CI框架源码学习笔记3——Log.php

上一节说完了Common.php，然而跟代码打交道总是免不了日志记录，所以这一节我们说说Log.php文件。

先看看类里面的几个属性，

protected $_log_path;  日志路径

protected $_file_permissions = 0644; 文件权限

protected $_threshold = 1;  日志的等级，用来判断出现的错误异常什么的是否需要记录

protected $_threshold_array = array();

protected $_date_fmt = 'Y-m-d H:i:s';  日期格式

protected $_file_ext; 日志文件扩展名

protected $_enabled = TRUE; 是否可用

protected $_levels = array('ERROR' => 1, 'DEBUG' => 2, 'INFO' => 3, 'ALL' => 4);  log等级

protected static $func_override;  判断mbstring扩展函数重载配置是否开启

再来看构造函数，主要是对上面的属性赋值。

public function __construct()
    {
        $config =& get_config();//获取config.php配置

        //判断变量function_override是否设置，如果没有设置，根据是否载入mbstring扩展，以及扩展的重载配置是否开启来赋值true或false
        isset(self::$func_override) OR self::$func_override = (extension_loaded('mbstring') && ini_get('mbstring.func_override'));

        //设置日志记载的目录，若config没有配置，默认在application的logs文件夹下
        $this->_log_path = ($config['log_path'] !== '') ? $config['log_path'] : APPPATH.'logs/';
        //根据配置设置扩展名，默认为php
        $this->_file_ext = (isset($config['log_file_extension']) && $config['log_file_extension'] !== '')
            ? ltrim($config['log_file_extension'], '.') : 'php';

        //判断记录日志的目录是否存在，若不存在则新建
        file_exists($this->_log_path) OR mkdir($this->_log_path, 0755, TRUE);

        //判断日志目录是否可写，若不可写，设置可用性判断的变量_enabled为false
        if ( ! is_dir($this->_log_path) OR ! is_really_writable($this->_log_path))
        {
            $this->_enabled = FALSE;
        }

        //如果配置log_threshold是数字那么直接设置为变量;否则如果配置为数组，那么设置变量_threshold为0,同时设置_threshold_array为配置log_threshold调换key与value后的数组
        if (is_numeric($config['log_threshold']))
        {
            $this->_threshold = (int) $config['log_threshold'];
        }
        elseif (is_array($config['log_threshold']))
        {
            $this->_threshold = 0;
            $this->_threshold_array = array_flip($config['log_threshold']);
        }
        //设置日期格式
        if ( ! empty($config['log_date_format']))
        {
            $this->_date_fmt = $config['log_date_format'];
        }
        //设置日志文件权限
        if ( ! empty($config['log_file_permissions']) && is_int($config['log_file_permissions']))
        {
            $this->_file_permissions = $config['log_file_permissions'];
        }
    }

我们在看看几个辅助用到的方法

　　protected function _format_line($level, $date, $message)
    {
        return $level.' - '.$date.' --> '.$message."\n";
    }

方法内容很简单，就是构造成指定格式的。

    protected static function strlen($str)
    {
        return (self::$func_override)
            ? mb_strlen($str, '8bit')
            : strlen($str);
    }

用来测量字符串长度，当mb_string扩展开启时使用mb_strlen，否则使用php函数strlen。

　　protected static function substr($str, $start, $length = NULL)
    {
        if (self::$func_override)
        {
            // mb_substr($str, $start, null, '8bit') returns an empty
            // string on PHP 5.3
            isset($length) OR $length = ($start >= 0 ? self::strlen($str) - $start : -$start);
            return mb_substr($str, $start, $length, '8bit');
        }

        return isset($length)
            ? substr($str, $start, $length)
            : substr($str, $start);
    }

截取字符串的方法。

其实整个类里面真正对外使用的方法就一个write_log，而且通常只会被函数log_message调用(这个函数我们在Common.php中有讲过)。

public function write_log($level, $msg)
    {
        //先判断变量$this->_enabled,若为false则不执行写入日志操作了(此时日志目录的属性不可写)
        if ($this->_enabled === FALSE)
        {
            return FALSE;
        }

        $level = strtoupper($level);//转换字符串为大写

        //这里主要是判断我们要写入日志的错误信息的等级是否比我们在配置中配置的可写入日志的错误等级高
        //配置中默认的为0，所以此时我们实际上是不会有写日志的操作的，所以我们需要把配置改成1后才能记录error日志
        if (( ! isset($this->_levels[$level]) OR ($this->_levels[$level] > $this->_threshold))
            && ! isset($this->_threshold_array[$this->_levels[$level]]))
        {
            return FALSE;
        }

        $filepath = $this->_log_path.'log-'.date('Y-m-d').'.'.$this->_file_ext;//文件路径
        $message = '';

        //判断文件是否存在，若不存在那么说明是第一次创建，此时需要写入一段php代码，判断常量BASEPARH是否定义
        if ( ! file_exists($filepath))
        {
            $newfile = TRUE;
            // Only add protection to php files
            if ($this->_file_ext === 'php')
            {
                $message .= "<?php defined('BASEPATH') OR exit('No direct script access allowed'); ?>\n\n";
            }
        }

        //打开文件，若失败则退出
        if ( ! $fp = @fopen($filepath, 'ab'))
        {
            return FALSE;
        }

        //文件写锁
        flock($fp, LOCK_EX);

        // Instantiating DateTime with microseconds appended to initial date is needed for proper support of this format
        //获取时间信息，用来记录到日志内容中
        if (strpos($this->_date_fmt, 'u') !== FALSE)
        {
            $microtime_full = microtime(TRUE);
            $microtime_short = sprintf("%06d", ($microtime_full - floor($microtime_full)) * 1000000);
            $date = new DateTime(date('Y-m-d H:i:s.'.$microtime_short, $microtime_full));
            $date = $date->format($this->_date_fmt);
        }
        else
        {
            $date = date($this->_date_fmt);
        }

        //根据上面的内容，构造完整的日志信息
        $message .= $this->_format_line($level, $date, $msg);

        //将日志信息写入到文件中
        for ($written = 0, $length = self::strlen($message); $written < $length; $written += $result)
        {
            if (($result = fwrite($fp, self::substr($message, $written))) === FALSE)
            {
                break;
            }
        }

        //释放锁
        flock($fp, LOCK_UN);
        //释放文件资源
        fclose($fp);

        //设置日志文件权限
        if (isset($newfile) && $newfile === TRUE)
        {
            chmod($filepath, $this->_file_permissions);
        }

        //通过返回的result是否为int来判断写入是否成功，因为fwrite成功时返回写入的字符数，失败时返回false
        return is_int($result);
    }

Log.php文件的内容不是很多，分析完毕，最后贴上完整代码。

class CI_Log {

    /**
     * Path to save log files
     *
     * @var string
     */
    protected $_log_path;

    /**
     * File permissions
     *
     * @var    int
     */
    protected $_file_permissions = 0644;

    /**
     * Level of logging
     *
     * @var int
     */
    protected $_threshold = 1;

    /**
     * Array of threshold levels to log
     *
     * @var array
     */
    protected $_threshold_array = array();

    /**
     * Format of timestamp for log files
     *
     * @var string
     */
    protected $_date_fmt = 'Y-m-d H:i:s';

    /**
     * Filename extension
     *
     * @var    string
     */
    protected $_file_ext;

    /**
     * Whether or not the logger can write to the log files
     *
     * @var bool
     */
    protected $_enabled = TRUE;

    /**
     * Predefined logging levels
     *
     * @var array
     */
    protected $_levels = array('ERROR' => 1, 'DEBUG' => 2, 'INFO' => 3, 'ALL' => 4);

    /**
     * mbstring.func_override flag
     *
     * @var    bool
     */
    protected static $func_override;

    // --------------------------------------------------------------------

    /**
     * Class constructor
     *
     * @return    void
     */
    public function __construct()
    {
        $config =& get_config();

        isset(self::$func_override) OR self::$func_override = (extension_loaded('mbstring') && ini_get('mbstring.func_override'));

        $this->_log_path = ($config['log_path'] !== '') ? $config['log_path'] : APPPATH.'logs/';
        $this->_file_ext = (isset($config['log_file_extension']) && $config['log_file_extension'] !== '')
            ? ltrim($config['log_file_extension'], '.') : 'php';

        file_exists($this->_log_path) OR mkdir($this->_log_path, 0755, TRUE);

        if ( ! is_dir($this->_log_path) OR ! is_really_writable($this->_log_path))
        {
            $this->_enabled = FALSE;
        }

        if (is_numeric($config['log_threshold']))
        {
            $this->_threshold = (int) $config['log_threshold'];
        }
        elseif (is_array($config['log_threshold']))
        {
            $this->_threshold = 0;
            $this->_threshold_array = array_flip($config['log_threshold']);
        }

        if ( ! empty($config['log_date_format']))
        {
            $this->_date_fmt = $config['log_date_format'];
        }

        if ( ! empty($config['log_file_permissions']) && is_int($config['log_file_permissions']))
        {
            $this->_file_permissions = $config['log_file_permissions'];
        }
    }

    // --------------------------------------------------------------------

    /**
     * Write Log File
     *
     * Generally this function will be called using the global log_message() function
     *
     * @param    string    $level     The error level: 'error', 'debug' or 'info'
     * @param    string    $msg     The error message
     * @return    bool
     */
    public function write_log($level, $msg)
    {
        if ($this->_enabled === FALSE)
        {
            return FALSE;
        }

        $level = strtoupper($level);

        if (( ! isset($this->_levels[$level]) OR ($this->_levels[$level] > $this->_threshold))
            && ! isset($this->_threshold_array[$this->_levels[$level]]))
        {
            return FALSE;
        }

        $filepath = $this->_log_path.'log-'.date('Y-m-d').'.'.$this->_file_ext;
        $message = '';

        if ( ! file_exists($filepath))
        {
            $newfile = TRUE;
            // Only add protection to php files
            if ($this->_file_ext === 'php')
            {
                $message .= "<?php defined('BASEPATH') OR exit('No direct script access allowed'); ?>\n\n";
            }
        }

        if ( ! $fp = @fopen($filepath, 'ab'))
        {
            return FALSE;
        }

        flock($fp, LOCK_EX);

        // Instantiating DateTime with microseconds appended to initial date is needed for proper support of this format
        if (strpos($this->_date_fmt, 'u') !== FALSE)
        {
            $microtime_full = microtime(TRUE);
            $microtime_short = sprintf("%06d", ($microtime_full - floor($microtime_full)) * 1000000);
            $date = new DateTime(date('Y-m-d H:i:s.'.$microtime_short, $microtime_full));
            $date = $date->format($this->_date_fmt);
        }
        else
        {
            $date = date($this->_date_fmt);
        }

        $message .= $this->_format_line($level, $date, $msg);

        for ($written = 0, $length = self::strlen($message); $written < $length; $written += $result)
        {
            if (($result = fwrite($fp, self::substr($message, $written))) === FALSE)
            {
                break;
            }
        }

        flock($fp, LOCK_UN);
        fclose($fp);

        if (isset($newfile) && $newfile === TRUE)
        {
            chmod($filepath, $this->_file_permissions);
        }

        return is_int($result);
    }

    // --------------------------------------------------------------------

    /**
     * Format the log line.
     *
     * This is for extensibility of log formatting
     * If you want to change the log format, extend the CI_Log class and override this method
     *
     * @param    string    $level     The error level
     * @param    string    $date     Formatted date string
     * @param    string    $message     The log message
     * @return    string    Formatted log line with a new line character '\n' at the end
     */
    protected function _format_line($level, $date, $message)
    {
        return $level.' - '.$date.' --> '.$message."\n";
    }

    // --------------------------------------------------------------------

    /**
     * Byte-safe strlen()
     *
     * @param    string    $str
     * @return    int
     */
    protected static function strlen($str)
    {
        return (self::$func_override)
            ? mb_strlen($str, '8bit')
            : strlen($str);
    }

    // --------------------------------------------------------------------

    /**
     * Byte-safe substr()
     *
     * @param    string    $str
     * @param    int    $start
     * @param    int    $length
     * @return    string
     */
    protected static function substr($str, $start, $length = NULL)
    {
        if (self::$func_override)
        {
            // mb_substr($str, $start, null, '8bit') returns an empty
            // string on PHP 5.3
            isset($length) OR $length = ($start >= 0 ? self::strlen($str) - $start : -$start);
            return mb_substr($str, $start, $length, '8bit');
        }

        return isset($length)
            ? substr($str, $start, $length)
            : substr($str, $start);
    }
}