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      1 /* obstack.h - object stack macros
      2    Copyright (C) 1988-1994,1996-1999,2003,2004,2005
      3 	Free Software Foundation, Inc.
      4    This file is part of the GNU C Library.
      5 
      6    The GNU C Library is free software; you can redistribute it and/or
      7    modify it under the terms of the GNU Lesser General Public
      8    License as published by the Free Software Foundation; either
      9    version 2.1 of the License, or (at your option) any later version.
     10 
     11    The GNU C Library is distributed in the hope that it will be useful,
     12    but WITHOUT ANY WARRANTY; without even the implied warranty of
     13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     14    Lesser General Public License for more details.
     15 
     16    You should have received a copy of the GNU Lesser General Public
     17    License along with the GNU C Library; if not, write to the Free
     18    Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     19    Boston, MA 02110-1301, USA.  */
     20 
     21 /* Summary:
     22 
     23 All the apparent functions defined here are macros. The idea
     24 is that you would use these pre-tested macros to solve a
     25 very specific set of problems, and they would run fast.
     26 Caution: no side-effects in arguments please!! They may be
     27 evaluated MANY times!!
     28 
     29 These macros operate a stack of objects.  Each object starts life
     30 small, and may grow to maturity.  (Consider building a word syllable
     31 by syllable.)  An object can move while it is growing.  Once it has
     32 been "finished" it never changes address again.  So the "top of the
     33 stack" is typically an immature growing object, while the rest of the
     34 stack is of mature, fixed size and fixed address objects.
     35 
     36 These routines grab large chunks of memory, using a function you
     37 supply, called `obstack_chunk_alloc'.  On occasion, they free chunks,
     38 by calling `obstack_chunk_free'.  You must define them and declare
     39 them before using any obstack macros.
     40 
     41 Each independent stack is represented by a `struct obstack'.
     42 Each of the obstack macros expects a pointer to such a structure
     43 as the first argument.
     44 
     45 One motivation for this package is the problem of growing char strings
     46 in symbol tables.  Unless you are "fascist pig with a read-only mind"
     47 --Gosper's immortal quote from HAKMEM item 154, out of context--you
     48 would not like to put any arbitrary upper limit on the length of your
     49 symbols.
     50 
     51 In practice this often means you will build many short symbols and a
     52 few long symbols.  At the time you are reading a symbol you don't know
     53 how long it is.  One traditional method is to read a symbol into a
     54 buffer, realloc()ating the buffer every time you try to read a symbol
     55 that is longer than the buffer.  This is beaut, but you still will
     56 want to copy the symbol from the buffer to a more permanent
     57 symbol-table entry say about half the time.
     58 
     59 With obstacks, you can work differently.  Use one obstack for all symbol
     60 names.  As you read a symbol, grow the name in the obstack gradually.
     61 When the name is complete, finalize it.  Then, if the symbol exists already,
     62 free the newly read name.
     63 
     64 The way we do this is to take a large chunk, allocating memory from
     65 low addresses.  When you want to build a symbol in the chunk you just
     66 add chars above the current "high water mark" in the chunk.  When you
     67 have finished adding chars, because you got to the end of the symbol,
     68 you know how long the chars are, and you can create a new object.
     69 Mostly the chars will not burst over the highest address of the chunk,
     70 because you would typically expect a chunk to be (say) 100 times as
     71 long as an average object.
     72 
     73 In case that isn't clear, when we have enough chars to make up
     74 the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
     75 so we just point to it where it lies.  No moving of chars is
     76 needed and this is the second win: potentially long strings need
     77 never be explicitly shuffled. Once an object is formed, it does not
     78 change its address during its lifetime.
     79 
     80 When the chars burst over a chunk boundary, we allocate a larger
     81 chunk, and then copy the partly formed object from the end of the old
     82 chunk to the beginning of the new larger chunk.  We then carry on
     83 accreting characters to the end of the object as we normally would.
     84 
     85 A special macro is provided to add a single char at a time to a
     86 growing object.  This allows the use of register variables, which
     87 break the ordinary 'growth' macro.
     88 
     89 Summary:
     90 	We allocate large chunks.
     91 	We carve out one object at a time from the current chunk.
     92 	Once carved, an object never moves.
     93 	We are free to append data of any size to the currently
     94 	  growing object.
     95 	Exactly one object is growing in an obstack at any one time.
     96 	You can run one obstack per control block.
     97 	You may have as many control blocks as you dare.
     98 	Because of the way we do it, you can `unwind' an obstack
     99 	  back to a previous state. (You may remove objects much
    100 	  as you would with a stack.)
    101 */
    102 
    103 
    104 /* Don't do the contents of this file more than once.  */
    105 
    106 #ifndef _OBSTACK_H
    107 #define _OBSTACK_H 1
    108 
    109 #ifdef __cplusplus
    110 extern "C" {
    111 #endif
    112 
    113 /* We need the type of a pointer subtraction.  If __PTRDIFF_TYPE__ is
    115    defined, as with GNU C, use that; that way we don't pollute the
    116    namespace with <stddef.h>'s symbols.  Otherwise, include <stddef.h>
    117    and use ptrdiff_t.  */
    118 
    119 #ifdef __PTRDIFF_TYPE__
    120 # define PTR_INT_TYPE __PTRDIFF_TYPE__
    121 #else
    122 # include <stddef.h>
    123 # define PTR_INT_TYPE ptrdiff_t
    124 #endif
    125 
    126 /* If B is the base of an object addressed by P, return the result of
    127    aligning P to the next multiple of A + 1.  B and P must be of type
    128    char *.  A + 1 must be a power of 2.  */
    129 
    130 #define __BPTR_ALIGN(B, P, A) ((B) + (((P) - (B) + (A)) & ~(A)))
    131 
    132 /* Similiar to _BPTR_ALIGN (B, P, A), except optimize the common case
    133    where pointers can be converted to integers, aligned as integers,
    134    and converted back again.  If PTR_INT_TYPE is narrower than a
    135    pointer (e.g., the AS/400), play it safe and compute the alignment
    136    relative to B.  Otherwise, use the faster strategy of computing the
    137    alignment relative to 0.  */
    138 
    139 #define __PTR_ALIGN(B, P, A)						    \
    140   __BPTR_ALIGN (sizeof (PTR_INT_TYPE) < sizeof (void *) ? (B) : (char *) 0, \
    141 		P, A)
    142 
    143 #include <string.h>
    144 
    145 struct _obstack_chunk		/* Lives at front of each chunk. */
    146 {
    147   char  *limit;			/* 1 past end of this chunk */
    148   struct _obstack_chunk *prev;	/* address of prior chunk or NULL */
    149   char	contents[4];		/* objects begin here */
    150 };
    151 
    152 struct obstack		/* control current object in current chunk */
    153 {
    154   long	chunk_size;		/* preferred size to allocate chunks in */
    155   struct _obstack_chunk *chunk;	/* address of current struct obstack_chunk */
    156   char	*object_base;		/* address of object we are building */
    157   char	*next_free;		/* where to add next char to current object */
    158   char	*chunk_limit;		/* address of char after current chunk */
    159   union
    160   {
    161     PTR_INT_TYPE tempint;
    162     void *tempptr;
    163   } temp;			/* Temporary for some macros.  */
    164   int   alignment_mask;		/* Mask of alignment for each object. */
    165   /* These prototypes vary based on `use_extra_arg', and we use
    166      casts to the prototypeless function type in all assignments,
    167      but having prototypes here quiets -Wstrict-prototypes.  */
    168   struct _obstack_chunk *(*chunkfun) (void *, long);
    169   void (*freefun) (void *, struct _obstack_chunk *);
    170   void *extra_arg;		/* first arg for chunk alloc/dealloc funcs */
    171   unsigned use_extra_arg:1;	/* chunk alloc/dealloc funcs take extra arg */
    172   unsigned maybe_empty_object:1;/* There is a possibility that the current
    173 				   chunk contains a zero-length object.  This
    174 				   prevents freeing the chunk if we allocate
    175 				   a bigger chunk to replace it. */
    176   unsigned alloc_failed:1;	/* No longer used, as we now call the failed
    177 				   handler on error, but retained for binary
    178 				   compatibility.  */
    179 };
    180 
    181 /* Declare the external functions we use; they are in obstack.c.  */
    182 
    183 extern void _obstack_newchunk (struct obstack *, int);
    184 extern int _obstack_begin (struct obstack *, int, int,
    185 			    void *(*) (long), void (*) (void *));
    186 extern int _obstack_begin_1 (struct obstack *, int, int,
    187 			     void *(*) (void *, long),
    188 			     void (*) (void *, void *), void *);
    189 extern int _obstack_memory_used (struct obstack *);
    190 
    191 void obstack_free (struct obstack *obstack, void *block);
    192 
    193 
    194 /* Error handler called when `obstack_chunk_alloc' failed to allocate
    196    more memory.  This can be set to a user defined function which
    197    should either abort gracefully or use longjump - but shouldn't
    198    return.  The default action is to print a message and abort.  */
    199 extern void (*obstack_alloc_failed_handler) (void);
    200 
    201 /* Exit value used when `print_and_abort' is used.  */
    202 extern int obstack_exit_failure;
    203 
    204 /* Pointer to beginning of object being allocated or to be allocated next.
    206    Note that this might not be the final address of the object
    207    because a new chunk might be needed to hold the final size.  */
    208 
    209 #define obstack_base(h) ((void *) (h)->object_base)
    210 
    211 /* Size for allocating ordinary chunks.  */
    212 
    213 #define obstack_chunk_size(h) ((h)->chunk_size)
    214 
    215 /* Pointer to next byte not yet allocated in current chunk.  */
    216 
    217 #define obstack_next_free(h)	((h)->next_free)
    218 
    219 /* Mask specifying low bits that should be clear in address of an object.  */
    220 
    221 #define obstack_alignment_mask(h) ((h)->alignment_mask)
    222 
    223 /* To prevent prototype warnings provide complete argument list.  */
    224 #define obstack_init(h)						\
    225   _obstack_begin ((h), 0, 0,					\
    226 		  (void *(*) (long)) obstack_chunk_alloc,	\
    227 		  (void (*) (void *)) obstack_chunk_free)
    228 
    229 #define obstack_begin(h, size)					\
    230   _obstack_begin ((h), (size), 0,				\
    231 		  (void *(*) (long)) obstack_chunk_alloc,	\
    232 		  (void (*) (void *)) obstack_chunk_free)
    233 
    234 #define obstack_specify_allocation(h, size, alignment, chunkfun, freefun)  \
    235   _obstack_begin ((h), (size), (alignment),				   \
    236 		  (void *(*) (long)) (chunkfun),			   \
    237 		  (void (*) (void *)) (freefun))
    238 
    239 #define obstack_specify_allocation_with_arg(h, size, alignment, chunkfun, freefun, arg) \
    240   _obstack_begin_1 ((h), (size), (alignment),				\
    241 		    (void *(*) (void *, long)) (chunkfun),		\
    242 		    (void (*) (void *, void *)) (freefun), (arg))
    243 
    244 #define obstack_chunkfun(h, newchunkfun) \
    245   ((h) -> chunkfun = (struct _obstack_chunk *(*)(void *, long)) (newchunkfun))
    246 
    247 #define obstack_freefun(h, newfreefun) \
    248   ((h) -> freefun = (void (*)(void *, struct _obstack_chunk *)) (newfreefun))
    249 
    250 #define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = (achar))
    251 
    252 #define obstack_blank_fast(h,n) ((h)->next_free += (n))
    253 
    254 #define obstack_memory_used(h) _obstack_memory_used (h)
    255 
    256 #if defined __GNUC__ && defined __STDC__ && __STDC__
    258 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
    259    does not implement __extension__.  But that compiler doesn't define
    260    __GNUC_MINOR__.  */
    261 # if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
    262 #  define __extension__
    263 # endif
    264 
    265 /* For GNU C, if not -traditional,
    266    we can define these macros to compute all args only once
    267    without using a global variable.
    268    Also, we can avoid using the `temp' slot, to make faster code.  */
    269 
    270 # define obstack_object_size(OBSTACK)					\
    271   __extension__								\
    272   ({ struct obstack const *__o = (OBSTACK);				\
    273      (unsigned) (__o->next_free - __o->object_base); })
    274 
    275 # define obstack_room(OBSTACK)						\
    276   __extension__								\
    277   ({ struct obstack const *__o = (OBSTACK);				\
    278      (unsigned) (__o->chunk_limit - __o->next_free); })
    279 
    280 # define obstack_make_room(OBSTACK,length)				\
    281 __extension__								\
    282 ({ struct obstack *__o = (OBSTACK);					\
    283    int __len = (length);						\
    284    if (__o->chunk_limit - __o->next_free < __len)			\
    285      _obstack_newchunk (__o, __len);					\
    286    (void) 0; })
    287 
    288 # define obstack_empty_p(OBSTACK)					\
    289   __extension__								\
    290   ({ struct obstack const *__o = (OBSTACK);				\
    291      (__o->chunk->prev == 0						\
    292       && __o->next_free == __PTR_ALIGN ((char *) __o->chunk,		\
    293 					__o->chunk->contents,		\
    294 					__o->alignment_mask)); })
    295 
    296 # define obstack_grow(OBSTACK,where,length)				\
    297 __extension__								\
    298 ({ struct obstack *__o = (OBSTACK);					\
    299    int __len = (length);						\
    300    if (__o->next_free + __len > __o->chunk_limit)			\
    301      _obstack_newchunk (__o, __len);					\
    302    memcpy (__o->next_free, where, __len);				\
    303    __o->next_free += __len;						\
    304    (void) 0; })
    305 
    306 # define obstack_grow0(OBSTACK,where,length)				\
    307 __extension__								\
    308 ({ struct obstack *__o = (OBSTACK);					\
    309    int __len = (length);						\
    310    if (__o->next_free + __len + 1 > __o->chunk_limit)			\
    311      _obstack_newchunk (__o, __len + 1);				\
    312    memcpy (__o->next_free, where, __len);				\
    313    __o->next_free += __len;						\
    314    *(__o->next_free)++ = 0;						\
    315    (void) 0; })
    316 
    317 # define obstack_1grow(OBSTACK,datum)					\
    318 __extension__								\
    319 ({ struct obstack *__o = (OBSTACK);					\
    320    if (__o->next_free + 1 > __o->chunk_limit)				\
    321      _obstack_newchunk (__o, 1);					\
    322    obstack_1grow_fast (__o, datum);					\
    323    (void) 0; })
    324 
    325 /* These assume that the obstack alignment is good enough for pointers
    326    or ints, and that the data added so far to the current object
    327    shares that much alignment.  */
    328 
    329 # define obstack_ptr_grow(OBSTACK,datum)				\
    330 __extension__								\
    331 ({ struct obstack *__o = (OBSTACK);					\
    332    if (__o->next_free + sizeof (void *) > __o->chunk_limit)		\
    333      _obstack_newchunk (__o, sizeof (void *));				\
    334    obstack_ptr_grow_fast (__o, datum); })				\
    335 
    336 # define obstack_int_grow(OBSTACK,datum)				\
    337 __extension__								\
    338 ({ struct obstack *__o = (OBSTACK);					\
    339    if (__o->next_free + sizeof (int) > __o->chunk_limit)		\
    340      _obstack_newchunk (__o, sizeof (int));				\
    341    obstack_int_grow_fast (__o, datum); })
    342 
    343 # define obstack_ptr_grow_fast(OBSTACK,aptr)				\
    344 __extension__								\
    345 ({ struct obstack *__o1 = (OBSTACK);					\
    346    *(const void **) __o1->next_free = (aptr);				\
    347    __o1->next_free += sizeof (const void *);				\
    348    (void) 0; })
    349 
    350 # define obstack_int_grow_fast(OBSTACK,aint)				\
    351 __extension__								\
    352 ({ struct obstack *__o1 = (OBSTACK);					\
    353    *(int *) __o1->next_free = (aint);					\
    354    __o1->next_free += sizeof (int);					\
    355    (void) 0; })
    356 
    357 # define obstack_blank(OBSTACK,length)					\
    358 __extension__								\
    359 ({ struct obstack *__o = (OBSTACK);					\
    360    int __len = (length);						\
    361    if (__o->chunk_limit - __o->next_free < __len)			\
    362      _obstack_newchunk (__o, __len);					\
    363    obstack_blank_fast (__o, __len);					\
    364    (void) 0; })
    365 
    366 # define obstack_alloc(OBSTACK,length)					\
    367 __extension__								\
    368 ({ struct obstack *__h = (OBSTACK);					\
    369    obstack_blank (__h, (length));					\
    370    obstack_finish (__h); })
    371 
    372 # define obstack_copy(OBSTACK,where,length)				\
    373 __extension__								\
    374 ({ struct obstack *__h = (OBSTACK);					\
    375    obstack_grow (__h, (where), (length));				\
    376    obstack_finish (__h); })
    377 
    378 # define obstack_copy0(OBSTACK,where,length)				\
    379 __extension__								\
    380 ({ struct obstack *__h = (OBSTACK);					\
    381    obstack_grow0 (__h, (where), (length));				\
    382    obstack_finish (__h); })
    383 
    384 /* The local variable is named __o1 to avoid a name conflict
    385    when obstack_blank is called.  */
    386 # define obstack_finish(OBSTACK)					\
    387 __extension__								\
    388 ({ struct obstack *__o1 = (OBSTACK);					\
    389    void *__value = (void *) __o1->object_base;				\
    390    if (__o1->next_free == __value)					\
    391      __o1->maybe_empty_object = 1;					\
    392    __o1->next_free							\
    393      = __PTR_ALIGN (__o1->object_base, __o1->next_free,			\
    394 		    __o1->alignment_mask);				\
    395    if (__o1->next_free - (char *)__o1->chunk				\
    396        > __o1->chunk_limit - (char *)__o1->chunk)			\
    397      __o1->next_free = __o1->chunk_limit;				\
    398    __o1->object_base = __o1->next_free;					\
    399    __value; })
    400 
    401 # define obstack_free(OBSTACK, OBJ)					\
    402 __extension__								\
    403 ({ struct obstack *__o = (OBSTACK);					\
    404    void *__obj = (OBJ);							\
    405    if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit)  \
    406      __o->next_free = __o->object_base = (char *)__obj;			\
    407    else (obstack_free) (__o, __obj); })
    408 
    409 #else /* not __GNUC__ or not __STDC__ */
    411 
    412 # define obstack_object_size(h) \
    413  (unsigned) ((h)->next_free - (h)->object_base)
    414 
    415 # define obstack_room(h)		\
    416  (unsigned) ((h)->chunk_limit - (h)->next_free)
    417 
    418 # define obstack_empty_p(h) \
    419  ((h)->chunk->prev == 0							\
    420   && (h)->next_free == __PTR_ALIGN ((char *) (h)->chunk,		\
    421 				    (h)->chunk->contents,		\
    422 				    (h)->alignment_mask))
    423 
    424 /* Note that the call to _obstack_newchunk is enclosed in (..., 0)
    425    so that we can avoid having void expressions
    426    in the arms of the conditional expression.
    427    Casting the third operand to void was tried before,
    428    but some compilers won't accept it.  */
    429 
    430 # define obstack_make_room(h,length)					\
    431 ( (h)->temp.tempint = (length),						\
    432   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)		\
    433    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0))
    434 
    435 # define obstack_grow(h,where,length)					\
    436 ( (h)->temp.tempint = (length),						\
    437   (((h)->next_free + (h)->temp.tempint > (h)->chunk_limit)		\
    438    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),		\
    439   memcpy ((h)->next_free, where, (h)->temp.tempint),			\
    440   (h)->next_free += (h)->temp.tempint)
    441 
    442 # define obstack_grow0(h,where,length)					\
    443 ( (h)->temp.tempint = (length),						\
    444   (((h)->next_free + (h)->temp.tempint + 1 > (h)->chunk_limit)		\
    445    ? (_obstack_newchunk ((h), (h)->temp.tempint + 1), 0) : 0),		\
    446   memcpy ((h)->next_free, where, (h)->temp.tempint),			\
    447   (h)->next_free += (h)->temp.tempint,					\
    448   *((h)->next_free)++ = 0)
    449 
    450 # define obstack_1grow(h,datum)						\
    451 ( (((h)->next_free + 1 > (h)->chunk_limit)				\
    452    ? (_obstack_newchunk ((h), 1), 0) : 0),				\
    453   obstack_1grow_fast (h, datum))
    454 
    455 # define obstack_ptr_grow(h,datum)					\
    456 ( (((h)->next_free + sizeof (char *) > (h)->chunk_limit)		\
    457    ? (_obstack_newchunk ((h), sizeof (char *)), 0) : 0),		\
    458   obstack_ptr_grow_fast (h, datum))
    459 
    460 # define obstack_int_grow(h,datum)					\
    461 ( (((h)->next_free + sizeof (int) > (h)->chunk_limit)			\
    462    ? (_obstack_newchunk ((h), sizeof (int)), 0) : 0),			\
    463   obstack_int_grow_fast (h, datum))
    464 
    465 # define obstack_ptr_grow_fast(h,aptr)					\
    466   (((const void **) ((h)->next_free += sizeof (void *)))[-1] = (aptr))
    467 
    468 # define obstack_int_grow_fast(h,aint)					\
    469   (((int *) ((h)->next_free += sizeof (int)))[-1] = (aint))
    470 
    471 # define obstack_blank(h,length)					\
    472 ( (h)->temp.tempint = (length),						\
    473   (((h)->chunk_limit - (h)->next_free < (h)->temp.tempint)		\
    474    ? (_obstack_newchunk ((h), (h)->temp.tempint), 0) : 0),		\
    475   obstack_blank_fast (h, (h)->temp.tempint))
    476 
    477 # define obstack_alloc(h,length)					\
    478  (obstack_blank ((h), (length)), obstack_finish ((h)))
    479 
    480 # define obstack_copy(h,where,length)					\
    481  (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
    482 
    483 # define obstack_copy0(h,where,length)					\
    484  (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
    485 
    486 # define obstack_finish(h)						\
    487 ( ((h)->next_free == (h)->object_base					\
    488    ? (((h)->maybe_empty_object = 1), 0)					\
    489    : 0),								\
    490   (h)->temp.tempptr = (h)->object_base,					\
    491   (h)->next_free							\
    492     = __PTR_ALIGN ((h)->object_base, (h)->next_free,			\
    493 		   (h)->alignment_mask),				\
    494   (((h)->next_free - (char *) (h)->chunk				\
    495     > (h)->chunk_limit - (char *) (h)->chunk)				\
    496    ? ((h)->next_free = (h)->chunk_limit) : 0),				\
    497   (h)->object_base = (h)->next_free,					\
    498   (h)->temp.tempptr)
    499 
    500 # define obstack_free(h,obj)						\
    501 ( (h)->temp.tempint = (char *) (obj) - (char *) (h)->chunk,		\
    502   ((((h)->temp.tempint > 0						\
    503     && (h)->temp.tempint < (h)->chunk_limit - (char *) (h)->chunk))	\
    504    ? (int) ((h)->next_free = (h)->object_base				\
    505 	    = (h)->temp.tempint + (char *) (h)->chunk)			\
    506    : (((obstack_free) ((h), (h)->temp.tempint + (char *) (h)->chunk), 0), 0)))
    507 
    508 #endif /* not __GNUC__ or not __STDC__ */
    509 
    510 #ifdef __cplusplus
    511 }	/* C++ */
    512 #endif
    513 
    514 #endif /* obstack.h */
    515