fs/GzipOutputStream: new class wrapping zlib

src/fs/output/GzipOutputStream.cxx

@@ -0,0 +1,106 @@
+/*
+ * 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 "GzipOutputStream.hxx"
+#include "util/Error.hxx"
+#include "util/Domain.hxx"
+
+const Domain zlib_domain("zlib");
+
+GzipOutputStream::GzipOutputStream(OutputStream &_next, Error &error)
+	:next(_next)
+{
+	z.next_in = nullptr;
+	z.avail_in = 0;
+	z.zalloc = Z_NULL;
+	z.zfree = Z_NULL;
+	z.opaque = Z_NULL;
+
+	constexpr int windowBits = 15;
+	constexpr int gzip_encoding = 16;
+
+	int result = deflateInit2(&z, Z_DEFAULT_COMPRESSION, Z_DEFLATED,
+				  windowBits | gzip_encoding,
+				  8, Z_DEFAULT_STRATEGY);
+	if (result != Z_OK) {
+		z.opaque = this;
+		error.Set(zlib_domain, result, zError(result));
+	}
+}
+
+GzipOutputStream::~GzipOutputStream()
+{
+	if (IsDefined())
+		deflateEnd(&z);
+}
+
+bool
+GzipOutputStream::Flush(Error &error)
+{
+	/* no more input */
+	z.next_in = nullptr;
+	z.avail_in = 0;
+
+	while (true) {
+		Bytef output[4096];
+		z.next_out = output;
+		z.avail_out = sizeof(output);
+
+		int result = deflate(&z, Z_FINISH);
+		if (z.next_out > output &&
+		    !next.Write(output, z.next_out - output, error))
+			return false;
+
+		if (result == Z_STREAM_END)
+			return true;
+		else if (result != Z_OK) {
+			error.Set(zlib_domain, result, zError(result));
+			return false;
+		}
+    }
+}
+
+bool
+GzipOutputStream::Write(const void *_data, size_t size, Error &error)
+{
+	/* zlib's API requires non-const input pointer */
+	void *data = const_cast<void *>(_data);
+
+	z.next_in = reinterpret_cast<Bytef *>(data);
+	z.avail_in = size;
+
+	while (z.avail_in > 0) {
+		Bytef output[4096];
+		z.next_out = output;
+		z.avail_out = sizeof(output);
+
+		int result = deflate(&z, Z_NO_FLUSH);
+		if (result != Z_OK) {
+			error.Set(zlib_domain, result, zError(result));
+			return false;
+		}
+
+		if (z.next_out > output &&
+		    !next.Write(output, z.next_out - output, error))
+			return false;
+	}
+
+	return true;
+}

src/fs/output/GzipOutputStream.hxx

@@ -0,0 +1,71 @@
+/*
+ * 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_GZIP_OUTPUT_STREAM_HXX
+#define MPD_GZIP_OUTPUT_STREAM_HXX
+
+#include "check.h"
+#include "OutputStream.hxx"
+
+#include <assert.h>
+#include <zlib.h>
+
+class Error;
+class Domain;
+
+extern const Domain zlib_domain;
+
+/**
+ * A filter that compresses data written to it using zlib, forwarding
+ * compressed data in the "gzip" format.
+ *
+ * Don't forget to call Flush() before destructing this object.
+ */
+class GzipOutputStream final : public OutputStream {
+	OutputStream &next;
+
+	z_stream z;
+
+public:
+	/**
+	 * Construct the filter.  Call IsDefined() to check whether
+	 * the constructor has succeeded.  If not, #error will hold
+	 * information about the failure.
+	 */
+	GzipOutputStream(OutputStream &_next, Error &error);
+	~GzipOutputStream();
+
+	/**
+	 * Check whether the constructor has succeeded.
+	 */
+	bool IsDefined() const {
+		return z.opaque == nullptr;
+	}
+
+	/**
+	 * Finish the file and write all data remaining in zlib's
+	 * output buffer.
+	 */
+	bool Flush(Error &error);
+
+	/* virtual methods from class OutputStream */
+	bool Write(const void *data, size_t size, Error &error) override;
+};
+
+#endif