fs/io/AutoGunzipReader: new class

Makefile.am

@@ -532,6 +532,7 @@ if HAVE_ZLIB
 libfs_a_SOURCES += \
 	src/lib/zlib/Domain.cxx src/lib/zlib/Domain.hxx \
 	src/fs/io/GunzipReader.cxx src/fs/io/GunzipReader.hxx \
+	src/fs/io/AutoGunzipReader.cxx src/fs/io/AutoGunzipReader.hxx \
 	src/fs/io/GzipOutputStream.cxx src/fs/io/GzipOutputStream.hxx
 FS_LIBS += $(ZLIB_LIBS)
 endif

src/fs/io/AutoGunzipReader.cxx

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2003-2014 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.
+ */
+
+#include "config.h"
+#include "AutoGunzipReader.hxx"
+#include "GunzipReader.hxx"
+#include "util/Error.hxx"
+
+AutoGunzipReader::~AutoGunzipReader()
+{
+	delete gunzip;
+}
+
+gcc_pure
+static bool
+IsGzip(const uint8_t data[4])
+{
+	return data[0] == 0x1f && data[1] == 0x8b && data[2] == 0x08 &&
+		(data[3] & 0xe0) == 0;
+}
+
+inline bool
+AutoGunzipReader::Detect(Error &error)
+{
+	const uint8_t *data = (const uint8_t *)peek.Peek(4, error);
+	if (data == nullptr) {
+		if (error.IsDefined())
+			return false;
+
+		next = &peek;
+		return true;
+	}
+
+	if (IsGzip(data)) {
+		gunzip = new GunzipReader(peek, error);
+		if (!gunzip->IsDefined())
+			return false;
+
+
+		next = gunzip;
+	} else
+		next = &peek;
+
+	return true;
+}
+
+size_t
+AutoGunzipReader::Read(void *data, size_t size, Error &error)
+{
+	if (next == nullptr && !Detect(error))
+		return false;
+
+	return next->Read(data, size, error);
+}

src/fs/io/AutoGunzipReader.hxx

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2003-2014 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_AUTO_GUNZIP_READER_HXX
+#define MPD_AUTO_GUNZIP_READER_HXX
+
+#include "check.h"
+#include "PeekReader.hxx"
+
+#include <stdint.h>
+
+class GunzipReader;
+
+/**
+ * A filter that detects gzip compression and optionally inserts a
+ * #GunzipReader.
+ */
+class AutoGunzipReader final : public Reader {
+	Reader *next;
+	PeekReader peek;
+	GunzipReader *gunzip;
+
+public:
+	AutoGunzipReader(Reader &_next)
+		:next(nullptr), peek(_next), gunzip(nullptr) {}
+	~AutoGunzipReader();
+
+	/* virtual methods from class Reader */
+	virtual size_t Read(void *data, size_t size, Error &error) override;
+
+private:
+	bool Detect(Error &error);
+};
+
+#endif