/*  ibicc - The Ibi C Compiler
    Copyright (C) 2004 Antti-Juhani Kaijanaho

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

    1. Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.

    2. Redistributions in binary form must reproduce the above
       copyright notice, this list of conditions and the following
       disclaimer in the documentation and/or other materials provided
       with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
    OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
    DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
    GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
    WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef ARENA_H
#define ARENA_H

#include <stddef.h>

#define ARENA_ALIGNMENT 4

/* An arena is a mechanism for fast allocation of objects that are
 * freed together.  DON'T TRY TO MALLOC an arena - use arena_init to
 * give you an arena.  arena_fini deallocates the arena and all objects
 * allocated from it.
 *
 * An arena_t object is a pointer and may be assigned at will; this
 * will effect sharing of the arena (but as with malloc/free, an arena
 * must not be deallocated twice).
 *
 * Arena allocation does not interfere with malloc.
 */

struct arena {
	void *buf;
	size_t capacity;
	size_t freeinx;
};

typedef struct arena *arena_t;

arena_t arena_init(void);
void arena_more(arena_t); /* Don't call directly.  */
void arena_fini(arena_t);

/* Usage example:

    struct obj *o;
    new(o, arena);

   allocates *one* struct obj from arena and stores the pointer to o.
   Allocation failure will call enomem(); new will not return if no
   memory is available.

   newa(var,n,arena) is used to allocate an n-element array, the
   address of which is stored in var.

   The type of var is used to determine the size of the allocated
   object(s).
*/
#define newapad(var,n,arena,pad) do { \
        size_t newa__tmp__ = (n)*sizeof *(var) + (pad) + \
		(((n)*sizeof *(var) + (pad)) % ARENA_ALIGNMENT == 0 \
		 ? 0 \
		 : ARENA_ALIGNMENT - ((n)*sizeof *(var) + (pad)) % ARENA_ALIGNMENT); \
	if ((arena)->freeinx + newa__tmp__ > (arena)->capacity) { \
		arena_more((arena)); \
	} \
	assert((arena)->freeinx + newa__tmp__ <= (arena)->capacity); \
	(var) = (arena)->buf + (arena)->freeinx; \
	(arena)->freeinx += newa__tmp__; \
} while (0)

#define newa(var,n,arena) newapad((var),(n),(arena),0)

#define new(var,arena) newa((var),1,(arena))

#define newpad(var,arena,pad) newapad((var),1,(arena),(pad))

#endif /* ARENA_H */