[unix-history] / lib / libpthread / pthreads / malloc.c

/* ==== malloc.c ============================================================
 * Copyright (c) 1983 Regents of the University of California.
 * Copyright (c) 1993 by Chris Provenzano, proven@mit.edu
 * All rights reserved.
 *
 * 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.
 *
 * 	Description : Malloc functions.
 * 	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-10) bytes long.
 * 	This is designed for use in a virtual memory environment.
 *
 * 	0.00 82/02/21 Chris Kingsley kingsley@cit-20 
 *
 *  1.00 93/11/06 proven
 *      -Modified BSD libc malloc to be threadsafe.
 *
 */

#if defined(LIBC_SCCS) && !defined(lint)
/*static char *sccsid = "from: @(#)malloc.c     5.11 (Berkeley) 2/23/91";*/
static char *rcsid = "$Id: malloc.c,v 1.2 1993/11/15 10:06:09 proven Exp $";
#endif /* LIBC_SCCS and not lint */

#include <pthread.h>
#include <sys/types.h>
#include <string.h>
#include <pthread/posix.h>

/*
 * 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 then a second word holds the size of the
 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
 * The order of elements is critical: ov_magic must overlay the low order
 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
 */
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_rmagic;	/* range magic number */
		u_int	ovu_size;	/* actual block size */
#endif
	} ovu;
#define	ov_magic	ovu.ovu_magic
#define	ov_index	ovu.ovu_index
#define	ov_rmagic	ovu.ovu_rmagic
#define	ov_size		ovu.ovu_size
};

#define	MAGIC		0xef		/* magic # on accounting info */
#define RMAGIC		0x5555		/* magic # on range info */

#ifdef RCHECK
#define	RSLOP		sizeof (u_short)
#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();

static	int pagesz;				/* page size */
static	int pagebucket;			/* page size bucket */
static 	semaphore malloc_lock = SEMAPHORE_CLEAR;

#if defined(DEBUG) || defined(RCHECK)
#define	ASSERT(p)   if (!(p)) botch("p")
#include <stdio.h>
static
botch(s)
	char *s;
{
	fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
 	(void) fflush(stderr);		/* just in case user buffered it */
	abort();
}
#else
#define	ASSERT(p)
#endif

/* ==========================================================================
 * morecore()
 *
 * Allocate more memory to the indicated bucket
 */
static inline void morecore(int bucket)
{
  	register union overhead *op;
	register int sz;		/* size of desired block */
  	int amt;			/* amount to allocate */
  	int nblks;			/* how many blocks we get */

	/*
	 * sbrk_size <= 0 only for big, FLUFFY, requests (about
	 * 2^30 bytes on a VAX, I think) or for a negative arg.
	 */
	sz = 1 << (bucket + 3);
#ifdef DEBUG
	ASSERT(sz > 0);
#else
	if (sz <= 0)
		return;
#endif
	if (sz < pagesz) {
		amt = pagesz;
  		nblks = amt / sz;
	} else {
		amt = sz + pagesz;
		nblks = 1;
	}
	op = (union overhead *)sbrk(amt);
	/* no more room! */
  	if ((int)op == -1)
  		return;
	/*
	 * Add new memory allocated to that on
	 * free list for this hash bucket.
	 */
  	nextf[bucket] = op;
  	while (--nblks > 0) {
		op->ov_next = (union overhead *)((caddr_t)op + sz);
		op = (union overhead *)((caddr_t)op + sz);
  	}
}

/* ==========================================================================
 * malloc()
 */
void *malloc(size_t nbytes)
{
  	union overhead *op;
	unsigned int amt;
  	int bucket, n;
	semaphore *lock;

	lock = &malloc_lock;
	while(SEMAPHORE_TEST_AND_SET(lock)) {
		pthread_yield();
	}
	/*
	 * First time malloc is called, setup page size and
	 * align break pointer so all data will be page aligned.
	 */
	if (pagesz == 0) {
		pagesz = n = getpagesize();
		op = (union overhead *)sbrk(0);
  		n = n - sizeof (*op) - ((int)op & (n - 1));
		if (n < 0)
			n += pagesz;
  		if (n) {
  			if (sbrk(n) == (char *)-1)
				return (NULL);
		}
		bucket = 0;
		amt = 8;
		while (pagesz > amt) {
			amt <<= 1;
			bucket++;
		}
		pagebucket = bucket;
	}
	/*
	 * Convert amount of memory requested into closest block size
	 * stored in hash buckets which satisfies request.
	 * Account for space used per block for accounting.
	 */
	if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) {
#ifndef RCHECK
		amt = 8;	/* size of first bucket */
		bucket = 0;
#else
		amt = 16;	/* size of first bucket */
		bucket = 1;
#endif
		n = -(sizeof (*op) + RSLOP);
	} else {
		amt = pagesz;
		bucket = pagebucket;
	}
	while (nbytes > amt + n) {
		amt <<= 1;
		if (amt == 0) {
			SEMAPHORE_RESET(lock);
			return (NULL);
		}
		bucket++;
	}
	/*
	 * If nothing in hash bucket right now,
	 * request more memory from the system.
	 */
  	if ((op = nextf[bucket]) == NULL) {
  		morecore(bucket);
  		if ((op = nextf[bucket]) == NULL) {
			SEMAPHORE_RESET(lock);
  			return (NULL);
		}
	}
	/* remove from linked list */
  	nextf[bucket] = op->ov_next;
	op->ov_magic = MAGIC;
	op->ov_index = bucket;
#ifdef RCHECK
	/*
	 * Record allocated size of block and
	 * bound space with magic numbers.
	 */
	op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
	op->ov_rmagic = RMAGIC;
  	*(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
#endif
	SEMAPHORE_RESET(lock);
  	return ((char *)(op + 1));
}

/* ==========================================================================
 * free()
 */
void free(void *cp)
{   
	union overhead *op;
	semaphore *lock;
  	int size;

	lock = &malloc_lock;
	while(SEMAPHORE_TEST_AND_SET(lock)) {
		pthread_yield();
	}
  	if (cp == NULL) {
		SEMAPHORE_RESET(lock);
  		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) {
		SEMAPHORE_RESET(lock);
		return;				/* sanity */
	}
#endif
#ifdef RCHECK
  	ASSERT(op->ov_rmagic == RMAGIC);
	ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
#endif
  	size = op->ov_index;
  	ASSERT(size < NBUCKETS);
	op->ov_next = nextf[size];	/* also clobbers ov_magic */
  	nextf[size] = op;

	SEMAPHORE_RESET(lock);
}

/* ==========================================================================
 * realloc()
 *
 * Storage compaction is no longer supported, fix program and try again.
 */
void *realloc(void *cp, size_t nbytes)
{   
  	u_int onb;
	int i;
	semaphore *lock;
	union overhead *op;
  	char *res;

  	if (cp == NULL)
  		return (malloc(nbytes));
	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));

	if (op->ov_magic == MAGIC) {
		i = op->ov_index;
	} else {
		/*
		 * This will cause old programs using storage compaction feature of
		 * realloc to break in a pseudo resonable way that is easy to debug.
		 * Returning a malloced buffer without the copy may cause
		 * indeterministic behavior.
		 */
	    return(NULL);
	}

	lock = &malloc_lock;
	while(SEMAPHORE_TEST_AND_SET(lock)) {
		pthread_yield();
	}
	onb = 1 << (i + 3);
	if (onb < pagesz)
		onb -= sizeof (*op) + RSLOP;
	else
		onb += pagesz - sizeof (*op) - RSLOP;

	/* avoid the copy if same size block */
	if (i) {
		i = 1 << (i + 2);
		if (i < pagesz)
			i -= sizeof (*op) + RSLOP;
		else
			i += pagesz - sizeof (*op) - RSLOP;
	}

	if (nbytes <= onb && nbytes > i) {
#ifdef RCHECK
		op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
		*(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
#endif
		SEMAPHORE_RESET(lock);
		return(cp);
	}
	SEMAPHORE_RESET(lock);

  	if ((res = malloc(nbytes)) == NULL) {
		free(cp);
  		return (NULL);
	}

	bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
	free(cp);

  	return (res);
}
Commit	Line	Data
90269d47 AM	1	/* ==== malloc.c ============================================================
	2	* Copyright (c) 1983 Regents of the University of California.
	3	* Copyright (c) 1993 by Chris Provenzano, proven@mit.edu
	4	* All rights reserved.
	5	*
	6	* Redistribution and use in source and binary forms, with or without
	7	* modification, are permitted provided that the following conditions
	8	* are met:
	9	* 1. Redistributions of source code must retain the above copyright
	10	* notice, this list of conditions and the following disclaimer.
	11	* 2. Redistributions in binary form must reproduce the above copyright
	12	* notice, this list of conditions and the following disclaimer in the
	13	* documentation and/or other materials provided with the distribution.
	14	* 3. All advertising materials mentioning features or use of this software
	15	* must display the following acknowledgement:
	16	* This product includes software developed by the University of
	17	* California, Berkeley and its contributors.
	18	* 4. Neither the name of the University nor the names of its contributors
	19	* may be used to endorse or promote products derived from this software
	20	* without specific prior written permission.
	21	*
	22	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	* SUCH DAMAGE.
	33	*
	34	* Description : Malloc functions.
	35	* This is a very fast storage allocator. It allocates blocks of a small
	36	* number of different sizes, and keeps free lists of each size. Blocks that
	37	* don't exactly fit are passed up to the next larger size. In this
	38	* implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long.
	39	* This is designed for use in a virtual memory environment.
	40	*
	41	* 0.00 82/02/21 Chris Kingsley kingsley@cit-20
	42	*
	43	* 1.00 93/11/06 proven
	44	* -Modified BSD libc malloc to be threadsafe.
	45	*
	46	*/
	47
	48	#if defined(LIBC_SCCS) && !defined(lint)
	49	/static char sccsid = "from: @(#)malloc.c 5.11 (Berkeley) 2/23/91";*/
56a62443	50	static char *rcsid = "$Id: malloc.c,v 1.2 1993/11/15 10:06:09 proven Exp $";
90269d47 AM	51	#endif /* LIBC_SCCS and not lint */
90269d47 AM	52
90269d47 AM	53	#include <pthread.h>
	54	#include <sys/types.h>
	55	#include <string.h>
	56	#include <pthread/posix.h>
	57
	58	/*
	59	* The overhead on a block is at least 4 bytes. When free, this space
	60	* contains a pointer to the next free block, and the bottom two bits must
	61	* be zero. When in use, the first byte is set to MAGIC, and the second
	62	* byte is the size index. The remaining bytes are for alignment.
	63	* If range checking is enabled then a second word holds the size of the
	64	* requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
	65	* The order of elements is critical: ov_magic must overlay the low order
	66	* bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
	67	*/
	68	union overhead {
	69	union overhead ov_next; / when free */
	70	struct {
	71	u_char ovu_magic; /* magic number */
	72	u_char ovu_index; /* bucket # */
	73	#ifdef RCHECK
	74	u_short ovu_rmagic; /* range magic number */
	75	u_int ovu_size; /* actual block size */
	76	#endif
	77	} ovu;
	78	#define ov_magic ovu.ovu_magic
	79	#define ov_index ovu.ovu_index
	80	#define ov_rmagic ovu.ovu_rmagic
	81	#define ov_size ovu.ovu_size
	82	};
	83
	84	#define MAGIC 0xef /* magic # on accounting info */
	85	#define RMAGIC 0x5555 /* magic # on range info */
	86
	87	#ifdef RCHECK
	88	#define RSLOP sizeof (u_short)
	89	#else
	90	#define RSLOP 0
	91	#endif
	92
	93	/*
	94	* nextf[i] is the pointer to the next free block of size 2^(i+3). The
	95	* smallest allocatable block is 8 bytes. The overhead information
	96	* precedes the data area returned to the user.
	97	*/
	98	#define NBUCKETS 30
	99	static union overhead *nextf[NBUCKETS];
	100	extern char *sbrk();
	101
	102	static int pagesz; /* page size */
	103	static int pagebucket; /* page size bucket */
	104	static semaphore malloc_lock = SEMAPHORE_CLEAR;
	105
	106	#if defined(DEBUG) \|\| defined(RCHECK)
	107	#define ASSERT(p) if (!(p)) botch("p")
	108	#include <stdio.h>
	109	static
	110	botch(s)
	111	char *s;
	112	{
	113	fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
	114	(void) fflush(stderr); /* just in case user buffered it */
	115	abort();
	116	}
117	#else
118	#define ASSERT(p)
119	#endif
120
121	/* ==========================================================================
122	* morecore()
123	*
124	* Allocate more memory to the indicated bucket
125	*/
126	static inline void morecore(int bucket)
127	{
128	register union overhead *op;
129	register int sz; /* size of desired block */
130	int amt; /* amount to allocate */
131	int nblks; /* how many blocks we get */
132
133	/*
134	* sbrk_size <= 0 only for big, FLUFFY, requests (about
135	* 2^30 bytes on a VAX, I think) or for a negative arg.
136	*/
137	sz = 1 << (bucket + 3);
138	#ifdef DEBUG
139	ASSERT(sz > 0);
140	#else
141	if (sz <= 0)
142	return;
143	#endif
144	if (sz < pagesz) {
145	amt = pagesz;
146	nblks = amt / sz;
147	} else {
148	amt = sz + pagesz;
149	nblks = 1;
150	}
151	op = (union overhead *)sbrk(amt);
152	/* no more room! */
153	if ((int)op == -1)
154	return;
155	/*
156	* Add new memory allocated to that on
157	* free list for this hash bucket.
158	*/
159	nextf[bucket] = op;
160	while (--nblks > 0) {
161	op->ov_next = (union overhead *)((caddr_t)op + sz);
162	op = (union overhead *)((caddr_t)op + sz);
163	}
164	}
165
166	/* ==========================================================================
167	* malloc()
168	*/
169	void *malloc(size_t nbytes)
170	{
171	union overhead *op;
172	unsigned int amt;
173	int bucket, n;
174	semaphore *lock;
175
176	lock = &malloc_lock;
177	while(SEMAPHORE_TEST_AND_SET(lock)) {
178	pthread_yield();
179	}
180	/*
181	* First time malloc is called, setup page size and
182	* align break pointer so all data will be page aligned.
183	*/
184	if (pagesz == 0) {
185	pagesz = n = getpagesize();
186	op = (union overhead *)sbrk(0);
187	n = n - sizeof (*op) - ((int)op & (n - 1));
188	if (n < 0)
189	n += pagesz;
190	if (n) {
191	if (sbrk(n) == (char *)-1)
192	return (NULL);
193	}
194	bucket = 0;
195	amt = 8;
196	while (pagesz > amt) {
197	amt <<= 1;
198	bucket++;
199	}
200	pagebucket = bucket;
201	}
202	/*
203	* Convert amount of memory requested into closest block size
204	* stored in hash buckets which satisfies request.
205	* Account for space used per block for accounting.
206	*/
207	if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) {
208	#ifndef RCHECK
209	amt = 8; /* size of first bucket */
210	bucket = 0;
211	#else
212	amt = 16; /* size of first bucket */
213	bucket = 1;
214	#endif
215	n = -(sizeof (*op) + RSLOP);
216	} else {
217	amt = pagesz;
218	bucket = pagebucket;
219	}
220	while (nbytes > amt + n) {
221	amt <<= 1;
222	if (amt == 0) {
223	SEMAPHORE_RESET(lock);
224	return (NULL);
225	}
226	bucket++;
227	}
228	/*
229	* If nothing in hash bucket right now,
230	* request more memory from the system.
231	*/
232	if ((op = nextf[bucket]) == NULL) {
233	morecore(bucket);
234	if ((op = nextf[bucket]) == NULL) {
235	SEMAPHORE_RESET(lock);
236	return (NULL);
237	}
238	}
239	/* remove from linked list */
240	nextf[bucket] = op->ov_next;
241	op->ov_magic = MAGIC;
242	op->ov_index = bucket;
243	#ifdef RCHECK
244	/*
245	* Record allocated size of block and
246	* bound space with magic numbers.
247	*/
248	op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
249	op->ov_rmagic = RMAGIC;
250	(u_short )((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
251	#endif
252	SEMAPHORE_RESET(lock);
253	return ((char *)(op + 1));
254	}
255
256	/* ==========================================================================
257	* free()
258	*/
259	void free(void *cp)
260	{
261	union overhead *op;
262	semaphore *lock;
263	int size;
264
265	lock = &malloc_lock;
266	while(SEMAPHORE_TEST_AND_SET(lock)) {
267	pthread_yield();
268	}
269	if (cp == NULL) {
270	SEMAPHORE_RESET(lock);
271	return;
272	}
273	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
274	#ifdef DEBUG
275	ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
276	#else
277	if (op->ov_magic != MAGIC) {
278	SEMAPHORE_RESET(lock);
279	return; /* sanity */
280	}
281	#endif
282	#ifdef RCHECK
283	ASSERT(op->ov_rmagic == RMAGIC);
284	ASSERT((u_short )((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
285	#endif
286	size = op->ov_index;
287	ASSERT(size < NBUCKETS);
288	op->ov_next = nextf[size]; /* also clobbers ov_magic */
289	nextf[size] = op;
290
291	SEMAPHORE_RESET(lock);
292	}
293
294	/* ==========================================================================
295	* realloc()
296	*
297	* Storage compaction is no longer supported, fix program and try again.
298	*/
299	void realloc(void cp, size_t nbytes)
300	{
301	u_int onb;
302	int i;
303	semaphore *lock;
304	union overhead *op;
305	char *res;
306
307	if (cp == NULL)
308	return (malloc(nbytes));
309	op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
310
311	if (op->ov_magic == MAGIC) {
312	i = op->ov_index;
313	} else {
314	/*
315	* This will cause old programs using storage compaction feature of
316	* realloc to break in a pseudo resonable way that is easy to debug.
317	* Returning a malloced buffer without the copy may cause
318	* indeterministic behavior.
319	*/
320	return(NULL);
321	}
322
323	lock = &malloc_lock;
324	while(SEMAPHORE_TEST_AND_SET(lock)) {
325	pthread_yield();
326	}
327	onb = 1 << (i + 3);
328	if (onb < pagesz)
329	onb -= sizeof (*op) + RSLOP;
330	else
331	onb += pagesz - sizeof (*op) - RSLOP;
332
333	/* avoid the copy if same size block */
334	if (i) {
335	i = 1 << (i + 2);
336	if (i < pagesz)
337	i -= sizeof (*op) + RSLOP;
338	else
339	i += pagesz - sizeof (*op) - RSLOP;
340	}
341
342	if (nbytes <= onb && nbytes > i) {
343	#ifdef RCHECK
344	op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
345	(u_short )((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
346	#endif
347	SEMAPHORE_RESET(lock);
348	return(cp);
349	}
350	SEMAPHORE_RESET(lock);
351
352	if ((res = malloc(nbytes)) == NULL) {
353	free(cp);
354	return (NULL);
355	}
356
357	bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
358	free(cp);
359
360	return (res);
361	}
362