Queue: move code to new class IdTable

1 files changed, 91 insertions, 0 deletions

diff --git a/src/IdTable.hxx b/src/IdTable.hxx
new file mode 100644
index 000000000..8925fe8ab
--- /dev/null
+++ b/src/IdTable.hxx
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2003-2013 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_ID_TABLE_HXX
+#define MPD_ID_TABLE_HXX
+
+#include "gcc.h"
+
+#include <algorithm>
+
+#include <assert.h>
+
+/**
+ * A table that maps id numbers to position numbers.
+ */
+class IdTable {
+	unsigned size;
+
+	unsigned next;
+
+	int *data;
+
+public:
+	IdTable(unsigned _size):size(_size), next(1), data(new int[size]) {
+		std::fill(data, data + size, -1);
+	}
+
+	~IdTable() {
+		delete[] data;
+	}
+
+	int IdToPosition(unsigned id) const {
+		return id < size
+			? data[id]
+			: -1;
+	}
+
+	unsigned GenerateId() {
+		assert(next > 0);
+		assert(next < size);
+
+		while (true) {
+			unsigned id = next;
+
+			++next;
+			if (next == size)
+				next = 1;
+
+			if (data[id] < 0)
+				return id;
+		}
+	}
+
+	unsigned Insert(unsigned position) {
+		unsigned id = GenerateId();
+		data[id] = position;
+		return id;
+	}
+
+	void Move(unsigned id, unsigned position) {
+		assert(id < size);
+		assert(data[id] >= 0);
+
+		data[id] = position;
+	}
+
+	void Erase(unsigned id) {
+		assert(id < size);
+		assert(data[id] >= 0);
+
+		data[id] = -1;
+	}
+};
+
+#endif