malloc/obstack.h

   1 /* obstack.h - object stack macros
   2    Copyright (C) 1988-1994,1996-1999,2003,2004,2005,2009,2011,2012
   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 accreting 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 /* Similiar 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   __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \
 139                 P, A)
 140
 141 #include <string.h>
 142
 143 struct _obstack_chunk           /* Lives at front of each chunk. */
 144 {
 145   char  *limit;                 /* 1 past end of this chunk */
 146   struct _obstack_chunk *prev;  /* address of prior chunk or NULL */
 147   char  contents[4];            /* objects begin here */
 148 };
 149
 150 struct obstack          /* control current object in current chunk */
 151 {
 152   long  chunk_size;             /* preferred size to allocate chunks in */
 153   struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
 154   char  *object_base;           /* address of object we are building */
 155   char  *next_free;             /* where to add next char to current object */
 156   char  *chunk_limit;           /* address of char after current chunk */
 157   union
 158   {
 159     PTR_INT_TYPE tempint;
 160     void *tempptr;
 161   } temp;                       /* Temporary for some macros.  */
 162   int   alignment_mask;         /* Mask of alignment for each object. */
 163   /* These prototypes vary based on `use_extra_arg', and we use
 164      casts to the prototypeless function type in all assignments,
 165      but having prototypes here quiets -Wstrict-prototypes.  */
 166   struct _obstack_chunk *(*chunkfun) (void *, long);
 167   void (*freefun) (void *, struct _obstack_chunk *);
 168   void *extra_arg;              /* first arg for chunk alloc/dealloc funcs */
 169   unsigned use_extra_arg:1;     /* chunk alloc/dealloc funcs take extra arg */
 170   unsigned maybe_empty_object:1;/* There is a possibility that the current
 171                                    chunk contains a zero-length object.  This
 172                                    prevents freeing the chunk if we allocate
 173                                    a bigger chunk to replace it. */
 174   unsigned alloc_failed:1;      /* No longer used, as we now call the failed
 175                                    handler on error, but retained for binary
 176                                    compatibility.  */
 177 };
 178
 179 /* Declare the external functions we use; they are in obstack.c.  */
 180
 181 extern void _obstack_newchunk (struct obstack *, int);
 182 extern int _obstack_begin (struct obstack *, int, int,
 183                             void *(*) (long), void (*) (void *));
 184 extern int _obstack_begin_1 (struct obstack *, int, int,
 185                              void *(*) (void *, long),
 186                              void (*) (void *, void *), void *);
 187 extern int _obstack_memory_used (struct obstack *);
 188
 189 void obstack_free (struct obstack *__obstack, void *__block);
 190
 191 \f
 192 /* Error handler called when `obstack_chunk_alloc' failed to allocate
 193    more memory.  This can be set to a user defined function which
 194    should either abort gracefully or use longjump - but shouldn't
 195    return.  The default action is to print a message and abort.  */
 196 extern void (*obstack_alloc_failed_handler) (void);
 197
 198 /* Exit value used when `print_and_abort' is used.  */
 199 extern int obstack_exit_failure;
 200 \f
 201 /* Pointer to beginning of object being allocated or to be allocated next.
 202    Note that this might not be the final address of the object
 203    because a new chunk might be needed to hold the final size.  */
 204
 205 #define obstack_base(h) ((void *) (h)->object_base)
 206
 207 /* Size for allocating ordinary chunks.  */
 208
 209 #define obstack_chunk_size(h) ((h)->chunk_size)
 210
 211 /* Pointer to next byte not yet allocated in current chunk.  */
 212
 213 #define obstack_next_free(h)    ((h)->next_free)
 214
 215 /* Mask specifying low bits that should be clear in address of an object.  */
 216
 217 #define obstack_alignment_mask(h) ((h)->alignment_mask)
 218
 219 /* To prevent prototype warnings provide complete argument list.  */
 220 #define obstack_init(h)                                         \
 221   _obstack_begin ((h), 0, 0,                                    \
 222                   (void *(*) (long)) obstack_chunk_alloc,       \
 223                   (void (*) (void *)) obstack_chunk_free)
 224
 225 #define obstack_begin(h, size)                                  \
 226   _obstack_begin ((h), (size), 0,                               \
 227                   (void *(*) (long)) obstack_chunk_alloc,       \
 228                   (void (*) (void *)) obstack_chunk_free)
 229
 230 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun)  \
 231   _obstack_begin ((h), (size), (alignment),                                \
 232                   (void *(*) (long)) (chunkfun),                           \
 233                   (void (*) (void *)) (freefun))
 234
 235 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
 236   _obstack_begin_1 ((h), (size), (alignment),                           \
 237                     (void *(*) (void *, long)) (chunkfun),              \
 238                     (void (*) (void *, void *)) (freefun), (arg))
 239
 240 #define obstack_chunkfun(h, newchunkfun) \
 241   ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
 242
 243 #define obstack_freefun(h, newfreefun) \
 244   ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
 245
 246 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
 247
 248 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
 249
 250 #define obstack_memory_used(h) _obstack_memory_used (h)
 251 \f
 252 #if defined __GNUC__
 253 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
 254    does not implement __extension__.  But that compiler doesn't define
 255    __GNUC_MINOR__.  */
 256 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
 257 #  define __extension__
 258 # endif
 259
 260 /* For GNU C, if not -traditional,
 261    we can define these macros to compute all args only once
 262    without using a global variable.
 263    Also, we can avoid using the `temp' slot, to make faster code.  */
 264
 265 # define obstack_object_size(OBSTACK)                                   \
 266   __extension__                                                         \
 267   ({ struct obstack const *__o = (OBSTACK);                             \
 268      (unsigned) (__o->next_free - __o->object_base); })
 269
 270 # define obstack_room(OBSTACK)                                          \
 271   __extension__                                                         \
 272   ({ struct obstack const *__o = (OBSTACK);                             \
 273      (unsigned) (__o->chunk_limit - __o->next_free); })
 274
 275 # define obstack_make_room(OBSTACK,length)                              \
 276 __extension__                                                           \
 277 ({ struct obstack *__o = (OBSTACK);                                     \
 278    int __len = (length);                                                \
 279    if (__o->chunk_limit - __o->next_free < __len)                       \
 280      _obstack_newchunk (__o, __len);                                    \
 281    (void) 0; })
 282
 283 # define obstack_empty_p(OBSTACK)                                       \
 284   __extension__                                                         \
 285   ({ struct obstack const *__o = (OBSTACK);                             \
 286      (__o->chunk->prev == 0                                             \
 287       && __o->next_free == __PTR_ALIGN ((char *) __o->chunk,            \
 288                                         __o->chunk->contents,           \
 289                                         __o->alignment_mask)); })
 290
 291 # define obstack_grow(OBSTACK,where,length)                             \
 292 __extension__                                                           \
 293 ({ struct obstack *__o = (OBSTACK);                                     \
 294    int __len = (length);                                                \
 295    if (__o->next_free + __len > __o->chunk_limit)                       \
 296      _obstack_newchunk (__o, __len);                                    \
 297    memcpy (__o->next_free, where, __len);                               \
 298    __o->next_free += __len;                                             \
 299    (void) 0; })
 300
 301 # define obstack_grow0(OBSTACK,where,length)                            \
 302 __extension__                                                           \
 303 ({ struct obstack *__o = (OBSTACK);                                     \
 304    int __len = (length);                                                \
 305    if (__o->next_free + __len + 1 > __o->chunk_limit)                   \
 306      _obstack_newchunk (__o, __len + 1);                                \
 307    memcpy (__o->next_free, where, __len);                               \
 308    __o->next_free += __len;                                             \
 309    *(__o->next_free)++ = 0;                                             \
 310    (void) 0; })
 311
 312 # define obstack_1grow(OBSTACK,datum)                                   \
 313 __extension__                                                           \
 314 ({ struct obstack *__o = (OBSTACK);                                     \
 315    if (__o->next_free + 1 > __o->chunk_limit)                           \
 316      _obstack_newchunk (__o, 1);                                        \
 317    obstack_1grow_fast (__o, datum);                                     \
 318    (void) 0; })
 319
 320 /* These assume that the obstack alignment is good enough for pointers
 321    or ints, and that the data added so far to the current object
 322    shares that much alignment.  */
 323
 324 # define obstack_ptr_grow(OBSTACK,datum)                                \
 325 __extension__                                                           \
 326 ({ struct obstack *__o = (OBSTACK);                                     \
 327    if (__o->next_free + sizeof (void *) > __o->chunk_limit)             \
 328      _obstack_newchunk (__o, sizeof (void *));                          \
 329    obstack_ptr_grow_fast (__o, datum); })                               \
 330
 331 # define obstack_int_grow(OBSTACK,datum)                                \
 332 __extension__                                                           \
 333 ({ struct obstack *__o = (OBSTACK);                                     \
 334    if (__o->next_free + sizeof (int) > __o->chunk_limit)                \
 335      _obstack_newchunk (__o, sizeof (int));                             \
 336    obstack_int_grow_fast (__o, datum); })
 337
 338 # define obstack_ptr_grow_fast(OBSTACK,aptr)                            \
 339 __extension__                                                           \
 340 ({ struct obstack *__o1 = (OBSTACK);                                    \
 341    *(const void **) __o1->next_free = (aptr);                           \
 342    __o1->next_free += sizeof (const void *);                            \
 343    (void) 0; })
 344
 345 # define obstack_int_grow_fast(OBSTACK,aint)                            \
 346 __extension__                                                           \
 347 ({ struct obstack *__o1 = (OBSTACK);                                    \
 348    *(int *) __o1->next_free = (aint);                                   \
 349    __o1->next_free += sizeof (int);                                     \
 350    (void) 0; })
 351
 352 # define obstack_blank(OBSTACK,length)                                  \
 353 __extension__                                                           \
 354 ({ struct obstack *__o = (OBSTACK);                                     \
 355    int __len = (length);                                                \
 356    if (__o->chunk_limit - __o->next_free < __len)                       \
 357      _obstack_newchunk (__o, __len);                                    \
 358    obstack_blank_fast (__o, __len);                                     \
 359    (void) 0; })
 360
 361 # define obstack_alloc(OBSTACK,length)                                  \
 362 __extension__                                                           \
 363 ({ struct obstack *__h = (OBSTACK);                                     \
 364    obstack_blank (__h, (length));                                       \
 365    obstack_finish (__h); })
 366
 367 # define obstack_copy(OBSTACK,where,length)                             \
 368 __extension__                                                           \
 369 ({ struct obstack *__h = (OBSTACK);                                     \
 370    obstack_grow (__h, (where), (length));                               \
 371    obstack_finish (__h); })
 372
 373 # define obstack_copy0(OBSTACK,where,length)                            \
 374 __extension__                                                           \
 375 ({ struct obstack *__h = (OBSTACK);                                     \
 376    obstack_grow0 (__h, (where), (length));                              \
 377    obstack_finish (__h); })
 378
 379 /* The local variable is named __o1 to avoid a name conflict
 380    when obstack_blank is called.  */
 381 # define obstack_finish(OBSTACK)                                        \
 382 __extension__                                                           \
 383 ({ struct obstack *__o1 = (OBSTACK);                                    \
 384    void *__value = (void *) __o1->object_base;                          \
 385    if (__o1->next_free == __value)                                      \
 386      __o1->maybe_empty_object = 1;                                      \
 387    __o1->next_free                                                      \
 388      = __PTR_ALIGN (__o1->object_base, __o1->next_free,                 \
 389                     __o1->alignment_mask);                              \
 390    if (__o1->next_free - (char *)__o1->chunk                            \
 391        > __o1->chunk_limit - (char *)__o1->chunk)                       \
 392      __o1->next_free = __o1->chunk_limit;                               \
 393    __o1->object_base = __o1->next_free;                                 \
 394    __value; })
 395
 396 # define obstack_free(OBSTACK, OBJ)                                     \
 397 __extension__                                                           \
 398 ({ struct obstack *__o = (OBSTACK);                                     \
 399    void *__obj = (OBJ);                                                 \
 400    if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit)  \
 401      __o->next_free = __o->object_base = (char *)__obj;                 \
 402    else (obstack_free) (__o, __obj); })
 403 \f
 404 #else /* not __GNUC__ */
 405
 406 # define obstack_object_size(h) \
 407  (unsigned) ((h)->next_free - (h)->object_base)
 408
 409 # define obstack_room(h)                \
 410  (unsigned) ((h)->chunk_limit - (h)->next_free)
 411
 412 # define obstack_empty_p(h) \
 413  ((h)->chunk->prev == 0                                                 \
 414   && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk,                \
 415                                     (h)->chunk->contents,               \
 416                                     (h)->alignment_mask))
 417
 418 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
 419    so that we can avoid having void expressions
 420    in the arms of the conditional expression.
 421    Casting the third operand to void was tried before,
 422    but some compilers won't accept it.  */
 423
 424 # define obstack_make_room(h,length)                                    \
 425 ( (h)->temp.tempint = (length),                                         \
 426   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)              \
 427    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
 428
 429 # define obstack_grow(h,where,length)                                   \
 430 ( (h)->temp.tempint = (length),                                         \
 431   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)              \
 432    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),              \
 433   memcpy ((h)->next_free, where, (h)->temp.tempint),                    \
 434   (h)->next_free += (h)->temp.tempint)
 435
 436 # define obstack_grow0(h,where,length)                                  \
 437 ( (h)->temp.tempint = (length),                                         \
 438   (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit)          \
 439    ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0),          \
 440   memcpy ((h)->next_free, where, (h)->temp.tempint),                    \
 441   (h)->next_free += (h)->temp.tempint,                                  \
 442   *((h)->next_free)++ = 0)
 443
 444 # define obstack_1grow(h,datum)                                         \
 445 ( (((h)->next_free + 1 > (h)->chunk_limit)                              \
 446    ? (_obstack_newchunk ((h), 1), 0) : 0),                              \
 447   obstack_1grow_fast (h, datum))
 448
 449 # define obstack_ptr_grow(h,datum)                                      \
 450 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit)                \
 451    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),                \
 452   obstack_ptr_grow_fast (h, datum))
 453
 454 # define obstack_int_grow(h,datum)                                      \
 455 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit)                   \
 456    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),                   \
 457   obstack_int_grow_fast (h, datum))
 458
 459 # define obstack_ptr_grow_fast(h,aptr)                                  \
 460   (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
 461
 462 # define obstack_int_grow_fast(h,aint)                                  \
 463   (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
 464
 465 # define obstack_blank(h,length)                                        \
 466 ( (h)->temp.tempint = (length),                                         \
 467   (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint)              \
 468    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),              \
 469   obstack_blank_fast (h, (h)->temp.tempint))
 470
 471 # define obstack_alloc(h,length)                                        \
 472  (obstack_blank ((h), (length)), obstack_finish ((h)))
 473
 474 # define obstack_copy(h,where,length)                                   \
 475  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
 476
 477 # define obstack_copy0(h,where,length)                                  \
 478  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
 479
 480 # define obstack_finish(h)                                              \
 481 ( ((h)->next_free == (h)->object_base                                   \
 482    ? (((h)->maybe_empty_object = 1), 0)                                 \
 483    : 0),                                                                \
 484   (h)->temp.tempptr = (h)->object_base,                                 \
 485   (h)->next_free                                                        \
 486     = __PTR_ALIGN ((h)->object_base, (h)->next_free,                    \
 487                    (h)->alignment_mask),                                \
 488   (((h)->next_free - (char *) (h)->chunk                                \
 489     > (h)->chunk_limit - (char *) (h)->chunk)                           \
 490    ? ((h)->next_free = (h)->chunk_limit) : 0),                          \
 491   (h)->object_base = (h)->next_free,                                    \
 492   (h)->temp.tempptr)
 493
 494 # define obstack_free(h,obj)                                            \
 495 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk,             \
 496   ((((h)->temp.tempint > 0                                              \
 497     && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk))     \
 498    ? (((h)->next_free = (h)->object_base                                \
 499        = (h)->temp.tempint + (char *) (h)->chunk), 0)                   \
 500    : ((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0)))
 501
 502 #endif /* not __GNUC__ */
 503
 504 #ifdef __cplusplus
 505 }       /* C++ */
 506 #endif
 507
 508 #endif /* obstack.h */