[unix-history] / usr / src / bin / csh / alloc.c

/*
 * Copyright (c) 1980 Regents of the University of California.
 * All rights reserved.  The Berkeley Software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#ifndef lint
static char *sccsid = "@(#)alloc.c	5.2 (Berkeley) %G%";
#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 <sys/types.h>

#define	NULL 0

/*
 * 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 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();

/*
 * nmalloc[i] is the difference between the number of mallocs and frees
 * for a given block size.
 */
static	u_int nmalloc[NBUCKETS];

#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 */
  	nextf[bucket] = nextf[bucket]->ov_next;
	p->ov_magic = MAGIC;
	p->ov_index= bucket;
  	nmalloc[bucket]++;
#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)
  		(void) 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));

	/* 
	** The following botch is because csh tries to free a free block
	** when processing the =~ or !~ operators. -- layer@ucbmonet
	*/
#ifdef CSHbotch /* was debug */
  	ASSERT(op->ov_magic == MAGIC);		/* make sure it was in use */
#else
	if (op->ov_magic != MAGIC)
		return;				/* sanity */
#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;
  	nmalloc[size]--;
}

/*
 * 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
 * ``realloc_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 realloc_srchlen = 4;	/* 4 should be plenty.  -1 means 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: he is doing "compaction" (tee hee) */
		if ((i = findbucket(op, 1)) < 0 &&
		    (i = findbucket(op, realloc_srchlen)) < 0)
			i = 0;		/* assume smallest possible */
	}
	onb = (1 << (i + 3)) - sizeof (*op) - RSLOP;
	if (was_alloced &&		/* avoid the copy if same size block */
	    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++)
		for (j = 0, p = nextf[i]; p && j != srchlen; j++, p = p->ov_next)
			if (p == freep)
				return (i);
	return (-1);
}

/*
 * 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.
 */
showall(s)
char **s;
{
	register int i, j;
	register union overhead *p;
	int totfree = 0,
	totused = 0;

	if (s[1])
		printf("Memory allocation statistics %s\nfree:", s[1]);
	for (i = 0; i < NBUCKETS; i++) {
		for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
			;

		if (s[1])
			printf(" %d", j);
		totfree += j * (1 << (i + 3));
	}
	if (s[1])
		printf("\nused:");
	for (i = 0; i < NBUCKETS; i++) {
		if (s[1])
			printf(" %d", nmalloc[i]);
		totused += nmalloc[i] * (1 << (i + 3));
	}
	if (s[1])
		printf("\n");
	printf("Total in use: %d, total free: %d\n", totused, totfree);
}
Commit	Line	Data
b79f4fa9 DF	1	/*
b79f4fa9 DF	2	* Copyright (c) 1980 Regents of the University of California.
094e80ed	3	* All rights reserved. The Berkeley Software License Agreement
b79f4fa9 DF	4	* specifies the terms and conditions for redistribution.
	5	*/
	6
3fb44be6	7	#ifndef lint
094e80ed EW	8	static char *sccsid = "@(#)alloc.c 5.2 (Berkeley) %G%";
094e80ed EW	9	#endif
3fb44be6 KL	10
	11	/*
	12	* malloc.c (Caltech) 2/21/82
	13	* Chris Kingsley, kingsley@cit-20.
	14	*
	15	* This is a very fast storage allocator. It allocates blocks of a small
	16	* number of different sizes, and keeps free lists of each size. Blocks that
	17	* don't exactly fit are passed up to the next larger size. In this
	18	* implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
	19	* This is designed for use in a program that uses vast quantities of memory,
	20	* but bombs when it runs out.
	21	*/
	22
	23	#include <sys/types.h>
	24
	25	#define NULL 0
	26
	27	/*
	28	* The overhead on a block is at least 4 bytes. When free, this space
	29	* contains a pointer to the next free block, and the bottom two bits must
	30	* be zero. When in use, the first byte is set to MAGIC, and the second
	31	* byte is the size index. The remaining bytes are for alignment.
	32	* If range checking is enabled and the size of the block fits
	33	* in two bytes, then the top two bytes hold the size of the requested block
	34	* plus the range checking words, and the header word MINUS ONE.
	35	*/
	36	union overhead {
	37	union overhead ov_next; / when free */
	38	struct {
	39	u_char ovu_magic; /* magic number */
	40	u_char ovu_index; /* bucket # */
	41	#ifdef RCHECK
	42	u_short ovu_size; /* actual block size */
	43	u_int ovu_rmagic; /* range magic number */
	44	#endif
	45	} ovu;
	46	#define ov_magic ovu.ovu_magic
	47	#define ov_index ovu.ovu_index
	48	#define ov_size ovu.ovu_size
	49	#define ov_rmagic ovu.ovu_rmagic
	50	};
	51
	52	#define MAGIC 0xff /* magic # on accounting info */
	53	#define RMAGIC 0x55555555 /* magic # on range info */
	54	#ifdef RCHECK
	55	#define RSLOP sizeof (u_int)
	56	#else
	57	#define RSLOP 0
	58	#endif
	59
	60	/*
	61	* nextf[i] is the pointer to the next free block of size 2^(i+3). The
	62	* smallest allocatable block is 8 bytes. The overhead information
	63	* precedes the data area returned to the user.
	64	*/
	65	#define NBUCKETS 30
	66	static union overhead *nextf[NBUCKETS];
	67	extern char *sbrk();
	68
3fb44be6 KL	69	/*
	70	* nmalloc[i] is the difference between the number of mallocs and frees
	71	* for a given block size.
	72	*/
	73	static u_int nmalloc[NBUCKETS];
fc71ebc6	74
fc71ebc6	75	#ifdef debug
3fb44be6 KL	76	#define ASSERT(p) if (!(p)) botch("p"); else
3fb44be6 KL	77	static
fc71ebc6 BJ	78	botch(s)
	79	char *s;
	80	{
	81	printf("assertion botched: %s\n",s);
	82	abort();
	83	}
	84	#else
3fb44be6	85	#define ASSERT(p)
fc71ebc6 BJ	86	#endif
fc71ebc6 BJ	87
fc71ebc6 BJ	88	char *
fc71ebc6 BJ	89	malloc(nbytes)
3fb44be6	90	register unsigned nbytes;
fc71ebc6	91	{
3fb44be6 KL	92	register union overhead *p;
	93	register int bucket = 0;
	94	register unsigned shiftr;
	95
	96	/*
	97	* Convert amount of memory requested into
	98	* closest block size stored in hash buckets
	99	* which satisfies request. Account for
	100	* space used per block for accounting.
	101	*/
	102	nbytes += sizeof (union overhead) + RSLOP;
	103	nbytes = (nbytes + 3) &~ 3;
	104	shiftr = (nbytes - 1) >> 2;
	105	/* apart from this loop, this is O(1) */
	106	while (shiftr >>= 1)
	107	bucket++;
	108	/*
	109	* If nothing in hash bucket right now,
	110	* request more memory from the system.
	111	*/
	112	if (nextf[bucket] == NULL)
	113	morecore(bucket);
	114	if ((p = (union overhead *)nextf[bucket]) == NULL)
	115	return (NULL);
	116	/* remove from linked list */
	117	nextf[bucket] = nextf[bucket]->ov_next;
	118	p->ov_magic = MAGIC;
	119	p->ov_index= bucket;
3fb44be6	120	nmalloc[bucket]++;
3fb44be6 KL	121	#ifdef RCHECK
	122	/*
	123	* Record allocated size of block and
	124	* bound space with magic numbers.
	125	*/
	126	if (nbytes <= 0x10000)
	127	p->ov_size = nbytes - 1;
	128	p->ov_rmagic = RMAGIC;
	129	((u_int )((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
	130	#endif
	131	return ((char *)(p + 1));
fc71ebc6 BJ	132	}
fc71ebc6 BJ	133
3fb44be6 KL	134	/*
	135	* Allocate more memory to the indicated bucket.
	136	*/
	137	static
	138	morecore(bucket)
	139	register bucket;
fc71ebc6	140	{
3fb44be6 KL	141	register union overhead *op;
	142	register int rnu; /* 2^rnu bytes will be requested */
	143	register int nblks; /* become nblks blocks of the desired size */
	144	register int siz;
	145
	146	if (nextf[bucket])
	147	return;
	148	/*
	149	* Insure memory is allocated
	150	* on a page boundary. Should
	151	* make getpageize call?
	152	*/
	153	op = (union overhead *)sbrk(0);
	154	if ((int)op & 0x3ff)
35371dec	155	(void) sbrk(1024 - ((int)op & 0x3ff));
3fb44be6 KL	156	/* take 2k unless the block is bigger than that */
	157	rnu = (bucket <= 8) ? 11 : bucket + 3;
	158	nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
	159	if (rnu < bucket)
	160	rnu = bucket;
	161	op = (union overhead *)sbrk(1 << rnu);
	162	/* no more room! */
	163	if ((int)op == -1)
	164	return;
	165	/*
	166	* Round up to minimum allocation size boundary
	167	* and deduct from block count to reflect.
	168	*/
	169	if ((int)op & 7) {
	170	op = (union overhead *)(((int)op + 8) &~ 7);
	171	nblks--;
	172	}
	173	/*
	174	* Add new memory allocated to that on
	175	* free list for this hash bucket.
	176	*/
	177	nextf[bucket] = op;
	178	siz = 1 << (bucket + 3);
	179	while (--nblks > 0) {
	180	op->ov_next = (union overhead *)((caddr_t)op + siz);
	181	op = (union overhead *)((caddr_t)op + siz);
	182	}
fc71ebc6 BJ	183	}
fc71ebc6 BJ	184
3fb44be6 KL	185	free(cp)
	186	char *cp;
	187	{
	188	register int size;
	189	register union overhead *op;
fc71ebc6	190
3fb44be6 KL	191	if (cp == NULL)
	192	return;
	193	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
	194
	195	/*
	196	** The following botch is because csh tries to free a free block
	197	** when processing the =~ or !~ operators. -- layer@ucbmonet
	198	*/
	199	#ifdef CSHbotch /* was debug */
	200	ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
fc71ebc6	201	#else
3fb44be6 KL	202	if (op->ov_magic != MAGIC)
3fb44be6 KL	203	return; /* sanity */
fc71ebc6	204	#endif
fc71ebc6	205
3fb44be6 KL	206	#ifdef RCHECK
	207	ASSERT(op->ov_rmagic == RMAGIC);
	208	if (op->ov_index <= 13)
	209	ASSERT((u_int )((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC);
	210	#endif
	211	ASSERT(op->ov_index < NBUCKETS);
	212	size = op->ov_index;
	213	op->ov_next = nextf[size];
	214	nextf[size] = op;
3fb44be6	215	nmalloc[size]--;
fc71ebc6	216	}
3fb44be6 KL	217
	218	/*
	219	* When a program attempts "storage compaction" as mentioned in the
	220	* old malloc man page, it realloc's an already freed block. Usually
	221	* this is the last block it freed; occasionally it might be farther
	222	* back. We have to search all the free lists for the block in order
	223	* to determine its bucket: 1st we make one pass thru the lists
	224	* checking only the first block in each; if that fails we search
	225	* ``realloc_srchlen'' blocks in each list for a match (the variable
	226	* is extern so the caller can modify it). If that fails we just copy
	227	* however many bytes was given to realloc() and hope it's not huge.
	228	*/
	229	int realloc_srchlen = 4; /* 4 should be plenty. -1 means whole list */
	230
	231	char *
	232	realloc(cp, nbytes)
	233	char *cp;
	234	unsigned nbytes;
	235	{
	236	register u_int onb;
	237	union overhead *op;
	238	char *res;
	239	register int i;
	240	int was_alloced = 0;
	241
	242	if (cp == NULL)
	243	return (malloc(nbytes));
	244	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
	245	if (op->ov_magic == MAGIC) {
	246	was_alloced++;
	247	i = op->ov_index;
	248	}
	249	else { /* already free: he is doing "compaction" (tee hee) */
	250	if ((i = findbucket(op, 1)) < 0 &&
	251	(i = findbucket(op, realloc_srchlen)) < 0)
	252	i = 0; /* assume smallest possible */
	253	}
	254	onb = (1 << (i + 3)) - sizeof (*op) - RSLOP;
	255	if (was_alloced && /* avoid the copy if same size block */
	256	nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP)
	257	return(cp);
	258	if ((res = malloc(nbytes)) == NULL)
	259	return (NULL);
	260	if (cp != res) /* common optimization */
	261	bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
	262	if (was_alloced)
	263	free(cp);
	264	return (res);
	265	}
	266
	267	/*
	268	* Search ``srchlen'' elements of each free list for a block whose
	269	* header starts at ``freep''. If srchlen is -1 search the whole list.
	270	* Return bucket number, or -1 if not found.
	271	*/
	272	static
	273	findbucket(freep, srchlen)
	274	union overhead *freep;
	275	int srchlen;
	276	{
	277	register union overhead *p;
	278	register int i, j;
	279
	280	for (i = 0; i < NBUCKETS; i++)
281	for (j = 0, p = nextf[i]; p && j != srchlen; j++, p = p->ov_next)
282	if (p == freep)
283	return (i);
284	return (-1);
285	}
fc71ebc6	286
3fb44be6 KL	287	/*
	288	* mstats - print out statistics about malloc
	289	*
	290	* Prints two lines of numbers, one showing the length of the free list
	291	* for each size category, the second showing the number of mallocs -
	292	* frees for each size category.
	293	*/
	294	showall(s)
35371dec	295	char **s;
fc71ebc6	296	{
35371dec EW	297	register int i, j;
	298	register union overhead *p;
	299	int totfree = 0,
	300	totused = 0;
3fb44be6 KL	301
3fb44be6 KL	302	if (s[1])
35371dec EW	303	printf("Memory allocation statistics %s\nfree:", s[1]);
	304	for (i = 0; i < NBUCKETS; i++) {
	305	for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
	306	;
	307
	308	if (s[1])
	309	printf(" %d", j);
	310	totfree += j * (1 << (i + 3));
	311	}
3fb44be6	312	if (s[1])
35371dec EW	313	printf("\nused:");
	314	for (i = 0; i < NBUCKETS; i++) {
	315	if (s[1])
	316	printf(" %d", nmalloc[i]);
	317	totused += nmalloc[i] * (1 << (i + 3));
	318	}
3fb44be6	319	if (s[1])
35371dec EW	320	printf("\n");
35371dec EW	321	printf("Total in use: %d, total free: %d\n", totused, totfree);
fc71ebc6	322	}