MXS-2005: Move Logger into maxutils

Moved the logger into the maxutils library as it is a generic
utility. Also moved mxs_strerror into it as it depends on it.

maxutils/maxbase/include/maxbase/logger.hh

@@ -0,0 +1,171 @@
+#pragma once
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2022-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxbase/ccdefs.hh>
+
+#include <string>
+#include <mutex>
+#include <memory>
+
+#include <unistd.h>
+
+namespace maxbase
+{
+
+// Minimal logger interface
+class Logger
+{
+public:
+    Logger(const Logger&) = delete;
+    Logger& operator=(const Logger&) = delete;
+
+    virtual ~Logger()
+    {
+    }
+
+    /**
+     * Write a message to the log
+     *
+     * @param msg Message to write
+     * @param len Length of message
+     *
+     * @return True on success
+     */
+    virtual bool write(const char* msg, int len) = 0;
+
+    /**
+     * Rotate the logfile
+     *
+     * @return True if the log was rotated
+     */
+    virtual bool rotate() = 0;
+
+    /**
+     * Get the name of the log file
+     *
+     * @return The name of the log file
+     */
+    const char* filename() const
+    {
+        return m_filename.c_str();
+    }
+
+protected:
+    Logger(const std::string& filename):
+        m_filename(filename)
+    {
+    }
+
+    std::string m_filename;
+};
+
+class FileLogger: public Logger
+{
+public:
+    FileLogger(const FileLogger&) = delete;
+    FileLogger& operator=(const FileLogger&) = delete;
+
+    /**
+     * Create a new logger that writes to a file
+     *
+     * @param logdir Log file to open
+     *
+     * @return New logger instance or an empty unique_ptr on error
+     */
+    static std::unique_ptr<Logger> create(const std::string& filename);
+
+    /**
+     * Close the log
+     *
+     * A footer is written to the log and the file is closed.
+     */
+    ~FileLogger();
+
+    /**
+     * Write a message to the log
+     *
+     * @param msg Message to write
+     * @param len Length of message
+     *
+     * @return True on success
+     */
+    bool write(const char* msg, int len);
+
+    /**
+     * Rotate the logfile by reopening it
+     *
+     * @return True if the log was rotated. False if the opening of the new file
+     *         descriptor failed in which case the old file descriptor will be used.
+     */
+    bool rotate();
+
+private:
+    int              m_fd;
+    std::mutex       m_lock;
+
+    FileLogger(int fd, const std::string& filename);
+    bool write_header();
+    bool write_footer(const char* suffix);
+    void close(const char* msg);
+};
+
+class StdoutLogger: public Logger
+{
+public:
+    StdoutLogger(const StdoutLogger&) = delete;
+    StdoutLogger& operator=(const StdoutLogger&) = delete;
+
+    /**
+     * Create a new logger that writes to stdout
+     *
+     * @param logdir Log file to open, has no functional effect on this logger
+     *
+     * @return New logger instance or an empty unique_ptr on error
+     */
+    static std::unique_ptr<Logger> create(const std::string& filename)
+    {
+        return std::unique_ptr<Logger>(new StdoutLogger(filename));
+    }
+
+    /**
+     * Write a message to stdout
+     *
+     * @param msg Message to write
+     * @param len Length of message
+     *
+     * @return True on success
+     */
+    bool write(const char* msg, int len)
+    {
+        return ::write(STDOUT_FILENO, msg, len) != -1;
+    }
+
+    /**
+     * Rotate the "logfile"
+     *
+     * @return Always true
+     */
+    bool rotate()
+    {
+        return true;
+    };
+
+private:
+    StdoutLogger(const std::string& filename):
+        Logger(filename)
+    {
+    }
+};
+
+}