1 files changed, 122 insertions, 0 deletions
diff --git a/lib/extendbuf.c b/lib/extendbuf.c
new file mode 100644
index 0000000..e6e9103
--- /dev/null
+++ b/lib/extendbuf.c
@@ -0,0 +1,122 @@
+/* extendbuf.c -- manage a dynamically-allocated buffer
+
+   Copyright 2004, 2010, 2011 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/* Written by James Yougnman <jay@gnu.org>. */
+
+/* config.h must be included first. */
+#include <config.h>
+
+/* system headers. */
+#include <assert.h>
+#include <errno.h>
+#include <stdlib.h>
+
+/* gnulib headers. */
+#include "xalloc.h"
+
+/* find headers. */
+#include "extendbuf.h"
+
+
+/* We initially use a small default size to ensure that this code
+ * gets exercised.
+ */
+#ifndef SIZE_DEFAULT
+# define SIZE_DEFAULT 16
+#endif
+
+static size_t
+decide_size (size_t current, size_t wanted)
+{
+  size_t newsize;
+
+  if (0 == current)
+    newsize = SIZE_DEFAULT;
+  else
+    newsize = current;
+
+  while (newsize < wanted)
+    {
+      if (2 * newsize < newsize)
+	return wanted;
+      newsize *= 2;
+    }
+  return newsize;
+}
+
+
+void *
+extendbuf (void* existing, size_t wanted, size_t *allocated)
+{
+  int saved_errno;
+  size_t newsize;
+  void *result; /* leave uninitialized to allow static code checkers to identify bugs */
+
+  saved_errno = errno;
+
+  assert (wanted > 0u);
+  newsize = decide_size (*allocated, wanted);
+
+  if ( (*allocated) == 0 )
+    {
+      /* Sanity check: If there is no existing allocation size, there
+       * must be no existing allocated buffer.
+       */
+      assert (NULL == existing);
+
+      (*allocated) = newsize;
+      result = malloc (newsize);
+    }
+  else
+    {
+      if (newsize != (*allocated) )
+	{
+	  (*allocated) = newsize;
+	  result = realloc (existing, newsize);
+	  if (NULL == result)
+	    {
+	      saved_errno = errno;
+	    }
+	}
+      else
+	{
+	  result = existing;
+	}
+    }
+
+  if (result)
+    {
+      /* malloc () or realloc () may have changed errno, but in the
+	 success case we want to preserve the previous value.
+      */
+      errno = saved_errno;
+    }
+  return result;
+}
+
+
+void *
+xextendbuf (void* existing, size_t wanted, size_t *allocated)
+{
+  void *p = extendbuf (existing, wanted, allocated);
+  if (NULL == p)
+    {
+      free (existing);
+      xalloc_die ();
+    }
+  return p;
+}