src/common/malloc.c

/* Copyright (c) 1990 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 * Fast malloc for memory hogs and VM environments.
 * Performs a minimum of searching through free lists.
 * malloc(), realloc() and free() use buckets
 *      containing blocks in powers of two, similar to CIT routines.
 * bfree() puts memory from any source into malloc free lists.
 * bmalloc() doesn't keep track of free lists -- it's usually
 *      just a buffered call to sbrk(2).  However, bmalloc will
 *      call mscrounge() if sbrk fails.
 * mscrounge() returns whatever memory it can find to satisfy the
 *      request along with the number of bytes (modified).
 *
 *      Greg Ward       Lawrence Berkeley Laboratory
 */

#include  <errno.h>

#define  NULL           0

#ifndef ALIGN
#define  ALIGN          int                     /* align type */
#endif
#define  BYTES_WORD     sizeof(ALIGN)

#define  MAXINCR        (1<<18)                 /* largest sbrk(2) increment */

#ifdef  NOVMEM
#define  getpagesize()  BYTES_WORD
#endif
                                        /* malloc free lists */
typedef union m_head {
        union m_head    *next;
        int             bucket;
        ALIGN           dummy;
} M_HEAD;

#define FIRSTBUCKET     3
#define NBUCKETS        30

static M_HEAD   *free_list[NBUCKETS];


char *
mscrounge(np)           /* search free lists to satisfy request */
register unsigned       *np;
{
        char    *p;
        register int    bucket;
        register unsigned       bsiz;

        for (bucket = FIRSTBUCKET, bsiz = 1<<FIRSTBUCKET;
                        bucket < NBUCKETS; bucket++, bsiz <<= 1)
                if (free_list[bucket] != NULL && bsiz+sizeof(M_HEAD) >= *np) {
                        *np = bsiz+sizeof(M_HEAD);
                        p = (char *)free_list[bucket];
                        free_list[bucket] = free_list[bucket]->next;
                        return(p);
                }
        *np = 0;
        return(NULL);
}


char *
bmalloc(n)              /* allocate a block of n bytes, sans header */
register unsigned  n;
{
        extern char  *sbrk();
        static unsigned  pagesz = 0;
        static unsigned  amnt;
        static char  *bpos;
        static unsigned  nrem;
        unsigned  thisamnt;
        register char   *p;

        if (pagesz == 0) {                              /* initialize */
                pagesz = amnt = getpagesize();
                nrem = (int)sbrk(0);                    /* page align break */
                nrem = pagesz - (nrem&(pagesz-1));
                bpos = sbrk(nrem);                      /* word aligned! */
                if ((int)bpos == -1)
                        return(NULL);
        }

        n = (n+(BYTES_WORD-1))&~(BYTES_WORD-1);         /* word align rqst. */

        if (n > nrem) {                                 /* need more core */
                if (n > amnt) {                         /* big chunk */
                        thisamnt = (n+(pagesz-1))&~(pagesz-1);
                        if (thisamnt <= MAXINCR)        /* increase amnt */
                                amnt = thisamnt;
                } else
                        thisamnt = amnt;
                p = sbrk(thisamnt);
                if ((int)p == -1) {                     /* uh-oh, ENOMEM */
                        thisamnt = n;                   /* search free lists */
                        p = mscrounge(&thisamnt);
                        if (p == NULL)                  /* we're really out */
                                return(NULL);
                }
                if (p != bpos+nrem) {                   /* not an increment */
                        bfree(bpos, nrem);              /* free what we have */
                        bpos = p;
                        nrem = thisamnt;
                } else                                  /* otherwise tack on */
                        nrem += thisamnt;
        }
        p = bpos;
        bpos += n;                                      /* advance */
        nrem -= n;
        return(p);
}


bfree(p, n)                     /* free n bytes of random memory */
register char  *p;
register unsigned  n;
{
        register int    bucket;
        register unsigned       bsiz;
                                        /* align pointer */
        bsiz = BYTES_WORD - ((unsigned)p&(BYTES_WORD-1));
        if (bsiz < BYTES_WORD) {
                p += bsiz;
                n -= bsiz;
        }
                                        /* fill big buckets first */
        for (bucket = NBUCKETS-1, bsiz = 1<<(NBUCKETS-1);
                        bucket >= FIRSTBUCKET; bucket--, bsiz >>= 1)
                if (n >= bsiz+sizeof(M_HEAD)) {
                        ((M_HEAD *)p)->next = free_list[bucket];
                        free_list[bucket] = (M_HEAD *)p;
                        p += bsiz+sizeof(M_HEAD);
                        n -= bsiz+sizeof(M_HEAD);
                }
}


char *
malloc(n)                       /* allocate n bytes of memory */
unsigned        n;
{
        extern int  errno;
        register M_HEAD *mp;
        register int    bucket;
        register unsigned       bsiz;
                                        /* find first bucket that fits */
        for (bucket = FIRSTBUCKET, bsiz = 1<<FIRSTBUCKET;
                        bucket < NBUCKETS; bucket++, bsiz <<= 1)
                if (bsiz >= n)
                        break;
        if (bucket >= NBUCKETS) {
                errno = EINVAL;
                return(NULL);
        }
        if (free_list[bucket] == NULL) {        /* need more core */
                mp = (M_HEAD *)bmalloc(bsiz+sizeof(M_HEAD));
                if (mp == NULL)
                        return(NULL);
        } else {                                /* got it */
                mp = free_list[bucket];
                free_list[bucket] = mp->next;
        }
        mp->bucket = bucket;                    /* tag block */
        return((char *)(mp+1));
}


char *
realloc(op, n)                  /* reallocate memory using malloc() */
register char   *op;
unsigned        n;
{
        char    *p;
        register unsigned       on;
                                        /* get old size */
        if (op != NULL)
                on = 1 << ((M_HEAD *)op-1)->bucket;
        else
                on = 0;
        if (n <= on && (n > on>>1 || on == 1<<FIRSTBUCKET))
                return(op);             /* same bucket */
        p = malloc(n);
        if (p != NULL)
#ifdef  BSD
                bcopy(op, p, n>on ? on : n);
#else
                (void)memcpy(p, op, n>on ? on : n);
#endif
        free(op);
        return(p);
}


free(p)                 /* free memory allocated by malloc */
char    *p;
{
        register M_HEAD *mp;
        register int    bucket;

        if (p == NULL)
                return;
        mp = (M_HEAD *)p - 1;
        bucket = mp->bucket;
        mp->next = free_list[bucket];
        free_list[bucket] = mp;
}


#ifndef NOVMEM
#ifndef BSD
#include <sys/var.h>
int
getpagesize()                   /* use SYSV var structure to get page size */
{
        static int  pagesz = 0;
        struct var  v;

        if (pagesz == 0) {
                uvar(&v);
                pagesz = 1 << v.v_pageshift;
        }
        return(pagesz);
}
#endif
#endif
Revision:	1.7
Committed:	Tue Oct 2 12:00:03 1990 UTC (35 years, 1 month ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.6:	+0 -3 lines
Log Message:	made sure malloc(0) doesn't return NULL -- Xlib bug
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1990 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* Fast malloc for memory hogs and VM environments.
9			* Performs a minimum of searching through free lists.
10	greg	1.4	* malloc(), realloc() and free() use buckets
11			* containing blocks in powers of two, similar to CIT routines.
12			* bfree() puts memory from any source into malloc free lists.
13			* bmalloc() doesn't keep track of free lists -- it's usually
14	greg	1.3	* just a buffered call to sbrk(2). However, bmalloc will
15			* call mscrounge() if sbrk fails.
16			* mscrounge() returns whatever memory it can find to satisfy the
17			* request along with the number of bytes (modified).
18	greg	1.1	*
19			* Greg Ward Lawrence Berkeley Laboratory
20			*/
21
22	greg	1.6	#include <errno.h>
23
24	greg	1.1	#define NULL 0
25
26			#ifndef ALIGN
27			#define ALIGN int /* align type */
28			#endif
29			#define BYTES_WORD sizeof(ALIGN)
30
31	greg	1.3	#define MAXINCR (1<<18) /* largest sbrk(2) increment */
32
33	greg	1.1	#ifdef NOVMEM
34			#define getpagesize() BYTES_WORD
35			#endif
36			/* malloc free lists */
37			typedef union m_head {
38			union m_head *next;
39			int bucket;
40			ALIGN dummy;
41			} M_HEAD;
42
43			#define FIRSTBUCKET 3
44			#define NBUCKETS 30
45
46			static M_HEAD *free_list[NBUCKETS];
47
48
49			char *
50	greg	1.4	mscrounge(np) /* search free lists to satisfy request */
51	greg	1.3	register unsigned *np;
52			{
53			char *p;
54			register int bucket;
55			register unsigned bsiz;
56
57			for (bucket = FIRSTBUCKET, bsiz = 1<<FIRSTBUCKET;
58			bucket < NBUCKETS; bucket++, bsiz <<= 1)
59			if (free_list[bucket] != NULL && bsiz+sizeof(M_HEAD) >= *np) {
60			*np = bsiz+sizeof(M_HEAD);
61			p = (char *)free_list[bucket];
62			free_list[bucket] = free_list[bucket]->next;
63			return(p);
64			}
65			*np = 0;
66			return(NULL);
67			}
68
69
70			char *
71	greg	1.1	bmalloc(n) /* allocate a block of n bytes, sans header */
72			register unsigned n;
73			{
74			extern char *sbrk();
75	greg	1.3	static unsigned pagesz = 0;
76			static unsigned amnt;
77	greg	1.1	static char *bpos;
78	greg	1.3	static unsigned nrem;
79			unsigned thisamnt;
80	greg	1.1	register char *p;
81
82			if (pagesz == 0) { /* initialize */
83	greg	1.2	pagesz = amnt = getpagesize();
84	greg	1.1	nrem = (int)sbrk(0); /* page align break */
85			nrem = pagesz - (nrem&(pagesz-1));
86			bpos = sbrk(nrem); /* word aligned! */
87			if ((int)bpos == -1)
88			return(NULL);
89			}
90
91			n = (n+(BYTES_WORD-1))&~(BYTES_WORD-1); /* word align rqst. */
92
93			if (n > nrem) { /* need more core */
94	greg	1.3	if (n > amnt) { /* big chunk */
95			thisamnt = (n+(pagesz-1))&~(pagesz-1);
96			if (thisamnt <= MAXINCR) /* increase amnt */
97			amnt = thisamnt;
98			} else
99			thisamnt = amnt;
100			p = sbrk(thisamnt);
101	greg	1.4	if ((int)p == -1) { /* uh-oh, ENOMEM */
102	greg	1.3	thisamnt = n; /* search free lists */
103			p = mscrounge(&thisamnt);
104			if (p == NULL) /* we're really out */
105			return(NULL);
106			}
107			if (p != bpos+nrem) { /* not an increment */
108	greg	1.4	bfree(bpos, nrem); /* free what we have */
109	greg	1.1	bpos = p;
110	greg	1.3	nrem = thisamnt;
111	greg	1.4	} else /* otherwise tack on */
112	greg	1.3	nrem += thisamnt;
113	greg	1.1	}
114			p = bpos;
115			bpos += n; /* advance */
116			nrem -= n;
117			return(p);
118			}
119
120
121			bfree(p, n) /* free n bytes of random memory */
122	greg	1.2	register char *p;
123			register unsigned n;
124	greg	1.1	{
125			register int bucket;
126			register unsigned bsiz;
127	greg	1.4	/* align pointer */
128	greg	1.6	bsiz = BYTES_WORD - ((unsigned)p&(BYTES_WORD-1));
129	greg	1.4	if (bsiz < BYTES_WORD) {
130			p += bsiz;
131			n -= bsiz;
132	greg	1.1	}
133	greg	1.4	/* fill big buckets first */
134			for (bucket = NBUCKETS-1, bsiz = 1<<(NBUCKETS-1);
135			bucket >= FIRSTBUCKET; bucket--, bsiz >>= 1)
136			if (n >= bsiz+sizeof(M_HEAD)) {
137			((M_HEAD *)p)->next = free_list[bucket];
138			free_list[bucket] = (M_HEAD *)p;
139			p += bsiz+sizeof(M_HEAD);
140			n -= bsiz+sizeof(M_HEAD);
141			}
142	greg	1.1	}
143
144
145			char *
146			malloc(n) /* allocate n bytes of memory */
147			unsigned n;
148			{
149	greg	1.6	extern int errno;
150	greg	1.1	register M_HEAD *mp;
151			register int bucket;
152			register unsigned bsiz;
153	greg	1.2	/* find first bucket that fits */
154	greg	1.6	for (bucket = FIRSTBUCKET, bsiz = 1<<FIRSTBUCKET;
155			bucket < NBUCKETS; bucket++, bsiz <<= 1)
156			if (bsiz >= n)
157			break;
158			if (bucket >= NBUCKETS) {
159			errno = EINVAL;
160			return(NULL);
161			}
162	greg	1.4	if (free_list[bucket] == NULL) { /* need more core */
163	greg	1.1	mp = (M_HEAD *)bmalloc(bsiz+sizeof(M_HEAD));
164			if (mp == NULL)
165			return(NULL);
166	greg	1.4	} else { /* got it */
167	greg	1.1	mp = free_list[bucket];
168			free_list[bucket] = mp->next;
169			}
170	greg	1.4	mp->bucket = bucket; /* tag block */
171	greg	1.1	return((char *)(mp+1));
172			}
173
174
175			char *
176			realloc(op, n) /* reallocate memory using malloc() */
177	greg	1.6	register char *op;
178	greg	1.1	unsigned n;
179			{
180	greg	1.6	char *p;
181	greg	1.1	register unsigned on;
182	greg	1.6	/* get old size */
183	greg	1.5	if (op != NULL)
184			on = 1 << ((M_HEAD *)op-1)->bucket;
185			else
186			on = 0;
187	greg	1.6	if (n <= on && (n > on>>1 \|\| on == 1<<FIRSTBUCKET))
188	greg	1.5	return(op); /* same bucket */
189			p = malloc(n);
190			if (p != NULL)
191	greg	1.1	#ifdef BSD
192	greg	1.2	bcopy(op, p, n>on ? on : n);
193	greg	1.1	#else
194	greg	1.2	(void)memcpy(p, op, n>on ? on : n);
195	greg	1.1	#endif
196	greg	1.5	free(op);
197	greg	1.1	return(p);
198			}
199
200
201			free(p) /* free memory allocated by malloc */
202			char *p;
203			{
204			register M_HEAD *mp;
205			register int bucket;
206
207	greg	1.2	if (p == NULL)
208			return;
209	greg	1.1	mp = (M_HEAD *)p - 1;
210			bucket = mp->bucket;
211			mp->next = free_list[bucket];
212			free_list[bucket] = mp;
213			}
214
215
216			#ifndef NOVMEM
217			#ifndef BSD
218			#include <sys/var.h>
219			int
220			getpagesize() /* use SYSV var structure to get page size */
221			{
222			static int pagesz = 0;
223			struct var v;
224
225			if (pagesz == 0) {
226			uvar(&v);
227			pagesz = 1 << v.v_pageshift;
228			}
229			return(pagesz);
230			}
231			#endif
232			#endif