text: /*	$NetBSD: alloc.c,v 1.26 2011/07/30 03:43:20 jakllsch Exp $	*/
  
  /*
   * Copyright (c) 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * This code is derived from software contributed to Berkeley by
   * The Mach Operating System project at Carnegie-Mellon University.
   *
   * 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.
   * 3. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
   *
   *	@(#)alloc.c	8.1 (Berkeley) 6/11/93
   *
   *
   * Copyright (c) 1997 Christopher G. Demetriou.  All rights reserved.
   * Copyright (c) 1996
   *	Matthias Drochner.  All rights reserved.
   *
   * This code is derived from software contributed to Berkeley by
   * The Mach Operating System project at Carnegie-Mellon University.
   *
   * 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.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *	This product includes software developed by the University of
   *	California, Berkeley and its contributors.
   * 4. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
   *
   *	@(#)alloc.c	8.1 (Berkeley) 6/11/93
   *
   *
   * Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
   * All Rights Reserved.
   *
   * Author: Alessandro Forin
   *
   * Permission to use, copy, modify and distribute this software and its
   * documentation is hereby granted, provided that both the copyright
   * notice and this permission notice appear in all copies of the
   * software, derivative works or modified versions, and any portions
   * thereof, and that both notices appear in supporting documentation.
   *
   * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
   * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   *
   * Carnegie Mellon requests users of this software to return to
   *
   *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   *  School of Computer Science
   *  Carnegie Mellon University
   *  Pittsburgh PA 15213-3890
   *
   * any improvements or extensions that they make and grant Carnegie the
   * rights to redistribute these changes.
   */
  
  /*
   * Dynamic memory allocator.
   *
   * Compile options:
   *
   *	ALLOC_TRACE	enable tracing of allocations/deallocations
  
   *	ALLOC_FIRST_FIT	use a first-fit allocation algorithm, rather than
   *			the default best-fit algorithm.
   *
   *	HEAP_LIMIT	heap limit address (defaults to "no limit").
   *
   *	HEAP_START	start address of heap (defaults to '&end').
   *
   *	DEBUG		enable debugging sanity checks.
   */
  
  #include <sys/param.h>
  #include "stand.h"
  
  /*
   * Each block actually has ALIGN(unsigned int) + ALIGN(size) bytes allocated
   * to it, as follows:
   *
   * 0 ... (sizeof(unsigned int) - 1)
   *	allocated or unallocated: holds size of user-data part of block.
   *
   * sizeof(unsigned int) ... (ALIGN(sizeof(unsigned int)) - 1)
   *	allocated: unused
   *	unallocated: depends on packing of struct fl
   *
   * ALIGN(sizeof(unsigned int)) ...
   *     (ALIGN(sizeof(unsigned int)) + ALIGN(data size) - 1)
   *	allocated: user data
   *	unallocated: depends on packing of struct fl
   *
   * 'next' is only used when the block is unallocated (i.e. on the free list).
   * However, note that ALIGN(sizeof(unsigned int)) + ALIGN(data size) must
   * be at least 'sizeof(struct fl)', so that blocks can be used as structures
   * when on the free list.
   */
  struct fl {
  	unsigned int	size;
  	struct fl	*next;
  } *freelist;
  
  #ifdef HEAP_VARIABLE
  static char *top, *heapstart, *heaplimit;
  void
  setheap(void *start, void *limit)
  {
  	heapstart = top = start;
  	heaplimit = limit;
  }
  #define HEAP_START heapstart
  #define HEAP_LIMIT heaplimit
  #else /* !HEAP_VARIABLE */
  #ifndef HEAP_START
  extern char end[];
  #define HEAP_START end
  #endif
  static char *top = (char *)HEAP_START;
  #endif /* HEAP_VARIABLE */
  
  __compactcall void *
  alloc(size_t size)
  {
  	struct fl **f = &freelist, **bestf = NULL;
  #ifndef ALLOC_FIRST_FIT
  	unsigned int bestsize = 0xffffffff;	/* greater than any real size */
  #endif
  	char *help;
  	int failed;
  
  #ifdef ALLOC_TRACE
  	printf("alloc(%zu)", size);
  #endif
  
  #ifdef ALLOC_FIRST_FIT
  	while (*f != (struct fl *)0 && (size_t)(*f)->size < size)
  		f = &((*f)->next);
  	bestf = f;
  	failed = (*bestf == (struct fl *)0);
  #else
  	/* scan freelist */
  	while (*f) {
  		if ((size_t)(*f)->size >= size) {
  			if ((size_t)(*f)->size == size) /* exact match */
  				goto found;
  
  			if ((*f)->size < bestsize) {
  				/* keep best fit */
  				bestf = f;
  				bestsize = (*f)->size;
  			}
  		}
  		f = &((*f)->next);
  	}
  
  	/* no match in freelist if bestsize unchanged */
  	failed = (bestsize == 0xffffffff);
  #endif
  
  	if (failed) { /* nothing found */
  		/*
  		 * allocate from heap, keep chunk len in
  		 * first word
  		 */
  		help = top;
  
  		/* make _sure_ the region can hold a struct fl. */
  		if (size < ALIGN(sizeof (struct fl *)))
  			size = ALIGN(sizeof (struct fl *));
  		top += ALIGN(sizeof(unsigned int)) + ALIGN(size);
  #ifdef HEAP_LIMIT
  		if (top > (char *)HEAP_LIMIT)
  			panic("heap full (%p+%zu)", help, size);
  #endif
  		*(unsigned int *)(void *)help = (unsigned int)ALIGN(size);
  #ifdef ALLOC_TRACE
  		printf("=%lx\n", (u_long)help + ALIGN(sizeof(unsigned int)));
  #endif
  		return help + ALIGN(sizeof(unsigned int));
  	}
  
  	/* we take the best fit */
  	f = bestf;
  
  #ifndef ALLOC_FIRST_FIT
  found:
  #endif
  	/* remove from freelist */
  	help = (char *)(void *)*f;
  	*f = (*f)->next;
  #ifdef ALLOC_TRACE
  	printf("=%lx (origsize %u)\n",
  	    (u_long)help + ALIGN(sizeof(unsigned int)), *(unsigned int *)help);
  #endif
  	return help + ALIGN(sizeof(unsigned int));
  }
  
  __compactcall void
  /*ARGSUSED*/
  dealloc(void *ptr, size_t size)
  {
  	struct fl *f =
  	    (struct fl *)(void *)((char *)(void *)ptr -
  	    ALIGN(sizeof(unsigned int)));
  #ifdef ALLOC_TRACE
  	printf("dealloc(%lx, %zu) (origsize %u)\n", (u_long)ptr, size, f->size);
  #endif
  #ifdef DEBUG
  	if (size > (size_t)f->size) {
  		printf("dealloc %zu bytes @%lx, should be <=%u\n",
  			size, (u_long)ptr, f->size);
  	}
  
  	if (ptr < (void *)HEAP_START)
  		printf("dealloc: %lx before start of heap.\n", (u_long)ptr);
  
  #ifdef HEAP_LIMIT
  	if (ptr > (void *)HEAP_LIMIT)
  		printf("dealloc: %lx beyond end of heap.\n", (u_long)ptr);
  #endif
  #endif /* DEBUG */
  	/* put into freelist */
  	f->next = freelist;
  	freelist = f;
  }
  