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authorJohn Gilmore <gnu@cygnus>1991-04-25 04:20:11 +0000
committerJohn Gilmore <gnu@cygnus>1991-04-25 04:20:11 +0000
commita07cc61341225966fd714e8715aeca6c558b5b8e (patch)
tree4619bd0c087f07b5b8cd155e1bf34ecdce2dbf0e /include/obstack.h
parenta6ac0c5998db0fb3b89c11800507b7307dba692b (diff)
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+/* obstack.h - object stack macros
+ Copyright (C) 1988 Free Software Foundation, Inc.
+
+This program is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 1, or (at your option) any
+later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+/* Summary:
+
+All the apparent functions defined here are macros. The idea
+is that you would use these pre-tested macros to solve a
+very specific set of problems, and they would run fast.
+Caution: no side-effects in arguments please!! They may be
+evaluated MANY times!!
+
+These macros operate a stack of objects. Each object starts life
+small, and may grow to maturity. (Consider building a word syllable
+by syllable.) An object can move while it is growing. Once it has
+been "finished" it never changes address again. So the "top of the
+stack" is typically an immature growing object, while the rest of the
+stack is of mature, fixed size and fixed address objects.
+
+These routines grab large chunks of memory, using a function you
+supply, called `obstack_chunk_alloc'. On occasion, they free chunks,
+by calling `obstack_chunk_free'. You must define them and declare
+them before using any obstack macros.
+
+Each independent stack is represented by a `struct obstack'.
+Each of the obstack macros expects a pointer to such a structure
+as the first argument.
+
+One motivation for this package is the problem of growing char strings
+in symbol tables. Unless you are "fascist pig with a read-only mind"
+[Gosper's immortal quote from HAKMEM item 154, out of context] you
+would not like to put any arbitrary upper limit on the length of your
+symbols.
+
+In practice this often means you will build many short symbols and a
+few long symbols. At the time you are reading a symbol you don't know
+how long it is. One traditional method is to read a symbol into a
+buffer, realloc()ating the buffer every time you try to read a symbol
+that is longer than the buffer. This is beaut, but you still will
+want to copy the symbol from the buffer to a more permanent
+symbol-table entry say about half the time.
+
+With obstacks, you can work differently. Use one obstack for all symbol
+names. As you read a symbol, grow the name in the obstack gradually.
+When the name is complete, finalize it. Then, if the symbol exists already,
+free the newly read name.
+
+The way we do this is to take a large chunk, allocating memory from
+low addresses. When you want to build a symbol in the chunk you just
+add chars above the current "high water mark" in the chunk. When you
+have finished adding chars, because you got to the end of the symbol,
+you know how long the chars are, and you can create a new object.
+Mostly the chars will not burst over the highest address of the chunk,
+because you would typically expect a chunk to be (say) 100 times as
+long as an average object.
+
+In case that isn't clear, when we have enough chars to make up
+the object, THEY ARE ALREADY CONTIGUOUS IN THE CHUNK (guaranteed)
+so we just point to it where it lies. No moving of chars is
+needed and this is the second win: potentially long strings need
+never be explicitly shuffled. Once an object is formed, it does not
+change its address during its lifetime.
+
+When the chars burst over a chunk boundary, we allocate a larger
+chunk, and then copy the partly formed object from the end of the old
+chunk to the beginning of the new larger chunk. We then carry on
+accreting characters to the end of the object as we normally would.
+
+A special macro is provided to add a single char at a time to a
+growing object. This allows the use of register variables, which
+break the ordinary 'growth' macro.
+
+Summary:
+ We allocate large chunks.
+ We carve out one object at a time from the current chunk.
+ Once carved, an object never moves.
+ We are free to append data of any size to the currently
+ growing object.
+ Exactly one object is growing in an obstack at any one time.
+ You can run one obstack per control block.
+ You may have as many control blocks as you dare.
+ Because of the way we do it, you can `unwind' a obstack
+ back to a previous state. (You may remove objects much
+ as you would with a stack.)
+*/
+
+
+/* Don't do the contents of this file more than once. */
+
+#ifndef __OBSTACKS__
+#define __OBSTACKS__
+
+/* We use subtraction of (char *)0 instead of casting to int
+ because on word-addressable machines a simple cast to int
+ may ignore the byte-within-word field of the pointer. */
+
+#ifndef __PTR_TO_INT
+#define __PTR_TO_INT(P) ((P) - (char *)0)
+#endif
+
+#ifndef __INT_TO_PTR
+#define __INT_TO_PTR(P) ((P) + (char *)0)
+#endif
+
+struct _obstack_chunk /* Lives at front of each chunk. */
+{
+ char *limit; /* 1 past end of this chunk */
+ struct _obstack_chunk *prev; /* address of prior chunk or NULL */
+ char contents[4]; /* objects begin here */
+};
+
+struct obstack /* control current object in current chunk */
+{
+ long chunk_size; /* preferred size to allocate chunks in */
+ struct _obstack_chunk* chunk; /* address of current struct obstack_chunk */
+ char *object_base; /* address of object we are building */
+ char *next_free; /* where to add next char to current object */
+ char *chunk_limit; /* address of char after current chunk */
+ int temp; /* Temporary for some macros. */
+ int alignment_mask; /* Mask of alignment for each object. */
+#ifdef __STDC__
+ void *(*chunkfun) (); /* User's fcn to allocate a chunk. */
+#else
+ char *(*chunkfun) (); /* User's fcn to allocate a chunk. */
+#endif
+ void (*freefun) (); /* User's function to free a chunk. */
+};
+
+#ifdef __STDC__
+
+/* Do the function-declarations after the structs
+ but before defining the macros. */
+
+void obstack_init (struct obstack *obstack);
+
+void * obstack_alloc (struct obstack *obstack, int size);
+
+void * obstack_copy (struct obstack *obstack, void *address, int size);
+void * obstack_copy0 (struct obstack *obstack, void *address, int size);
+
+void obstack_free (struct obstack *obstack, void *block);
+
+void obstack_blank (struct obstack *obstack, int size);
+
+void obstack_grow (struct obstack *obstack, void *data, int size);
+void obstack_grow0 (struct obstack *obstack, void *data, int size);
+
+void obstack_1grow (struct obstack *obstack, int data_char);
+void obstack_ptr_grow (struct obstack *obstack, void *data);
+void obstack_int_grow (struct obstack *obstack, int data);
+
+void * obstack_finish (struct obstack *obstack);
+
+int obstack_object_size (struct obstack *obstack);
+
+int obstack_room (struct obstack *obstack);
+void obstack_1grow_fast (struct obstack *obstack, int data_char);
+void obstack_ptr_grow_fast (struct obstack *obstack, void *data);
+void obstack_int_grow_fast (struct obstack *obstack, int data);
+void obstack_blank_fast (struct obstack *obstack, int size);
+
+void * obstack_base (struct obstack *obstack);
+void * obstack_next_free (struct obstack *obstack);
+int obstack_alignment_mask (struct obstack *obstack);
+int obstack_chunk_size (struct obstack *obstack);
+
+#endif /* __STDC__ */
+
+/* Non-ANSI C cannot really support alternative functions for these macros,
+ so we do not declare them. */
+
+/* Pointer to beginning of object being allocated or to be allocated next.
+ Note that this might not be the final address of the object
+ because a new chunk might be needed to hold the final size. */
+
+#define obstack_base(h) ((h)->object_base)
+
+/* Size for allocating ordinary chunks. */
+
+#define obstack_chunk_size(h) ((h)->chunk_size)
+
+/* Pointer to next byte not yet allocated in current chunk. */
+
+#define obstack_next_free(h) ((h)->next_free)
+
+/* Mask specifying low bits that should be clear in address of an object. */
+
+#define obstack_alignment_mask(h) ((h)->alignment_mask)
+
+#define obstack_init(h) \
+ _obstack_begin ((h), 0, 0, obstack_chunk_alloc, obstack_chunk_free)
+
+#define obstack_begin(h, size) \
+ _obstack_begin ((h), (size), 0, obstack_chunk_alloc, obstack_chunk_free)
+
+#define obstack_1grow_fast(h,achar) (*((h)->next_free)++ = achar)
+
+#define obstack_blank_fast(h,n) ((h)->next_free += (n))
+
+#if defined (__GNUC__) && defined (__STDC__)
+
+/* For GNU C, if not -traditional,
+ we can define these macros to compute all args only once
+ without using a global variable.
+ Also, we can avoid using the `temp' slot, to make faster code. */
+
+#define obstack_object_size(OBSTACK) \
+ ({ struct obstack *__o = (OBSTACK); \
+ (unsigned) (__o->next_free - __o->object_base); })
+
+#define obstack_room(OBSTACK) \
+ ({ struct obstack *__o = (OBSTACK); \
+ (unsigned) (__o->chunk_limit - __o->next_free); })
+
+#define obstack_grow(OBSTACK,where,length) \
+({ struct obstack *__o = (OBSTACK); \
+ int __len = (length); \
+ ((__o->next_free + __len > __o->chunk_limit) \
+ ? _obstack_newchunk (__o, __len) : 0); \
+ bcopy (where, __o->next_free, __len); \
+ __o->next_free += __len; \
+ (void) 0; })
+
+#define obstack_grow0(OBSTACK,where,length) \
+({ struct obstack *__o = (OBSTACK); \
+ int __len = (length); \
+ ((__o->next_free + __len + 1 > __o->chunk_limit) \
+ ? _obstack_newchunk (__o, __len + 1) : 0), \
+ bcopy (where, __o->next_free, __len), \
+ __o->next_free += __len, \
+ *(__o->next_free)++ = 0; \
+ (void) 0; })
+
+#define obstack_1grow(OBSTACK,datum) \
+({ struct obstack *__o = (OBSTACK); \
+ ((__o->next_free + 1 > __o->chunk_limit) \
+ ? _obstack_newchunk (__o, 1) : 0), \
+ *(__o->next_free)++ = (datum); \
+ (void) 0; })
+
+/* These assume that the obstack alignment is good enough for pointers or ints,
+ and that the data added so far to the current object
+ shares that much alignment. */
+
+#define obstack_ptr_grow(OBSTACK,datum) \
+({ struct obstack *__o = (OBSTACK); \
+ ((__o->next_free + sizeof (void *) > __o->chunk_limit) \
+ ? _obstack_newchunk (__o, sizeof (void *)) : 0), \
+ *(*(void ***)&__o->next_free)++ = ((void *)datum); \
+ (void) 0; })
+
+#define obstack_int_grow(OBSTACK,datum) \
+({ struct obstack *__o = (OBSTACK); \
+ ((__o->next_free + sizeof (int) > __o->chunk_limit) \
+ ? _obstack_newchunk (__o, sizeof (int)) : 0), \
+ *(*(int **)&__o->next_free)++ = ((int)datum); \
+ (void) 0; })
+
+#define obstack_ptr_grow_fast(h,aptr) (*(*(void ***)&(h)->next_free)++ = (void *)aptr)
+#define obstack_int_grow_fast(h,aint) (*(*(int **)&(h)->next_free)++ = (int)aint)
+
+#define obstack_blank(OBSTACK,length) \
+({ struct obstack *__o = (OBSTACK); \
+ int __len = (length); \
+ ((__o->chunk_limit - __o->next_free < __len) \
+ ? _obstack_newchunk (__o, __len) : 0); \
+ __o->next_free += __len; \
+ (void) 0; })
+
+#define obstack_alloc(OBSTACK,length) \
+({ struct obstack *__h = (OBSTACK); \
+ obstack_blank (__h, (length)); \
+ obstack_finish (__h); })
+
+#define obstack_copy(OBSTACK,where,length) \
+({ struct obstack *__h = (OBSTACK); \
+ obstack_grow (__h, (where), (length)); \
+ obstack_finish (__h); })
+
+#define obstack_copy0(OBSTACK,where,length) \
+({ struct obstack *__h = (OBSTACK); \
+ obstack_grow0 (__h, (where), (length)); \
+ obstack_finish (__h); })
+
+#define obstack_finish(OBSTACK) \
+({ struct obstack *__o = (OBSTACK); \
+ void *value = (void *) __o->object_base; \
+ __o->next_free \
+ = __INT_TO_PTR ((__PTR_TO_INT (__o->next_free)+__o->alignment_mask)\
+ & ~ (__o->alignment_mask)); \
+ ((__o->next_free - (char *)__o->chunk \
+ > __o->chunk_limit - (char *)__o->chunk) \
+ ? (__o->next_free = __o->chunk_limit) : 0); \
+ __o->object_base = __o->next_free; \
+ value; })
+
+#define obstack_free(OBSTACK, OBJ) \
+({ struct obstack *__o = (OBSTACK); \
+ void *__obj = (OBJ); \
+ if (__obj > (void *)__o->chunk && __obj < (void *)__o->chunk_limit) \
+ __o->next_free = __o->object_base = __obj; \
+ else (obstack_free) (__o, __obj); })
+
+#else /* not __GNUC__ or not __STDC__ */
+
+#define obstack_object_size(h) \
+ (unsigned) ((h)->next_free - (h)->object_base)
+
+#define obstack_room(h) \
+ (unsigned) ((h)->chunk_limit - (h)->next_free)
+
+#define obstack_grow(h,where,length) \
+( (h)->temp = (length), \
+ (((h)->next_free + (h)->temp > (h)->chunk_limit) \
+ ? _obstack_newchunk ((h), (h)->temp) : 0), \
+ bcopy (where, (h)->next_free, (h)->temp), \
+ (h)->next_free += (h)->temp)
+
+#define obstack_grow0(h,where,length) \
+( (h)->temp = (length), \
+ (((h)->next_free + (h)->temp + 1 > (h)->chunk_limit) \
+ ? _obstack_newchunk ((h), (h)->temp + 1) : 0), \
+ bcopy (where, (h)->next_free, (h)->temp), \
+ (h)->next_free += (h)->temp, \
+ *((h)->next_free)++ = 0)
+
+#define obstack_1grow(h,datum) \
+( (((h)->next_free + 1 > (h)->chunk_limit) \
+ ? _obstack_newchunk ((h), 1) : 0), \
+ *((h)->next_free)++ = (datum))
+
+#define obstack_ptr_grow(h,datum) \
+( (((h)->next_free + sizeof (char *) > (h)->chunk_limit) \
+ ? _obstack_newchunk ((h), sizeof (char *)) : 0), \
+ *(*(char ***)&(h)->next_free)++ = ((char *)datum))
+
+#define obstack_int_grow(h,datum) \
+( (((h)->next_free + sizeof (int) > (h)->chunk_limit) \
+ ? _obstack_newchunk ((h), sizeof (int)) : 0), \
+ *(*(int **)&(h)->next_free)++ = ((int)datum))
+
+#define obstack_ptr_grow_fast(h,aptr) (*(*(char ***)&(h)->next_free)++ = (char *)aptr)
+#define obstack_int_grow_fast(h,aint) (*(*(int **)&(h)->next_free)++ = (int)aint)
+
+#define obstack_blank(h,length) \
+( (h)->temp = (length), \
+ (((h)->chunk_limit - (h)->next_free < (h)->temp) \
+ ? _obstack_newchunk ((h), (h)->temp) : 0), \
+ (h)->next_free += (h)->temp)
+
+#define obstack_alloc(h,length) \
+ (obstack_blank ((h), (length)), obstack_finish ((h)))
+
+#define obstack_copy(h,where,length) \
+ (obstack_grow ((h), (where), (length)), obstack_finish ((h)))
+
+#define obstack_copy0(h,where,length) \
+ (obstack_grow0 ((h), (where), (length)), obstack_finish ((h)))
+
+#define obstack_finish(h) \
+( (h)->temp = __PTR_TO_INT ((h)->object_base), \
+ (h)->next_free \
+ = __INT_TO_PTR ((__PTR_TO_INT ((h)->next_free)+(h)->alignment_mask) \
+ & ~ ((h)->alignment_mask)), \
+ (((h)->next_free - (char *)(h)->chunk \
+ > (h)->chunk_limit - (char *)(h)->chunk) \
+ ? ((h)->next_free = (h)->chunk_limit) : 0), \
+ (h)->object_base = (h)->next_free, \
+ __INT_TO_PTR ((h)->temp))
+
+#ifdef __STDC__
+#define obstack_free(h,obj) \
+( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \
+ (((h)->temp >= 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
+ ? (int) ((h)->next_free = (h)->object_base \
+ = (h)->temp + (char *) (h)->chunk) \
+ : ((obstack_free) ((h), (h)->temp + (char *) (h)->chunk), 0)))
+#else
+#define obstack_free(h,obj) \
+( (h)->temp = (char *)(obj) - (char *) (h)->chunk, \
+ (((h)->temp >= 0 && (h)->temp < (h)->chunk_limit - (char *) (h)->chunk)\
+ ? (int) ((h)->next_free = (h)->object_base \
+ = (h)->temp + (char *) (h)->chunk) \
+ : (int) _obstack_free ((h), (h)->temp + (char *) (h)->chunk)))
+#endif
+
+#endif /* not __GNUC__ or not __STDC__ */
+
+/* Declare the external functions we use; they are in obstack.c. */
+
+#ifdef __STDC__
+ extern int _obstack_newchunk (struct obstack *h, int length);
+ extern int _obstack_free (struct obstack *h, void *obj);
+ extern void _obstack_begin (struct obstack *h, int size, int alignment,
+ void *(*chunkfun) (), void (*freefun) ());
+#else
+ extern int _obstack_newchunk ();
+ extern int _obstack_free ();
+ extern void _obstack_begin ();
+#endif
+
+#endif /* not __OBSTACKS__ */
+