fs/OutputStream: new infrastructure for writing to files

Makefile.am

@@ -503,6 +503,10 @@ endif
 # File system library
 
 libfs_a_SOURCES = \
+	src/fs/output/OutputStream.hxx \
+	src/fs/output/StdoutOutputStream.hxx \
+	src/fs/output/FileOutputStream.cxx src/fs/output/FileOutputStream.hxx \
+	src/fs/output/BufferedOutputStream.cxx src/fs/output/BufferedOutputStream.hxx \
 	src/fs/Domain.cxx src/fs/Domain.hxx \
 	src/fs/Limits.hxx \
 	src/fs/Traits.cxx src/fs/Traits.hxx \

src/fs/output/BufferedOutputStream.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 "BufferedOutputStream.hxx"
+#include "OutputStream.hxx"
+
+#include <stdarg.h>
+#include <string.h>
+#include <stdio.h>
+
+bool
+BufferedOutputStream::AppendToBuffer(const void *data, size_t size)
+{
+	auto r = buffer.Write();
+	if (r.size < size)
+		return false;
+
+	memcpy(r.data, data, size);
+	buffer.Append(size);
+	return true;
+}
+
+bool
+BufferedOutputStream::Write(const void *data, size_t size)
+{
+	if (gcc_unlikely(last_error.IsDefined()))
+		return false;
+
+	if (AppendToBuffer(data, size))
+		return true;
+
+	if (!Flush())
+		return false;
+
+	if (AppendToBuffer(data, size))
+		return true;
+
+	return os.Write(data, size, last_error);
+}
+
+bool
+BufferedOutputStream::Write(const char *p)
+{
+	return Write(p, strlen(p));
+}
+
+bool
+BufferedOutputStream::Format(const char *fmt, ...)
+{
+	if (gcc_unlikely(last_error.IsDefined()))
+		return false;
+
+	auto r = buffer.Write();
+	if (r.IsEmpty()) {
+		if (!Flush())
+			return false;
+
+		r = buffer.Write();
+	}
+
+	/* format into the buffer */
+	va_list ap;
+	va_start(ap, fmt);
+	size_t size = vsnprintf(r.data, r.size, fmt, ap);
+	va_end(ap);
+
+	if (gcc_unlikely(size >= r.size)) {
+		/* buffer was not large enough; flush it and try
+		   again */
+
+		if (!Flush())
+			return false;
+
+		r = buffer.Write();
+
+		if (gcc_unlikely(size >= r.size)) {
+			/* still not enough space: grow the buffer and
+			   try again */
+			r.size = size + 1;
+			r.data = buffer.Write(r.size);
+		}
+
+		/* format into the new buffer */
+		va_start(ap, fmt);
+		size = vsnprintf(r.data, r.size, fmt, ap);
+		va_end(ap);
+
+		/* this time, it must fit */
+		assert(size < r.size);
+	}
+
+	buffer.Append(size);
+	return true;
+}
+
+bool
+BufferedOutputStream::Flush()
+{
+	if (!Check())
+		return false;
+
+	auto r = buffer.Read();
+	if (r.IsEmpty())
+		return true;
+
+	bool success = os.Write(r.data, r.size, last_error);
+	if (gcc_likely(success))
+		buffer.Consume(r.size);
+	return success;
+}
+
+bool
+BufferedOutputStream::Flush(Error &error)
+{
+	if (!Check(error))
+		return false;
+
+	auto r = buffer.Read();
+	if (r.IsEmpty())
+		return true;
+
+	bool success = os.Write(r.data, r.size, error);
+	if (gcc_likely(success))
+		buffer.Consume(r.size);
+	return success;
+}

src/fs/output/BufferedOutputStream.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_BUFFERED_OUTPUT_STREAM_HXX
+#define MPD_BUFFERED_OUTPUT_STREAM_HXX
+
+#include "check.h"
+#include "Compiler.h"
+#include "util/DynamicFifoBuffer.hxx"
+#include "util/Error.hxx"
+
+#include <stddef.h>
+
+class OutputStream;
+class Error;
+
+class BufferedOutputStream {
+	OutputStream &os;
+
+	DynamicFifoBuffer<char> buffer;
+
+	Error last_error;
+
+public:
+	BufferedOutputStream(OutputStream &_os)
+		:os(_os), buffer(32768) {}
+
+	bool Write(const void *data, size_t size);
+	bool Write(const char *p);
+
+	gcc_printf(2,3)
+	bool Format(const char *fmt, ...);
+
+	gcc_pure
+	bool Check() const {
+		return !last_error.IsDefined();
+	}
+
+	bool Check(Error &error) const {
+		if (last_error.IsDefined()) {
+			error.Set(last_error);
+			return false;
+		} else
+			return true;
+	}
+
+	bool Flush();
+
+	bool Flush(Error &error);
+
+private:
+	bool AppendToBuffer(const void *data, size_t size);
+};
+
+#endif

src/fs/output/FileOutputStream.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 "FileOutputStream.hxx"
+#include "fs/FileSystem.hxx"
+#include "util/Error.hxx"
+
+#ifdef WIN32
+
+FileOutputStream::FileOutputStream(Path _path, Error &error)
+	:path(_path),
+	 handle(CreateFile(path.c_str(), GENERIC_WRITE, 0, nullptr,
+			   TRUNCATE_EXISTING,
+			   FILE_ATTRIBUTE_NORMAL|FILE_FLAG_WRITE_THROUGH,
+			   nullptr))
+{
+	if (handle == INVALID_HANDLE_VALUE)
+		error.FormatLastError("Failed to create %s", path.c_str());
+}
+
+bool
+FileOutputStream::Write(const void *data, size_t size, Error &error)
+{
+	assert(IsDefined());
+
+	DWORD nbytes;
+	if (!WriteFile(handle, data, size, &nbytes, nullptr)) {
+		error.FormatLastError("Failed to write to %s", path.c_str());
+		return false;
+	}
+
+	if (size_t(nbytes) != size) {
+		error.FormatLastError(ERROR_DISK_FULL,
+				      "Failed to write to %s", path.c_str());
+		return false;
+	}
+
+	return true;
+}
+
+bool
+FileOutputStream::Commit(gcc_unused Error &error)
+{
+	assert(IsDefined());
+
+	CloseHandle(handle);
+	return true;
+}
+
+void
+FileOutputStream::Cancel()
+{
+	assert(IsDefined());
+
+	CloseHandle(handle);
+	RemoveFile(path);
+}
+
+#else
+
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+
+FileOutputStream::FileOutputStream(Path _path, Error &error)
+	:path(_path),
+	 fd(open(path.c_str(),
+		 O_WRONLY|O_CLOEXEC|O_CREAT|O_TRUNC|O_NOCTTY,
+		 0666))
+{
+	if (fd < 0)
+		error.FormatErrno("Failed to create %s", path.c_str());
+}
+
+bool
+FileOutputStream::Write(const void *data, size_t size, Error &error)
+{
+	assert(IsDefined());
+
+	ssize_t nbytes = write(fd, data, size);
+	if (nbytes < 0) {
+		error.FormatErrno("Failed to write to %s", path.c_str());
+		return false;
+	} else if ((size_t)nbytes < size) {
+		error.FormatErrno(ENOSPC,
+				  "Failed to write to %s", path.c_str());
+		return false;
+	}
+
+	return true;
+}
+
+bool
+FileOutputStream::Commit(Error &error)
+{
+	assert(IsDefined());
+
+	bool success = close(fd) == 0;
+	fd = -1;
+	if (!success)
+		error.FormatErrno("Failed to commit %s", path.c_str());
+
+	return success;
+}
+
+void
+FileOutputStream::Cancel()
+{
+	assert(IsDefined());
+
+	close(fd);
+	fd = -1;
+
+	RemoveFile(path);
+}
+
+#endif

src/fs/output/FileOutputStream.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_FILE_OUTPUT_STREAM_HXX
+#define MPD_FILE_OUTPUT_STREAM_HXX
+
+#include "check.h"
+#include "OutputStream.hxx"
+#include "fs/AllocatedPath.hxx"
+
+#include <assert.h>
+
+#ifdef WIN32
+#include <windows.h>
+#endif
+
+class Path;
+
+class FileOutputStream final : public OutputStream {
+	AllocatedPath path;
+
+#ifdef WIN32
+	HANDLE handle;
+#else
+	int fd;
+#endif
+
+public:
+	FileOutputStream(Path _path, Error &error);
+
+	~FileOutputStream() {
+		if (IsDefined())
+			Cancel();
+	}
+
+
+	bool IsDefined() const {
+#ifdef WIN32
+		return handle != INVALID_HANDLE_VALUE;
+#else
+		return fd >= 0;
+#endif
+	}
+
+	bool Commit(Error &error);
+	void Cancel();
+
+	/* virtual methods from class OutputStream */
+	bool Write(const void *data, size_t size, Error &error) override;
+};
+
+#endif

src/fs/output/OutputStream.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_OUTPUT_STREAM_HXX
+#define MPD_OUTPUT_STREAM_HXX
+
+#include "check.h"
+#include "Compiler.h"
+
+#include <stddef.h>
+
+class Error;
+
+class OutputStream {
+public:
+	OutputStream() = default;
+	OutputStream(const OutputStream &) = delete;
+
+	virtual bool Write(const void *data, size_t size, Error &error) = 0;
+};
+
+#endif

src/fs/output/StdioOutputStream.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_STDIO_OUTPUT_STREAM_HXX
+#define MPD_STDIO_OUTPUT_STREAM_HXX
+
+#include "check.h"
+#include "OutputStream.hxx"
+#include "fs/AllocatedPath.hxx"
+
+#include <stdio.h>
+
+class StdioOutputStream final : public OutputStream {
+	FILE *const file;
+
+public:
+	StdioOutputStream(FILE *_file):file(_file) {}
+
+	/* virtual methods from class OutputStream */
+	bool Write(const void *data, size_t size,
+		   gcc_unused Error &error) override {
+		fwrite(data, 1, size, file);
+
+		/* this class is debug-only and ignores errors */
+		return true;
+	}
+};
+
+#endif