Cleanup: move overflow safe alloc code into libsquashfs

There were only a hand full of instances outside libsquashfs that used
the alloc code. In most cases, the thing allocated hat its size derived
from something already in memory anyway, so it is safe to assume its
size fits into a size_t.

At the same time, the opencoded Windows path conversion functions are
all unified into a single helper function.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 31 insertions, 0 deletions

diff --git a/lib/sqfs/util.h b/lib/sqfs/util.h
new file mode 100644
index 0000000..a379c0d
--- /dev/null
+++ b/lib/sqfs/util.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * util.h
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#ifndef SQFS_UTIL_H
+#define SQFS_UTIL_H
+
+#include "config.h"
+#include "sqfs/predef.h"
+#include "compat.h"
+
+#include <stddef.h>
+
+/*
+  Helper for allocating data structures with flexible array members.
+
+  'base_size' is the size of the struct itself, 'item_size' the size of a
+  single array element and 'nmemb' the number of elements.
+
+  Iternally checks for arithmetic overflows when allocating the combined thing.
+ */
+SQFS_INTERNAL
+void *alloc_flex(size_t base_size, size_t item_size, size_t nmemb);
+
+/* Basically the same as calloc, but *ALWAYS* does overflow checking */
+SQFS_INTERNAL
+void *alloc_array(size_t item_size, size_t nmemb);
+
+#endif /* SQFS_UTIL_H */