fs/io/BufferedReader: new class to replace class TextFile

The new class is pluggable, to prepare for gzipped database files.

For now, the TextFile class remains, and will be refactored away
later.

src/fs/io/BufferedReader.cxx

@@ -0,0 +1,82 @@
+/*
+ * 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 "BufferedReader.hxx"
+#include "Reader.hxx"
+#include "util/TextFile.hxx"
+
+bool
+BufferedReader::Fill(bool need_more)
+{
+	if (gcc_unlikely(last_error.IsDefined()))
+		return false;
+
+	if (eof)
+		return !need_more;
+
+	auto w = buffer.Write();
+	if (w.IsEmpty()) {
+		if (buffer.GetCapacity() >= MAX_SIZE)
+			return !need_more;
+
+		buffer.Grow(buffer.GetCapacity() * 2);
+		w = buffer.Write();
+		assert(!w.IsEmpty());
+	}
+
+	size_t nbytes = reader.Read(w.data, w.size, last_error);
+	if (nbytes == 0) {
+		if (gcc_unlikely(last_error.IsDefined()))
+			return false;
+
+		eof = true;
+		return !need_more;
+	}
+
+	buffer.Append(nbytes);
+	return true;
+}
+
+char *
+BufferedReader::ReadLine()
+{
+	do {
+		char *line = ReadBufferedLine(buffer);
+		if (line != nullptr)
+			return line;
+	} while (Fill(true));
+
+	if (last_error.IsDefined() || !eof || buffer.IsEmpty())
+		return nullptr;
+
+	auto w = buffer.Write();
+	if (w.IsEmpty()) {
+		buffer.Grow(buffer.GetCapacity() + 1);
+		w = buffer.Write();
+		assert(!w.IsEmpty());
+	}
+
+	/* terminate the last line */
+	w[0] = 0;
+
+	char *line = buffer.Read().data;
+	buffer.Clear();
+	return line;
+}