debugger/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   void  *area_id;               /* Select which region to alloc/free in */
 137   int   flags;                  /* Miscellaneous special purpose flags */
 138 };
 139
 140 /* Declare bits for flags word. */
 141
 142 /* Means there is a possibility the current chunk contains a zero-length
 143    object.  This prevents freeing the chunk if we allocate a bigger chunk
 144    to replace it.  */
 145
 146 #define OBSTACK_MAYBE_EMPTY_OBJECT      (1 << 0)
 147
 148 /* Means that the allocation and deallocation functions take two arguments,
 149    ala the mmalloc package.  The first argument is a generic pointer that
 150    is saved in the area_id member of the obstack struct. */
 151
 152 #define OBSTACK_MMALLOC_LIKE            (1 << 1)
 153
 154 /* Declare the external functions we use; they are in obstack.c.  */
 155
 156 #ifdef __STDC__
 157   extern void _obstack_newchunk (struct obstack *, int);
 158   extern void _obstack_free (struct obstack *, void *);
 159   extern void _obstack_begin (struct obstack *, int, int,
 160                               void *(*) (int), void (*) (int), void *, int);
 161 #else
 162   extern void _obstack_newchunk ();
 163   extern void _obstack_free ();
 164   extern void _obstack_begin ();
 165 #endif
 166 \f
 167 #ifdef __STDC__
 168
 169 /* Do the function-declarations after the structs
 170    but before defining the macros.  */
 171
 172 void obstack_init (struct obstack *obstack);
 173
 174 void * obstack_alloc (struct obstack *obstack, int size);
 175
 176 void * obstack_copy (struct obstack *obstack, void *address, int size);
 177 void * obstack_copy0 (struct obstack *obstack, void *address, int size);
 178
 179 void obstack_free (struct obstack *obstack, void *block);
 180
 181 void obstack_blank (struct obstack *obstack, int size);
 182
 183 void obstack_grow (struct obstack *obstack, void *data, int size);
 184 void obstack_grow0 (struct obstack *obstack, void *data, int size);
 185
 186 void obstack_1grow (struct obstack *obstack, int data_char);
 187 void obstack_ptr_grow (struct obstack *obstack, void *data);
 188 void obstack_int_grow (struct obstack *obstack, int data);
 189
 190 void * obstack_finish (struct obstack *obstack);
 191
 192 int obstack_object_size (struct obstack *obstack);
 193
 194 int obstack_room (struct obstack *obstack);
 195 void obstack_1grow_fast (struct obstack *obstack, int data_char);
 196 void obstack_ptr_grow_fast (struct obstack *obstack, void *data);
 197 void obstack_int_grow_fast (struct obstack *obstack, int data);
 198 void obstack_blank_fast (struct obstack *obstack, int size);
 199
 200 void * obstack_base (struct obstack *obstack);
 201 void * obstack_next_free (struct obstack *obstack);
 202 int obstack_alignment_mask (struct obstack *obstack);
 203 int obstack_chunk_size (struct obstack *obstack);
 204
 205 #endif /* __STDC__ */
 206
 207 /* Non-ANSI C cannot really support alternative functions for these macros,
 208    so we do not declare them.  */
 209 \f
 210 /* Pointer to beginning of object being allocated or to be allocated next.
 211    Note that this might not be the final address of the object
 212    because a new chunk might be needed to hold the final size.  */
 213
 214 #define obstack_base(h) ((h)->object_base)
 215
 216 /* Size for allocating ordinary chunks.  */
 217
 218 #define obstack_chunk_size(h) ((h)->chunk_size)
 219
 220 /* Pointer to next byte not yet allocated in current chunk.  */
 221
 222 #define obstack_next_free(h)    ((h)->next_free)
 223
 224 /* Mask specifying low bits that should be clear in address of an object.  */
 225
 226 #define obstack_alignment_mask(h) ((h)->alignment_mask)
 227
 228 #define obstack_init(h) \
 229   _obstack_begin ((h), 0, 0, \
 230                   (void *(*) ()) obstack_chunk_alloc, (void (*) ())obstack_chunk_free, (void *) 0, 0)
 231
 232 #define obstack_begin(h, size) \
 233   _obstack_begin ((h), (size), 0, \
 234                   (void *(*) ()) obstack_chunk_alloc, (void (*) ())obstack_chunk_free, (void *) 0, 0)
 235
 236 #define obstack_full_begin(h,size,alignment,chunkfun,freefun,area_id,flags) \
 237   _obstack_begin ((h), (size), (alignment), \
 238                   (void *(*) ()) (chunkfun), (void (*) ()) (freefun), \
 239                   (area_id), (flags))
 240
 241 #define obstack_chunkfun(h, newchunkfun) \
 242   ((h) -> chunkfun = (struct _obstack_chunk *(*)()) (newchunkfun))
 243
 244 #define obstack_freefun(h, newfreefun) \
 245   ((h) -> freefun = (void (*)()) (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 \f
 251 #if defined (__GNUC__) && defined (__STDC__)
 252 #if __GNUC__ < 2
 253 #define __extension__
 254 #endif
 255
 256 /* For GNU C, if not -traditional,
 257    we can define these macros to compute all args only once
 258    without using a global variable.
 259    Also, we can avoid using the `temp' slot, to make faster code.  */
 260
 261 #define obstack_object_size(OBSTACK)                                    \
 262   __extension__                                                         \
 263   ({ struct obstack *__o = (OBSTACK);                                   \
 264      (unsigned) (__o->next_free - __o->object_base); })
 265
 266 #define obstack_room(OBSTACK)                                           \
 267   __extension__                                                         \
 268   ({ struct obstack *__o = (OBSTACK);                                   \
 269      (unsigned) (__o->chunk_limit - __o->next_free); })
 270
 271 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
 272    so that we can avoid having void expressions
 273    in the arms of the conditional expression.
 274    Casting the third operand to void was tried before,
 275    but some compilers won't accept it.  */
 276 #define obstack_grow(OBSTACK,where,length)                              \
 277 __extension__                                                           \
 278 ({ struct obstack *__o = (OBSTACK);                                     \
 279    int __len = (length);                                                \
 280    ((__o->next_free + __len > __o->chunk_limit)                         \
 281     ? (_obstack_newchunk (__o, __len), 0) : 0);                         \
 282    bcopy (where, __o->next_free, __len);                                \
 283    __o->next_free += __len;                                             \
 284    (void) 0; })
 285
 286 #define obstack_grow0(OBSTACK,where,length)                             \
 287 __extension__                                                           \
 288 ({ struct obstack *__o = (OBSTACK);                                     \
 289    int __len = (length);                                                \
 290    ((__o->next_free + __len + 1 > __o->chunk_limit)                     \
 291     ? (_obstack_newchunk (__o, __len + 1), 0) : 0),                     \
 292    bcopy (where, __o->next_free, __len),                                \
 293    __o->next_free += __len,                                             \
 294    *(__o->next_free)++ = 0;                                             \
 295    (void) 0; })
 296
 297 #define obstack_1grow(OBSTACK,datum)                                    \
 298 __extension__                                                           \
 299 ({ struct obstack *__o = (OBSTACK);                                     \
 300    ((__o->next_free + 1 > __o->chunk_limit)                             \
 301     ? (_obstack_newchunk (__o, 1), 0) : 0),                             \
 302    *(__o->next_free)++ = (datum);                                       \
 303    (void) 0; })
 304
 305 /* These assume that the obstack alignment is good enough for pointers or ints,
 306    and that the data added so far to the current object
 307    shares that much alignment.  */
 308
 309 #define obstack_ptr_grow(OBSTACK,datum)                                 \
 310 __extension__                                                           \
 311 ({ struct obstack *__o = (OBSTACK);                                     \
 312    ((__o->next_free + sizeof (void *) > __o->chunk_limit)               \
 313     ? (_obstack_newchunk (__o, sizeof (void *)), 0) : 0),               \
 314    *(*(void ***)&__o->next_free)++ = ((void *)datum);                   \
 315    (void) 0; })
 316
 317 #define obstack_int_grow(OBSTACK,datum)                                 \
 318 __extension__                                                           \
 319 ({ struct obstack *__o = (OBSTACK);                                     \
 320    ((__o->next_free + sizeof (int) > __o->chunk_limit)                  \
 321     ? (_obstack_newchunk (__o, sizeof (int)), 0) : 0),                  \
 322    *(*(int **)&__o->next_free)++ = ((int)datum);                        \
 323    (void) 0; })
 324
 325 #define obstack_ptr_grow_fast(h,aptr) (*(*(void ***)&(h)->next_free)++ = (void *)aptr)
 326 #define obstack_int_grow_fast(h,aint) (*(*(int **)&(h)->next_free)++ = (int)aint)
 327
 328 #define obstack_blank(OBSTACK,length)                                   \
 329 __extension__                                                           \
 330 ({ struct obstack *__o = (OBSTACK);                                     \
 331    int __len = (length);                                                \
 332    ((__o->chunk_limit - __o->next_free < __len)                         \
 333     ? (_obstack_newchunk (__o, __len), 0) : 0);                         \
 334    __o->next_free += __len;                                             \
 335    (void) 0; })
 336
 337 #define obstack_alloc(OBSTACK,length)                                   \
 338 __extension__                                                           \
 339 ({ struct obstack *__h = (OBSTACK);                                     \
 340    obstack_blank (__h, (length));                                       \
 341    obstack_finish (__h); })
 342
 343 #define obstack_copy(OBSTACK,where,length)                              \
 344 __extension__                                                           \
 345 ({ struct obstack *__h = (OBSTACK);                                     \
 346    obstack_grow (__h, (where), (length));                               \
 347    obstack_finish (__h); })
 348
 349 #define obstack_copy0(OBSTACK,where,length)                             \
 350 __extension__                                                           \
 351 ({ struct obstack *__h = (OBSTACK);                                     \
 352    obstack_grow0 (__h, (where), (length));                              \
 353    obstack_finish (__h); })
 354
 355 /* The local variable is named __o1 to avoid a name conflict
 356    when obstack_blank is called.  */
 357 #define obstack_finish(OBSTACK)                                         \
 358 __extension__                                                           \
 359 ({ struct obstack *__o1 = (OBSTACK);                                    \
 360    void *value = (void *) __o1->object_base;                            \
 361    if (__o1->next_free == value)                                        \
 362      __o1->flags |= OBSTACK_MAYBE_EMPTY_OBJECT;                         \
 363    __o1->next_free                                                      \
 364      = __INT_TO_PTR ((__PTR_TO_INT (__o1->next_free)+__o1->alignment_mask)\
 365                      & ~ (__o1->alignment_mask));                       \
 366    ((__o1->next_free - (char *)__o1->chunk                              \
 367      > __o1->chunk_limit - (char *)__o1->chunk)                         \
 368     ? (__o1->next_free = __o1->chunk_limit) : 0);                       \
 369    __o1->object_base = __o1->next_free;                                 \
 370    value; })
 371
 372 #define obstack_free(OBSTACK, OBJ)                                      \
 373 __extension__                                                           \
 374 ({ struct obstack *__o = (OBSTACK);                                     \
 375    void *__obj = (OBJ);                                                 \
 376    if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit)  \
 377      __o->next_free = __o->object_base = __obj;                         \
 378    else (obstack_free) (__o, __obj); })
 379 \f
 380 #else /* not __GNUC__ or not __STDC__ */
 381
 382 #define obstack_object_size(h) \
 383  (unsigned) ((h)->next_free - (h)->object_base)
 384
 385 #define obstack_room(h)         \
 386  (unsigned) ((h)->chunk_limit - (h)->next_free)
 387
 388 #define obstack_grow(h,where,length)                                    \
 389 ( (h)->temp = (length),                                                 \
 390   (((h)->next_free + (h)->temp > (h)->chunk_limit)                      \
 391    ? (_obstack_newchunk ((h), (h)->temp), 0) : 0),                      \
 392   bcopy (where, (h)->next_free, (h)->temp),                             \
 393   (h)->next_free += (h)->temp)
 394
 395 #define obstack_grow0(h,where,length)                                   \
 396 ( (h)->temp = (length),                                                 \
 397   (((h)->next_free + (h)->temp + 1 > (h)->chunk_limit)                  \
 398    ? (_obstack_newchunk ((h), (h)->temp + 1), 0) : 0),                  \
 399   bcopy (where, (h)->next_free, (h)->temp),                             \
 400   (h)->next_free += (h)->temp,                                          \
 401   *((h)->next_free)++ = 0)
 402
 403 #define obstack_1grow(h,datum)                                          \
 404 ( (((h)->next_free + 1 > (h)->chunk_limit)                              \
 405    ? (_obstack_newchunk ((h), 1), 0) : 0),                              \
 406   *((h)->next_free)++ = (datum))
 407
 408 #define obstack_ptr_grow(h,datum)                                       \
 409 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit)                \
 410    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),                \
 411   *(*(char ***)&(h)->next_free)++ = ((char *)datum))
 412
 413 #define obstack_int_grow(h,datum)                                       \
 414 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit)                   \
 415    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),                   \
 416   *(*(int **)&(h)->next_free)++ = ((int)datum))
 417
 418 #define obstack_ptr_grow_fast(h,aptr) (*(*(char ***)&(h)->next_free)++ = (char *)aptr)
 419 #define obstack_int_grow_fast(h,aint) (*(*(int **)&(h)->next_free)++ = (int)aint)
 420 #define obstack_blank(h,length)                                         \
 421 ( (h)->temp = (length),                                                 \
 422   (((h)->chunk_limit - (h)->next_free < (h)->temp)                      \
 423    ? (_obstack_newchunk ((h), (h)->temp), 0) : 0),                      \
 424   (h)->next_free += (h)->temp)
 425
 426 #define obstack_alloc(h,length)                                         \
 427  (obstack_blank ((h), (length)), obstack_finish ((h)))
 428
 429 #define obstack_copy(h,where,length)                                    \
 430  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
 431
 432 #define obstack_copy0(h,where,length)                                   \
 433  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
 434
 435 #define obstack_finish(h)                                               \
 436 ( ((h)->next_free == (h)->object_base                                   \
 437    ? (((h)->flags |= OBSTACK_MAYBE_EMPTY_OBJECT), 0)                    \
 438    : 0),                                                                \
 439   (h)->temp = __PTR_TO_INT ((h)->object_base),                          \
 440   (h)->next_free                                                        \
 441     = __INT_TO_PTR ((__PTR_TO_INT ((h)->next_free)+(h)->alignment_mask) \
 442                     & ~ ((h)->alignment_mask)),                         \
 443   (((h)->next_free - (char *)(h)->chunk                                 \
 444     > (h)->chunk_limit - (char *)(h)->chunk)                            \
 445    ? ((h)->next_free = (h)->chunk_limit) : 0),                          \
 446   (h)->object_base = (h)->next_free,                                    \
 447   __INT_TO_PTR ((h)->temp))
 448
 449 #ifdef __STDC__
 450 #define obstack_free(h,obj)                                             \
 451 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk,                      \
 452   (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
 453    ? (int) ((h)->next_free = (h)->object_base                           \
 454             = (h)->temp + (char *) (h)->chunk)                          \
 455    : (((obstack_free) ((h), (h)->temp + (char *) (h)->chunk), 0), 0)))
 456 #else
 457 #define obstack_free(h,obj)                                             \
 458 ( (h)->temp = (char *)(obj) - (char *) (h)->chunk,                      \
 459   (((h)->temp > 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
 460    ? (int) ((h)->next_free = (h)->object_base                           \
 461             = (h)->temp + (char *) (h)->chunk)                          \
 462    : (_obstack_free ((h), (h)->temp + (char *) (h)->chunk), 0)))
 463 #endif
 464
 465 #endif /* not __GNUC__ or not __STDC__ */
 466
 467 #endif /* not __OBSTACKS__ */