fs/GzipOutputStream: new class wrapping zlib

Makefile.am

@@ -521,6 +521,13 @@ libfs_a_SOURCES = \
 	src/fs/StandardDirectory.cxx src/fs/StandardDirectory.hxx \
 	src/fs/CheckFile.cxx src/fs/CheckFile.hxx \
 	src/fs/DirectoryReader.hxx
+libfs_a_CPPFLAGS = $(AM_CPPFLAGS) $(ZLIB_CFLAGS)
+
+if HAVE_ZLIB
+libfs_a_SOURCES += \
+	src/fs/output/GzipOutputStream.cxx src/fs/output/GzipOutputStream.hxx
+FS_LIBS += $(ZLIB_LIBS)
+endif
 
 # Storage library
 
@@ -1596,6 +1603,16 @@ test_visit_archive_SOURCES = test/visit_archive.cxx \
 
 endif
 
+if HAVE_ZLIB
+
+noinst_PROGRAMS += test/run_gzip
+test_run_gzip_LDADD = \
+	libutil.a \
+	$(FS_LIBS)
+test_run_gzip_SOURCES = test/run_gzip.cxx
+
+endif
+
 test_dump_text_file_LDADD = \
 	$(INPUT_LIBS) \
 	$(ARCHIVE_LIBS) \

configure.ac

@@ -329,6 +329,11 @@ AC_ARG_ENABLE(audiofile,
 		[enable audiofile support (WAV and others)]),,
 	enable_audiofile=auto)
 
+AC_ARG_ENABLE(zlib,
+	AS_HELP_STRING([--enable-zlib],
+		[enable zlib support (default: auto)]),,
+	enable_zlib=auto)
+
 AC_ARG_ENABLE(bzip2,
 	AS_HELP_STRING([--enable-bzip2],
 		[enable bzip2 archive support (default: auto)]),,
@@ -1031,6 +1036,16 @@ fi
 
 AM_CONDITIONAL(ENABLE_ISO9660_TEST, test x$MKISOFS != xno)
 
+dnl ---------------------------------- zlib ---------------------------------
+
+MPD_AUTO_PKG(zlib, ZLIB, [zlib],
+	[zlib support], [zlib not found])
+
+AM_CONDITIONAL(HAVE_ZLIB, test x$enable_zlib = xyes)
+if test x$enable_zlib = xyes; then
+	AC_DEFINE(HAVE_ZLIB, 1, [Define to enable zlib support])
+fi
+
 dnl ---------------------------------- libbz2 ---------------------------------
 
 MPD_AUTO_LIB(bzip2, BZ2, bz2, BZ2_bzDecompressInit, [-lbz2], [],

src/fs/output/GzipOutputStream.cxx

+/*
+ * 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

+/*
+ * 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

test/run_gzip.cxx

+/*
+ * 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 "fs/output/GzipOutputStream.hxx"
+#include "fs/output/StdioOutputStream.hxx"
+#include "util/Error.hxx"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+static bool
+Copy(OutputStream &dest, int src, Error &error)
+{
+	while (true) {
+		char buffer[4096];
+		ssize_t nbytes = read(src, buffer, sizeof(buffer));
+		if (nbytes <= 0) {
+			if (nbytes < 0) {
+				error.SetErrno();
+				return false;
+			} else
+				return true;
+		}
+
+		if (!dest.Write(buffer, nbytes, error))
+			return false;
+	}
+}
+
+static bool
+CopyGzip(OutputStream &_dest, int src, Error &error)
+{
+	GzipOutputStream dest(_dest, error);
+	return dest.IsDefined() &&
+		Copy(dest, src, error) &&
+		dest.Flush(error);
+}
+
+static bool
+CopyGzip(FILE *_dest, int src, Error &error)
+{
+	StdioOutputStream dest(_dest);
+	return CopyGzip(dest, src, error);
+}
+
+int
+main(int argc, gcc_unused char **argv)
+{
+	if (argc != 1) {
+		fprintf(stderr, "Usage: run_gzip\n");
+		return EXIT_FAILURE;
+	}
+
+	Error error;
+	if (!CopyGzip(stdout, STDIN_FILENO, error)) {
+		fprintf(stderr, "%s\n", error.GetMessage());
+		return EXIT_FAILURE;
+	}
+
+	return EXIT_SUCCESS;
+}