Add syslog writer

refs #5683

library/Icinga/Logger/Writer/SyslogWriter.php

@@ -0,0 +1,108 @@
+<?php
+// {{{ICINGA_LICENSE_HEADER}}}
+// {{{ICINGA_LICENSE_HEADER}}}
+
+namespace Icinga\Logger\Writer;
+
+use \Exception;
+use \Zend_Config;
+use Icinga\Logger\Logger;
+use Icinga\Logger\LogWriter;
+use Icinga\Exception\ConfigurationError;
+
+/**
+ * Class to write messages to syslog
+ */
+class SyslogWriter extends LogWriter
+{
+    /**
+     * The facility where to write messages to
+     *
+     * @var string
+     */
+    protected $facility;
+
+    /**
+     * The prefix to prepend to each message
+     *
+     * @var string
+     */
+    protected $ident;
+
+    /**
+     * Known syslog facilities
+     *
+     * @var array
+     */
+    protected $facilities = array(
+        'LOG_USER' => LOG_USER
+    );
+
+    /**
+     * Create a new log writer initialized with the given configuration
+     */
+    public function __construct(Zend_Config $config)
+    {
+        if (!array_key_exists($config->facility, $this->facilities)) {
+            throw new ConfigurationError(
+                'Cannot create syslog writer with unknown facility "' . $config->facility . '"'
+            );
+        }
+
+        $this->ident = $config->application;
+        $this->facility = $this->facilities[$config->facility];
+    }
+
+    /**
+     * Log a message with the given severity
+     *
+     * @param   int     $severity   The severity to use
+     * @param   string  $message    The message to log
+     *
+     * @throws  Exception           In case the given severity cannot be mapped to a valid syslog priority
+     */
+    public function log($severity, $message)
+    {
+        $priorities = array(
+            Logger::$ERROR      => LOG_ERR,
+            Logger::$WARNING    => LOG_WARNING,
+            Logger::$INFO       => LOG_INFO,
+            Logger::$DEBUG      => LOG_DEBUG
+        );
+
+        if (!array_key_exists($severity, $priorities)) {
+            throw new Exception('Severity "' . $severity . '" cannot be mapped to a valid syslog priority');
+        }
+
+        $this->open();
+        $this->write($priorities[$severity], $message);
+        $this->close();
+    }
+
+    /**
+     * Open a new syslog connection
+     */
+    protected function open()
+    {
+        openlog($this->ident, 0, $this->facility);
+    }
+
+    /**
+     * Write a message to the syslog connection
+     *
+     * @param   int     $priority   The priority to use
+     * @param   string  $message    The message to write
+     */
+    protected function write($priority, $message)
+    {
+        syslog($priority, $message);
+    }
+
+    /**
+     * Close the syslog connection
+     */
+    protected function close()
+    {
+        closelog();
+    }
+}