fs/io: move to io/

src/io/BufferedOutputStream.hxx

@@ -0,0 +1,142 @@
+/*
+ * Copyright 2014-2021 Max Kellermann <max.kellermann@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef BUFFERED_OUTPUT_STREAM_HXX
+#define BUFFERED_OUTPUT_STREAM_HXX
+
+#include "util/Compiler.h"
+#include "util/DynamicFifoBuffer.hxx"
+
+#include <cstddef>
+
+#ifdef _UNICODE
+#include <wchar.h>
+#endif
+
+class OutputStream;
+
+/**
+ * An #OutputStream wrapper that buffers its output to reduce the
+ * number of OutputStream::Write() calls.
+ *
+ * All wchar_t based strings are converted to UTF-8.
+ *
+ * To make sure everything is written to the underlying #OutputStream,
+ * call Flush() before destructing this object.
+ */
+class BufferedOutputStream {
+	OutputStream &os;
+
+	DynamicFifoBuffer<char> buffer;
+
+public:
+	explicit BufferedOutputStream(OutputStream &_os,
+				      size_t buffer_size=32768) noexcept
+		:os(_os), buffer(buffer_size) {}
+
+	/**
+	 * Write the contents of a buffer.
+	 */
+	void Write(const void *data, std::size_t size);
+
+	/**
+	 * Write the given object.  Note that this is only safe with
+	 * POD types.  Types with padding can expose sensitive data.
+	 */
+	template<typename T>
+	void WriteT(const T &value) {
+		Write(&value, sizeof(value));
+	}
+
+	/**
+	 * Write one narrow character.
+	 */
+	void Write(const char &ch) {
+		WriteT(ch);
+	}
+
+	/**
+	 * Write a null-terminated string.
+	 */
+	void Write(const char *p);
+
+	/**
+	 * Write a printf-style formatted string.
+	 */
+	gcc_printf(2,3)
+	void Format(const char *fmt, ...);
+
+#ifdef _UNICODE
+	/**
+	 * Write one narrow character.
+	 */
+	void Write(const wchar_t &ch) {
+		WriteWideToUTF8(&ch, 1);
+	}
+
+	/**
+	 * Write a null-terminated wide string.
+	 */
+	void Write(const wchar_t *p);
+#endif
+
+	/**
+	 * Write buffer contents to the #OutputStream.
+	 */
+	void Flush();
+
+	/**
+	 * Discard buffer contents.
+	 */
+	void Discard() noexcept {
+		buffer.Clear();
+	}
+
+private:
+	bool AppendToBuffer(const void *data, std::size_t size) noexcept;
+
+#ifdef _UNICODE
+	void WriteWideToUTF8(const wchar_t *p, std::size_t length);
+#endif
+};
+
+/**
+ * Helper function which constructs a #BufferedOutputStream, calls the
+ * given function and flushes the #BufferedOutputStream.
+ */
+template<typename F>
+void
+WithBufferedOutputStream(OutputStream &os, F &&f)
+{
+	BufferedOutputStream bos(os);
+	f(bos);
+	bos.Flush();
+}
+
+#endif