malloc.c

UNIX下SH的实现源码

#ifdef MALLOC_STATS
  _mstats.nsbrk++;
  _mstats.tsbrk += sbrk_amt;
#endif

  mp = (union mhead *) sbrk (sbrk_amt);

  /* Totally out of memory. */
  if ((long)mp == -1)
    goto morecore_done;

  /* shouldn't happen, but just in case -- require 8-byte alignment */
  if ((long)mp & 7)
    {
      mp = (union mhead *) (((long)mp + 8) & ~7);
      nblks--;
    }

  /* save new header and link the nblks blocks together */
  nextf[nu] = mp;
  while (1)
    {
      mp->mh_alloc = ISFREE;
      mp->mh_index = nu;
      if (--nblks <= 0) break;
      CHAIN (mp) = (union mhead *)((char *)mp + siz);
      mp = (union mhead *)((char *)mp + siz);
    }
  CHAIN (mp) = 0;

morecore_done:
#if defined (HAVE_BSD_SIGNALS)
  sigsetmask (oldmask);
#else
#  if defined (HAVE_POSIX_SIGNALS)
  sigprocmask (SIG_SETMASK, &oset, (sigset_t *)NULL);
#  else
  ; /* nothing to do, but need a null statement before the brace */
#  endif
#endif /* HAVE_BSD_SIGNALS */
}

#if defined (MEMSCRAMBLE) || !defined (NO_CALLOC)
static char *
zmemset (s, c, n)
     char *s;
     int c;
     register int n;
{
  register char *sp;

  sp = s;
  while (--n >= 0)
    *sp++ = c;
  return (s);
}
#endif /* MEMSCRAMBLE || !NO_CALLOC */

static void
malloc_debug_dummy ()
{
  write (1, "malloc_debug_dummy\n", 19);
}

PTR_T
malloc (n)		/* get a block */
     size_t n;
{
  register union mhead *p;
  register long nbytes;
  register int nunits;

  /* Get the system page size and align break pointer so everything will
     be page-aligned.  The page size must be at least 1K -- anything
     smaller is increased. */
  if (pagesz == 0)
    {
      register long sbrk_needed;

      pagesz = getpagesize ();
      if (pagesz < 1024)
        pagesz = 1024;
      /* OK, how much do we need to allocate to make things page-aligned?
         This partial page is wasted space.  Once we figure out how much
         to advance the break pointer, go ahead and do it. */
      sbrk_needed = pagesz - ((long)sbrk (0) & (pagesz - 1));	/* sbrk(0) % pagesz */
      if (sbrk_needed < 0)
        sbrk_needed += pagesz;
      /* Now allocate the wasted space. */
      if (sbrk_needed)
        {
#ifdef MALLOC_STATS
	  _mstats.nsbrk++;
	  _mstats.tsbrk += sbrk_needed;
#endif
          if ((long)sbrk (sbrk_needed) == -1)
            return (NULL);
        }
      nunits = 0;
      nbytes = 8;
      while (pagesz > nbytes)
        {
          nbytes <<= 1;
          nunits++;
        }
      pagebucket = nunits;
    }
 
  /* Figure out how many bytes are required, rounding up to the nearest
     multiple of 4, then figure out which nextf[] area to use.  Try to
     be smart about where to start searching -- if the number of bytes
     needed is greater than the page size, we can start at pagebucket. */
  nbytes = (n + sizeof *p + MSLOP + 3) & ~3;
  nunits = 0;
  if (nbytes <= (pagesz >> 1))
    {
      register unsigned int shiftr;

      shiftr = (nbytes - 1) >> 2;	/* == (nbytes - 1) / 4 */
      while (shiftr >>= 1)		/* == (nbytes - 1) / {8,16,32,...} */
	nunits++;
    }
  else
    {
      register u_bits32_t amt;

      nunits = pagebucket;
      amt = pagesz;
      while (nbytes > amt)
        {
          amt <<= 1;
          nunits++;
        }
    }

  /* In case this is reentrant use of malloc from signal handler,
     pick a block size that no other malloc level is currently
     trying to allocate.  That's the easiest harmless way not to
     interfere with the other level of execution.  */
#ifdef MALLOC_STATS
  if (busy[nunits]) _mstats.nrecurse++;
#endif
  while (busy[nunits]) nunits++;
  busy[nunits] = 1;

  if (nunits > maxbuck)
    maxbuck = nunits;

  /* If there are no blocks of the appropriate size, go get some */
  if (nextf[nunits] == 0)
    morecore (nunits);

  /* Get one block off the list, and set the new list head */
  if ((p = nextf[nunits]) == NULL)
    {
      busy[nunits] = 0;
      return NULL;
    }
  nextf[nunits] = CHAIN (p);
  busy[nunits] = 0;

  /* 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)
    botch ("malloc: block on free list clobbered");

  /* Fill in the info, and if range checking, set up the magic numbers */
  p->mh_alloc = ISALLOC;
  p->mh_nbytes = n;
  p->mh_magic2 = MAGIC2;
  {
    register char  *m = (char *) (p + 1) + n;

    *m++ = MAGIC1, *m++ = MAGIC1, *m++ = MAGIC1, *m = MAGIC1;
  }

#ifdef MEMSCRAMBLE
  zmemset ((char *)(p + 1), 0xdf, n);	/* scramble previous contents */
#endif
#ifdef MALLOC_STATS
  _mstats.nmalloc[nunits]++;
  _mstats.tmalloc[nunits]++;
  _mstats.nmal++;
#endif /* MALLOC_STATS */
  return (char *) (p + 1);	/* XXX - should be cast to PTR_T? */
}

void
free (mem)
     PTR_T mem;
{
  register union mhead *p;
  register char *ap;
  register int nunits;

  if ((ap = (char *)mem) == 0)
    return;

  p = (union mhead *) ap - 1;

  if (p->mh_alloc == ISMEMALIGN)
    {
      ap -= p->mh_nbytes;
      p = (union mhead *) ap - 1;
    }

  if (p->mh_alloc != ISALLOC)
    {
      if (p->mh_alloc == ISFREE)
	botch ("free: called with already freed block argument");
      else
	botch ("free: called with unallocated block argument");
    }

  ASSERT (p->mh_magic2 == MAGIC2);
  ap += p->mh_nbytes;
  ASSERT (*ap++ == MAGIC1); ASSERT (*ap++ == MAGIC1);
  ASSERT (*ap++ == MAGIC1); ASSERT (*ap   == MAGIC1);

#ifdef MEMSCRAMBLE
  zmemset (mem, 0xcf, p->mh_nbytes);
#endif

  nunits = p->mh_index;

  ASSERT (nunits < NBUCKETS);
  p->mh_alloc = ISFREE;

#if 0
  if (busy[nunits] == 1)
    botch ("calling free %d while in malloc for %d", nunits, nunits);    
#endif

  /* Protect against signal handlers calling malloc.  */
  busy[nunits] = 1;
  /* Put this block on the free list.  */
  CHAIN (p) = nextf[nunits];
  nextf[nunits] = p;
  busy[nunits] = 0;

#ifdef MALLOC_STATS
  _mstats.nmalloc[nunits]--;
  _mstats.nfre++;
#endif /* MALLOC_STATS */
}

PTR_T
realloc (mem, n)
     PTR_T mem;
     register size_t n;
{
  register union mhead *p;
  register u_bits32_t tocopy;
  register unsigned int nbytes;
  register int nunits;
  register char *m;

#ifdef MALLOC_STATS
  _mstats.nrealloc++;
#endif

  if (n == 0)
    {
      free (mem);
      return (NULL);
    }
  if ((p = (union mhead *) mem) == 0)
    return malloc (n);
  p--;
  nunits = p->mh_index;
  ASSERT (p->mh_alloc == ISALLOC);
  ASSERT (p->mh_magic2 == MAGIC2);

  m = (char *)mem + (tocopy = p->mh_nbytes);
  ASSERT (*m++ == MAGIC1); ASSERT (*m++ == MAGIC1);
  ASSERT (*m++ == MAGIC1); ASSERT (*m   == MAGIC1);

  /* See if desired size rounds to same power of 2 as actual size. */
  nbytes = (n + sizeof *p + MSLOP + 7) & ~7;

  /* If ok, use the same block, just marking its size as changed.  */
  if (nbytes > (4 << nunits) && nbytes <= (8 << nunits))
    {
      m = (char *)mem + tocopy;
      *m++ = 0;  *m++ = 0;  *m++ = 0;  *m++ = 0;
      p->mh_nbytes = n;
      m = (char *)mem + n;
      *m++ = MAGIC1;  *m++ = MAGIC1;  *m++ = MAGIC1;  *m++ = MAGIC1;
      return mem;
    }

#ifdef MALLOC_STATS
  _mstats.nrcopy++;
#endif

  if (n < tocopy)
    tocopy = n;

  if ((m = malloc (n)) == 0)
    return 0;
  FASTCOPY (mem, m, tocopy);
  free (mem);
  return m;
}

PTR_T
memalign (alignment, size)
     unsigned int alignment;
     size_t size;
{
  register char *ptr;
  register char *aligned;
  register union mhead *p;

  ptr = malloc (size + alignment);

  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 = (union mhead *) aligned - 1;
  p->mh_nbytes = aligned - ptr;
  p->mh_alloc = ISMEMALIGN;
  return aligned;
}

#if !defined (HPUX)
/* This runs into trouble with getpagesize on HPUX, and Multimax machines.
   Patching out seems cleaner than the ugly fix needed.  */
PTR_T
valloc (size)
     size_t size;
{
  return memalign (getpagesize (), size);
}
#endif /* !HPUX */

#ifndef NO_CALLOC
PTR_T
calloc (n, s)
     size_t n, s;
{
  size_t total;
  char *result;

  total = n * s;
  result = malloc (total);
  if (result)
    zmemset (result, 0, total);
  return result;  
}

void
cfree (p)
     PTR_T p;
{
  free (p);
}
#endif /* !NO_CALLOC */

#ifdef MALLOC_STATS

struct bucket_stats
malloc_bucket_stats (size)
     int size;
{
  struct bucket_stats v;
  register union mhead *p;

  v.nfree = 0;

  if (size < 0 || size >= NBUCKETS)
    {
      v.blocksize = 0;
      v.nused = v.nmal = v.nmorecore = v.nsplit = 0;
      return v;
    }

  v.blocksize = 1 << (size + 3);
  v.nused = _mstats.nmalloc[size];
  v.nmal = _mstats.tmalloc[size];
  v.nmorecore = _mstats.nmorecore[size];
  v.nsplit = _mstats.nsplit[size];

  for (p = nextf[size]; p; p = CHAIN (p))
    v.nfree++;

  return v;
}

/* Return a copy of _MSTATS, with two additional fields filled in:
   BYTESFREE is the total number of bytes on free lists.  BYTESUSED
   is the total number of bytes in use.  These two fields are fairly
   expensive to compute, so we do it only when asked to. */
struct _malstats
malloc_stats ()
{
  struct _malstats result;
  struct bucket_stats v;
  register int i;

  result = _mstats;
  result.bytesused = result.bytesfree = 0;
  for (i = 0; i < NBUCKETS; i++)
    {
      v = malloc_bucket_stats (i);
      result.bytesfree += v.nfree * v.blocksize;
      result.bytesused += v.nused * v.blocksize;
    }
  return (result);
}

static void
_print_malloc_stats (s, fp)
     char *s;
     FILE *fp;
{
  register int i;
  int totused, totfree;
  struct bucket_stats v;

  fprintf (fp, "Memory allocation statistics: %s\n\tsize\tfree\tin use\ttotal\tmorecore\tsplit\n", s ? s : "");
  for (i = totused = totfree = 0; i < NBUCKETS; i++)
    {
      v = malloc_bucket_stats (i);
      fprintf (fp, "%12lu\t%4d\t%6d\t%5d\t%8d\t%5d\n", v.blocksize, v.nfree, v.nused, v.nmal, v.nmorecore, v.nsplit);
      totfree += v.nfree * v.blocksize;
      totused += v.nused * v.blocksize;
    }
  fprintf (fp, "\nTotal bytes in use: %d, total bytes free: %d\n",
	   totused, totfree);
  fprintf (fp, "Total mallocs: %d, total frees: %d, total reallocs: %d (%d copies)\n",
	   _mstats.nmal, _mstats.nfre, _mstats.nrealloc, _mstats.nrcopy);
  fprintf (fp, "Total sbrks: %d, total bytes via sbrk: %d\n",
  	   _mstats.nsbrk, _mstats.tsbrk);
  fprintf (fp, "Total blocks split: %d, total block coalesces: %d\n",
  	   _mstats.tbsplit, _mstats.tbcoalesce);
}

void
print_malloc_stats (s)
{
  _print_malloc_stats (s, stderr);
}

#define TRACEROOT "/var/tmp/maltrace/trace."
extern char *inttostr ();

void
trace_malloc_stats (s)
{
  char ibuf[32], *ip;
  char fname[64];
  int p;
  FILE *fp;

  p = (int)getpid();
  ip = inttostr(p, ibuf, sizeof(ibuf));
  strcpy (fname, TRACEROOT);
  strcat (fname, ip);
  fp = fopen(fname, "w");
  if (fp)
    {
      _print_malloc_stats (s, fp);
      fflush(fp);
      fclose(fp);
    }
}
#endif /* MALLOC_STATS */