4.3BSD/usr/contrib/emacs/src/malloc.c
/* Dynamic memory allocation for GNU.
Copyright (C) 1985 Richard M. Stallman,
based mostly on the public domain work of others.
This program is distributed in the hope that it will be useful,
but without any warranty. No author or distributor
accepts responsibility to anyone for the consequences of using it
or for whether it serves any particular purpose or works at all,
unless he says so in writing.
Permission is granted to anyone to distribute verbatim copies
of this program's source code as received, in any medium, provided that
the copyright notice, the nonwarraty notice above
and this permission notice are preserved,
and that the distributor grants the recipient all rights
for further redistribution as permitted by this notice,
and informs him of these rights.
Permission is granted to distribute modified versions of this
program's source code, or of portions of it, under the above
conditions, plus the conditions that all changed files carry
prominent notices stating who last changed them and that the
derived material, including anything packaged together with it and
conceptually functioning as a modification of it rather than an
application of it, is in its entirety subject to a permission
notice identical to this one.
Permission is granted to distribute this program (verbatim or
as modified) in compiled or executable form, provided verbatim
redistribution is permitted as stated above for source code, and
A. it is accompanied by the corresponding machine-readable
source code, under the above conditions, or
B. it is accompanied by a written offer, with no time limit,
to distribute the corresponding machine-readable source code,
under the above conditions, to any one, in return for reimbursement
of the cost of distribution. Verbatim redistribution of the
written offer must be permitted. Or,
C. it is distributed by someone who received only the
compiled or executable form, and is accompanied by a copy of the
written offer of source code which he received along with it.
Permission is granted to distribute this program (verbatim or as modified)
in executable form as part of a larger system provided that the source
code for this program, including any modifications used,
is also distributed or offered as stated in the preceding paragraph.
In other words, you are welcome to use, share and improve this program.
You are forbidden to forbid anyone else to use, share and improve
what you give them. Help stamp out software-hoarding! */
/*
* @(#)nmalloc.c 1 (Caltech) 2/21/82
*
* U of M Modified: 20 Jun 1983 ACT: strange hacks for Emacs
*
* Nov 1983, Mike@BRL, Added support for 4.1C/4.2 BSD.
*
* 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 -16) bytes long.
* This is designed for use in a program that uses vast quantities of
* memory, but bombs when it runs out. To make it a little better, it
* warns the user when he starts to get near the end.
*
* June 84, ACT: modified rcheck code to check the range given to malloc,
* rather than the range determined by the 2-power used.
*
* Jan 85, RMS: calls malloc_warning to issue warning on nearly full.
* No longer Emacs-specific; can serve as all-purpose malloc for GNU.
* You should call malloc_init to reinitialize after loading dumped Emacs.
* Call malloc_stats to get info on memory stats if MSTATS turned on.
* realloc knows how to return same block given, just changing its size,
* if the power of 2 is correct.
*/
/*
* 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 will
* go in the first int of the block, and the returned pointer will point
* to the second.
*
#ifdef MSTATS
* nmalloc[i] is the difference between the number of mallocs and frees
* for a given block size.
#endif /* MSTATS */
#ifdef emacs
#include "config.h"
#endif /* emacs */
#include <sys/param.h>
/* Determine which kind of system this is. */
#include <signal.h>
#ifndef SIGTSTP
#define USG
#else /* SIGTSTP */
#ifdef SIGIO
#define BSD42
#endif /* SIGIO */
#endif /* SIGTSTP */
#ifndef BSD42
#ifndef USG
#include <sys/vlimit.h> /* warn the user when near the end */
#endif
#else /* if BSD42 */
#include <sys/time.h>
#include <sys/resource.h>
#endif /* BSD42 */
#if defined (BSD4_1) || defined (USG)
#ifdef EXEC_PAGESIZE
#define getpagesize() EXEC_PAGESIZE
#else
#ifdef NBPG
#define getpagesize() NBPG * CLSIZE
#ifndef CLSIZE
#define CLSIZE 1
#endif /* no CLSIZE */
#else /* no NBPG */
#define getpagesize() NBPC
#endif /* no NBPG */
#endif /* no EXEC_PAGESIZE */
#endif /* BSD4_1 or USG */
#define ISALLOC ((char) 0xf7) /* magic byte that implies allocation */
#define ISFREE ((char) 0x54) /* magic byte that implies free block */
/* this is for error checking only */
#define ISMEMALIGN ((char) 0xd6) /* Stored before the value returned by
memalign, with the rest of the word
being the distance to the true
beginning of the block. */
extern char etext;
extern char *start_of_data ();
/* These two are for user programs to look at, when they are interested. */
int malloc_sbrk_used; /* amount of data space used now */
int malloc_sbrk_unused; /* amount more we can have */
/* start of data space; can be changed by calling init_malloc */
static char *data_space_start;
#ifdef MSTATS
static int nmalloc[30];
static int nmal, nfre;
#endif /* MSTATS */
/* If range checking is not turned on, all we have is a flag indicating
whether memory is allocated, an index in nextf[], and a size field; to
realloc() memory we copy either size bytes or 1<<(index+3) bytes depending
on whether the former can hold the exact size (given the value of
'index'). If range checking is on, we always need to know how much space
is allocated, so the 'size' field is never used. */
struct mhead {
char mh_alloc; /* ISALLOC or ISFREE */
char mh_index; /* index in nextf[] */
/* Remainder are valid only when block is allocated */
unsigned short mh_size; /* size, if < 0x10000 */
#ifdef rcheck
unsigned mh_nbytes; /* number of bytes allocated */
int mh_magic4; /* should be == MAGIC4 */
#endif /* rcheck */
};
/* Access free-list pointer of a block.
It is stored at block + 4.
This is not a field in the mhead structure
because we want sizeof (struct mhead)
to describe the overhead for when the block is in use,
and we do not want the free-list pointer to count in that. */
#define CHAIN(a) \
(*(struct mhead **) (sizeof (char *) + (char *) (a)))
#ifdef rcheck
/* To implement range checking, we write magic values in at the beginning and
end of each allocated block, and make sure they are undisturbed whenever a
free or a realloc occurs. */
/* Written in each of the 4 bytes following the block's real space */
#define MAGIC1 0x55
/* Written in the 4 bytes before the block's real space */
#define MAGIC4 0x55555555
#define ASSERT(p) if (!(p)) botch("p"); else
#define EXTRA 4 /* 4 bytes extra for MAGIC1s */
#else
#define ASSERT(p)
#define EXTRA 0
#endif /* rcheck */
/* nextf[i] is free list of blocks of size 2**(i + 3) */
static struct mhead *nextf[30];
/* Number of bytes of writable memory we can expect to be able to get */
static int lim_data;
/* Level number of warnings already issued.
0 -- no warnings issued.
1 -- 75% warning already issued.
2 -- 85% warning already issued.
*/
static int warnlevel;
/* nonzero once initial bunch of free blocks made */
static int gotpool;
/* Cause reinitialization based on job parameters;
also declare where the end of pure storage is. */
malloc_init (start)
char *start;
{
data_space_start = start;
lim_data = 0;
warnlevel = 0;
}
static
morecore (nu) /* ask system for more memory */
register int nu; /* size index to get more of */
{
char *sbrk ();
register char *cp;
register int nblks;
register int siz;
if (!data_space_start)
{
#if defined(USG) && defined (emacs)
data_space_start = start_of_data ();
#else /* not USG, or not Emacs */
data_space_start = &etext;
#endif /* not USG, or not Emacs */
}
if (lim_data == 0)
get_lim_data ();
/* On initial startup, get two blocks of each size up to 1k bytes */
if (!gotpool)
getpool (), getpool (), gotpool = 1;
/* Find current end of memory and issue warning if getting near max */
cp = sbrk (0);
siz = cp - data_space_start;
malloc_sbrk_used = siz;
malloc_sbrk_unused = lim_data - siz;
switch (warnlevel)
{
case 0:
if (siz > (lim_data / 4) * 3)
{
warnlevel++;
malloc_warning ("Warning: past 75% of memory limit");
}
break;
case 1:
if (siz > (lim_data / 20) * 17)
{
warnlevel++;
malloc_warning ("Warning: past 85% of memory limit");
}
break;
case 2:
if (siz > (lim_data / 20) * 19)
{
warnlevel++;
malloc_warning ("Warning: past 95% of memory limit");
}
break;
}
if ((int) cp & 0x3ff) /* land on 1K boundaries */
sbrk (1024 - ((int) cp & 0x3ff));
/* Take at least 2k, and figure out how many blocks of the desired size
we're about to get */
nblks = 1;
if ((siz = nu) < 8)
nblks = 1 << ((siz = 8) - nu);
if ((cp = sbrk (1 << (siz + 3))) == (char *) -1)
return; /* no more room! */
if ((int) cp & 7)
{ /* shouldn't happen, but just in case */
cp = (char *) (((int) cp + 8) & ~7);
nblks--;
}
/* save new header and link the nblks blocks together */
nextf[nu] = (struct mhead *) cp;
siz = 1 << (nu + 3);
while (1)
{
((struct mhead *) cp) -> mh_alloc = ISFREE;
((struct mhead *) cp) -> mh_index = nu;
if (--nblks <= 0) break;
CHAIN ((struct mhead *) cp) = (struct mhead *) (cp + siz);
cp += siz;
}
/* CHAIN ((struct mhead *) cp) = 0; */
/* since sbrk() returns cleared core, this is already set */
}
static
getpool ()
{
register int nu;
register char *cp = sbrk (0);
if ((int) cp & 0x3ff) /* land on 1K boundaries */
sbrk (1024 - ((int) cp & 0x3ff));
/* Get 2k of storage */
cp = sbrk (04000);
if (cp == (char *) -1)
return;
/* Divide it into an initial 8-word block
plus one block of size 2**nu for nu = 3 ... 10. */
CHAIN (cp) = nextf[0];
nextf[0] = (struct mhead *) cp;
((struct mhead *) cp) -> mh_alloc = ISFREE;
((struct mhead *) cp) -> mh_index = 0;
cp += 8;
for (nu = 0; nu < 7; nu++)
{
CHAIN (cp) = nextf[nu];
nextf[nu] = (struct mhead *) cp;
((struct mhead *) cp) -> mh_alloc = ISFREE;
((struct mhead *) cp) -> mh_index = nu;
cp += 8 << nu;
}
}
char *
malloc (n) /* get a block */
unsigned n;
{
register struct mhead *p;
register unsigned int nbytes;
register int nunits = 0;
/* Figure out how many bytes are required, rounding up to the nearest
multiple of 4, then figure out which nextf[] area to use */
nbytes = (n + sizeof *p + EXTRA + 3) & ~3;
{
register unsigned int shiftr = (nbytes - 1) >> 2;
while (shiftr >>= 1)
nunits++;
}
/* If there are no blocks of the appropriate size, go get some */
/* COULD SPLIT UP A LARGER BLOCK HERE ... ACT */
if (nextf[nunits] == 0)
morecore (nunits);
/* Get one block off the list, and set the new list head */
if ((p = nextf[nunits]) == 0)
return 0;
nextf[nunits] = CHAIN (p);
/* Check for free block clobbered */
/* If not for this check, we would gobble a clobbered free chain ptr */
/* and bomb out on the NEXT allocate of this size block */
if (p -> mh_alloc != ISFREE || p -> mh_index != nunits)
#ifdef rcheck
botch ("block on free list clobbered");
#else /* not rcheck */
abort ();
#endif /* not rcheck */
/* Fill in the info, and if range checking, set up the magic numbers */
p -> mh_alloc = ISALLOC;
#ifdef rcheck
p -> mh_nbytes = n;
p -> mh_magic4 = MAGIC4;
{
register char *m = (char *) (p + 1) + n;
*m++ = MAGIC1, *m++ = MAGIC1, *m++ = MAGIC1, *m = MAGIC1;
}
#else /* not rcheck */
p -> mh_size = n;
#endif /* not rcheck */
#ifdef MSTATS
nmalloc[nunits]++;
nmal++;
#endif /* MSTATS */
return (char *) (p + 1);
}
free (mem)
char *mem;
{
register struct mhead *p;
{
register char *ap = mem;
if (ap == 0)
return;
p = (struct mhead *) ap - 1;
if (p -> mh_alloc == ISMEMALIGN)
{
ap -= p->mh_size;
p = (struct mhead *) ap - 1;
}
if (p -> mh_alloc != ISALLOC)
abort ();
#ifdef rcheck
ASSERT (p -> mh_magic4 == MAGIC4);
ap += p -> mh_nbytes;
ASSERT (*ap++ == MAGIC1); ASSERT (*ap++ == MAGIC1);
ASSERT (*ap++ == MAGIC1); ASSERT (*ap == MAGIC1);
#endif /* rcheck */
}
{
register int nunits = p -> mh_index;
ASSERT (nunits <= 29);
p -> mh_alloc = ISFREE;
CHAIN (p) = nextf[nunits];
nextf[nunits] = p;
#ifdef MSTATS
nmalloc[nunits]--;
nfre++;
#endif /* MSTATS */
}
}
char *
realloc (mem, n)
char *mem;
register unsigned n;
{
register struct mhead *p;
register unsigned int tocopy;
register int nbytes;
register int nunits;
if ((p = (struct mhead *) mem) == 0)
return malloc (n);
p--;
nunits = p -> mh_index;
ASSERT (p -> mh_alloc == ISALLOC);
#ifdef rcheck
ASSERT (p -> mh_magic4 == MAGIC4);
{
register char *m = mem + (tocopy = p -> mh_nbytes);
ASSERT (*m++ == MAGIC1); ASSERT (*m++ == MAGIC1);
ASSERT (*m++ == MAGIC1); ASSERT (*m == MAGIC1);
}
#else /* not rcheck */
if (p -> mh_index >= 13)
tocopy = (1 << (p -> mh_index + 3)) - sizeof *p;
else
tocopy = p -> mh_size;
#endif /* not rcheck */
/* See if desired size rounds to same power of 2 as actual size. */
nbytes = (n + sizeof *p + EXTRA + 7) & ~7;
/* If ok, use the same block, just marking its size as changed. */
if (nbytes > (4 << nunits) && nbytes <= (8 << nunits))
{
#ifdef rcheck
register char *m = mem + tocopy;
*m++ = 0; *m++ = 0; *m++ = 0; *m++ = 0;
p-> mh_nbytes = n;
m = mem + n;
*m++ = MAGIC1; *m++ = MAGIC1; *m++ = MAGIC1; *m++ = MAGIC1;
#else /* not rcheck */
p -> mh_size = n;
#endif /* not rcheck */
return mem;
}
if (n < tocopy)
tocopy = n;
{
register char *new;
if ((new = malloc (n)) == 0)
return 0;
bcopy (mem, new, tocopy);
free (mem);
return new;
}
}
char *
memalign (alignment, size)
unsigned alignment, size;
{
register char *ptr = malloc (size + alignment);
register char *aligned;
register struct mhead *p;
if (ptr == 0)
return 0;
/* If entire block has the desired alignment, just accept it. */
if (((int) ptr & (alignment - 1)) == 0)
return ptr;
/* Otherwise, get address of byte in the block that has that alignment. */
aligned = (char *) (((int) ptr + alignment - 1) & -alignment);
/* Store a suitable indication of how to free the block,
so that free can find the true beginning of it. */
p = (struct mhead *) aligned - 1;
p -> mh_size = aligned - ptr;
p -> mh_alloc = ISMEMALIGN;
return aligned;
}
#ifndef HPUX
/* This runs into trouble with getpagesize on HPUX.
Patching out seems cleaner than the ugly fix needed. */
char *
valloc (size)
{
return memalign (getpagesize (), size);
}
#endif /* not HPUX */
#ifdef MSTATS
/* Return statistics describing allocation of blocks of size 2**n. */
struct mstats_value
{
int blocksize;
int nfree;
int nused;
};
struct mstats_value
malloc_stats (size)
int size;
{
struct mstats_value v;
register int i;
register struct mhead *p;
v.nfree = 0;
if (size < 0 || size >= 30)
{
v.blocksize = 0;
v.nused = 0;
return v;
}
v.blocksize = 1 << (size + 3);
v.nused = nmalloc[size];
for (p = nextf[size]; p; p = CHAIN (p))
v.nfree++;
return v;
}
#endif /* MSTATS */
/*
* This function returns the total number of bytes that the process
* will be allowed to allocate via the sbrk(2) system call. On
* BSD systems this is the total space allocatable to stack and
* data. On USG systems this is the data space only.
*/
#ifdef USG
get_lim_data ()
{
extern long ulimit ();
lim_data = ulimit (3, 0);
lim_data -= (long) data_space_start;
}
#else /* not USG */
#ifndef BSD42
get_lim_data ()
{
lim_data = vlimit (LIM_DATA, -1);
}
#else /* BSD42 */
get_lim_data ()
{
struct rlimit XXrlimit;
getrlimit (RLIMIT_DATA, &XXrlimit);
lim_data = XXrlimit.rlim_cur; /* soft limit */
}
#endif /* BSD42 */
#endif /* not USG */