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