Initial creation of sourceware repository

mmalloc/mrealloc.c

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+/* Change the size of a block allocated by `mmalloc'.
+   Copyright 1990, 1991 Free Software Foundation
+		  Written May 1989 by Mike Haertel.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA.
+
+   The author may be reached (Email) at the address mike@ai.mit.edu,
+   or (US mail) as Mike Haertel c/o Free Software Foundation. */
+
+#include <string.h>	/* Prototypes for memcpy, memmove, memset, etc */
+
+#include "mmprivate.h"
+
+/* Resize the given region to the new size, returning a pointer
+   to the (possibly moved) region.  This is optimized for speed;
+   some benchmarks seem to indicate that greater compactness is
+   achieved by unconditionally allocating and copying to a
+   new region.  This module has incestuous knowledge of the
+   internals of both mfree and mmalloc. */
+
+PTR
+mrealloc (md, ptr, size)
+  PTR md;
+  PTR ptr;
+  size_t size;
+{
+  struct mdesc *mdp;
+  PTR result;
+  int type;
+  size_t block, blocks, oldlimit;
+
+  if (size == 0)
+    {
+      mfree (md, ptr);
+      return (mmalloc (md, 0));
+    }
+  else if (ptr == NULL)
+    {
+      return (mmalloc (md, size));
+    }
+
+  mdp = MD_TO_MDP (md);
+
+  if (mdp -> mrealloc_hook != NULL)
+    {
+      return ((*mdp -> mrealloc_hook) (md, ptr, size));
+    }
+
+  block = BLOCK (ptr);
+
+  type = mdp -> heapinfo[block].busy.type;
+  switch (type)
+    {
+    case 0:
+      /* Maybe reallocate a large block to a small fragment.  */
+      if (size <= BLOCKSIZE / 2)
+	{
+	  result = mmalloc (md, size);
+	  if (result != NULL)
+	    {
+	      memcpy (result, ptr, size);
+	      mfree (md, ptr);
+	      return (result);
+	    }
+	}
+
+      /* The new size is a large allocation as well;
+	 see if we can hold it in place. */
+      blocks = BLOCKIFY (size);
+      if (blocks < mdp -> heapinfo[block].busy.info.size)
+	{
+	  /* The new size is smaller; return excess memory to the free list. */
+	  mdp -> heapinfo[block + blocks].busy.type = 0;
+	  mdp -> heapinfo[block + blocks].busy.info.size
+	    = mdp -> heapinfo[block].busy.info.size - blocks;
+	  mdp -> heapinfo[block].busy.info.size = blocks;
+	  mfree (md, ADDRESS (block + blocks));
+	  result = ptr;
+	}
+      else if (blocks == mdp -> heapinfo[block].busy.info.size)
+	{
+	  /* No size change necessary.  */
+	  result = ptr;
+	}
+      else
+	{
+	  /* Won't fit, so allocate a new region that will.
+	     Free the old region first in case there is sufficient
+	     adjacent free space to grow without moving. */
+	  blocks = mdp -> heapinfo[block].busy.info.size;
+	  /* Prevent free from actually returning memory to the system.  */
+	  oldlimit = mdp -> heaplimit;
+	  mdp -> heaplimit = 0;
+	  mfree (md, ptr);
+	  mdp -> heaplimit = oldlimit;
+	  result = mmalloc (md, size);
+	  if (result == NULL)
+	    {
+	      mmalloc (md, blocks * BLOCKSIZE);
+	      return (NULL);
+	    }
+	  if (ptr != result)
+	    {
+	      memmove (result, ptr, blocks * BLOCKSIZE);
+	    }
+	}
+      break;
+
+    default:
+      /* Old size is a fragment; type is logarithm
+	 to base two of the fragment size.  */
+      if (size > (size_t) (1 << (type - 1)) && size <= (size_t) (1 << type))
+	{
+	  /* The new size is the same kind of fragment.  */
+	  result = ptr;
+	}
+      else
+	{
+	  /* The new size is different; allocate a new space,
+	     and copy the lesser of the new size and the old. */
+	  result = mmalloc (md, size);
+	  if (result == NULL)
+	    {
+	      return (NULL);
+	    }
+	  memcpy (result, ptr, MIN (size, (size_t) 1 << type));
+	  mfree (md, ptr);
+	}
+      break;
+    }
+
+  return (result);
+}
+
+/* When using this package, provide a version of malloc/realloc/free built
+   on top of it, so that if we use the default sbrk() region we will not
+   collide with another malloc package trying to do the same thing, if
+   the application contains any "hidden" calls to malloc/realloc/free (such
+   as inside a system library). */
+
+PTR
+realloc (ptr, size)
+  PTR ptr;
+  size_t size;
+{
+  PTR result;
+
+  result = mrealloc ((PTR) NULL, ptr, size);
+  return (result);
+}