[perl5.git] / malloc.c

/* $Header: malloc.c,v 1.0 87/12/18 13:05:35 root Exp $
 *
 * $Log:	malloc.c,v $
 * Revision 1.0  87/12/18  13:05:35  root
 * Initial revision
 * 
 */

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

#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 <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();

#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)
		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;
#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
 * ``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 =>'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 ``realloc_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, realloc_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
8d063cd8 LW	1	/* $Header: malloc.c,v 1.0 87/12/18 13:05:35 root Exp $
	2	*
	3	* $Log: malloc.c,v $
	4	* Revision 1.0 87/12/18 13:05:35 root
	5	* Initial revision
	6	*
	7	*/
	8
	9	#ifndef lint
	10	static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83";
	11	#endif
	12	#include <stdio.h>
	13
	14	#define RCHECK
	15	/*
	16	* malloc.c (Caltech) 2/21/82
	17	* Chris Kingsley, kingsley@cit-20.
	18	*
	19	* This is a very fast storage allocator. It allocates blocks of a small
	20	* number of different sizes, and keeps free lists of each size. Blocks that
	21	* don't exactly fit are passed up to the next larger size. In this
	22	* implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
	23	* This is designed for use in a program that uses vast quantities of memory,
	24	* but bombs when it runs out.
	25	*/
	26
	27	#include <sys/types.h>
	28
	29	#define NULL 0
	30
	31	/*
	32	* The overhead on a block is at least 4 bytes. When free, this space
	33	* contains a pointer to the next free block, and the bottom two bits must
	34	* be zero. When in use, the first byte is set to MAGIC, and the second
	35	* byte is the size index. The remaining bytes are for alignment.
	36	* If range checking is enabled and the size of the block fits
	37	* in two bytes, then the top two bytes hold the size of the requested block
	38	* plus the range checking words, and the header word MINUS ONE.
	39	*/
	40	union overhead {
	41	union overhead ov_next; / when free */
	42	struct {
	43	u_char ovu_magic; /* magic number */
	44	u_char ovu_index; /* bucket # */
	45	#ifdef RCHECK
	46	u_short ovu_size; /* actual block size */
	47	u_int ovu_rmagic; /* range magic number */
	48	#endif
	49	} ovu;
	50	#define ov_magic ovu.ovu_magic
	51	#define ov_index ovu.ovu_index
	52	#define ov_size ovu.ovu_size
	53	#define ov_rmagic ovu.ovu_rmagic
	54	};
	55
	56	#define MAGIC 0xff /* magic # on accounting info */
	57	#define RMAGIC 0x55555555 /* magic # on range info */
	58	#ifdef RCHECK
	59	#define RSLOP sizeof (u_int)
	60	#else
	61	#define RSLOP 0
	62	#endif
	63
	64	/*
65	* nextf[i] is the pointer to the next free block of size 2^(i+3). The
66	* smallest allocatable block is 8 bytes. The overhead information
67	* precedes the data area returned to the user.
68	*/
69	#define NBUCKETS 30
70	static union overhead *nextf[NBUCKETS];
71	extern char *sbrk();
72
73	#ifdef MSTATS
74	/*
75	* nmalloc[i] is the difference between the number of mallocs and frees
76	* for a given block size.
77	*/
78	static u_int nmalloc[NBUCKETS];
79	#include <stdio.h>
80	#endif
81
82	#ifdef debug
83	#define ASSERT(p) if (!(p)) botch("p"); else
84	static
85	botch(s)
86	char *s;
87	{
88
89	printf("assertion botched: %s\n", s);
90	abort();
91	}
92	#else
93	#define ASSERT(p)
94	#endif
95
96	char *
97	malloc(nbytes)
98	register unsigned nbytes;
99	{
100	register union overhead *p;
101	register int bucket = 0;
102	register unsigned shiftr;
103
104	/*
105	* Convert amount of memory requested into
106	* closest block size stored in hash buckets
107	* which satisfies request. Account for
108	* space used per block for accounting.
109	*/
110	nbytes += sizeof (union overhead) + RSLOP;
111	nbytes = (nbytes + 3) &~ 3;
112	shiftr = (nbytes - 1) >> 2;
113	/* apart from this loop, this is O(1) */
114	while (shiftr >>= 1)
115	bucket++;
116	/*
117	* If nothing in hash bucket right now,
118	* request more memory from the system.
119	*/
120	if (nextf[bucket] == NULL)
121	morecore(bucket);
122	if ((p = (union overhead *)nextf[bucket]) == NULL)
123	return (NULL);
124	/* remove from linked list */
125	if (((int)p) > 0x10000000)
126	fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",((int)p),p);
127	nextf[bucket] = nextf[bucket]->ov_next;
128	p->ov_magic = MAGIC;
129	p->ov_index= bucket;
130	#ifdef MSTATS
131	nmalloc[bucket]++;
132	#endif
133	#ifdef RCHECK
134	/*
135	* Record allocated size of block and
136	* bound space with magic numbers.
137	*/
138	if (nbytes <= 0x10000)
139	p->ov_size = nbytes - 1;
140	p->ov_rmagic = RMAGIC;
141	((u_int )((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
142	#endif
143	return ((char *)(p + 1));
144	}
145
146	/*
147	* Allocate more memory to the indicated bucket.
148	*/
149	static
150	morecore(bucket)
151	register bucket;
152	{
153	register union overhead *op;
154	register int rnu; /* 2^rnu bytes will be requested */
155	register int nblks; /* become nblks blocks of the desired size */
156	register int siz;
157
158	if (nextf[bucket])
159	return;
160	/*
161	* Insure memory is allocated
162	* on a page boundary. Should
163	* make getpageize call?
164	*/
165	op = (union overhead *)sbrk(0);
166	if ((int)op & 0x3ff)
167	sbrk(1024 - ((int)op & 0x3ff));
168	/* take 2k unless the block is bigger than that */
169	rnu = (bucket <= 8) ? 11 : bucket + 3;
170	nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */
171	if (rnu < bucket)
172	rnu = bucket;
173	op = (union overhead *)sbrk(1 << rnu);
174	/* no more room! */
175	if ((int)op == -1)
176	return;
177	/*
178	* Round up to minimum allocation size boundary
179	* and deduct from block count to reflect.
180	*/
181	if ((int)op & 7) {
182	op = (union overhead *)(((int)op + 8) &~ 7);
183	nblks--;
184	}
185	/*
186	* Add new memory allocated to that on
187	* free list for this hash bucket.
188	*/
189	nextf[bucket] = op;
190	siz = 1 << (bucket + 3);
191	while (--nblks > 0) {
192	op->ov_next = (union overhead *)((caddr_t)op + siz);
193	op = (union overhead *)((caddr_t)op + siz);
194	}
195	}
196
197	free(cp)
198	char *cp;
199	{
200	register int size;
201	register union overhead *op;
202
203	if (cp == NULL)
204	return;
205	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
206	#ifdef debug
207	ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
208	#else
209	if (op->ov_magic != MAGIC)
210	return; /* sanity */
211	#endif
212	#ifdef RCHECK
213	ASSERT(op->ov_rmagic == RMAGIC);
214	if (op->ov_index <= 13)
215	ASSERT((u_int )((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC);
216	#endif
217	ASSERT(op->ov_index < NBUCKETS);
218	size = op->ov_index;
219	op->ov_next = nextf[size];
220	nextf[size] = op;
221	#ifdef MSTATS
222	nmalloc[size]--;
223	#endif
224	}
225
226	/*
227	* When a program attempts "storage compaction" as mentioned in the
228	* old malloc man page, it realloc's an already freed block. Usually
229	* this is the last block it freed; occasionally it might be farther
230	* back. We have to search all the free lists for the block in order
231	* to determine its bucket: 1st we make one pass thru the lists
232	* checking only the first block in each; if that fails we search
233	* ``realloc_srchlen'' blocks in each list for a match (the variable
234	* is extern so the caller can modify it). If that fails we just copy
235	* however many bytes was given to realloc() and hope it's not huge.
236	*/
237	int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
238
239	char *
240	realloc(cp, nbytes)
241	char *cp;
242	unsigned nbytes;
243	{
244	register u_int onb;
245	union overhead *op;
246	char *res;
247	register int i;
248	int was_alloced = 0;
249
250	if (cp == NULL)
251	return (malloc(nbytes));
252	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
253	if (op->ov_magic == MAGIC) {
254	was_alloced++;
255	i = op->ov_index;
256	} else {
257	/*
258	* Already free, doing "compaction".
259	*
260	* Search for the old block of memory on the
261	* free list. First, check the most common
262	* case (last element free'd), then (this failing)
263	* the last ``realloc_srchlen'' items free'd.
264	* If all lookups fail, then assume the size of
265	* the memory block being realloc'd is the
266	* smallest possible.
267	*/
268	if ((i = findbucket(op, 1)) < 0 &&
269	(i = findbucket(op, realloc_srchlen)) < 0)
270	i = 0;
271	}
272	onb = (1 << (i + 3)) - sizeof (*op) - RSLOP;
273	/* avoid the copy if same size block */
274	if (was_alloced &&
275	nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP)
276	return(cp);
277	if ((res = malloc(nbytes)) == NULL)
278	return (NULL);
279	if (cp != res) /* common optimization */
280	bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
281	if (was_alloced)
282	free(cp);
283	return (res);
284	}
285
286	/*
287	* Search ``srchlen'' elements of each free list for a block whose
288	* header starts at ``freep''. If srchlen is -1 search the whole list.
289	* Return bucket number, or -1 if not found.
290	*/
291	static
292	findbucket(freep, srchlen)
293	union overhead *freep;
294	int srchlen;
295	{
296	register union overhead *p;
297	register int i, j;
298
299	for (i = 0; i < NBUCKETS; i++) {
300	j = 0;
301	for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
302	if (p == freep)
303	return (i);
304	j++;
305	}
306	}
307	return (-1);
308	}
309
310	#ifdef MSTATS
311	/*
312	* mstats - print out statistics about malloc
313	*
314	* Prints two lines of numbers, one showing the length of the free list
315	* for each size category, the second showing the number of mallocs -
316	* frees for each size category.
317	*/
318	mstats(s)
319	char *s;
320	{
321	register int i, j;
322	register union overhead *p;
323	int totfree = 0,
324	totused = 0;
325
326	fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
327	for (i = 0; i < NBUCKETS; i++) {
328	for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
329	;
330	fprintf(stderr, " %d", j);
331	totfree += j * (1 << (i + 3));
332	}
333	fprintf(stderr, "\nused:\t");
334	for (i = 0; i < NBUCKETS; i++) {
335	fprintf(stderr, " %d", nmalloc[i]);
336	totused += nmalloc[i] * (1 << (i + 3));
337	}
338	fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
339	totused, totfree);
340	}
341	#endif