Add level_for_xp udf

.gitignore

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+CMakeCache.txt
+CMakeFiles
+Makefile
+cmake_install.cmake
+*.so

CMakeLists.txt

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+project(xp_udf)
+cmake_minimum_required(VERSION 3.9)
+
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall")
+
+include_directories(/usr/include/mysql)
+
+add_library(xp MODULE xp.cpp)

xp.cpp

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+/*
+ * Copyright (c) 2018, Adam <[email protected]>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ * 2. 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 COPYRIGHT OWNER 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.
+ */
+#include <my_global.h>
+#include <mysql.h>
+#include <string.h>
+
+static void con()  __attribute__((constructor));
+extern "C" my_bool level_for_xp_init(UDF_INIT *initid, UDF_ARGS *args, char *message);
+extern "C" longlong level_for_xp(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error);
+extern "C" void level_for_xp_deinit(UDF_INIT *initid);
+
+static constexpr int MAX_VIRT_LEVEL = 126;
+static int XP_FOR_LEVEL[MAX_VIRT_LEVEL];
+
+static void con()
+{
+	int xp = 0;
+
+	for (int level = 1; level <= MAX_VIRT_LEVEL; ++level)
+	{
+		XP_FOR_LEVEL[level - 1] = xp / 4;
+
+		int difference = (int) ((double) level + 300.0 * pow(2.0, (double) level / 7.0));
+		xp += difference;
+	}
+}
+
+static int _level_for_xp(int xp)
+{
+	if (xp < 0)
+	{
+		return -1;
+	}
+
+	int low = 0;
+	int high = MAX_VIRT_LEVEL - 1;
+
+	while (low <= high)
+	{
+		int mid = low + (high - low) / 2;
+		int xpForLevel = XP_FOR_LEVEL[mid];
+
+		if (xp < xpForLevel)
+		{
+			high = mid - 1;
+		}
+		else if (xp > xpForLevel)
+		{
+			low = mid + 1;
+		}
+		else
+		{
+			return mid + 1;
+		}
+	}
+
+	return high + 1;
+}
+
+my_bool level_for_xp_init(UDF_INIT *initid, UDF_ARGS *args, char *message)
+{
+	if (args->arg_count != 1 || args->arg_type[0] != INT_RESULT)
+	{
+		strcpy(message, "Wrong number and/or type of arguments");
+		return 1;
+	}
+
+	return 0;
+}
+
+longlong level_for_xp(UDF_INIT *initid, UDF_ARGS *args, char *is_null, char *error)
+{
+	longlong xp = * (longlong *) args->args[0];
+	return _level_for_xp(xp);
+}
+
+void level_for_xp_deinit(UDF_INIT *initid)
+{
+}