gas/obstack.h

   1 /* obstack.h - object stack macros
   2    Copyright (C) 1988 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' a 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 struct _obstack_chunk           /* Lives at front of each chunk. */
 119 {
 120   char *limit;                  /* 1 past end of this chunk */
 121   struct _obstack_chunk *prev;  /* address of prior chunk or NULL */
 122   char contents[4];             /* objects begin here */
 123 };
 124
 125 struct obstack                  /* control current object in current chunk */
 126 {
 127   long chunk_size;              /* preferred size to allocate chunks in */
 128   struct _obstack_chunk *chunk; /* address of current struct obstack_chunk */
 129   char *object_base;            /* address of object we are building */
 130   char *next_free;              /* where to add next char to current object */
 131   char *chunk_limit;            /* address of char after current chunk */
 132   int temp;                     /* Temporary for some macros.  */
 133   int alignment_mask;           /* Mask of alignment for each object. */
 134   struct _obstack_chunk *(*chunkfun) ();        /* User's fcn to allocate a chunk.  */
 135   void (*freefun) ();           /* User's function to free a chunk.  */
 136   /* Nonzero means there is a possibility the current chunk contains
 137      a zero-length object.  This prevents freeing the chunk
 138      if we allocate a bigger chunk to replace it.  */
 139   char maybe_empty_object;
 140 };
 141
 142 /* Declare the external functions we use; they are in obstack.c.  */
 143
 144 #ifdef __STDC__
 145 extern void _obstack_newchunk (struct obstack *, int);
 146 extern void _obstack_free (struct obstack *, void *);
 147 extern void _obstack_begin (struct obstack *, int, int,
 148                             void *(*)(), void (*)());
 149 #else
 150 extern void _obstack_newchunk ();
 151 extern void _obstack_free ();
 152 extern void _obstack_begin ();
 153 #endif
 154 \f
 155 #ifdef __STDC__
 156
 157 /* Do the function-declarations after the structs
 158    but before defining the macros.  */
 159
 160 void obstack_init (struct obstack *obstack);
 161
 162 void *obstack_alloc (struct obstack *obstack, int size);
 163
 164 void *obstack_copy (struct obstack *obstack, void *address, int size);
 165 void *obstack_copy0 (struct obstack *obstack, void *address, int size);
 166
 167 void obstack_free (struct obstack *obstack, void *block);
 168
 169 void obstack_blank (struct obstack *obstack, int size);
 170
 171 void obstack_grow (struct obstack *obstack, void *data, int size);
 172 void obstack_grow0 (struct obstack *obstack, void *data, int size);
 173
 174 void obstack_1grow (struct obstack *obstack, int data_char);
 175 void obstack_ptr_grow (struct obstack *obstack, void *data);
 176 void obstack_int_grow (struct obstack *obstack, int data);
 177
 178 void *obstack_finish (struct obstack *obstack);
 179
 180 int obstack_object_size (struct obstack *obstack);
 181
 182 int obstack_room (struct obstack *obstack);
 183 void obstack_1grow_fast (struct obstack *obstack, int data_char);
 184 void obstack_ptr_grow_fast (struct obstack *obstack, void *data);
 185 void obstack_int_grow_fast (struct obstack *obstack, int data);
 186 void obstack_blank_fast (struct obstack *obstack, int size);
 187
 188 void *obstack_base (struct obstack *obstack);
 189 void *obstack_next_free (struct obstack *obstack);
 190 int obstack_alignment_mask (struct obstack *obstack);
 191 int obstack_chunk_size (struct obstack *obstack);
 192
 193 #endif /* __STDC__ */
 194
 195 /* Non-ANSI C cannot really support alternative functions for these macros,
 196    so we do not declare them.  */
 197 \f
 198 /* Pointer to beginning of object being allocated or to be allocated next.
 199    Note that this might not be the final address of the object
 200    because a new chunk might be needed to hold the final size.  */
 201
 202 #define obstack_base(h) ((h)->object_base)
 203
 204 /* Size for allocating ordinary chunks.  */
 205
 206 #define obstack_chunk_size(h) ((h)->chunk_size)
 207
 208 /* Pointer to next byte not yet allocated in current chunk.  */
 209
 210 #define obstack_next_free(h)    ((h)->next_free)
 211
 212 /* Mask specifying low bits that should be clear in address of an object.  */
 213
 214 #define obstack_alignment_mask(h) ((h)->alignment_mask)
 215
 216 #define obstack_init(h) \
 217   _obstack_begin ((h), 0, 0, \
 218                   (void *(*) ()) obstack_chunk_alloc, (void (*) ())obstack_chunk_free)
 219
 220 #define obstack_begin(h, size) \
 221   _obstack_begin ((h), (size), 0, \
 222                   (void *(*) ()) obstack_chunk_alloc, (void (*) ())obstack_chunk_free)
 223
 224 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = achar)
 225
 226 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
 227 \f
 228 #if defined (__GNUC__) && defined (__STDC__)
 229 #if __GNUC__ < 2
 230 #define __extension__
 231 #endif
 232
 233 /* For GNU C, if not -traditional,
 234    we can define these macros to compute all args only once
 235    without using a global variable.
 236    Also, we can avoid using the `temp' slot, to make faster code.  */
 237
 238 #define obstack_object_size(OBSTACK)                                    \
 239   __extension__                                                         \
 240   ({ struct obstack *__o = (OBSTACK);                                   \
 241      (unsigned) (__o->next_free - __o->object_base); })
 242
 243 #define obstack_room(OBSTACK)                                           \
 244   __extension__                                                         \
 245   ({ struct obstack *__o = (OBSTACK);                                   \
 246      (unsigned) (__o->chunk_limit - __o->next_free); })
 247
 248 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
 249    so that we can avoid having void expressions
 250    in the arms of the conditional expression.
 251    Casting the third operand to void was tried before,
 252    but some compilers won't accept it.  */
 253 #define obstack_grow(OBSTACK,where,length)                              \
 254 __extension__                                                           \
 255 ({ struct obstack *__o = (OBSTACK);                                     \
 256    int __len = (length);                                                \
 257    ((__o->next_free + __len > __o->chunk_limit)                         \
 258     ? (_obstack_newchunk (__o, __len), 0) : 0);                         \
 259    memcpy (__o->next_free, where, __len);                               \
 260    __o->next_free += __len;                                             \
 261    (void) 0; })
 262
 263 #define obstack_grow0(OBSTACK,where,length)                             \
 264 __extension__                                                           \
 265 ({ struct obstack *__o = (OBSTACK);                                     \
 266    int __len = (length);                                                \
 267    ((__o->next_free + __len + 1 > __o->chunk_limit)                     \
 268     ? (_obstack_newchunk (__o, __len + 1), 0) : 0),                     \
 269    memcpy (__o->next_free, where, __len),                               \
 270    __o->next_free += __len,                                             \
 271    *(__o->next_free)++ = 0;                                             \
 272    (void) 0; })
 273
 274 #define obstack_1grow(OBSTACK,datum)                                    \
 275 __extension__                                                           \
 276 ({ struct obstack *__o = (OBSTACK);                                     \
 277    ((__o->next_free + 1 > __o->chunk_limit)                             \
 278     ? (_obstack_newchunk (__o, 1), 0) : 0),                             \
 279    *(__o->next_free)++ = (datum);                                       \
 280    (void) 0; })
 281
 282 /* These assume that the obstack alignment is good enough for pointers or ints,
 283    and that the data added so far to the current object
 284    shares that much alignment.  */
 285
 286 #define obstack_ptr_grow(OBSTACK,datum)                                 \
 287 __extension__                                                           \
 288 ({ struct obstack *__o = (OBSTACK);                                     \
 289    ((__o->next_free + sizeof (void *) > __o->chunk_limit)               \
 290     ? (_obstack_newchunk (__o, sizeof (void *)), 0) : 0),               \
 291    *(*(void ***)&__o->next_free)++ = ((void *)datum);                   \
 292    (void) 0; })
 293
 294 #define obstack_int_grow(OBSTACK,datum)                                 \
 295 __extension__                                                           \
 296 ({ struct obstack *__o = (OBSTACK);                                     \
 297    ((__o->next_free + sizeof (int) > __o->chunk_limit)                  \
 298     ? (_obstack_newchunk (__o, sizeof (int)), 0) : 0),                  \
 299    *(*(int **)&__o->next_free)++ = ((int)datum);                        \
 300    (void) 0; })
 301
 302 #define obstack_ptr_grow_fast(h,aptr) (*(*(void ***)&(h)->next_free)++ = (void *)aptr)
 303 #define obstack_int_grow_fast(h,aint) (*(*(int **)&(h)->next_free)++ = (int)aint)
 304
 305 #define obstack_blank(OBSTACK,length)                                   \
 306 __extension__                                                           \
 307 ({ struct obstack *__o = (OBSTACK);                                     \
 308    int __len = (length);                                                \
 309    ((__o->chunk_limit - __o->next_free < __len)                         \
 310     ? (_obstack_newchunk (__o, __len), 0) : 0);                         \
 311    __o->next_free += __len;                                             \
 312    (void) 0; })
 313
 314 #define obstack_alloc(OBSTACK,length)                                   \
 315 __extension__                                                           \
 316 ({ struct obstack *__h = (OBSTACK);                                     \
 317    obstack_blank (__h, (length));                                       \
 318    obstack_finish (__h); })
 319
 320 #define obstack_copy(OBSTACK,where,length)                              \
 321 __extension__                                                           \
 322 ({ struct obstack *__h = (OBSTACK);                                     \
 323    obstack_grow (__h, (where), (length));                               \
 324    obstack_finish (__h); })
 325
 326 #define obstack_copy0(OBSTACK,where,length)                             \
 327 __extension__                                                           \
 328 ({ struct obstack *__h = (OBSTACK);                                     \
 329    obstack_grow0 (__h, (where), (length));                              \
 330    obstack_finish (__h); })
 331
 332 /* The local variable is named __o1 to avoid a name conflict
 333    when obstack_blank is called.  */
 334 #define obstack_finish(OBSTACK)                                         \
 335 __extension__                                                           \
 336 ({ struct obstack *__o1 = (OBSTACK);                                    \
 337    void *value = (void *) __o1->object_base;                            \
 338    if (__o1->next_free == value)                                        \
 339      __o1->maybe_empty_object = 1;                                      \
 340    __o1->next_free                                                      \
 341      = __INT_TO_PTR ((__PTR_TO_INT (__o1->next_free)+__o1->alignment_mask)\
 342                      & ~ (__o1->alignment_mask));                       \
 343    ((__o1->next_free - (char *)__o1->chunk                              \
 344      > __o1->chunk_limit - (char *)__o1->chunk)                         \
 345     ? (__o1->next_free = __o1->chunk_limit) : 0);                       \
 346    __o1->object_base = __o1->next_free;                                 \
 347    value; })
 348
 349 #define obstack_free(OBSTACK, OBJ)                                      \
 350 __extension__                                                           \
 351 ({ struct obstack *__o = (OBSTACK);                                     \
 352    void *__obj = (OBJ);                                                 \
 353    if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit)  \
 354      __o->next_free = __o->object_base = __obj;                         \
 355    else (obstack_free) (__o, __obj); })
 356 \f
 357 #else /* not __GNUC__ or not __STDC__ */
 358
 359 #define obstack_object_size(h) \
 360  (unsigned) ((h)->next_free - (h)->object_base)
 361
 362 #define obstack_room(h)         \
 363  (unsigned) ((h)->chunk_limit - (h)->next_free)
 364
 365 #define obstack_grow(h,where,length)                                    \
 366 ( (h)->temp = (length),                                                 \
 367   (((h)->next_free + (h)->temp > (h)->chunk_limit)                      \
 368    ? (_obstack_newchunk ((h), (h)->temp), 0) : 0),                      \
 369   memcpy ((h)->next_free, where, (h)->temp),                            \
 370   (h)->next_free += (h)->temp)
 371
 372 #define obstack_grow0(h,where,length)                                   \
 373 ( (h)->temp = (length),                                                 \
 374   (((h)->next_free + (h)->temp + 1 > (h)->chunk_limit)                  \
 375    ? (_obstack_newchunk ((h), (h)->temp + 1), 0) : 0),                  \
 376   memcpy ((h)->next_free, where, (h)->temp),                            \
 377   (h)->next_free += (h)->temp,                                          \
 378   *((h)->next_free)++ = 0)
 379
 380 #define obstack_1grow(h,datum)                                          \
 381 ( (((h)->next_free + 1 > (h)->chunk_limit)                              \
 382    ? (_obstack_newchunk ((h), 1), 0) : 0),                              \
 383   *((h)->next_free)++ = (datum))
 384
 385 #define obstack_ptr_grow(h,datum)                                       \
 386 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit)                \
 387    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),                \
 388   *(*(char ***)&(h)->next_free)++ = ((char *)datum))
 389
 390 #define obstack_int_grow(h,datum)                                       \
 391 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit)                   \
 392    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),                   \
 393   *(*(int **)&(h)->next_free)++ = ((int)datum))
 394
 395 #define obstack_ptr_grow_fast(h,aptr) (*(*(char ***)&(h)->next_free)++ = (char *)aptr)
 396 #define obstack_int_grow_fast(h,aint) (*(*(int **)&(h)->next_free)++ = (int)aint)
 397 #define obstack_blank(h,length)                                         \
 398 ( (h)->temp = (length),                                                 \
 399   (((h)->chunk_limit - (h)->next_free < (h)->temp)                      \
 400    ? (_obstack_newchunk ((h), (h)->temp), 0) : 0),                      \
 401   (h)->next_free += (h)->temp)
 402
 403 #define obstack_alloc(h,length)                                         \
 404  (obstack_blank ((h), (length)), obstack_finish ((h)))
 405
 406 #define obstack_copy(h,where,length)                                    \
 407  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
 408
 409 #define obstack_copy0(h,where,length)                                   \
 410  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
 411
 412 #define obstack_finish(h)                                               \
 413 ( ((h)->next_free == (h)->object_base                                   \
 414    ? (((h)->maybe_empty_object = 1), 0)                                 \
 415    : 0),                                                                \
 416   (h)->temp = __PTR_TO_INT ((h)->object_base),                          \
 417   (h)->next_free                                                        \
 418     = __INT_TO_PTR ((__PTR_TO_INT ((h)->next_free)+(h)->alignment_mask) \
 419                     & ~ ((h)->alignment_mask)),                         \
 420   (((h)->next_free - (char *)(h)->chunk                                 \
 421     > (h)->chunk_limit - (char *)(h)->chunk)                            \
 422    ? ((h)->next_free = (h)->chunk_limit) : 0),                          \
 423   (h)->object_base = (h)->next_free,                                    \
 424   __INT_TO_PTR ((h)->temp))
 425
 426 #ifdef __STDC__
 427 #define obstack_free(h,obj)                                             \
 428 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk,                      \
 429   (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
 430    ? (int) ((h)->next_free = (h)->object_base                           \
 431             = (h)->temp + (char *) (h)->chunk)                          \
 432    : (((obstack_free) ((h), (h)->temp + (char *) (h)->chunk), 0), 0)))
 433 #else
 434 #define obstack_free(h,obj)                                             \
 435 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk,                      \
 436   (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
 437    ? (int) ((h)->next_free = (h)->object_base                           \
 438             = (h)->temp + (char *) (h)->chunk)                          \
 439    : (_obstack_free ((h), (h)->temp + (char *) (h)->chunk), 0)))
 440 #endif
 441
 442 #endif /* not __GNUC__ or not __STDC__ */
 443
 444 #endif /* not __OBSTACKS__ */