New module 'safe-alloc'.

[gnulib.git] / lib / safe-alloc.c

diff --git a/lib/safe-alloc.c b/lib/safe-alloc.c
new file mode 100644 (file)
index 0000000..fca8754
--- /dev/null
+++ b/lib/safe-alloc.c
@@ -0,0 +1,124 @@
+/*
+ * safe-alloc.c: safer memory allocation
+ *
+ * Copyright (C) 2009 Free Software Foundation, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
+ *
+ */
+
+/* Written by Daniel Berrange <berrange@redhat.com>, 2008 */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include <stddef.h>
+#include <errno.h>
+
+#include "safe-alloc.h"
+
+
+/* Return 1 if an array of N objects, each of size S, cannot exist due
+   to size arithmetic overflow.  S must be positive and N must be
+   nonnegative.  This is a macro, not an inline function, so that it
+   works correctly even when SIZE_MAX < N.
+
+   By gnulib convention, SIZE_MAX represents overflow in size
+   calculations, so the conservative dividend to use here is
+   SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
+   However, malloc (SIZE_MAX) fails on all known hosts where
+   sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
+   exactly-SIZE_MAX allocations on such hosts; this avoids a test and
+   branch when S is known to be 1.
+
+   This is the same as xalloc_oversized from xalloc.h
+*/
+#define safe_alloc_oversized(n, s)                                      \
+  ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
+
+
+/**
+ * safe_alloc_alloc_n:
+ * @ptrptr: pointer to pointer for address of allocated memory
+ * @size: number of bytes to allocate
+ * @count: number of elements to allocate
+ *
+ * Allocate an array of memory 'count' elements long,
+ * each with 'size' bytes. Return the address of the
+ * allocated memory in 'ptrptr'.  The newly allocated
+ * memory is filled with zeros.
+ *
+ * Return -1 on failure to allocate, zero on success
+ */
+int
+safe_alloc_alloc_n (void *ptrptr, size_t size, size_t count, int zeroed)
+{
+  if (size == 0 || count == 0)
+    {
+      *(void **) ptrptr = NULL;
+      return 0;
+    }
+
+  if (safe_alloc_oversized (count, size))
+    {
+      errno = ENOMEM;
+      return -1;
+    }
+
+  if (zeroed)
+    *(void **) ptrptr = calloc (count, size);
+  else
+    *(void **) ptrptr = malloc (count * size);
+
+  if (*(void **) ptrptr == NULL)
+    return -1;
+  return 0;
+}
+
+/**
+ * safe_alloc_realloc_n:
+ * @ptrptr: pointer to pointer for address of allocated memory
+ * @size: number of bytes to allocate
+ * @count: number of elements in array
+ *
+ * Resize the block of memory in 'ptrptr' to be an array of
+ * 'count' elements, each 'size' bytes in length. Update 'ptrptr'
+ * with the address of the newly allocated memory. On failure,
+ * 'ptrptr' is not changed and still points to the original memory
+ * block. The newly allocated memory is filled with zeros.
+ *
+ * Return -1 on failure to allocate, zero on success
+ */
+int
+safe_alloc_realloc_n (void *ptrptr, size_t size, size_t count)
+{
+  void *tmp;
+  if (size == 0 || count == 0)
+    {
+      free (*(void **) ptrptr);
+      *(void **) ptrptr = NULL;
+      return 0;
+    }
+  if (safe_alloc_oversized (count, size))
+    {
+      errno = ENOMEM;
+      return -1;
+    }
+  tmp = realloc (*(void **) ptrptr, size * count);
+  if (!tmp)
+    return -1;
+  *(void **) ptrptr = tmp;
+  return 0;
+}