[NaCl SDK] Expose Google Drive to nacl_io.

native_client_sdk/src/libraries/nacl_io/hash.cc

+// Copyright (c) 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "nacl_io/hash.h"
+#include "nacl_io/osdirent.h"
+
+namespace nacl_io {
+
+ino_t HashPathSegment(ino_t hash, const char* str, size_t len) {
+  // First add the path seperator
+  hash = (hash * static_cast<ino_t>(33)) ^ '/';
+  while (len--) {
+    hash = (hash * static_cast<ino_t>(33)) ^ *str++;
+  }
+  return hash;
+}
+
+ino_t HashPath(const Path& path) {
+  // Prime the DJB2a hash
+  ino_t hash = 5381;
+
+  // Apply a running DJB2a to each part of the path
+  for (size_t segment = 0; segment < path.Size(); segment++) {
+    const std::string& part = path.Part(segment);
+    hash = HashPathSegment(hash, part.c_str(), part.length());
+  }
+  return hash;
+}
+
+}  // namespace nacl_io