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/* $Header: malloc.c,v 3.0.1.5 91/01/11 18:09:52 lwall Locked $
*
* $Log: malloc.c,v $
* Revision 3.0.1.5 91/01/11 18:09:52 lwall
* patch42: Configure now checks alignment requirements
*
* Revision 3.0.1.4 90/11/13 15:23:45 lwall
* patch41: added hp malloc union overhead strut (that sounds very blue collar)
*
* Revision 3.0.1.3 90/10/16 15:27:47 lwall
* patch29: various portability fixes
*
* Revision 3.0.1.2 89/11/11 04:36:37 lwall
* patch2: malloc pointer corruption check made more portable
*
* Revision 3.0.1.1 89/10/26 23:15:05 lwall
* patch1: some declarations were missing from malloc.c
* patch1: sparc machines had alignment problems in malloc.c
*
* Revision 3.0 89/10/18 15:20:39 lwall
* 3.0 baseline
*
*/
#ifndef lint
static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83";
#ifdef DEBUGGING
#define RCHECK
#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 "EXTERN.h"
#include "perl.h"
static findbucket(), morecore();
/* 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 */
#if ALIGNBYTES > 4
double strut; /* alignment problems */
#endif
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 */
#ifdef RCHECK
if (*((int*)p) & (sizeof(union overhead) - 1))
#ifndef I286
fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p);
#else
fprintf(stderr,"Corrupt malloc ptr 0x%lx at 0x%lx\n",*((int*)p),p);
#endif
#endif
nextf[bucket] = p->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 int 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);
#ifndef I286
if ((int)op & 0x3ff)
(void)sbrk(1024 - ((int)op & 0x3ff));
#else
/* The sbrk(0) call on the I286 always returns the next segment */
#endif
#ifndef I286
/* take 2k unless the block is bigger than that */
rnu = (bucket <= 8) ? 11 : bucket + 3;
#else
/* take 16k unless the block is bigger than that
(80286s like large segments!) */
rnu = (bucket <= 11) ? 14 : bucket + 3;
#endif
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.
*/
#ifndef I286
if ((int)op & 7) {
op = (union overhead *)(((int)op + 8) &~ 7);
nblks--;
}
#else
/* Again, this should always be ok on an 80286 */
#endif
/*
* 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) {
warn("%s free() ignored",
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) {
#ifdef RCHECK
/*
* Record new allocated size of block and
* bound space with magic numbers.
*/
if (op->ov_index <= 13) {
/*
* 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;
op->ov_size = nbytes - 1;
*((u_int *)((caddr_t)op + nbytes - RSLOP)) = RMAGIC;
}
#endif
return(cp);
}
if ((res = malloc(nbytes)) == NULL)
return (NULL);
if (cp != res) /* common optimization */
(void)bcopy(cp, res, (int)((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
#endif /* lint */
|