[perl5.git] / malloc.c

/* $RCSfile: malloc.c,v $$Revision: 4.0.1.2 $$Date: 91/06/07 11:20:45 $
 *
 * $Log:	malloc.c,v $
 * Revision 4.0.1.2  91/06/07  11:20:45  lwall
 * patch4: many, many itty-bitty portability fixes
 * 
 * Revision 4.0.1.1  91/04/11  17:48:31  lwall
 * patch1: Configure now figures out malloc ptr type
 * 
 * Revision 4.0  91/03/20  01:28:52  lwall
 * 4.0 baseline.
 * 
 */

#ifndef lint
static char sccsid[] = "@(#)malloc.c	4.3 (Berkeley) 9/16/83";

#ifdef DEBUGGING
#define RCHECK
#endif
/*
 * malloc.c (Caltech) 2/21/82
 * Chris Kingsley, kingsley@cit-20.
 *
 * This is a very fast storage allocator.  It allocates blocks of a small 
 * number of different sizes, and keeps free lists of each size.  Blocks that
 * don't exactly fit are passed up to the next larger size.  In this 
 * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
 * This is designed for use in a program that uses vast quantities of memory,
 * but bombs when it runs out. 
 */

#include "EXTERN.h"
#include "perl.h"

static findbucket(), morecore();

/* I don't much care whether these are defined in sys/types.h--LAW */

#define u_char unsigned char
#define u_int unsigned int
#define u_short unsigned short

/*
 * The overhead on a block is at least 4 bytes.  When free, this space
 * contains a pointer to the next free block, and the bottom two bits must
 * be zero.  When in use, the first byte is set to MAGIC, and the second
 * byte is the size index.  The remaining bytes are for alignment.
 * If range checking is enabled and the size of the block fits
 * in two bytes, then the top two bytes hold the size of the requested block
 * plus the range checking words, and the header word MINUS ONE.
 */
union	overhead {
	union	overhead *ov_next;	/* when free */
#if ALIGNBYTES > 4
	double	strut;			/* alignment problems */
#endif
	struct {
		u_char	ovu_magic;	/* magic number */
		u_char	ovu_index;	/* bucket # */
#ifdef RCHECK
		u_short	ovu_size;	/* actual block size */
		u_int	ovu_rmagic;	/* range magic number */
#endif
	} ovu;
#define	ov_magic	ovu.ovu_magic
#define	ov_index	ovu.ovu_index
#define	ov_size		ovu.ovu_size
#define	ov_rmagic	ovu.ovu_rmagic
};

#define	MAGIC		0xff		/* magic # on accounting info */
#define OLDMAGIC	0x7f		/* same after a free() */
#define RMAGIC		0x55555555	/* magic # on range info */
#ifdef RCHECK
#define	RSLOP		sizeof (u_int)
#else
#define	RSLOP		0
#endif

/*
 * nextf[i] is the pointer to the next free block of size 2^(i+3).  The
 * smallest allocatable block is 8 bytes.  The overhead information
 * precedes the data area returned to the user.
 */
#define	NBUCKETS 30
static	union overhead *nextf[NBUCKETS];
extern	char *sbrk();

#ifdef MSTATS
/*
 * nmalloc[i] is the difference between the number of mallocs and frees
 * for a given block size.
 */
static	u_int nmalloc[NBUCKETS];
#include <stdio.h>
#endif

#ifdef debug
#define	ASSERT(p)   if (!(p)) botch("p"); else
static
botch(s)
	char *s;
{

	printf("assertion botched: %s\n", s);
	abort();
}
#else
#define	ASSERT(p)
#endif

MALLOCPTRTYPE *
malloc(nbytes)
	register unsigned nbytes;
{
  	register union overhead *p;
  	register int bucket = 0;
  	register unsigned shiftr;

	/*
	 * Convert amount of memory requested into
	 * closest block size stored in hash buckets
	 * which satisfies request.  Account for
	 * space used per block for accounting.
	 */
  	nbytes += sizeof (union overhead) + RSLOP;
  	nbytes = (nbytes + 3) &~ 3; 
  	shiftr = (nbytes - 1) >> 2;
	/* apart from this loop, this is O(1) */
  	while (shiftr >>= 1)
  		bucket++;
	/*
	 * If nothing in hash bucket right now,
	 * request more memory from the system.
	 */
  	if (nextf[bucket] == NULL)    
  		morecore(bucket);
  	if ((p = (union overhead *)nextf[bucket]) == NULL)
  		return (NULL);
	/* remove from linked list */
#ifdef RCHECK
	if (*((int*)p) & (sizeof(union overhead) - 1))
#ifndef I286
	    fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p);
#else
	    fprintf(stderr,"Corrupt malloc ptr 0x%lx at 0x%lx\n",*((int*)p),p);
#endif
#endif
  	nextf[bucket] = p->ov_next;
	p->ov_magic = MAGIC;
	p->ov_index= bucket;
#ifdef MSTATS
  	nmalloc[bucket]++;
#endif
#ifdef RCHECK
	/*
	 * Record allocated size of block and
	 * bound space with magic numbers.
	 */
  	if (nbytes <= 0x10000)
		p->ov_size = nbytes - 1;
	p->ov_rmagic = RMAGIC;
  	*((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
#endif
  	return ((MALLOCPTRTYPE *)(p + 1));
}

/*
 * Allocate more memory to the indicated bucket.
 */
static
morecore(bucket)
	register int bucket;
{
  	register union overhead *op;
  	register int rnu;       /* 2^rnu bytes will be requested */
  	register int nblks;     /* become nblks blocks of the desired size */
	register int siz;

  	if (nextf[bucket])
  		return;
	/*
	 * Insure memory is allocated
	 * on a page boundary.  Should
	 * make getpageize call?
	 */
  	op = (union overhead *)sbrk(0);
#ifndef I286
  	if ((int)op & 0x3ff)
  		(void)sbrk(1024 - ((int)op & 0x3ff));
#else
	/* The sbrk(0) call on the I286 always returns the next segment */
#endif

#ifndef I286
	/* take 2k unless the block is bigger than that */
  	rnu = (bucket <= 8) ? 11 : bucket + 3;
#else
	/* take 16k unless the block is bigger than that 
	   (80286s like large segments!)		*/
  	rnu = (bucket <= 11) ? 14 : bucket + 3;
#endif
  	nblks = 1 << (rnu - (bucket + 3));  /* how many blocks to get */
  	if (rnu < bucket)
		rnu = bucket;
	op = (union overhead *)sbrk(1 << rnu);
	/* no more room! */
  	if ((int)op == -1)
  		return;
	/*
	 * Round up to minimum allocation size boundary
	 * and deduct from block count to reflect.
	 */
#ifndef I286
  	if ((int)op & 7) {
  		op = (union overhead *)(((int)op + 8) &~ 7);
  		nblks--;
  	}
#else
	/* Again, this should always be ok on an 80286 */
#endif
	/*
	 * Add new memory allocated to that on
	 * free list for this hash bucket.
	 */
  	nextf[bucket] = op;
  	siz = 1 << (bucket + 3);
  	while (--nblks > 0) {
		op->ov_next = (union overhead *)((caddr_t)op + siz);
		op = (union overhead *)((caddr_t)op + siz);
  	}
}

void
free(mp)
	MALLOCPTRTYPE *mp;
{   
  	register int size;
	register union overhead *op;
	char *cp = (char*)mp;

  	if (cp == NULL)
  		return;
	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
#ifdef debug
  	ASSERT(op->ov_magic == MAGIC);		/* make sure it was in use */
#else
	if (op->ov_magic != MAGIC) {
		warn("%s free() ignored",
		    op->ov_magic == OLDMAGIC ? "Duplicate" : "Bad");
		return;				/* sanity */
	}
	op->ov_magic = OLDMAGIC;
#endif
#ifdef RCHECK
  	ASSERT(op->ov_rmagic == RMAGIC);
	if (op->ov_index <= 13)
		ASSERT(*(u_int *)((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC);
#endif
  	ASSERT(op->ov_index < NBUCKETS);
  	size = op->ov_index;
	op->ov_next = nextf[size];
  	nextf[size] = op;
#ifdef MSTATS
  	nmalloc[size]--;
#endif
}

/*
 * When a program attempts "storage compaction" as mentioned in the
 * old malloc man page, it realloc's an already freed block.  Usually
 * this is the last block it freed; occasionally it might be farther
 * back.  We have to search all the free lists for the block in order
 * to determine its bucket: 1st we make one pass thru the lists
 * checking only the first block in each; if that fails we search
 * ``reall_srchlen'' blocks in each list for a match (the variable
 * is extern so the caller can modify it).  If that fails we just copy
 * however many bytes was given to realloc() and hope it's not huge.
 */
int reall_srchlen = 4;	/* 4 should be plenty, -1 =>'s whole list */

MALLOCPTRTYPE *
realloc(mp, nbytes)
	MALLOCPTRTYPE *mp; 
	unsigned nbytes;
{   
  	register u_int onb;
	union overhead *op;
  	char *res;
	register int i;
	int was_alloced = 0;
	char *cp = (char*)mp;

  	if (cp == NULL)
  		return (malloc(nbytes));
	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
	if (op->ov_magic == MAGIC) {
		was_alloced++;
		i = op->ov_index;
	} else {
		/*
		 * Already free, doing "compaction".
		 *
		 * Search for the old block of memory on the
		 * free list.  First, check the most common
		 * case (last element free'd), then (this failing)
		 * the last ``reall_srchlen'' items free'd.
		 * If all lookups fail, then assume the size of
		 * the memory block being realloc'd is the
		 * smallest possible.
		 */
		if ((i = findbucket(op, 1)) < 0 &&
		    (i = findbucket(op, reall_srchlen)) < 0)
			i = 0;
	}
	onb = (1 << (i + 3)) - sizeof (*op) - RSLOP;
	/* avoid the copy if same size block */
	if (was_alloced &&
	    nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) {
#ifdef RCHECK
		/*
		 * Record new allocated size of block and
		 * bound space with magic numbers.
		 */
		if (op->ov_index <= 13) {
			/*
			 * Convert amount of memory requested into
			 * closest block size stored in hash buckets
			 * which satisfies request.  Account for
			 * space used per block for accounting.
			 */
			nbytes += sizeof (union overhead) + RSLOP;
			nbytes = (nbytes + 3) &~ 3; 
			op->ov_size = nbytes - 1;
			*((u_int *)((caddr_t)op + nbytes - RSLOP)) = RMAGIC;
		}
#endif
		return((MALLOCPTRTYPE*)cp);
	}
  	if ((res = (char*)malloc(nbytes)) == NULL)
  		return (NULL);
  	if (cp != res)			/* common optimization */
		(void)bcopy(cp, res, (int)((nbytes < onb) ? nbytes : onb));
  	if (was_alloced)
		free(cp);
  	return ((MALLOCPTRTYPE*)res);
}

/*
 * Search ``srchlen'' elements of each free list for a block whose
 * header starts at ``freep''.  If srchlen is -1 search the whole list.
 * Return bucket number, or -1 if not found.
 */
static
findbucket(freep, srchlen)
	union overhead *freep;
	int srchlen;
{
	register union overhead *p;
	register int i, j;

	for (i = 0; i < NBUCKETS; i++) {
		j = 0;
		for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
			if (p == freep)
				return (i);
			j++;
		}
	}
	return (-1);
}

#ifdef MSTATS
/*
 * mstats - print out statistics about malloc
 * 
 * Prints two lines of numbers, one showing the length of the free list
 * for each size category, the second showing the number of mallocs -
 * frees for each size category.
 */
mstats(s)
	char *s;
{
  	register int i, j;
  	register union overhead *p;
  	int totfree = 0,
  	totused = 0;

  	fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
  	for (i = 0; i < NBUCKETS; i++) {
  		for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
  			;
  		fprintf(stderr, " %d", j);
  		totfree += j * (1 << (i + 3));
  	}
  	fprintf(stderr, "\nused:\t");
  	for (i = 0; i < NBUCKETS; i++) {
  		fprintf(stderr, " %d", nmalloc[i]);
  		totused += nmalloc[i] * (1 << (i + 3));
  	}
  	fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
	    totused, totfree);
}
#endif
#endif /* lint */
Commit	Line	Data
352d5a3a	1	/* $RCSfile: malloc.c,v $$Revision: 4.0.1.2 $$Date: 91/06/07 11:20:45 $
8d063cd8 LW	2	*
8d063cd8 LW	3	* $Log: malloc.c,v $
352d5a3a LW	4	* Revision 4.0.1.2 91/06/07 11:20:45 lwall
	5	* patch4: many, many itty-bitty portability fixes
	6	*
35c8bce7 LW	7	* Revision 4.0.1.1 91/04/11 17:48:31 lwall
	8	* patch1: Configure now figures out malloc ptr type
	9	*
fe14fcc3 LW	10	* Revision 4.0 91/03/20 01:28:52 lwall
fe14fcc3 LW	11	* 4.0 baseline.
8d063cd8 LW	12	*
	13	*/
	14
	15	#ifndef lint
	16	static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83";
8d063cd8	17
a687059c	18	#ifdef DEBUGGING
8d063cd8	19	#define RCHECK
a687059c	20	#endif
8d063cd8 LW	21	/*
	22	* malloc.c (Caltech) 2/21/82
	23	* Chris Kingsley, kingsley@cit-20.
	24	*
	25	* This is a very fast storage allocator. It allocates blocks of a small
	26	* number of different sizes, and keeps free lists of each size. Blocks that
	27	* don't exactly fit are passed up to the next larger size. In this
	28	* implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
	29	* This is designed for use in a program that uses vast quantities of memory,
	30	* but bombs when it runs out.
	31	*/
	32
135863df	33	#include "EXTERN.h"
135863df AB	34	#include "perl.h"
135863df AB	35
03a14243 LW	36	static findbucket(), morecore();
03a14243 LW	37
135863df AB	38	/* I don't much care whether these are defined in sys/types.h--LAW */
	39
	40	#define u_char unsigned char
	41	#define u_int unsigned int
	42	#define u_short unsigned short
8d063cd8	43
8d063cd8 LW	44	/*
	45	* The overhead on a block is at least 4 bytes. When free, this space
	46	* contains a pointer to the next free block, and the bottom two bits must
	47	* be zero. When in use, the first byte is set to MAGIC, and the second
	48	* byte is the size index. The remaining bytes are for alignment.
	49	* If range checking is enabled and the size of the block fits
	50	* in two bytes, then the top two bytes hold the size of the requested block
	51	* plus the range checking words, and the header word MINUS ONE.
	52	*/
	53	union overhead {
	54	union overhead ov_next; / when free */
c623bd54 LW	55	#if ALIGNBYTES > 4
c623bd54 LW	56	double strut; /* alignment problems */
a687059c	57	#endif
8d063cd8 LW	58	struct {
	59	u_char ovu_magic; /* magic number */
	60	u_char ovu_index; /* bucket # */
	61	#ifdef RCHECK
	62	u_short ovu_size; /* actual block size */
	63	u_int ovu_rmagic; /* range magic number */
	64	#endif
	65	} ovu;
	66	#define ov_magic ovu.ovu_magic
	67	#define ov_index ovu.ovu_index
	68	#define ov_size ovu.ovu_size
	69	#define ov_rmagic ovu.ovu_rmagic
	70	};
	71
	72	#define MAGIC 0xff /* magic # on accounting info */
378cc40b	73	#define OLDMAGIC 0x7f /* same after a free() */
8d063cd8 LW	74	#define RMAGIC 0x55555555 /* magic # on range info */
	75	#ifdef RCHECK
	76	#define RSLOP sizeof (u_int)
	77	#else
	78	#define RSLOP 0
	79	#endif
	80
	81	/*
	82	* nextf[i] is the pointer to the next free block of size 2^(i+3). The
	83	* smallest allocatable block is 8 bytes. The overhead information
	84	* precedes the data area returned to the user.
	85	*/
	86	#define NBUCKETS 30
	87	static union overhead *nextf[NBUCKETS];
	88	extern char *sbrk();
	89
	90	#ifdef MSTATS
	91	/*
	92	* nmalloc[i] is the difference between the number of mallocs and frees
	93	* for a given block size.
	94	*/
	95	static u_int nmalloc[NBUCKETS];
	96	#include <stdio.h>
	97	#endif
	98
	99	#ifdef debug
	100	#define ASSERT(p) if (!(p)) botch("p"); else
	101	static
	102	botch(s)
	103	char *s;
	104	{
	105
	106	printf("assertion botched: %s\n", s);
	107	abort();
	108	}
	109	#else
	110	#define ASSERT(p)
	111	#endif
	112
35c8bce7	113	MALLOCPTRTYPE *
8d063cd8 LW	114	malloc(nbytes)
	115	register unsigned nbytes;
	116	{
	117	register union overhead *p;
	118	register int bucket = 0;
	119	register unsigned shiftr;
	120
	121	/*
	122	* Convert amount of memory requested into
	123	* closest block size stored in hash buckets
	124	* which satisfies request. Account for
	125	* space used per block for accounting.
	126	*/
	127	nbytes += sizeof (union overhead) + RSLOP;
	128	nbytes = (nbytes + 3) &~ 3;
	129	shiftr = (nbytes - 1) >> 2;
	130	/* apart from this loop, this is O(1) */
	131	while (shiftr >>= 1)
	132	bucket++;
	133	/*
	134	* If nothing in hash bucket right now,
	135	* request more memory from the system.
	136	*/
	137	if (nextf[bucket] == NULL)
	138	morecore(bucket);
	139	if ((p = (union overhead *)nextf[bucket]) == NULL)
	140	return (NULL);
	141	/* remove from linked list */
bf38876a LW	142	#ifdef RCHECK
bf38876a LW	143	if (((int)p) & (sizeof(union overhead) - 1))
a687059c	144	#ifndef I286
8d063cd8	145	fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",((int)p),p);
a687059c LW	146	#else
	147	fprintf(stderr,"Corrupt malloc ptr 0x%lx at 0x%lx\n",((int)p),p);
	148	#endif
bf38876a LW	149	#endif
bf38876a LW	150	nextf[bucket] = p->ov_next;
8d063cd8 LW	151	p->ov_magic = MAGIC;
	152	p->ov_index= bucket;
	153	#ifdef MSTATS
	154	nmalloc[bucket]++;
	155	#endif
	156	#ifdef RCHECK
	157	/*
	158	* Record allocated size of block and
	159	* bound space with magic numbers.
	160	*/
	161	if (nbytes <= 0x10000)
	162	p->ov_size = nbytes - 1;
	163	p->ov_rmagic = RMAGIC;
	164	((u_int )((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
	165	#endif
352d5a3a	166	return ((MALLOCPTRTYPE *)(p + 1));
8d063cd8 LW	167	}
	168
	169	/*
	170	* Allocate more memory to the indicated bucket.
	171	*/
	172	static
	173	morecore(bucket)
a687059c	174	register int bucket;
8d063cd8 LW	175	{
	176	register union overhead *op;
	177	register int rnu; /* 2^rnu bytes will be requested */
	178	register int nblks; /* become nblks blocks of the desired size */
	179	register int siz;
	180
	181	if (nextf[bucket])
	182	return;
	183	/*
	184	* Insure memory is allocated
	185	* on a page boundary. Should
	186	* make getpageize call?
	187	*/
	188	op = (union overhead *)sbrk(0);
a687059c	189	#ifndef I286
8d063cd8	190	if ((int)op & 0x3ff)
a687059c LW	191	(void)sbrk(1024 - ((int)op & 0x3ff));
	192	#else
	193	/* The sbrk(0) call on the I286 always returns the next segment */
	194	#endif
	195
	196	#ifndef I286
8d063cd8 LW	197	/* take 2k unless the block is bigger than that */
8d063cd8 LW	198	rnu = (bucket <= 8) ? 11 : bucket + 3;
a687059c LW	199	#else
	200	/* take 16k unless the block is bigger than that
	201	(80286s like large segments!) */
	202	rnu = (bucket <= 11) ? 14 : bucket + 3;
	203	#endif
8d063cd8 LW	204	nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
	205	if (rnu < bucket)
	206	rnu = bucket;
	207	op = (union overhead *)sbrk(1 << rnu);
	208	/* no more room! */
	209	if ((int)op == -1)
	210	return;
	211	/*
	212	* Round up to minimum allocation size boundary
	213	* and deduct from block count to reflect.
	214	*/
a687059c	215	#ifndef I286
8d063cd8 LW	216	if ((int)op & 7) {
	217	op = (union overhead *)(((int)op + 8) &~ 7);
	218	nblks--;
	219	}
a687059c LW	220	#else
	221	/* Again, this should always be ok on an 80286 */
	222	#endif
8d063cd8 LW	223	/*
	224	* Add new memory allocated to that on
	225	* free list for this hash bucket.
	226	*/
	227	nextf[bucket] = op;
	228	siz = 1 << (bucket + 3);
	229	while (--nblks > 0) {
	230	op->ov_next = (union overhead *)((caddr_t)op + siz);
	231	op = (union overhead *)((caddr_t)op + siz);
	232	}
	233	}
	234
fe14fcc3	235	void
352d5a3a LW	236	free(mp)
352d5a3a LW	237	MALLOCPTRTYPE *mp;
8d063cd8 LW	238	{
	239	register int size;
	240	register union overhead *op;
352d5a3a	241	char cp = (char)mp;
8d063cd8 LW	242
	243	if (cp == NULL)
	244	return;
	245	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
	246	#ifdef debug
	247	ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
	248	#else
378cc40b	249	if (op->ov_magic != MAGIC) {
a687059c	250	warn("%s free() ignored",
378cc40b	251	op->ov_magic == OLDMAGIC ? "Duplicate" : "Bad");
8d063cd8	252	return; /* sanity */
378cc40b LW	253	}
378cc40b LW	254	op->ov_magic = OLDMAGIC;
8d063cd8 LW	255	#endif
	256	#ifdef RCHECK
	257	ASSERT(op->ov_rmagic == RMAGIC);
	258	if (op->ov_index <= 13)
	259	ASSERT((u_int )((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC);
	260	#endif
	261	ASSERT(op->ov_index < NBUCKETS);
	262	size = op->ov_index;
	263	op->ov_next = nextf[size];
	264	nextf[size] = op;
	265	#ifdef MSTATS
	266	nmalloc[size]--;
	267	#endif
	268	}
	269
	270	/*
	271	* When a program attempts "storage compaction" as mentioned in the
	272	* old malloc man page, it realloc's an already freed block. Usually
	273	* this is the last block it freed; occasionally it might be farther
	274	* back. We have to search all the free lists for the block in order
	275	* to determine its bucket: 1st we make one pass thru the lists
	276	* checking only the first block in each; if that fails we search
378cc40b	277	* ``reall_srchlen'' blocks in each list for a match (the variable
8d063cd8 LW	278	* is extern so the caller can modify it). If that fails we just copy
	279	* however many bytes was given to realloc() and hope it's not huge.
	280	*/
378cc40b	281	int reall_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
8d063cd8	282
35c8bce7	283	MALLOCPTRTYPE *
352d5a3a LW	284	realloc(mp, nbytes)
352d5a3a LW	285	MALLOCPTRTYPE *mp;
8d063cd8 LW	286	unsigned nbytes;
	287	{
	288	register u_int onb;
	289	union overhead *op;
	290	char *res;
	291	register int i;
	292	int was_alloced = 0;
352d5a3a	293	char cp = (char)mp;
8d063cd8 LW	294
	295	if (cp == NULL)
	296	return (malloc(nbytes));
	297	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
	298	if (op->ov_magic == MAGIC) {
	299	was_alloced++;
	300	i = op->ov_index;
	301	} else {
	302	/*
	303	* Already free, doing "compaction".
	304	*
	305	* Search for the old block of memory on the
	306	* free list. First, check the most common
	307	* case (last element free'd), then (this failing)
378cc40b	308	* the last ``reall_srchlen'' items free'd.
8d063cd8 LW	309	* If all lookups fail, then assume the size of
	310	* the memory block being realloc'd is the
	311	* smallest possible.
	312	*/
	313	if ((i = findbucket(op, 1)) < 0 &&
378cc40b	314	(i = findbucket(op, reall_srchlen)) < 0)
8d063cd8 LW	315	i = 0;
	316	}
	317	onb = (1 << (i + 3)) - sizeof (*op) - RSLOP;
	318	/* avoid the copy if same size block */
	319	if (was_alloced &&
a687059c LW	320	nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) {
	321	#ifdef RCHECK
	322	/*
	323	* Record new allocated size of block and
	324	* bound space with magic numbers.
	325	*/
	326	if (op->ov_index <= 13) {
	327	/*
	328	* Convert amount of memory requested into
	329	* closest block size stored in hash buckets
	330	* which satisfies request. Account for
	331	* space used per block for accounting.
	332	*/
	333	nbytes += sizeof (union overhead) + RSLOP;
	334	nbytes = (nbytes + 3) &~ 3;
	335	op->ov_size = nbytes - 1;
	336	((u_int )((caddr_t)op + nbytes - RSLOP)) = RMAGIC;
	337	}
	338	#endif
352d5a3a	339	return((MALLOCPTRTYPE*)cp);
a687059c	340	}
352d5a3a	341	if ((res = (char*)malloc(nbytes)) == NULL)
8d063cd8 LW	342	return (NULL);
8d063cd8 LW	343	if (cp != res) /* common optimization */
a687059c	344	(void)bcopy(cp, res, (int)((nbytes < onb) ? nbytes : onb));
8d063cd8 LW	345	if (was_alloced)
8d063cd8 LW	346	free(cp);
352d5a3a	347	return ((MALLOCPTRTYPE*)res);
8d063cd8 LW	348	}
	349
	350	/*
	351	* Search ``srchlen'' elements of each free list for a block whose
	352	* header starts at ``freep''. If srchlen is -1 search the whole list.
	353	* Return bucket number, or -1 if not found.
	354	*/
	355	static
	356	findbucket(freep, srchlen)
	357	union overhead *freep;
	358	int srchlen;
	359	{
	360	register union overhead *p;
	361	register int i, j;
	362
	363	for (i = 0; i < NBUCKETS; i++) {
	364	j = 0;
	365	for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
	366	if (p == freep)
	367	return (i);
	368	j++;
	369	}
	370	}
	371	return (-1);
	372	}
	373
	374	#ifdef MSTATS
	375	/*
	376	* mstats - print out statistics about malloc
	377	*
	378	* Prints two lines of numbers, one showing the length of the free list
	379	* for each size category, the second showing the number of mallocs -
	380	* frees for each size category.
	381	*/
	382	mstats(s)
	383	char *s;
	384	{
	385	register int i, j;
	386	register union overhead *p;
	387	int totfree = 0,
	388	totused = 0;
	389
	390	fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
	391	for (i = 0; i < NBUCKETS; i++) {
	392	for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
	393	;
	394	fprintf(stderr, " %d", j);
	395	totfree += j * (1 << (i + 3));
	396	}
	397	fprintf(stderr, "\nused:\t");
	398	for (i = 0; i < NBUCKETS; i++) {
	399	fprintf(stderr, " %d", nmalloc[i]);
	400	totused += nmalloc[i] * (1 << (i + 3));
	401	}
	402	fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
	403	totused, totfree);
	404	}
	405	#endif
a687059c	406	#endif /* lint */