malloc/obstack.h

   1 /* obstack.h - object stack macros
   2    Copyright (C) 1988-1994,1996-1999,2003,2004,2005
   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 *obstack, void *block);
 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
 199 /* Exit value used when `print_and_abort' is used.  */
 200 extern int obstack_exit_failure;
 201 \f
 202 /* Pointer to beginning of object being allocated or to be allocated next.
 203    Note that this might not be the final address of the object
 204    because a new chunk might be needed to hold the final size.  */
 205
 206 #define obstack_base(h) ((void *) (h)->object_base)
 207
 208 /* Size for allocating ordinary chunks.  */
 209
 210 #define obstack_chunk_size(h) ((h)->chunk_size)
 211
 212 /* Pointer to next byte not yet allocated in current chunk.  */
 213
 214 #define obstack_next_free(h)    ((h)->next_free)
 215
 216 /* Mask specifying low bits that should be clear in address of an object.  */
 217
 218 #define obstack_alignment_mask(h) ((h)->alignment_mask)
 219
 220 /* To prevent prototype warnings provide complete argument list.  */
 221 #define obstack_init(h)                                         \
 222   _obstack_begin ((h), 0, 0,                                    \
 223                   (void *(*) (long)) obstack_chunk_alloc,       \
 224                   (void (*) (void *)) obstack_chunk_free)
 225
 226 #define obstack_begin(h, size)                                  \
 227   _obstack_begin ((h), (size), 0,                               \
 228                   (void *(*) (long)) obstack_chunk_alloc,       \
 229                   (void (*) (void *)) obstack_chunk_free)
 230
 231 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun)  \
 232   _obstack_begin ((h), (size), (alignment),                                \
 233                   (void *(*) (long)) (chunkfun),                           \
 234                   (void (*) (void *)) (freefun))
 235
 236 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
 237   _obstack_begin_1 ((h), (size), (alignment),                           \
 238                     (void *(*) (void *, long)) (chunkfun),              \
 239                     (void (*) (void *, void *)) (freefun), (arg))
 240
 241 #define obstack_chunkfun(h, newchunkfun) \
 242   ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
 243
 244 #define obstack_freefun(h, newfreefun) \
 245   ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
 246
 247 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
 248
 249 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
 250
 251 #define obstack_memory_used(h) _obstack_memory_used (h)
 252 \f
 253 #if defined __GNUC__ && defined __STDC__ && __STDC__
 254 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
 255    does not implement __extension__.  But that compiler doesn't define
 256    __GNUC_MINOR__.  */
 257 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
 258 #  define __extension__
 259 # endif
 260
 261 /* For GNU C, if not -traditional,
 262    we can define these macros to compute all args only once
 263    without using a global variable.
 264    Also, we can avoid using the `temp' slot, to make faster code.  */
 265
 266 # define obstack_object_size(OBSTACK)                                   \
 267   __extension__                                                         \
 268   ({ struct obstack const *__o = (OBSTACK);                             \
 269      (unsigned) (__o->next_free - __o->object_base); })
 270
 271 # define obstack_room(OBSTACK)                                          \
 272   __extension__                                                         \
 273   ({ struct obstack const *__o = (OBSTACK);                             \
 274      (unsigned) (__o->chunk_limit - __o->next_free); })
 275
 276 # define obstack_make_room(OBSTACK,length)                              \
 277 __extension__                                                           \
 278 ({ struct obstack *__o = (OBSTACK);                                     \
 279    int __len = (length);                                                \
 280    if (__o->chunk_limit - __o->next_free < __len)                       \
 281      _obstack_newchunk (__o, __len);                                    \
 282    (void) 0; })
 283
 284 # define obstack_empty_p(OBSTACK)                                       \
 285   __extension__                                                         \
 286   ({ struct obstack const *__o = (OBSTACK);                             \
 287      (__o->chunk->prev == 0                                             \
 288       && __o->next_free == __PTR_ALIGN ((char *) __o->chunk,            \
 289                                         __o->chunk->contents,           \
 290                                         __o->alignment_mask)); })
 291
 292 # define obstack_grow(OBSTACK,where,length)                             \
 293 __extension__                                                           \
 294 ({ struct obstack *__o = (OBSTACK);                                     \
 295    int __len = (length);                                                \
 296    if (__o->next_free + __len > __o->chunk_limit)                       \
 297      _obstack_newchunk (__o, __len);                                    \
 298    memcpy (__o->next_free, where, __len);                               \
 299    __o->next_free += __len;                                             \
 300    (void) 0; })
 301
 302 # define obstack_grow0(OBSTACK,where,length)                            \
 303 __extension__                                                           \
 304 ({ struct obstack *__o = (OBSTACK);                                     \
 305    int __len = (length);                                                \
 306    if (__o->next_free + __len + 1 > __o->chunk_limit)                   \
 307      _obstack_newchunk (__o, __len + 1);                                \
 308    memcpy (__o->next_free, where, __len);                               \
 309    __o->next_free += __len;                                             \
 310    *(__o->next_free)++ = 0;                                             \
 311    (void) 0; })
 312
 313 # define obstack_1grow(OBSTACK,datum)                                   \
 314 __extension__                                                           \
 315 ({ struct obstack *__o = (OBSTACK);                                     \
 316    if (__o->next_free + 1 > __o->chunk_limit)                           \
 317      _obstack_newchunk (__o, 1);                                        \
 318    obstack_1grow_fast (__o, datum);                                     \
 319    (void) 0; })
 320
 321 /* These assume that the obstack alignment is good enough for pointers
 322    or ints, and that the data added so far to the current object
 323    shares that much alignment.  */
 324
 325 # define obstack_ptr_grow(OBSTACK,datum)                                \
 326 __extension__                                                           \
 327 ({ struct obstack *__o = (OBSTACK);                                     \
 328    if (__o->next_free + sizeof (void *) > __o->chunk_limit)             \
 329      _obstack_newchunk (__o, sizeof (void *));                          \
 330    obstack_ptr_grow_fast (__o, datum); })                               \
 331
 332 # define obstack_int_grow(OBSTACK,datum)                                \
 333 __extension__                                                           \
 334 ({ struct obstack *__o = (OBSTACK);                                     \
 335    if (__o->next_free + sizeof (int) > __o->chunk_limit)                \
 336      _obstack_newchunk (__o, sizeof (int));                             \
 337    obstack_int_grow_fast (__o, datum); })
 338
 339 # define obstack_ptr_grow_fast(OBSTACK,aptr)                            \
 340 __extension__                                                           \
 341 ({ struct obstack *__o1 = (OBSTACK);                                    \
 342    *(const void **) __o1->next_free = (aptr);                           \
 343    __o1->next_free += sizeof (const void *);                            \
 344    (void) 0; })
 345
 346 # define obstack_int_grow_fast(OBSTACK,aint)                            \
 347 __extension__                                                           \
 348 ({ struct obstack *__o1 = (OBSTACK);                                    \
 349    *(int *) __o1->next_free = (aint);                                   \
 350    __o1->next_free += sizeof (int);                                     \
 351    (void) 0; })
 352
 353 # define obstack_blank(OBSTACK,length)                                  \
 354 __extension__                                                           \
 355 ({ struct obstack *__o = (OBSTACK);                                     \
 356    int __len = (length);                                                \
 357    if (__o->chunk_limit - __o->next_free < __len)                       \
 358      _obstack_newchunk (__o, __len);                                    \
 359    obstack_blank_fast (__o, __len);                                     \
 360    (void) 0; })
 361
 362 # define obstack_alloc(OBSTACK,length)                                  \
 363 __extension__                                                           \
 364 ({ struct obstack *__h = (OBSTACK);                                     \
 365    obstack_blank (__h, (length));                                       \
 366    obstack_finish (__h); })
 367
 368 # define obstack_copy(OBSTACK,where,length)                             \
 369 __extension__                                                           \
 370 ({ struct obstack *__h = (OBSTACK);                                     \
 371    obstack_grow (__h, (where), (length));                               \
 372    obstack_finish (__h); })
 373
 374 # define obstack_copy0(OBSTACK,where,length)                            \
 375 __extension__                                                           \
 376 ({ struct obstack *__h = (OBSTACK);                                     \
 377    obstack_grow0 (__h, (where), (length));                              \
 378    obstack_finish (__h); })
 379
 380 /* The local variable is named __o1 to avoid a name conflict
 381    when obstack_blank is called.  */
 382 # define obstack_finish(OBSTACK)                                        \
 383 __extension__                                                           \
 384 ({ struct obstack *__o1 = (OBSTACK);                                    \
 385    void *__value = (void *) __o1->object_base;                          \
 386    if (__o1->next_free == __value)                                      \
 387      __o1->maybe_empty_object = 1;                                      \
 388    __o1->next_free                                                      \
 389      = __PTR_ALIGN (__o1->object_base, __o1->next_free,                 \
 390                     __o1->alignment_mask);                              \
 391    if (__o1->next_free - (char *)__o1->chunk                            \
 392        > __o1->chunk_limit - (char *)__o1->chunk)                       \
 393      __o1->next_free = __o1->chunk_limit;                               \
 394    __o1->object_base = __o1->next_free;                                 \
 395    __value; })
 396
 397 # define obstack_free(OBSTACK, OBJ)                                     \
 398 __extension__                                                           \
 399 ({ struct obstack *__o = (OBSTACK);                                     \
 400    void *__obj = (OBJ);                                                 \
 401    if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit)  \
 402      __o->next_free = __o->object_base = (char *)__obj;                 \
 403    else (obstack_free) (__o, __obj); })
 404 \f
 405 #else /* not __GNUC__ or not __STDC__ */
 406
 407 # define obstack_object_size(h) \
 408  (unsigned) ((h)->next_free - (h)->object_base)
 409
 410 # define obstack_room(h)                \
 411  (unsigned) ((h)->chunk_limit - (h)->next_free)
 412
 413 # define obstack_empty_p(h) \
 414  ((h)->chunk->prev == 0                                                 \
 415   && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk,                \
 416                                     (h)->chunk->contents,               \
 417                                     (h)->alignment_mask))
 418
 419 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
 420    so that we can avoid having void expressions
 421    in the arms of the conditional expression.
 422    Casting the third operand to void was tried before,
 423    but some compilers won't accept it.  */
 424
 425 # define obstack_make_room(h,length)                                    \
 426 ( (h)->temp.tempint = (length),                                         \
 427   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)              \
 428    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
 429
 430 # define obstack_grow(h,where,length)                                   \
 431 ( (h)->temp.tempint = (length),                                         \
 432   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)              \
 433    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),              \
 434   memcpy ((h)->next_free, where, (h)->temp.tempint),                    \
 435   (h)->next_free += (h)->temp.tempint)
 436
 437 # define obstack_grow0(h,where,length)                                  \
 438 ( (h)->temp.tempint = (length),                                         \
 439   (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit)          \
 440    ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0),          \
 441   memcpy ((h)->next_free, where, (h)->temp.tempint),                    \
 442   (h)->next_free += (h)->temp.tempint,                                  \
 443   *((h)->next_free)++ = 0)
 444
 445 # define obstack_1grow(h,datum)                                         \
 446 ( (((h)->next_free + 1 > (h)->chunk_limit)                              \
 447    ? (_obstack_newchunk ((h), 1), 0) : 0),                              \
 448   obstack_1grow_fast (h, datum))
 449
 450 # define obstack_ptr_grow(h,datum)                                      \
 451 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit)                \
 452    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),                \
 453   obstack_ptr_grow_fast (h, datum))
 454
 455 # define obstack_int_grow(h,datum)                                      \
 456 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit)                   \
 457    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),                   \
 458   obstack_int_grow_fast (h, datum))
 459
 460 # define obstack_ptr_grow_fast(h,aptr)                                  \
 461   (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
 462
 463 # define obstack_int_grow_fast(h,aint)                                  \
 464   (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
 465
 466 # define obstack_blank(h,length)                                        \
 467 ( (h)->temp.tempint = (length),                                         \
 468   (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint)              \
 469    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),              \
 470   obstack_blank_fast (h, (h)->temp.tempint))
 471
 472 # define obstack_alloc(h,length)                                        \
 473  (obstack_blank ((h), (length)), obstack_finish ((h)))
 474
 475 # define obstack_copy(h,where,length)                                   \
 476  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
 477
 478 # define obstack_copy0(h,where,length)                                  \
 479  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
 480
 481 # define obstack_finish(h)                                              \
 482 ( ((h)->next_free == (h)->object_base                                   \
 483    ? (((h)->maybe_empty_object = 1), 0)                                 \
 484    : 0),                                                                \
 485   (h)->temp.tempptr = (h)->object_base,                                 \
 486   (h)->next_free                                                        \
 487     = __PTR_ALIGN ((h)->object_base, (h)->next_free,                    \
 488                    (h)->alignment_mask),                                \
 489   (((h)->next_free - (char *) (h)->chunk                                \
 490     > (h)->chunk_limit - (char *) (h)->chunk)                           \
 491    ? ((h)->next_free = (h)->chunk_limit) : 0),                          \
 492   (h)->object_base = (h)->next_free,                                    \
 493   (h)->temp.tempptr)
 494
 495 # define obstack_free(h,obj)                                            \
 496 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk,             \
 497   ((((h)->temp.tempint > 0                                              \
 498     && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk))     \
 499    ? (int) ((h)->next_free = (h)->object_base                           \
 500             = (h)->temp.tempint + (char *) (h)->chunk)                  \
 501    : (((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0)))
 502
 503 #endif /* not __GNUC__ or not __STDC__ */
 504
 505 #ifdef __cplusplus
 506 }       /* C++ */
 507 #endif
 508
 509 #endif /* obstack.h */