 by calling `obstack_chunk_free'.  You must define them and declare
  39 them before using any obstack macros.
  40
  41 Each independent stack is represented by a `struct obstack'.
  42 Each of the obstack macros expects a pointer to such a structure
  43 as the first argument.
  44
  45 One motivation for this package is the problem of growing char strings
  46 in symbol tables.  Unless you are "fascist pig with a read-only mind"
  47 --Gosper's immortal quote from HAKMEM item 154, out of context--you
  48 would not like to put any arbitrary upper limit on the length of your
  49 symbols.
  50
  51 In practice this often means you will build many short symbols and a
  52 few long symbols.  At the time you are reading a symbol you don't know
  53 how long it is.  One traditional method is to read a symbol into a
  54 buffer, realloc()ating the buffer every time you try to read a symbol
  55 that is longer than the buffer.  This is beaut, but you still will
  56 want to copy the symbol from the buffer to a more permanent
  57 symbol-table entry say about half the time.
  58
  59 With obstacks, you can work differently.  Use one obstack for all symbol
  60 names.  As you read a symbol, grow the name in the obstack gradually.
  61 When the name is complete, finalize it.  Then, if the symbol exists already,
  62 free the newly read name.
  63
  64 The way we do this is to take a large chunk, allocating memory from
  65 low addresses.  When you want to build a symbol in the chunk you just
  66 add chars above the current "high water mark" in the chunk.  When you
  67 have finished adding chars, because you got to the end of the symbol,
  68 you know how long the chars are, and you can create a new object.
  69 Mostly the chars will not burst over the highest address of the chunk,
  70 because you would typically expect a chunk to be (say) 100 times as
  71 long as an average object.
  72
  73 In case that isn't clear, when we have enough chars to make up
  74 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
  75 so we just point to it where it lies.  No moving of chars is
  76 needed and this is the second win: potentially long strings need
  77 never be explicitly shuffled. Once an object is formed, it does not
  78 change its address during its lifetime.
  79
  80 When the chars burst over a chunk boundary, we allocate a larger
  81 chunk, and then copy the partly formed object from the end of the old
  82 chunk to the beginning of the new larger chunk.  We then carry on
  83 accreting characters to the end of the object as we normally would.
  84
  85 A special macro is provided to add a single char at a time to a
  86 growing object.  This allows the use of register variables, which
  87 break the ordinary 'growth' macro.
  88
  89 Summary:
  90         We allocate large chunks.
  91         We carve out one object at a time from the current chunk.
  92         Once carved, an object never moves.
  93         We are free to append data of any size to the currently
  94           growing object.
  95         Exactly one object is growing in an obstack at any one time.
  96         You can run one obstack per control block.
  97         You may have as many control blocks as you dare.
  98         Because of the way we do it, you can `unwind' an obstack
  99           back to a previous state. (You may remove objects much
 100           as you would with a stack.)
 101 */
 102
 103
 104 /* Don't do the contents of this file more than once.  */
 105
 106 #ifndef _OBSTACK_H
 107 #define _OBSTACK_H 1
 108
 109 #ifdef __cplusplus
 110 extern "C" {
 111 #endif
 112 \f
 113 /* We need the type of a pointer subtraction.  If __PTRDIFF_TYPE__ is
 114    defined, as with GNU C, use that; that way we don't pollute the
 115    namespace with <stddef.h>'s symbols.  Otherwise, include <stddef.h>
 116    and use ptrdiff_t.  */
 117
 118 #ifdef __PTRDIFF_TYPE__
 119 # define PTR_INT_TYPE __PTRDIFF_TYPE__
 120 #else
 121 # include <stddef.h>
 122 # define PTR_INT_TYPE ptrdiff_t
 123 #endif
 124
 125 /* If B is the base of an object addressed by P, return the result of
 126    aligning P to the next multiple of A + 1.  B and P must be of type
 127    char *.  A + 1 must be a power of 2.  */
 128
 129 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A)))
 130
 131 /* Similiar to _BPTR_ALIGN (B, P, A), except optimize the common case
 132    where pointers can be converted to integers, aligned as integers,
 133    and converted back again.  If PTR_INT_TYPE is narrower than a
 134    pointer (e.g., the AS/400), play it safe and compute the alignment
 135    relative to B.  Otherwise, use the faster strategy of computing the
 136    alignment relative to 0.  */
 137
 138 #define __PTR_ALIGN(B, P, A)                                                \
 139   __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \
 140                 P, A)
 141
 142 #include <string.h>
 143
 144 struct _obstack_chunk           /* Lives at front of each chunk. */
 145 {
 146   char  *limit;                 /* 1 past end of this chunk */
 147   struct _obstack_chunk *prev;  /* address of prior chunk or NULL */
 148   char  contents[4];            /* objects begin here */
 149 };
 150
 151 struct obstack          /* control current object in current chunk */
 152 {
 153   long  chunk_size;             /* preferred size to allocate chunks in */
 154   struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
 155   char  *object_base;           /* address of object we are building */
 156   char  *next_free;             /* where to add next char to current object */
 157   char  *chunk_limit;           /* address of char after current chunk */
 158   union
 159   {
 160     PTR_INT_TYPE tempint;
 161     void *tempptr;
 162   } temp;                       /* Temporary for some macros.  */
 163   int   alignment_mask;         /* Mask of alignment for each object. */
 164   /* These prototypes vary based on `use_extra_arg', and we use
 165      casts to the prototypeless function type in all assignments,
 166      but having prototypes here quiets -Wstrict-prototypes.  */
 167   struct _obstack_chunk *(*chunkfun) (void *, long);
 168   void (*freefun) (void *, struct _obstack_chunk *);
 169   void *extra_arg;              /* first arg for chunk alloc/dealloc funcs */
 170   unsigned use_extra_arg:1;     /* chunk alloc/dealloc funcs take extra arg */
 171   unsigned maybe_empty_object:1;/* There is a possibility that the current
 172                                    chunk contains a zero-length object.  This
 173                                    prevents freeing the chunk if we allocate
 174                                    a bigger chunk to replace it. */
 175   unsigned alloc_failed:1;      /* No longer used, as we now call the failed
 176                                    handler on error, but retained for binary
 177                                    compatibility.  */
 178 };
 179
 180 /* Declare the external functions we use; they are in obstack.c.  */
 181
 182 extern void _obstack_newchunk (struct obstack *, int);
 183 extern int _obstack_begin (struct obstack *, int, int,
 184                             void *(*) (long), void (*) (void *));
 185 extern int _obstack_begin_1 (struct obstack *, int, int,
 186                              void *(*) (void *, long),
 187                              void (*) (void *, void *), void *);
 188 extern int _obstack_memory_used (struct obstack *);
 189
 190 void obstack_free (struct obstack *, void *);
 191
 192 \f
 193 /* Error handler called when `obstack_chunk_alloc' failed to allocate
 194    more memory.  This can be set to a user defined function which
 195    should either abort gracefully or use longjump - but shouldn't
 196    return.  The default action is to print a message and abort.  */
 197 extern void (*obstack_alloc_failed_handler) (void);
 198 \f
 199 /* Pointer to beginning of object being allocated or to be allocated next.
 200    Note that this might not be the final address of the object
 201    because a new chunk might be needed to hold the final size.  */
 202
 203 #define obstack_base(h) ((void *) (h)->object_base)
 204
 205 /* Size for allocating ordinary chunks.  */
 206
 207 #define obstack_chunk_size(h) ((h)->chunk_size)
 208
 209 /* Pointer to next byte not yet allocated in current chunk.  */
 210
 211 #define obstack_next_free(h)    ((h)->next_free)
 212
 213 /* Mask specifying low bits that should be clear in address of an object.  */
 214
 215 #define obstack_alignment_mask(h) ((h)->alignment_mask)
 216
 217 /* To prevent prototype warnings provide complete argument list.  */
 218 #define obstack_init(h)                                         \
 219   _obstack_begin ((h), 0, 0,                                    \
 220                   (void *(*) (long)) obstack_chunk_alloc,       \
 221                   (void (*) (void *)) obstack_chunk_free)
 222
 223 #define obstack_begin(h, size)                                  \
 224   _obstack_begin ((h), (size), 0,                               \
 225                   (void *(*) (long)) obstack_chunk_alloc,       \
 226                   (void (*) (void *)) obstack_chunk_free)
 227
 228 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun)  \
 229   _obstack_begin ((h), (size), (alignment),                                \
 230                   (void *(*) (long)) (chunkfun),                           \
 231                   (void (*) (void *)) (freefun))
 232
 233 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
 234   _obstack_begin_1 ((h), (size), (alignment),                           \
 235                     (void *(*) (void *, long)) (chunkfun),              \
 236                     (void (*) (void *, void *)) (freefun), (arg))
 237
 238 #define obstack_chunkfun(h, newchunkfun) \
 239   ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
 240
 241 #define obstack_freefun(h, newfreefun) \
 242   ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
 243
 244 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
 245
 246 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
 247
 248 #define obstack_memory_used(h) _obstack_memory_used (h)
 249 \f
 250 #if defined __GNUC__ && defined __STDC__ && __STDC__
 251 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
 252    does not implement __extension__.  But that compiler doesn't define
 253    __GNUC_MINOR__.  */
 254 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
 255 #  define __extension__
 256 # endif
 257
 258 /* For GNU C, if not -traditional,
 259    we can define these macros to compute all args only once
 260    without using a global variable.
 261    Also, we can avoid using the `temp' slot, to make faster code.  */
 262
 263 # define obstack_object_size(OBSTACK)                                   \
 264   __extension__                                                         \
 265   ({ struct obstack const *__o = (OBSTACK);                             \
 266      (unsigned) (__o->next_free - __o->object_base); })
 267
 268 # define obstack_room(OBSTACK)                                          \
 269   __extension__                                                         \
 270   ({ struct obstack const *__o = (OBSTACK);                             \
 271      (unsigned) (__o->chunk_limit - __o->next_free); })
 272
 273 # define obstack_make_room(OBSTACK,length)                              \
 274 __extension__                                                           \
 275 ({ struct obstack *__o = (OBSTACK);                                     \
 276    int __len = (length);                                                \
 277    if (__o->chunk_limit - __o->next_free < __len)                       \
 278      _obstack_newchunk (__o, __len);                                    \
 279    (void) 0; })
 280
 281 # define obstack_empty_p(OBSTACK)                                       \
 282   __extension__                                                         \
 283   ({ struct obstack const *__o = (OBSTACK);                             \
 284      (__o->chunk->prev == 0                                             \
 285       && __o->next_free == __PTR_ALIGN ((char *) __o->chunk,            \
 286                                         __o->chunk->contents,           \
 287                                         __o->alignment_mask)); })
 288
 289 # define obstack_grow(OBSTACK,where,length)                             \
 290 __extension__                                                           \
 291 ({ struct obstack *__o = (OBSTACK);                                     \
 292    int __len = (length);                                                \
 293    if (__o->next_free + __len > __o->chunk_limit)                       \
 294      _obstack_newchunk (__o, __len);                                    \
 295    memcpy (__o->next_free, where, __len);                               \
 296    __o->next_free += __len;                                             \
 297    (void) 0; })
 298
 299 # define obstack_grow0(OBSTACK,where,length)                            \
 300 __extension__                                                           \
 301 ({ struct obstack *__o = (OBSTACK);                                     \
 302    int __len = (length);                                                \
 303    if (__o->next_free + __len + 1 > __o->chunk_limit)                   \
 304      _obstack_newchunk (__o, __len + 1);                                \
 305    memcpy (__o->next_free, where, __len);                               \
 306    __o->next_free += __len;                                             \
 307    *(__o->next_free)++ = 0;                                             \
 308    (void) 0; })
 309
 310 # define obstack_1grow(OBSTACK,datum)                                   \
 311 __extension__                                                           \
 312 ({ struct obstack *__o = (OBSTACK);                                     \
 313    if (__o->next_free + 1 > __o->chunk_limit)                           \
 314      _obstack_newchunk (__o, 1);                                        \
 315    obstack_1grow_fast (__o, datum);                                     \
 316    (void) 0; })
 317
 318 /* These assume that the obstack alignment is good enough for pointers
 319    or ints, and that the data added so far to the current object
 320    shares that much alignment.  */
 321
 322 # define obstack_ptr_grow(OBSTACK,datum)                                \
 323 __extension__                                                           \
 324 ({ struct obstack *__o = (OBSTACK);                                     \
 325    if (__o->next_free + sizeof (void *) > __o->chunk_limit)             \
 326      _obstack_newchunk (__o, sizeof (void *));                          \
 327    obstack_ptr_grow_fast (__o, datum); })                               \
 328
 329 # define obstack_int_grow(OBSTACK,datum)                                \
 330 __extension__                                                           \
 331 ({ struct obstack *__o = (OBSTACK);                                     \
 332    if (__o->next_free + sizeof (int) > __o->chunk_limit)                \
 333      _obstack_newchunk (__o, sizeof (int));                             \
 334    obstack_int_grow_fast (__o, datum); })
 335
 336 # define obstack_ptr_grow_fast(OBSTACK,aptr)                            \
 337 __extension__                                                           \
 338 ({ struct obstack *__o1 = (OBSTACK);                                    \
 339    *(const void **) __o1->next_free = (aptr);                           \
 340    __o1->next_free += sizeof (const void *);                            \
 341    (void) 0; })
 342
 343 # define obstack_int_grow_fast(OBSTACK,aint)                            \
 344 __extension__                                                           \
 345 ({ struct obstack *__o1 = (OBSTACK);                                    \
 346    *(int *) __o1->next_free = (aint);                                   \
 347    __o1->next_free += sizeof (int);                                     \
 348    (void) 0; })
 349
 350 # define obstack_blank(OBSTACK,length)                                  \
 351 __extension__                                                           \
 352 ({ struct obstack *__o = (OBSTACK);                                     \
 353    int __len = (length);                                                \
 354    if (__o->chunk_limit - __o->next_free < __len)                       \
 355      _obstack_newchunk (__o, __len);                                    \
 356    obstack_blank_fast (__o, __len);                                     \
 357    (void) 0; })
 358
 359 # define obstack_alloc(OBSTACK,length)                                  \
 360 __extension__                                                           \
 361 ({ struct obstack *__h = (OBSTACK);                                     \
 362    obstack_blank (__h, (length));                                       \
 363    obstack_finish (__h); })
 364
 365 # define obstack_copy(OBSTACK,where,length)                             \
 366 __extension__                                                           \
 367 ({ struct obstack *__h = (OBSTACK);                                     \
 368    obstack_grow (__h, (where), (length));                               \
 369    obstack_finish (__h); })
 370
 371 # define obstack_copy0(OBSTACK,where,length)                            \
 372 __extension__                                                           \
 373 ({ struct obstack *__h = (OBSTACK);                                     \
 374    obstack_grow0 (__h, (where), (length));                              \
 375    obstack_finish (__h); })
 376
 377 /* The local variable is named __o1 to avoid a name conflict
 378    when obstack_blank is called.  */
 379 # define obstack_finish(OBSTACK)                                        \
 380 __extension__                                                           \
 381 ({ struct obstack *__o1 = (OBSTACK);                                    \
 382    void *__value = (void *) __o1->object_base;                          \
 383    if (__o1->next_free == __value)                                      \
 384      __o1->maybe_empty_object = 1;                                      \
 385    __o1->next_free                                                      \
 386      = __PTR_ALIGN (__o1->object_base, __o1->next_free,                 \
 387                     __o1->alignment_mask);                              \
 388    if (__o1->next_free - (char *)__o1->chunk                            \
 389        > __o1->chunk_limit - (char *)__o1->chunk)                       \
 390      __o1->next_free = __o1->chunk_limit;                               \
 391    __o1->object_base = __o1->next_free;                                 \
 392    __value; })
 393
 394 # define obstack_free(OBSTACK, OBJ)                                     \
 395 __extension__                                                           \
 396 ({ struct obstack *__o = (OBSTACK);                                     \
 397    void *__obj = (OBJ);                                                 \
 398    if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit)  \
 399      __o->next_free = __o->object_base = (char *)__obj;                 \
 400    else (obstack_free) (__o, __obj); })
 401 \f
 402 #else /* not __GNUC__ or not __STDC__ */
 403
 404 # define obstack_object_size(h) \
 405  (unsigned) ((h)->next_free - (h)->object_base)
 406
 407 # define obstack_room(h)                \
 408  (unsigned) ((h)->chunk_limit - (h)->next_free)
 409
 410 # define obstack_empty_p(h) \
 411  ((h)->chunk->prev == 0                                                 \
 412   && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk,                \
 413                                     (h)->chunk->contents,               \
 414                                     (h)->alignment_mask))
 415
 416 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
 417    so that we can avoid having void expressions
 418    in the arms of the conditional expression.
 419    Casting the third operand to void was tried before,
 420    but some compilers won't accept it.  */
 421
 422 # define obstack_make_room(h,length)                                    \
 423 ( (h)->temp.tempint = (length),                                         \
 424   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)              \
 425    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
 426
 427 # define obstack_grow(h,where,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   memcpy ((h)->next_free, where, (h)->temp.tempint),                    \
 432   (h)->next_free += (h)->temp.tempint)
 433
 434 # define obstack_grow0(h,where,length)                                  \
 435 ( (h)->temp.tempint = (length),                                         \
 436   (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit)          \
 437    ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0),          \
 438   memcpy ((h)->next_free, where, (h)->temp.tempint),                    \
 439   (h)->next_free += (h)->temp.tempint,                                  \
 440   *((h)->next_free)++ = 0)
 441
 442 # define obstack_1grow(h,datum)                                         \
 443 ( (((h)->next_free + 1 > (h)->chunk_limit)                              \
 444    ? (_obstack_newchunk ((h), 1), 0) : 0),                              \
 445   obstack_1grow_fast (h, datum))
 446
 447 # define obstack_ptr_grow(h,datum)                                      \
 448 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit)                \
 449    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),                \
 450   obstack_ptr_grow_fast (h, datum))
 451
 452 # define obstack_int_grow(h,datum)                                      \
 453 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit)                   \
 454    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),                   \
 455   obstack_int_grow_fast (h, datum))
 456
 457 # define obstack_ptr_grow_fast(h,aptr)                                  \
 458   (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
 459
 460 # define obstack_int_grow_fast(h,aint)                                  \
 461   (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
 462
 463 # define obstack_blank(h,length)                                        \
 464 ( (h)->temp.tempint = (length),                                         \
 465   (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint)              \
 466    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),              \
 467   obstack_blank_fast (h, (h)->temp.tempint))
 468
 469 # define obstack_alloc(h,length)                                        \
 470  (obstack_blank ((h), (length)), obstack_finish ((h)))
 471
 472 # define obstack_copy(h,where,length)                                   \
 473  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
 474
 475 # define obstack_copy0(h,where,length)                                  \
 476  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
 477
 478 # define obstack_finish(h)                                              \
 479 ( ((h)->next_free == (h)->object_base                                   \
 480    ? (((h)->maybe_empty_object = 1), 0)                                 \
 481    : 0),                                                                \
 482   (h)->temp.tempptr = (h)->object_base,                                 \
 483   (h)->next_free                                                        \
 484     = __PTR_ALIGN ((h)->object_base, (h)->next_free,                    \
 485                    (h)->alignment_mask),                                \
 486   (((h)->next_free - (char *) (h)->chunk                                \
 487     > (h)->chunk_limit - (char *) (h)->chunk)                           \
 488    ? ((h)->next_free = (h)->chunk_limit) : 0),                          \
 489   (h)->object_base = (h)->next_free,                                    \
 490   (h)->temp.tempptr)
 491
 492 # define obstack_free(h,obj)                                            \
 493 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk,             \
 494   ((((h)->temp.tempint > 0                                              \
 495     && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk))     \
 496    ? (int) ((h)->next_free = (h)->object_base                           \
 497             = (h)->temp.tempint + (char *) (h)->chunk)                  \
 498    : (((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0)))
 499
 500 #endif /* not __GNUC__ or not __STDC__ */
 501
 502 #ifdef __cplusplus
 503 }       /* C++ */
 504 #endif
 505
 506 #endif /* obstack.h */