log-driver.php: split up log driver

inc/Data/Driver/FileLogDriver.php

@@ -0,0 +1,60 @@
+<?php
+namespace Vichan\Data\Driver;
+
+defined('TINYBOARD') or exit;
+
+
+/**
+ * Log to a file.
+ */
+class FileLogDriver implements LogDriver {
+	use LogTrait;
+
+	private string $name;
+	private int $level;
+	private mixed $fd;
+
+	public function __construct(string $name, int $level, string $file_path) {
+		/*
+		 * error_log is slow as hell in it's 3rd mode, so use fopen + file locking instead.
+		 * https://grobmeier.solutions/performance-ofnonblocking-write-to-files-via-php-21082009.html
+		 *
+		 * Whatever file appending is atomic is contentious:
+		 *  - There are no POSIX guarantees: https://stackoverflow.com/a/7237901
+		 *  - But linus suggested they are on linux, on some filesystems: https://web.archive.org/web/20151201111541/http://article.gmane.org/gmane.linux.kernel/43445
+		 *  - But it doesn't seem to be always the case: https://www.notthewizard.com/2014/06/17/are-files-appends-really-atomic/
+		 *
+		 * So we just use file locking to be sure.
+		 */
+
+		$this->fd = \fopen($file_path, 'a');
+		if ($this->fd === false) {
+			throw new \RuntimeException("Unable to open log file at $file_path");
+		}
+
+		$this->name = $name;
+		$this->level = $level;
+
+		// In some cases PHP does not run the destructor.
+		\register_shutdown_function([$this, 'close']);
+	}
+
+	public function __destruct() {
+		$this->close();
+	}
+
+	public function log(int $level, string $message): void {
+		if ($level <= $this->level) {
+			$lv = $this->levelToString($level);
+			$line = "{$this->name} $lv: $message\n";
+			\flock($this->fd, LOCK_EX);
+			\fwrite($this->fd, $line);
+			\flock($this->fd, LOCK_UN);
+		}
+	}
+
+	public function close() {
+		\flock($this->fd, LOCK_UN);
+		\fclose($this->fd);
+	}
+}