include/obstack.h

   1 /* obstack.h - object stack macros
   2    Copyright (C) 1988, 1992 Free Software Foundation, Inc.
   3
   4 This program is free software; you can redistribute it and/or modify it
   5 under the terms of the GNU General Public License as published by the
   6 Free Software Foundation; either version 2, or (at your option) any
   7 later version.
   8
   9 This program is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 GNU General Public License for more details.
  13
  14 You should have received a copy of the GNU General Public License
  15 along with this program; if not, write to the Free Software
  16 Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
  17
  18 /* Summary:
  19
  20 All the apparent functions defined here are macros. The idea
  21 is that you would use these pre-tested macros to solve a
  22 very specific set of problems, and they would run fast.
  23 Caution: no side-effects in arguments please!! They may be
  24 evaluated MANY times!!
  25
  26 These macros operate a stack of objects.  Each object starts life
  27 small, and may grow to maturity.  (Consider building a word syllable
  28 by syllable.)  An object can move while it is growing.  Once it has
  29 been "finished" it never changes address again.  So the "top of the
  30 stack" is typically an immature growing object, while the rest of the
  31 stack is of mature, fixed size and fixed address objects.
  32
  33 These routines grab large chunks of memory, using a function you
  34 supply, called `obstack_chunk_alloc'.  On occasion, they free chunks,
  35 by calling `obstack_chunk_free'.  You must define them and declare
  36 them before using any obstack macros.
  37
  38 Each independent stack is represented by a `struct obstack'.
  39 Each of the obstack macros expects a pointer to such a structure
  40 as the first argument.
  41
  42 One motivation for this package is the problem of growing char strings
  43 in symbol tables.  Unless you are "fascist pig with a read-only mind"
  44 --Gosper's immortal quote from HAKMEM item 154, out of context--you
  45 would not like to put any arbitrary upper limit on the length of your
  46 symbols.
  47
  48 In practice this often means you will build many short symbols and a
  49 few long symbols.  At the time you are reading a symbol you don't know
  50 how long it is.  One traditional method is to read a symbol into a
  51 buffer, realloc()ating the buffer every time you try to read a symbol
  52 that is longer than the buffer.  This is beaut, but you still will
  53 want to copy the symbol from the buffer to a more permanent
  54 symbol-table entry say about half the time.
  55
  56 With obstacks, you can work differently.  Use one obstack for all symbol
  57 names.  As you read a symbol, grow the name in the obstack gradually.
  58 When the name is complete, finalize it.  Then, if the symbol exists already,
  59 free the newly read name.
  60
  61 The way we do this is to take a large chunk, allocating memory from
  62 low addresses.  When you want to build a symbol in the chunk you just
  63 add chars above the current "high water mark" in the chunk.  When you
  64 have finished adding chars, because you got to the end of the symbol,
  65 you know how long the chars are, and you can create a new object.
  66 Mostly the chars will not burst over the highest address of the chunk,
  67 because you would typically expect a chunk to be (say) 100 times as
  68 long as an average object.
  69
  70 In case that isn't clear, when we have enough chars to make up
  71 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
  72 so we just point to it where it lies.  No moving of chars is
  73 needed and this is the second win: potentially long strings need
  74 never be explicitly shuffled. Once an object is formed, it does not
  75 change its address during its lifetime.
  76
  77 When the chars burst over a chunk boundary, we allocate a larger
  78 chunk, and then copy the partly formed object from the end of the old
  79 chunk to the beginning of the new larger chunk.  We then carry on
  80 accreting characters to the end of the object as we normally would.
  81
  82 A special macro is provided to add a single char at a time to a
  83 growing object.  This allows the use of register variables, which
  84 break the ordinary 'growth' macro.
  85
  86 Summary:
  87         We allocate large chunks.
  88         We carve out one object at a time from the current chunk.
  89         Once carved, an object never moves.
  90         We are free to append data of any size to the currently
  91           growing object.
  92         Exactly one object is growing in an obstack at any one time.
  93         You can run one obstack per control block.
  94         You may have as many control blocks as you dare.
  95         Because of the way we do it, you can `unwind' an obstack
  96           back to a previous state. (You may remove objects much
  97           as you would with a stack.)
  98 */
  99
 100
 101 /* Don't do the contents of this file more than once.  */
 102
 103 #ifndef __OBSTACKS__
 104 #define __OBSTACKS__
 105 \f
 106 /* We use subtraction of (char *)0 instead of casting to int
 107    because on word-addressable machines a simple cast to int
 108    may ignore the byte-within-word field of the pointer.  */
 109
 110 #ifndef __PTR_TO_INT
 111 #define __PTR_TO_INT(P) ((P) - (char *)0)
 112 #endif
 113
 114 #ifndef __INT_TO_PTR
 115 #define __INT_TO_PTR(P) ((P) + (char *)0)
 116 #endif
 117
 118 /* We need the type of the resulting object.  In ANSI C it is ptrdiff_t
 119    but in traditional C it is usually long.  If we are in ANSI C and
 120    don't already have ptrdiff_t get it.  */
 121
 122 #if defined (__STDC__) && ! defined (offsetof)
 123 #if defined (__GNUC__) && defined (IN_GCC)
 124 /* On Next machine, the system's stddef.h screws up if included
 125    after we have defined just ptrdiff_t, so include all of gstddef.h.
 126    Otherwise, define just ptrdiff_t, which is all we need.  */
 127 #ifndef __NeXT__
 128 #define __need_ptrdiff_t
 129 #endif
 130
 131 /* While building GCC, the stddef.h that goes with GCC has this name.  */
 132 #include "gstddef.h"
 133 #else
 134 #include <stddef.h>
 135 #endif
 136 #endif
 137
 138 #ifdef __STDC__
 139 #define PTR_INT_TYPE ptrdiff_t
 140 #else
 141 #define PTR_INT_TYPE long
 142 #endif
 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   PTR_INT_TYPE temp;            /* Temporary for some macros.  */
 159   int   alignment_mask;         /* Mask of alignment for each object. */
 160   struct _obstack_chunk *(*chunkfun) (); /* User's fcn to allocate a chunk.  */
 161   void (*freefun) ();           /* User's function to free a chunk.  */
 162   char *extra_arg;              /* first arg for chunk alloc/dealloc funcs */
 163   unsigned use_extra_arg:1;     /* chunk alloc/dealloc funcs take extra arg */
 164   unsigned maybe_empty_object:1;/* There is a possibility that the current
 165                                    chunk contains a zero-length object.  This
 166                                    prevents freeing the chunk if we allocate
 167                                    a bigger chunk to replace it. */
 168 };
 169
 170 /* Declare the external functions we use; they are in obstack.c.  */
 171
 172 #ifdef __STDC__
 173 extern void _obstack_newchunk (struct obstack *, int);
 174 extern void _obstack_free (struct obstack *, void *);
 175 extern void _obstack_begin (struct obstack *, int, int,
 176                             void *(*) (), void (*) ());
 177 extern void _obstack_begin_1 (struct obstack *, int, int,
 178                               void *(*) (), void (*) (), void *);
 179 #else
 180 extern void _obstack_newchunk ();
 181 extern void _obstack_free ();
 182 extern void _obstack_begin ();
 183 extern void _obstack_begin_1 ();
 184 #endif
 185 \f
 186 #ifdef __STDC__
 187
 188 /* Do the function-declarations after the structs
 189    but before defining the macros.  */
 190
 191 void obstack_init (struct obstack *obstack);
 192
 193 void * obstack_alloc (struct obstack *obstack, int size);
 194
 195 void * obstack_copy (struct obstack *obstack, void *address, int size);
 196 void * obstack_copy0 (struct obstack *obstack, void *address, int size);
 197
 198 void obstack_free (struct obstack *obstack, void *block);
 199
 200 void obstack_blank (struct obstack *obstack, int size);
 201
 202 void obstack_grow (struct obstack *obstack, void *data, int size);
 203 void obstack_grow0 (struct obstack *obstack, void *data, int size);
 204
 205 void obstack_1grow (struct obstack *obstack, int data_char);
 206 void obstack_ptr_grow (struct obstack *obstack, void *data);
 207 void obstack_int_grow (struct obstack *obstack, int data);
 208
 209 void * obstack_finish (struct obstack *obstack);
 210
 211 int obstack_object_size (struct obstack *obstack);
 212
 213 int obstack_room (struct obstack *obstack);
 214 void obstack_1grow_fast (struct obstack *obstack, int data_char);
 215 void obstack_ptr_grow_fast (struct obstack *obstack, void *data);
 216 void obstack_int_grow_fast (struct obstack *obstack, int data);
 217 void obstack_blank_fast (struct obstack *obstack, int size);
 218
 219 void * obstack_base (struct obstack *obstack);
 220 void * obstack_next_free (struct obstack *obstack);
 221 int obstack_alignment_mask (struct obstack *obstack);
 222 int obstack_chunk_size (struct obstack *obstack);
 223
 224 #endif /* __STDC__ */
 225
 226 /* Non-ANSI C cannot really support alternative functions for these macros,
 227    so we do not declare them.  */
 228 \f
 229 /* Pointer to beginning of object being allocated or to be allocated next.
 230    Note that this might not be the final address of the object
 231    because a new chunk might be needed to hold the final size.  */
 232
 233 #define obstack_base(h) ((h)->object_base)
 234
 235 /* Size for allocating ordinary chunks.  */
 236
 237 #define obstack_chunk_size(h) ((h)->chunk_size)
 238
 239 /* Pointer to next byte not yet allocated in current chunk.  */
 240
 241 #define obstack_next_free(h)    ((h)->next_free)
 242
 243 /* Mask specifying low bits that should be clear in address of an object.  */
 244
 245 #define obstack_alignment_mask(h) ((h)->alignment_mask)
 246
 247 #define obstack_init(h) \
 248   _obstack_begin ((h), 0, 0, \
 249                   (void *(*) ()) obstack_chunk_alloc, (void (*) ()) obstack_chunk_free)
 250
 251 #define obstack_begin(h, size) \
 252   _obstack_begin ((h), (size), 0, \
 253                   (void *(*) ()) obstack_chunk_alloc, (void (*) ()) obstack_chunk_free)
 254
 255 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun) \
 256   _obstack_begin ((h), (size), (alignment), \
 257                     (void *(*) ()) (chunkfun), (void (*) ()) (freefun))
 258
 259 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
 260   _obstack_begin_1 ((h), (size), (alignment), \
 261                     (void *(*) ()) (chunkfun), (void (*) ()) (freefun), (arg))
 262
 263 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = achar)
 264
 265 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
 266 \f
 267 #if defined (__GNUC__) && defined (__STDC__)
 268 #if __GNUC__ < 2
 269 #define __extension__
 270 #endif
 271
 272 /* For GNU C, if not -traditional,
 273    we can define these macros to compute all args only once
 274    without using a global variable.
 275    Also, we can avoid using the `temp' slot, to make faster code.  */
 276
 277 #define obstack_object_size(OBSTACK)                                    \
 278   __extension__                                                         \
 279   ({ struct obstack *__o = (OBSTACK);                                   \
 280      (unsigned) (__o->next_free - __o->object_base); })
 281
 282 #define obstack_room(OBSTACK)                                           \
 283   __extension__                                                         \
 284   ({ struct obstack *__o = (OBSTACK);                                   \
 285      (unsigned) (__o->chunk_limit - __o->next_free); })
 286
 287 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
 288    so that we can avoid having void expressions
 289    in the arms of the conditional expression.
 290    Casting the third operand to void was tried before,
 291    but some compilers won't accept it.  */
 292 #define obstack_grow(OBSTACK,where,length)                              \
 293 __extension__                                                           \
 294 ({ struct obstack *__o = (OBSTACK);                                     \
 295    int __len = (length);                                                \
 296    ((__o->next_free + __len > __o->chunk_limit)                         \
 297     ? (_obstack_newchunk (__o, __len), 0) : 0);                         \
 298    bcopy (where, __o->next_free, __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    ((__o->next_free + __len + 1 > __o->chunk_limit)                     \
 307     ? (_obstack_newchunk (__o, __len + 1), 0) : 0),                     \
 308    bcopy (where, __o->next_free, __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    ((__o->next_free + 1 > __o->chunk_limit)                             \
 317     ? (_obstack_newchunk (__o, 1), 0) : 0),                             \
 318    *(__o->next_free)++ = (datum);                                       \
 319    (void) 0; })
 320
 321 /* These assume that the obstack alignment is good enough for pointers or ints,
 322    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    ((__o->next_free + sizeof (void *) > __o->chunk_limit)               \
 329     ? (_obstack_newchunk (__o, sizeof (void *)), 0) : 0),               \
 330    *((void **)__o->next_free)++ = ((void *)datum);                      \
 331    (void) 0; })
 332
 333 #define obstack_int_grow(OBSTACK,datum)                                 \
 334 __extension__                                                           \
 335 ({ struct obstack *__o = (OBSTACK);                                     \
 336    ((__o->next_free + sizeof (int) > __o->chunk_limit)                  \
 337     ? (_obstack_newchunk (__o, sizeof (int)), 0) : 0),                  \
 338    *((int *)__o->next_free)++ = ((int)datum);                           \
 339    (void) 0; })
 340
 341 #define obstack_ptr_grow_fast(h,aptr) (*((void **)(h)->next_free)++ = (void *)aptr)
 342 #define obstack_int_grow_fast(h,aint) (*((int *)(h)->next_free)++ = (int)aint)
 343
 344 #define obstack_blank(OBSTACK,length)                                   \
 345 __extension__                                                           \
 346 ({ struct obstack *__o = (OBSTACK);                                     \
 347    int __len = (length);                                                \
 348    ((__o->chunk_limit - __o->next_free < __len)                         \
 349     ? (_obstack_newchunk (__o, __len), 0) : 0);                         \
 350    __o->next_free += __len;                                             \
 351    (void) 0; })
 352
 353 #define obstack_alloc(OBSTACK,length)                                   \
 354 __extension__                                                           \
 355 ({ struct obstack *__h = (OBSTACK);                                     \
 356    obstack_blank (__h, (length));                                       \
 357    obstack_finish (__h); })
 358
 359 #define obstack_copy(OBSTACK,where,length)                              \
 360 __extension__                                                           \
 361 ({ struct obstack *__h = (OBSTACK);                                     \
 362    obstack_grow (__h, (where), (length));                               \
 363    obstack_finish (__h); })
 364
 365 #define obstack_copy0(OBSTACK,where,length)                             \
 366 __extension__                                                           \
 367 ({ struct obstack *__h = (OBSTACK);                                     \
 368    obstack_grow0 (__h, (where), (length));                              \
 369    obstack_finish (__h); })
 370
 371 /* The local variable is named __o1 to avoid a name conflict
 372    when obstack_blank is called.  */
 373 #define obstack_finish(OBSTACK)                                         \
 374 __extension__                                                           \
 375 ({ struct obstack *__o1 = (OBSTACK);                                    \
 376    void *value = (void *) __o1->object_base;                            \
 377    if (__o1->next_free == value)                                        \
 378      __o1->maybe_empty_object = 1;                                      \
 379    __o1->next_free                                                      \
 380      = __INT_TO_PTR ((__PTR_TO_INT (__o1->next_free)+__o1->alignment_mask)\
 381                      & ~ (__o1->alignment_mask));                       \
 382    ((__o1->next_free - (char *)__o1->chunk                              \
 383      > __o1->chunk_limit - (char *)__o1->chunk)                         \
 384     ? (__o1->next_free = __o1->chunk_limit) : 0);                       \
 385    __o1->object_base = __o1->next_free;                                 \
 386    value; })
 387
 388 #define obstack_free(OBSTACK, OBJ)                                      \
 389 __extension__                                                           \
 390 ({ struct obstack *__o = (OBSTACK);                                     \
 391    void *__obj = (OBJ);                                                 \
 392    if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit)  \
 393      __o->next_free = __o->object_base = __obj;                         \
 394    else (obstack_free) (__o, __obj); })
 395 \f
 396 #else /* not __GNUC__ or not __STDC__ */
 397
 398 #define obstack_object_size(h) \
 399  (unsigned) ((h)->next_free - (h)->object_base)
 400
 401 #define obstack_room(h)         \
 402  (unsigned) ((h)->chunk_limit - (h)->next_free)
 403
 404 #define obstack_grow(h,where,length)                                    \
 405 ( (h)->temp = (length),                                                 \
 406   (((h)->next_free + (h)->temp > (h)->chunk_limit)                      \
 407    ? (_obstack_newchunk ((h), (h)->temp), 0) : 0),                      \
 408   bcopy (where, (h)->next_free, (h)->temp),                             \
 409   (h)->next_free += (h)->temp)
 410
 411 #define obstack_grow0(h,where,length)                                   \
 412 ( (h)->temp = (length),                                                 \
 413   (((h)->next_free + (h)->temp + 1 > (h)->chunk_limit)                  \
 414    ? (_obstack_newchunk ((h), (h)->temp + 1), 0) : 0),                  \
 415   bcopy (where, (h)->next_free, (h)->temp),                             \
 416   (h)->next_free += (h)->temp,                                          \
 417   *((h)->next_free)++ = 0)
 418
 419 #define obstack_1grow(h,datum)                                          \
 420 ( (((h)->next_free + 1 > (h)->chunk_limit)                              \
 421    ? (_obstack_newchunk ((h), 1), 0) : 0),                              \
 422   *((h)->next_free)++ = (datum))
 423
 424 #define obstack_ptr_grow(h,datum)                                       \
 425 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit)                \
 426    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),                \
 427   *((char **)(((h)->next_free+=sizeof(char *))-sizeof(char *))) = ((char *)datum))
 428
 429 #define obstack_int_grow(h,datum)                                       \
 430 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit)                   \
 431    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),                   \
 432   *((int *)(((h)->next_free+=sizeof(int))-sizeof(int))) = ((int)datum))
 433
 434 #define obstack_ptr_grow_fast(h,aptr) (*((char **)(h)->next_free)++ = (char *)aptr)
 435 #define obstack_int_grow_fast(h,aint) (*((int *)(h)->next_free)++ = (int)aint)
 436
 437 #define obstack_blank(h,length)                                         \
 438 ( (h)->temp = (length),                                                 \
 439   (((h)->chunk_limit - (h)->next_free < (h)->temp)                      \
 440    ? (_obstack_newchunk ((h), (h)->temp), 0) : 0),                      \
 441   (h)->next_free += (h)->temp)
 442
 443 #define obstack_alloc(h,length)                                         \
 444  (obstack_blank ((h), (length)), obstack_finish ((h)))
 445
 446 #define obstack_copy(h,where,length)                                    \
 447  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
 448
 449 #define obstack_copy0(h,where,length)                                   \
 450  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
 451
 452 #define obstack_finish(h)                                               \
 453 ( ((h)->next_free == (h)->object_base                                   \
 454    ? (((h)->maybe_empty_object = 1), 0)                                 \
 455    : 0),                                                                \
 456   (h)->temp = __PTR_TO_INT ((h)->object_base),                          \
 457   (h)->next_free                                                        \
 458     = __INT_TO_PTR ((__PTR_TO_INT ((h)->next_free)+(h)->alignment_mask) \
 459                     & ~ ((h)->alignment_mask)),                         \
 460   (((h)->next_free - (char *)(h)->chunk                                 \
 461     > (h)->chunk_limit - (char *)(h)->chunk)                            \
 462    ? ((h)->next_free = (h)->chunk_limit) : 0),                          \
 463   (h)->object_base = (h)->next_free,                                    \
 464   __INT_TO_PTR ((h)->temp))
 465
 466 #ifdef __STDC__
 467 #define obstack_free(h,obj)                                             \
 468 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk,                      \
 469   (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
 470    ? (int) ((h)->next_free = (h)->object_base                           \
 471             = (h)->temp + (char *) (h)->chunk)                          \
 472    : (((obstack_free) ((h), (h)->temp + (char *) (h)->chunk), 0), 0)))
 473 #else
 474 #define obstack_free(h,obj)                                             \
 475 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk,                      \
 476   (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
 477    ? (int) ((h)->next_free = (h)->object_base                           \
 478             = (h)->temp + (char *) (h)->chunk)                          \
 479    : (_obstack_free ((h), (h)->temp + (char *) (h)->chunk), 0)))
 480 #endif
 481
 482 #endif /* not __GNUC__ or not __STDC__ */
 483
 484 #endif /* not __OBSTACKS__ */