input/failing: new class

src/input/FailingInputStream.hxx

+/*
+ * Copyright 2003-2018 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_FAILING_INPUT_STREAM_HXX
+#define MPD_FAILING_INPUT_STREAM_HXX
+
+#include "InputStream.hxx"
+
+#include <exception>
+
+/**
+ * An #InputStream which always fails.  This is useful for
+ * ProxyInputStream::SetInput() if the implementation fails to
+ * initialize the inner #InputStream instance.
+ */
+class FailingInputStream final : public InputStream {
+	const std::exception_ptr error;
+
+public:
+	explicit FailingInputStream(const char *_uri,
+				    const std::exception_ptr _error,
+				    Mutex &_mutex, Cond &_cond) noexcept
+		:InputStream(_uri, _mutex, _cond), error(_error) {
+		SetReady();
+	}
+
+	/* virtual methods from InputStream */
+	void Check() override {
+		std::rethrow_exception(error);
+	}
+
+	void Seek(offset_type) override {
+		std::rethrow_exception(error);
+	}
+
+	bool IsEOF() noexcept override {
+		return false;
+	}
+
+	std::unique_ptr<Tag> ReadTag() override {
+		std::rethrow_exception(error);
+	}
+
+	size_t Read(void *, size_t) override {
+		std::rethrow_exception(error);
+	}
+};
+
+#endif