FileSys: add PathParser

src/core/file_sys/path_parser.h

@@ -0,0 +1,61 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <string>
+#include <vector>
+#include "core/file_sys/archive_backend.h"
+
+namespace FileSys {
+
+/**
+ * A helper class parsing and verifying a string-type Path.
+ * Every archives with a sub file system should use this class to parse the path argument and check
+ * the status of the file / directory in question on the host file system.
+ */
+class PathParser {
+public:
+    PathParser(const Path& path);
+
+    /**
+     * Checks if the Path is valid.
+     * This function should be called once a PathParser is constructed.
+     * A Path is valid if:
+     *  - it is a string path (with type LowPathType::Char or LowPathType::Wchar),
+     *  - it starts with "/" (this seems a hard requirement in real 3DS),
+     *  - it doesn't contain invalid characters, and
+     *  - it doesn't go out of the root directory using "..".
+     */
+    bool IsValid() const {
+        return is_valid;
+    }
+
+    /// Checks if the Path represents the root directory.
+    bool IsRootDirectory() const {
+        return is_root;
+    }
+
+    enum HostStatus {
+        InvalidMountPoint,
+        PathNotFound,   // "/a/b/c" when "a" doesn't exist
+        FileInPath,     // "/a/b/c" when "a" is a file
+        FileFound,      // "/a/b/c" when "c" is a file
+        DirectoryFound, // "/a/b/c" when "c" is a directory
+        NotFound        // "/a/b/c" when "a/b/" exists but "c" doesn't exist
+    };
+
+    /// Checks the status of the specified file / directory by the Path on the host file system.
+    HostStatus GetHostStatus(const std::string& mount_point) const;
+
+    /// Builds a full path on the host file system.
+    std::string BuildHostPath(const std::string& mount_point) const;
+
+private:
+    std::vector<std::string> path_sequence;
+    bool is_valid{};
+    bool is_root{};
+};
+
+} // namespace FileSys