malloc/obstack.h

   1 /* obstack.h - object stack macros
   2    Copyright (C) 1988-1994,1996-1999,2003,2004 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.  Its master source is NOT part of
   4    the C library, however.  The master source lives in /gd/gnu/lib.
   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., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 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 use subtraction of (char *) 0 instead of casting to int
 114    because on word-addressable machines a simple cast to int
 115    may ignore the byte-within-word field of the pointer.  */
 116
 117 #ifndef __PTR_TO_INT
 118 # define __PTR_TO_INT(P) ((P) - (char *) 0)
 119 #endif
 120
 121 #ifndef __INT_TO_PTR
 122 # define __INT_TO_PTR(P) ((P) + (char *) 0)
 123 #endif
 124
 125 /* We need the type of the resulting object.  If __PTRDIFF_TYPE__ is
 126    defined, as with GNU C, use that; that way we don't pollute the
 127    namespace with <stddef.h>'s symbols.  Otherwise, include <stddef.h>
 128    and use ptrdiff_t.  */
 129
 130 #ifdef __PTRDIFF_TYPE__
 131 # define PTR_INT_TYPE __PTRDIFF_TYPE__
 132 #else
 133 # include <stddef.h>
 134 # define PTR_INT_TYPE ptrdiff_t
 135 #endif
 136
 137 #include <string.h>
 138
 139 struct _obstack_chunk           /* Lives at front of each chunk. */
 140 {
 141   char  *limit;                 /* 1 past end of this chunk */
 142   struct _obstack_chunk *prev;  /* address of prior chunk or NULL */
 143   char  contents[4];            /* objects begin here */
 144 };
 145
 146 struct obstack          /* control current object in current chunk */
 147 {
 148   long  chunk_size;             /* preferred size to allocate chunks in */
 149   struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
 150   char  *object_base;           /* address of object we are building */
 151   char  *next_free;             /* where to add next char to current object */
 152   char  *chunk_limit;           /* address of char after current chunk */
 153   PTR_INT_TYPE temp;            /* Temporary for some macros.  */
 154   int   alignment_mask;         /* Mask of alignment for each object. */
 155   /* These prototypes vary based on `use_extra_arg', and we use
 156      casts to the prototypeless function type in all assignments,
 157      but having prototypes here quiets -Wstrict-prototypes.  */
 158   struct _obstack_chunk *(*chunkfun) (void *, long);
 159   void (*freefun) (void *, struct _obstack_chunk *);
 160   void *extra_arg;              /* first arg for chunk alloc/dealloc funcs */
 161   unsigned use_extra_arg:1;     /* chunk alloc/dealloc funcs take extra arg */
 162   unsigned maybe_empty_object:1;/* There is a possibility that the current
 163                                    chunk contains a zero-length object.  This
 164                                    prevents freeing the chunk if we allocate
 165                                    a bigger chunk to replace it. */
 166   unsigned alloc_failed:1;      /* No longer used, as we now call the failed
 167                                    handler on error, but retained for binary
 168                                    compatibility.  */
 169 };
 170
 171 /* Declare the external functions we use; they are in obstack.c.  */
 172
 173 extern void _obstack_newchunk (struct obstack *, int);
 174 extern int _obstack_begin (struct obstack *, int, int,
 175                             void *(*) (long), void (*) (void *));
 176 extern int _obstack_begin_1 (struct obstack *, int, int,
 177                              void *(*) (void *, long),
 178                              void (*) (void *, void *), void *);
 179 extern int _obstack_memory_used (struct obstack *);
 180
 181 void obstack_free (struct obstack *obstack, void *block);
 182
 183 \f
 184 /* Error handler called when `obstack_chunk_alloc' failed to allocate
 185    more memory.  This can be set to a user defined function which
 186    should either abort gracefully or use longjump - but shouldn't
 187    return.  The default action is to print a message and abort.  */
 188 extern void (*obstack_alloc_failed_handler) (void);
 189
 190 /* Exit value used when `print_and_abort' is used.  */
 191 extern int obstack_exit_failure;
 192 \f
 193 /* Pointer to beginning of object being allocated or to be allocated next.
 194    Note that this might not be the final address of the object
 195    because a new chunk might be needed to hold the final size.  */
 196
 197 #define obstack_base(h) ((void *) (h)->object_base)
 198
 199 /* Size for allocating ordinary chunks.  */
 200
 201 #define obstack_chunk_size(h) ((h)->chunk_size)
 202
 203 /* Pointer to next byte not yet allocated in current chunk.  */
 204
 205 #define obstack_next_free(h)    ((h)->next_free)
 206
 207 /* Mask specifying low bits that should be clear in address of an object.  */
 208
 209 #define obstack_alignment_mask(h) ((h)->alignment_mask)
 210
 211 /* To prevent prototype warnings provide complete argument list.  */
 212 #define obstack_init(h)                                         \
 213   _obstack_begin ((h), 0, 0,                                    \
 214                   (void *(*) (long)) obstack_chunk_alloc,       \
 215                   (void (*) (void *)) obstack_chunk_free)
 216
 217 #define obstack_begin(h, size)                                  \
 218   _obstack_begin ((h), (size), 0,                               \
 219                   (void *(*) (long)) obstack_chunk_alloc,       \
 220                   (void (*) (void *)) obstack_chunk_free)
 221
 222 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun)  \
 223   _obstack_begin ((h), (size), (alignment),                                \
 224                   (void *(*) (long)) (chunkfun),                           \
 225                   (void (*) (void *)) (freefun))
 226
 227 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
 228   _obstack_begin_1 ((h), (size), (alignment),                           \
 229                     (void *(*) (void *, long)) (chunkfun),              \
 230                     (void (*) (void *, void *)) (freefun), (arg))
 231
 232 #define obstack_chunkfun(h, newchunkfun) \
 233   ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
 234
 235 #define obstack_freefun(h, newfreefun) \
 236   ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
 237
 238 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
 239
 240 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
 241
 242 #define obstack_memory_used(h) _obstack_memory_used (h)
 243 \f
 244 #if defined __GNUC__ && defined __STDC__ && __STDC__
 245 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
 246    does not implement __extension__.  But that compiler doesn't define
 247    __GNUC_MINOR__.  */
 248 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
 249 #  define __extension__
 250 # endif
 251
 252 /* For GNU C, if not -traditional,
 253    we can define these macros to compute all args only once
 254    without using a global variable.
 255    Also, we can avoid using the `temp' slot, to make faster code.  */
 256
 257 # define obstack_object_size(OBSTACK)                                   \
 258   __extension__                                                         \
 259   ({ struct obstack const *__o = (OBSTACK);                             \
 260      (unsigned) (__o->next_free - __o->object_base); })
 261
 262 # define obstack_room(OBSTACK)                                          \
 263   __extension__                                                         \
 264   ({ struct obstack const *__o = (OBSTACK);                             \
 265      (unsigned) (__o->chunk_limit - __o->next_free); })
 266
 267 # define obstack_make_room(OBSTACK,length)                              \
 268 __extension__                                                           \
 269 ({ struct obstack *__o = (OBSTACK);                                     \
 270    int __len = (length);                                                \
 271    if (__o->chunk_limit - __o->next_free < __len)                       \
 272      _obstack_newchunk (__o, __len);                                    \
 273    (void) 0; })
 274
 275 # define obstack_empty_p(OBSTACK)                                       \
 276   __extension__                                                         \
 277   ({ struct obstack const *__o = (OBSTACK);                             \
 278      (__o->chunk->prev == 0 && __o->next_free - __o->chunk->contents == 0); })
 279
 280 # define obstack_grow(OBSTACK,where,length)                             \
 281 __extension__                                                           \
 282 ({ struct obstack *__o = (OBSTACK);                                     \
 283    int __len = (length);                                                \
 284    if (__o->next_free + __len > __o->chunk_limit)                       \
 285      _obstack_newchunk (__o, __len);                                    \
 286    memcpy (__o->next_free, where, __len);                               \
 287    __o->next_free += __len;                                             \
 288    (void) 0; })
 289
 290 # define obstack_grow0(OBSTACK,where,length)                            \
 291 __extension__                                                           \
 292 ({ struct obstack *__o = (OBSTACK);                                     \
 293    int __len = (length);                                                \
 294    if (__o->next_free + __len + 1 > __o->chunk_limit)                   \
 295      _obstack_newchunk (__o, __len + 1);                                \
 296    memcpy (__o->next_free, where, __len);                               \
 297    __o->next_free += __len;                                             \
 298    *(__o->next_free)++ = 0;                                             \
 299    (void) 0; })
 300
 301 # define obstack_1grow(OBSTACK,datum)                                   \
 302 __extension__                                                           \
 303 ({ struct obstack *__o = (OBSTACK);                                     \
 304    if (__o->next_free + 1 > __o->chunk_limit)                           \
 305      _obstack_newchunk (__o, 1);                                        \
 306    obstack_1grow_fast (__o, datum);                                     \
 307    (void) 0; })
 308
 309 /* These assume that the obstack alignment is good enough for pointers
 310    or ints, and that the data added so far to the current object
 311    shares that much alignment.  */
 312
 313 # define obstack_ptr_grow(OBSTACK,datum)                                \
 314 __extension__                                                           \
 315 ({ struct obstack *__o = (OBSTACK);                                     \
 316    if (__o->next_free + sizeof (void *) > __o->chunk_limit)             \
 317      _obstack_newchunk (__o, sizeof (void *));                          \
 318    obstack_ptr_grow_fast (__o, datum); })                               \
 319
 320 # define obstack_int_grow(OBSTACK,datum)                                \
 321 __extension__                                                           \
 322 ({ struct obstack *__o = (OBSTACK);                                     \
 323    if (__o->next_free + sizeof (int) > __o->chunk_limit)                \
 324      _obstack_newchunk (__o, sizeof (int));                             \
 325    obstack_int_grow_fast (__o, datum); })
 326
 327 # define obstack_ptr_grow_fast(OBSTACK,aptr)                            \
 328 __extension__                                                           \
 329 ({ struct obstack *__o1 = (OBSTACK);                                    \
 330    *(const void **) __o1->next_free = (aptr);                           \
 331    __o1->next_free += sizeof (const void *);                            \
 332    (void) 0; })
 333
 334 # define obstack_int_grow_fast(OBSTACK,aint)                            \
 335 __extension__                                                           \
 336 ({ struct obstack *__o1 = (OBSTACK);                                    \
 337    *(int *) __o1->next_free = (aint);                                   \
 338    __o1->next_free += sizeof (int);                                     \
 339    (void) 0; })
 340
 341 # define obstack_blank(OBSTACK,length)                                  \
 342 __extension__                                                           \
 343 ({ struct obstack *__o = (OBSTACK);                                     \
 344    int __len = (length);                                                \
 345    if (__o->chunk_limit - __o->next_free < __len)                       \
 346      _obstack_newchunk (__o, __len);                                    \
 347    obstack_blank_fast (__o, __len);                                     \
 348    (void) 0; })
 349
 350 # define obstack_alloc(OBSTACK,length)                                  \
 351 __extension__                                                           \
 352 ({ struct obstack *__h = (OBSTACK);                                     \
 353    obstack_blank (__h, (length));                                       \
 354    obstack_finish (__h); })
 355
 356 # define obstack_copy(OBSTACK,where,length)                             \
 357 __extension__                                                           \
 358 ({ struct obstack *__h = (OBSTACK);                                     \
 359    obstack_grow (__h, (where), (length));                               \
 360    obstack_finish (__h); })
 361
 362 # define obstack_copy0(OBSTACK,where,length)                            \
 363 __extension__                                                           \
 364 ({ struct obstack *__h = (OBSTACK);                                     \
 365    obstack_grow0 (__h, (where), (length));                              \
 366    obstack_finish (__h); })
 367
 368 /* The local variable is named __o1 to avoid a name conflict
 369    when obstack_blank is called.  */
 370 # define obstack_finish(OBSTACK)                                        \
 371 __extension__                                                           \
 372 ({ struct obstack *__o1 = (OBSTACK);                                    \
 373    void *__value = (void *) __o1->object_base;                          \
 374    if (__o1->next_free == __value)                                      \
 375      __o1->maybe_empty_object = 1;                                      \
 376    __o1->next_free                                                      \
 377      = __INT_TO_PTR ((__PTR_TO_INT (__o1->next_free)+__o1->alignment_mask)\
 378                      & ~ (__o1->alignment_mask));                       \
 379    if (__o1->next_free - (char *)__o1->chunk                            \
 380        > __o1->chunk_limit - (char *)__o1->chunk)                       \
 381      __o1->next_free = __o1->chunk_limit;                               \
 382    __o1->object_base = __o1->next_free;                                 \
 383    __value; })
 384
 385 # define obstack_free(OBSTACK, OBJ)                                     \
 386 __extension__                                                           \
 387 ({ struct obstack *__o = (OBSTACK);                                     \
 388    void *__obj = (OBJ);                                                 \
 389    if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit)  \
 390      __o->next_free = __o->object_base = (char *)__obj;                 \
 391    else (obstack_free) (__o, __obj); })
 392 \f
 393 #else /* not __GNUC__ or not __STDC__ */
 394
 395 # define obstack_object_size(h) \
 396  (unsigned) ((h)->next_free - (h)->object_base)
 397
 398 # define obstack_room(h)                \
 399  (unsigned) ((h)->chunk_limit - (h)->next_free)
 400
 401 # define obstack_empty_p(h) \
 402  ((h)->chunk->prev == 0 && (h)->next_free - (h)->chunk->contents == 0)
 403
 404 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
 405    so that we can avoid having void expressions
 406    in the arms of the conditional expression.
 407    Casting the third operand to void was tried before,
 408    but some compilers won't accept it.  */
 409
 410 # define obstack_make_room(h,length)                                    \
 411 ( (h)->temp = (length),                                                 \
 412   (((h)->next_free + (h)->temp > (h)->chunk_limit)                      \
 413    ? (_obstack_newchunk ((h), (h)->temp), 0) : 0))
 414
 415 # define obstack_grow(h,where,length)                                   \
 416 ( (h)->temp = (length),                                                 \
 417   (((h)->next_free + (h)->temp > (h)->chunk_limit)                      \
 418    ? (_obstack_newchunk ((h), (h)->temp), 0) : 0),                      \
 419   memcpy ((h)->next_free, where, (h)->temp),                            \
 420   (h)->next_free += (h)->temp)
 421
 422 # define obstack_grow0(h,where,length)                                  \
 423 ( (h)->temp = (length),                                                 \
 424   (((h)->next_free + (h)->temp + 1 > (h)->chunk_limit)                  \
 425    ? (_obstack_newchunk ((h), (h)->temp + 1), 0) : 0),                  \
 426   memcpy ((h)->next_free, where, (h)->temp),                            \
 427   (h)->next_free += (h)->temp,                                          \
 428   *((h)->next_free)++ = 0)
 429
 430 # define obstack_1grow(h,datum)                                         \
 431 ( (((h)->next_free + 1 > (h)->chunk_limit)                              \
 432    ? (_obstack_newchunk ((h), 1), 0) : 0),                              \
 433   obstack_1grow_fast (h, datum))
 434
 435 # define obstack_ptr_grow(h,datum)                                      \
 436 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit)                \
 437    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),                \
 438   obstack_ptr_grow_fast (h, datum))
 439
 440 # define obstack_int_grow(h,datum)                                      \
 441 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit)                   \
 442    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),                   \
 443   obstack_int_grow_fast (h, datum))
 444
 445 # define obstack_ptr_grow_fast(h,aptr)                                  \
 446   (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
 447
 448 # define obstack_int_grow_fast(h,aint)                                  \
 449   (((int *) ((h)->next_free += sizeof (int)))[-1] = (aptr))
 450
 451 # define obstack_blank(h,length)                                        \
 452 ( (h)->temp = (length),                                                 \
 453   (((h)->chunk_limit - (h)->next_free < (h)->temp)                      \
 454    ? (_obstack_newchunk ((h), (h)->temp), 0) : 0),                      \
 455   obstack_blank_fast (h, (h)->temp))
 456
 457 # define obstack_alloc(h,length)                                        \
 458  (obstack_blank ((h), (length)), obstack_finish ((h)))
 459
 460 # define obstack_copy(h,where,length)                                   \
 461  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
 462
 463 # define obstack_copy0(h,where,length)                                  \
 464  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
 465
 466 # define obstack_finish(h)                                              \
 467 ( ((h)->next_free == (h)->object_base                                   \
 468    ? (((h)->maybe_empty_object = 1), 0)                                 \
 469    : 0),                                                                \
 470   (h)->temp = __PTR_TO_INT ((h)->object_base),                          \
 471   (h)->next_free                                                        \
 472     = __INT_TO_PTR ((__PTR_TO_INT ((h)->next_free)+(h)->alignment_mask) \
 473                     & ~ ((h)->alignment_mask)),                         \
 474   (((h)->next_free - (char *) (h)->chunk                                \
 475     > (h)->chunk_limit - (char *) (h)->chunk)                           \
 476    ? ((h)->next_free = (h)->chunk_limit) : 0),                          \
 477   (h)->object_base = (h)->next_free,                                    \
 478   (void *) __INT_TO_PTR ((h)->temp))
 479
 480 # define obstack_free(h,obj)                                            \
 481 ( (h)->temp = (char *) (obj) - (char *) (h)->chunk,                     \
 482   (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
 483    ? (int) ((h)->next_free = (h)->object_base                           \
 484             = (h)->temp + (char *) (h)->chunk)                          \
 485    : (((obstack_free) ((h), (h)->temp + (char *) (h)->chunk), 0), 0)))
 486
 487 #endif /* not __GNUC__ or not __STDC__ */
 488
 489 #ifdef __cplusplus
 490 }       /* C++ */
 491 #endif
 492
 493 #endif /* obstack.h */