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kmalloc.c

/*    $NetBSD: malloc.c,v 1.8 1997/04/07 03:12:14 christos Exp $  */

/*
 * Copyright (c) 1983 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. 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char *sccsid = "from: @(#)malloc.c 5.11 (Berkeley) 2/23/91";
#else
static char *rcsid = "$NetBSD: malloc.c,v 1.8 1997/04/07 03:12:14 christos 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>
#include  <stdlib.h>
#include  <string.h>

/* #define MSTATS 1 */

#ifndef _WIN32
#include  <unistd.h>
#define     NULL 0
#else

#define u_char unsigned char
#define u_long unsigned long
#define getpagesize() 4096
#define caddr_t size_t
#define bcopy(a,b,c) memcpy(b,a,c)
extern void * sbrk (long);

#endif


static void morecore();
static int findbucket();

/*
 * 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 */
#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 */

#ifdef MSTATS
/*
 * nmalloc[i] is the difference between the number of mallocs and frees
 * for a given block size.
 */
static      unsigned int nmalloc[NBUCKETS];
#include  <stdio.h>
#endif

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

#include <stdio.h>

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

      /*
       * 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) - ((long)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 = -((long)sizeof (*op) + RSLOP);
      } else {
            amt = pagesz;
            bucket = pagebucket;
      }
      while (nbytes > 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) {
                  return (NULL);
            }
      }
      /* remove from linked list */
      nextf[bucket] = op->ov_next;
      op->ov_magic = MAGIC;
      op->ov_index = bucket;
#ifdef MSTATS
      nmalloc[bucket]++;
#endif
#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 ((char *)(op + 1));
}

void * kcalloc (size_t nelem, size_t elsize) {
  void * ptr = kmalloc (nelem * elsize);
  // Zero out the malloc'd block.
  memset (ptr, 0, nelem * elsize);
  return ptr;
}


/*
 * Allocate more memory to the indicated bucket.
 */
static void
morecore(bucket)
      int bucket;
{
      register union overhead *op;
      register long sz;       /* size of desired block */
      long 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 ((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 *)((caddr_t)op + sz);
            op = (union overhead *)((caddr_t)op + sz);
      }
}

/*  */
/* free */
/* free */
void
kfree(cp)
      void *cp;
{   
      register long 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)
            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;
#ifdef MSTATS
      nmalloc[size]--;
#endif
}


/* EDB: added size lookup */

size_t kmalloc_usable_size (void * cp)
{
      register long size;
      register union overhead *op;

      if (cp == NULL)
            return 0;
      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)
            return 0;                     /* sanity */
#endif
#ifdef RCHECK
      ASSERT(op->ov_rmagic == RMAGIC);
      ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
#endif
      return op->ov_index;
}
/* End EDB */


/*
 * 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 */

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

      if (cp == NULL)
            return (kmalloc(nbytes));
      if (nbytes == 0) {
            kfree (cp);
            return NULL;
      }
      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 ``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 = 1 << (i + 3);
      if (onb < pagesz)
            onb -= sizeof (*op) + RSLOP;
      else
            onb += pagesz - sizeof (*op) - RSLOP;
      /* avoid the copy if same size block */
      if (was_alloced) {
            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
                  return(cp);
            } else
                  kfree(cp);
      }
      if ((res = kmalloc(nbytes)) == NULL)
            return (NULL);
      if (cp != res)          /* common optimization if "compacting" */
            bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
      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(void)
{
      register int i, j;
      register union overhead *p;
      int totfree = 0,
      totused = 0;

      fprintf(stderr, "Memory allocation statistics\nfree:\t");
      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, total allocated: %d\n",
          totused, totfree, totused + totfree);
}
#endif


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