[p5sagit/p5-mst-13.2.git] / malloc.c

/* $Header: malloc.c,v 2.0 88/06/05 00:09:16 root Exp $
 *
 * $Log:	malloc.c,v $
 * Revision 2.0  88/06/05  00:09:16  root
 * Baseline version 2.0.
 * 
 */

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

#define RCHECK
/*
 * 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"

/* 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 */
	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

char *
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 */
	if (*((int*)p) > 0x10000000)
	    fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p);
  	nextf[bucket] = nextf[bucket]->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 ((char *)(p + 1));
}

/*
 * Allocate more memory to the indicated bucket.
 */
static
morecore(bucket)
	register 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);
  	if ((int)op & 0x3ff)
  		sbrk(1024 - ((int)op & 0x3ff));
	/* take 2k unless the block is bigger than that */
  	rnu = (bucket <= 8) ? 11 : bucket + 3;
  	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.
	 */
  	if ((int)op & 7) {
  		op = (union overhead *)(((int)op + 8) &~ 7);
  		nblks--;
  	}
	/*
	 * 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);
  	}
}

free(cp)
	char *cp;
{   
  	register int size;
	register union overhead *op;

  	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) {
		fprintf(stderr,"%s free() ignored\n",
		    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 */

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

  	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)
		return(cp);
  	if ((res = malloc(nbytes)) == NULL)
  		return (NULL);
  	if (cp != res)			/* common optimization */
		bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
  	if (was_alloced)
		free(cp);
  	return (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
Commit	Line	Data
378cc40b	1	/* $Header: malloc.c,v 2.0 88/06/05 00:09:16 root Exp $
8d063cd8	2	*
8d063cd8	3	* $Log: malloc.c,v $
378cc40b	4	* Revision 2.0 88/06/05 00:09:16 root
378cc40b	5	* Baseline version 2.0.
8d063cd8	6	*
	7	*/
	8
	9	#ifndef lint
	10	static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83";
	11	#endif
8d063cd8	12
	13	#define RCHECK
	14	/*
	15	* malloc.c (Caltech) 2/21/82
	16	* Chris Kingsley, kingsley@cit-20.
	17	*
	18	* This is a very fast storage allocator. It allocates blocks of a small
	19	* number of different sizes, and keeps free lists of each size. Blocks that
	20	* don't exactly fit are passed up to the next larger size. In this
	21	* implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
	22	* This is designed for use in a program that uses vast quantities of memory,
	23	* but bombs when it runs out.
	24	*/
	25
135863df	26	#include "EXTERN.h"
135863df	27	#include "perl.h"
	28
	29	/* I don't much care whether these are defined in sys/types.h--LAW */
	30
	31	#define u_char unsigned char
	32	#define u_int unsigned int
	33	#define u_short unsigned short
8d063cd8	34
8d063cd8	35	/*
	36	* The overhead on a block is at least 4 bytes. When free, this space
	37	* contains a pointer to the next free block, and the bottom two bits must
	38	* be zero. When in use, the first byte is set to MAGIC, and the second
	39	* byte is the size index. The remaining bytes are for alignment.
	40	* If range checking is enabled and the size of the block fits
	41	* in two bytes, then the top two bytes hold the size of the requested block
	42	* plus the range checking words, and the header word MINUS ONE.
	43	*/
	44	union overhead {
	45	union overhead ov_next; / when free */
	46	struct {
	47	u_char ovu_magic; /* magic number */
	48	u_char ovu_index; /* bucket # */
	49	#ifdef RCHECK
	50	u_short ovu_size; /* actual block size */
	51	u_int ovu_rmagic; /* range magic number */
	52	#endif
	53	} ovu;
	54	#define ov_magic ovu.ovu_magic
	55	#define ov_index ovu.ovu_index
	56	#define ov_size ovu.ovu_size
	57	#define ov_rmagic ovu.ovu_rmagic
	58	};
	59
	60	#define MAGIC 0xff /* magic # on accounting info */
378cc40b	61	#define OLDMAGIC 0x7f /* same after a free() */
8d063cd8	62	#define RMAGIC 0x55555555 /* magic # on range info */
	63	#ifdef RCHECK
	64	#define RSLOP sizeof (u_int)
	65	#else
	66	#define RSLOP 0
	67	#endif
	68
	69	/*
	70	* nextf[i] is the pointer to the next free block of size 2^(i+3). The
	71	* smallest allocatable block is 8 bytes. The overhead information
	72	* precedes the data area returned to the user.
	73	*/
	74	#define NBUCKETS 30
	75	static union overhead *nextf[NBUCKETS];
	76	extern char *sbrk();
	77
	78	#ifdef MSTATS
	79	/*
	80	* nmalloc[i] is the difference between the number of mallocs and frees
	81	* for a given block size.
	82	*/
	83	static u_int nmalloc[NBUCKETS];
	84	#include <stdio.h>
	85	#endif
	86
	87	#ifdef debug
	88	#define ASSERT(p) if (!(p)) botch("p"); else
	89	static
	90	botch(s)
	91	char *s;
	92	{
	93
	94	printf("assertion botched: %s\n", s);
	95	abort();
	96	}
	97	#else
	98	#define ASSERT(p)
	99	#endif
	100
	101	char *
	102	malloc(nbytes)
	103	register unsigned nbytes;
	104	{
	105	register union overhead *p;
	106	register int bucket = 0;
	107	register unsigned shiftr;
	108
	109	/*
	110	* Convert amount of memory requested into
	111	* closest block size stored in hash buckets
	112	* which satisfies request. Account for
	113	* space used per block for accounting.
	114	*/
	115	nbytes += sizeof (union overhead) + RSLOP;
	116	nbytes = (nbytes + 3) &~ 3;
	117	shiftr = (nbytes - 1) >> 2;
	118	/* apart from this loop, this is O(1) */
	119	while (shiftr >>= 1)
	120	bucket++;
	121	/*
	122	* If nothing in hash bucket right now,
	123	* request more memory from the system.
	124	*/
	125	if (nextf[bucket] == NULL)
126	morecore(bucket);
127	if ((p = (union overhead *)nextf[bucket]) == NULL)
128	return (NULL);
129	/* remove from linked list */
130	if (((int)p) > 0x10000000)
131	fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",((int)p),p);
132	nextf[bucket] = nextf[bucket]->ov_next;
133	p->ov_magic = MAGIC;
134	p->ov_index= bucket;
135	#ifdef MSTATS
136	nmalloc[bucket]++;
137	#endif
138	#ifdef RCHECK
139	/*
140	* Record allocated size of block and
141	* bound space with magic numbers.
142	*/
143	if (nbytes <= 0x10000)
144	p->ov_size = nbytes - 1;
145	p->ov_rmagic = RMAGIC;
146	((u_int )((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
147	#endif
148	return ((char *)(p + 1));
149	}
150
151	/*
152	* Allocate more memory to the indicated bucket.
153	*/
154	static
155	morecore(bucket)
156	register bucket;
157	{
158	register union overhead *op;
159	register int rnu; /* 2^rnu bytes will be requested */
160	register int nblks; /* become nblks blocks of the desired size */
161	register int siz;
162
163	if (nextf[bucket])
164	return;
165	/*
166	* Insure memory is allocated
167	* on a page boundary. Should
168	* make getpageize call?
169	*/
170	op = (union overhead *)sbrk(0);
171	if ((int)op & 0x3ff)
172	sbrk(1024 - ((int)op & 0x3ff));
173	/* take 2k unless the block is bigger than that */
174	rnu = (bucket <= 8) ? 11 : bucket + 3;
175	nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
176	if (rnu < bucket)
177	rnu = bucket;
178	op = (union overhead *)sbrk(1 << rnu);
179	/* no more room! */
180	if ((int)op == -1)
181	return;
182	/*
183	* Round up to minimum allocation size boundary
184	* and deduct from block count to reflect.
185	*/
186	if ((int)op & 7) {
187	op = (union overhead *)(((int)op + 8) &~ 7);
188	nblks--;
189	}
190	/*
191	* Add new memory allocated to that on
192	* free list for this hash bucket.
193	*/
194	nextf[bucket] = op;
195	siz = 1 << (bucket + 3);
196	while (--nblks > 0) {
197	op->ov_next = (union overhead *)((caddr_t)op + siz);
198	op = (union overhead *)((caddr_t)op + siz);
199	}
200	}
201
202	free(cp)
203	char *cp;
204	{
205	register int size;
206	register union overhead *op;
207
208	if (cp == NULL)
209	return;
210	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
211	#ifdef debug
212	ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
213	#else
378cc40b	214	if (op->ov_magic != MAGIC) {
	215	fprintf(stderr,"%s free() ignored\n",
	216	op->ov_magic == OLDMAGIC ? "Duplicate" : "Bad");
8d063cd8	217	return; /* sanity */
378cc40b	218	}
378cc40b	219	op->ov_magic = OLDMAGIC;
8d063cd8	220	#endif
	221	#ifdef RCHECK
	222	ASSERT(op->ov_rmagic == RMAGIC);
	223	if (op->ov_index <= 13)
	224	ASSERT((u_int )((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC);
	225	#endif
	226	ASSERT(op->ov_index < NBUCKETS);
	227	size = op->ov_index;
	228	op->ov_next = nextf[size];
	229	nextf[size] = op;
	230	#ifdef MSTATS
	231	nmalloc[size]--;
	232	#endif
	233	}
	234
	235	/*
	236	* When a program attempts "storage compaction" as mentioned in the
	237	* old malloc man page, it realloc's an already freed block. Usually
	238	* this is the last block it freed; occasionally it might be farther
	239	* back. We have to search all the free lists for the block in order
	240	* to determine its bucket: 1st we make one pass thru the lists
	241	* checking only the first block in each; if that fails we search
378cc40b	242	* ``reall_srchlen'' blocks in each list for a match (the variable
8d063cd8	243	* is extern so the caller can modify it). If that fails we just copy
	244	* however many bytes was given to realloc() and hope it's not huge.
	245	*/
378cc40b	246	int reall_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
8d063cd8	247
	248	char *
	249	realloc(cp, nbytes)
	250	char *cp;
	251	unsigned nbytes;
	252	{
	253	register u_int onb;
	254	union overhead *op;
	255	char *res;
	256	register int i;
	257	int was_alloced = 0;
	258
	259	if (cp == NULL)
	260	return (malloc(nbytes));
	261	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
	262	if (op->ov_magic == MAGIC) {
	263	was_alloced++;
	264	i = op->ov_index;
	265	} else {
	266	/*
	267	* Already free, doing "compaction".
	268	*
	269	* Search for the old block of memory on the
	270	* free list. First, check the most common
	271	* case (last element free'd), then (this failing)
378cc40b	272	* the last ``reall_srchlen'' items free'd.
8d063cd8	273	* If all lookups fail, then assume the size of
	274	* the memory block being realloc'd is the
	275	* smallest possible.
	276	*/
	277	if ((i = findbucket(op, 1)) < 0 &&
378cc40b	278	(i = findbucket(op, reall_srchlen)) < 0)
8d063cd8	279	i = 0;
	280	}
	281	onb = (1 << (i + 3)) - sizeof (*op) - RSLOP;
	282	/* avoid the copy if same size block */
	283	if (was_alloced &&
	284	nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP)
	285	return(cp);
	286	if ((res = malloc(nbytes)) == NULL)
	287	return (NULL);
	288	if (cp != res) /* common optimization */
	289	bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
	290	if (was_alloced)
	291	free(cp);
	292	return (res);
	293	}
	294
	295	/*
	296	* Search ``srchlen'' elements of each free list for a block whose
	297	* header starts at ``freep''. If srchlen is -1 search the whole list.
	298	* Return bucket number, or -1 if not found.
	299	*/
	300	static
	301	findbucket(freep, srchlen)
	302	union overhead *freep;
	303	int srchlen;
	304	{
	305	register union overhead *p;
	306	register int i, j;
	307
	308	for (i = 0; i < NBUCKETS; i++) {
	309	j = 0;
	310	for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
	311	if (p == freep)
	312	return (i);
	313	j++;
	314	}
	315	}
	316	return (-1);
	317	}
	318
	319	#ifdef MSTATS
	320	/*
	321	* mstats - print out statistics about malloc
	322	*
	323	* Prints two lines of numbers, one showing the length of the free list
	324	* for each size category, the second showing the number of mallocs -
	325	* frees for each size category.
	326	*/
	327	mstats(s)
	328	char *s;
	329	{
	330	register int i, j;
	331	register union overhead *p;
	332	int totfree = 0,
	333	totused = 0;
	334
	335	fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
	336	for (i = 0; i < NBUCKETS; i++) {
	337	for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
	338	;
	339	fprintf(stderr, " %d", j);
	340	totfree += j * (1 << (i + 3));
	341	}
	342	fprintf(stderr, "\nused:\t");
343	for (i = 0; i < NBUCKETS; i++) {
344	fprintf(stderr, " %d", nmalloc[i]);
345	totused += nmalloc[i] * (1 << (i + 3));
346	}
347	fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
348	totused, totfree);
349	}
350	#endif