A first stab at supporting the housing shortage rules. From OpenBSD.

[bsdgames-darwin.git] / monop / malloc.c

/*      $NetBSD: malloc.c,v 1.5 2008/01/28 06:16:13 dholland Exp $      */

/*
 * Copyright (c) 1983, 1993
 *      The Regents of the University of California.  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. 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.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)malloc.c    8.1 (Berkeley) 6/4/93";
#else
__RCSID("$NetBSD: malloc.c,v 1.5 2008/01/28 06:16:13 dholland Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

/*
 * 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-10) bytes long.
 * This is designed for use in a virtual memory environment.
 */

#include <sys/types.h>
#if defined(DEBUG) || defined(RCHECK)
#include <sys/uio.h>
#endif
#if defined(RCHECK) || defined(MSTATS)
#include <stdio.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pthread.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_long  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 */
#ifdef RCHECK
#define RMAGIC          0x5555          /* magic # on range info */
#endif

#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];

static  long pagesz;                    /* page size */
static  int pagebucket;                 /* page size bucket */

#ifdef MSTATS
/*
 * nmalloc[i] is the difference between the number of mallocs and frees
 * for a given block size.
 */
static  u_int nmalloc[NBUCKETS];
#endif

static  pthread_mutex_t malloc_mutex = PTHREAD_MUTEX_INITIALIZER;

static void morecore(int);
static int findbucket(union overhead *, int);
#ifdef MSTATS
void mstats(const char *);
#endif

#if defined(DEBUG) || defined(RCHECK)
#define ASSERT(p)   if (!(p)) botch(__STRING(p))

static void botch(const char *);

/*
 * NOTE: since this may be called while malloc_mutex is locked, stdio must not
 *       be used in this function.
 */
static void
botch(s)
        const char *s;
{
        struct iovec iov[3];

        iov[0].iov_base = "\nassertion botched: ";
        iov[0].iov_len  = 20;
        iov[1].iov_base = (void *)s;
        iov[1].iov_len  = strlen(s);
        iov[2].iov_base = "\n";
        iov[2].iov_len  = 1;

        /*
         * This place deserves a word of warning: a cancellation point will
         * occur when executing writev(), and we might be still owning
         * malloc_mutex.  At this point we need to disable cancellation
         * until `after' abort() because i) establishing a cancellation handler
         * might, depending on the implementation, result in another malloc()
         * to be executed, and ii) it is really not desirable to let execution
         * continue.  `Fix me.'
         * 
         * Note that holding mutex_lock during abort() is safe.
         */

        (void)writev(STDERR_FILENO, iov, 3);
        abort();
}
#else
#define ASSERT(p)
#endif

void *
malloc(nbytes)
        size_t nbytes;
{
        union overhead *op;
        int bucket;
        long n;
        unsigned amt;

        pthread_mutex_lock(&malloc_mutex);

        /*
         * 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();
                ASSERT(pagesz > 0);
                op = (union overhead *)(void *)sbrk(0);
                n = n - sizeof (*op) - ((long)op & (n - 1));
                if (n < 0)
                        n += pagesz;
                if (n) {
                        if (sbrk((int)n) == (void *)-1) {
                                pthread_mutex_unlock(&malloc_mutex);
                                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 <= (size_t)(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 = -((long)sizeof (*op) + RSLOP);
        } else {
                amt = (unsigned)pagesz;
                bucket = pagebucket;
        }
        while (nbytes > (size_t)(amt + n)) {
                amt <<= 1;
                if (amt == 0)
                        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) {
                        pthread_mutex_unlock(&malloc_mutex);
                        return (NULL);
                }
        }
        /* remove from linked list */
        nextf[bucket] = op->ov_next;
        op->ov_magic = MAGIC;
        op->ov_index = bucket;
#ifdef MSTATS
        nmalloc[bucket]++;
#endif
        pthread_mutex_unlock(&malloc_mutex);
#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
        return ((void *)(op + 1));
}

/*
 * Allocate more memory to the indicated bucket.
 */
static void
morecore(bucket)
        int bucket;
{
        union overhead *op;
        long sz;                /* size of desired block */
        long amt;                       /* amount to allocate */
        long 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 *)(void *)sbrk((int)amt);
        /* no more room! */
        if ((long)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 *)(void *)((caddr_t)(void *)op+(size_t)sz);
                op = op->ov_next;
        }
}

void
free(cp)
        void *cp;
{   
        long size;
        union overhead *op;

        if (cp == NULL)
                return;
        op = (union overhead *)(void *)((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);
        ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
#endif
        size = op->ov_index;
        ASSERT(size < NBUCKETS);
        pthread_mutex_lock(&malloc_mutex);
        op->ov_next = nextf[(unsigned int)size];/* also clobbers ov_magic */
        nextf[(unsigned int)size] = op;
#ifdef MSTATS
        nmalloc[(size_t)size]--;
#endif
        pthread_mutex_unlock(&malloc_mutex);
}

/*
 * 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 */

void *
realloc(cp, nbytes)
        void *cp; 
        size_t nbytes;
{   
        u_long onb;
        long i;
        union overhead *op;
        char *res;
        int was_alloced = 0;

        if (cp == NULL)
                return (malloc(nbytes));
        if (nbytes == 0) {
                free (cp);
                return (NULL);
        }
        op = (union overhead *)(void *)((caddr_t)cp - sizeof (union overhead));
        pthread_mutex_lock(&malloc_mutex);
        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
                 * largest possible (so that all "nbytes" of new
                 * memory are copied into).  Note that this could cause
                 * a memory fault if the old area was tiny, and the moon
                 * is gibbous.  However, that is very unlikely.
                 */
                if ((i = findbucket(op, 1)) < 0 &&
                    (i = findbucket(op, __realloc_srchlen)) < 0)
                        i = NBUCKETS;
        }
        onb = (u_long)1 << (u_long)(i + 3);
        if (onb < (u_long)pagesz)
                onb -= sizeof (*op) + RSLOP;
        else
                onb += pagesz - sizeof (*op) - RSLOP;
        /* avoid the copy if same size block */
        if (was_alloced) {
                if (i) {
                        i = (long)1 << (long)(i + 2);
                        if (i < pagesz)
                                i -= sizeof (*op) + RSLOP;
                        else
                                i += pagesz - sizeof (*op) - RSLOP;
                }
                if (nbytes <= onb && nbytes > (size_t) i) {
#ifdef RCHECK
                        op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
                        *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
#endif
                        pthread_mutex_unlock(&malloc_mutex);
                        return (cp);
                        
                }
#ifndef _REENT
                else
                        free(cp);
#endif
        }
        pthread_mutex_unlock(&malloc_mutex);
        if ((res = malloc(nbytes)) == NULL) {
#ifdef _REENT
                free(cp);
#endif
                return (NULL);
        }
#ifndef _REENT
        if (cp != res)          /* common optimization if "compacting" */
                (void)memmove(res, cp, (size_t)((nbytes < onb) ? nbytes : onb));
#else
        (void)memmove(res, cp, (size_t)((nbytes < onb) ? nbytes : onb));
        free(cp);
#endif
        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 int
findbucket(freep, srchlen)
        union overhead *freep;
        int srchlen;
{
        union overhead *p;
        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.
 */
void
mstats(s)
        char *s;
{
        int i, j;
        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