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