/*	$OpenBSD: alloc.c,v 1.5 2002/03/01 13:06:18 espie Exp $	*/
/*
 * Copyright (c) 2002 Marc Espie.
 *
 * 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 OPENBSD PROJECT AND CONTRIBUTORS
 * ``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 OPENBSD
 * PROJECT OR CONTRIBUTORS 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.
 */

/*
 * area-based allocation built on malloc/free
 */

#include "sh.h"

struct link {
	struct link *prev;
	struct link *next;
};

Area *
ainit(Area *ap)
{
	ap->freelist = NULL;
	return ap;
}

void
afreeall(Area *ap)
{
	struct link *l, *l2;

	for (l = ap->freelist; l != NULL; l = l2) {
		l2 = l->next;
		free(l);
	}
	ap->freelist = NULL;
}

#define L2P(l)	( (void *)(((char *)(l)) + sizeof(struct link)) )
#define P2L(p)	( (struct link *)(((char *)(p)) - sizeof(struct link)) )

void *
alloc(size_t size, Area *ap)
{
	struct link *l;

	l = malloc(size + sizeof(struct link));
	if (!l)
		return NULL;
	l->next = ap->freelist;
	l->prev = NULL;
	if (ap->freelist)
		ap->freelist->prev = l;
	ap->freelist = l;

	return L2P(l);
}

void *
aresize(void *ptr, size_t size, Area *ap)
{
	struct link *l, *l2, *lprev, *lnext;

	if (ptr == NULL)
		return alloc(size, ap);

	l = P2L(ptr);
	lprev = l->prev;
	lnext = l->next;

	l2 = realloc(l, size+sizeof(struct link));
	if (l2) {
		if (lprev)
		    lprev->next = l2;
	    	else
		    ap->freelist = l2;
		if (lnext)
		    lnext->prev = l2;
		}
	return L2P(l2);
}

void
afree(void *ptr, Area *ap)
{
	struct link *l;

	if (!ptr)
		return;

	l = P2L(ptr);

	if (l->prev)
		l->prev->next = l->next;
	else
		ap->freelist = l->next;
	if (l->next)
		l->next->prev = l->prev;

	free(l);
}