Implement FUSE readdir Function

Returns the buffer with directory entries. readdir gets most of the
directory entries by querying MediaProvider database. Paths that are not
indexed by MediaProvider database are handled by querying the lower file
system.

Bug: 142806973
Bug: 142475473
Test: ls -R /storage/emulated/0/ Returns a list of files and directories filtered
based on the visibility of the app to the corresponding file/directory.

Change-Id: Ic9840d71483d7abe1b950c90f06f96ef9895ca61

1 files changed, 65 insertions, 0 deletions

diff --git a/jni/include/libfuse_jni/ReaddirHelper.h b/jni/include/libfuse_jni/ReaddirHelper.h
new file mode 100644
index 000000000..04746133f
--- /dev/null
+++ b/jni/include/libfuse_jni/ReaddirHelper.h
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MEDIA_PROVIDER_FUSE_READDIR_HELPER_H
+#define MEDIA_PROVIDER_FUSE_READDIR_HELPER_H
+
+#include <dirent.h>
+#include <string>
+#include <vector>
+
+namespace mediaprovider {
+namespace fuse {
+
+/**
+ * Holds a directory entry.
+ *
+ * DirectoryEntry object holds information about the directory entry such as
+ * name and type of the file or directory.
+ */
+struct DirectoryEntry {
+    /**
+     * Create a directory entry.
+     *
+     * @param name directory entry name.
+     * @param type directory entry type. Directory entry type corresponds to
+     * d_type of dirent structure defined in dirent.h
+     */
+    DirectoryEntry(const std::string& name, int type) : d_name(name), d_type(type) {}
+    const std::string d_name;
+    const int d_type;
+};
+
+/**
+ * Gets directory entries from lower file system.
+ *
+ * This will be used for FUSE root node and other paths which are not indexed by
+ * MediaProvider database.
+ */
+std::vector<std::shared_ptr<DirectoryEntry>> getDirectoryEntriesFromLowerFs(DIR* d);
+
+/**
+ * Checks if the given path is indexed by MediaProvider database.
+ *
+ * TODO(b/142806973): App based filtering of directory contents can not be done for
+ * some of the paths here. Remove/Modify this function to obtain the filtering option
+ * information from MediaProvider instead of comparing raw path.
+ */
+bool IsDirectoryEntryFilteringNeeded(const std::string& path);
+
+}  // namespace fuse
+}  // namespace mediaprovider
+#endif