added upload_of validation rule.

system/input.php

@@ -70,6 +70,18 @@ class Input {
 	}
 
 	/**
+	 * Get an item from the uploaded file data.
+	 *
+	 * @param  string  $key
+	 * @param  mixed   $default
+	 * @return array
+	 */
+	public static function file($key, $default = null)
+	{
+		return Arr::get($_FILES, $key, $default);
+	}
+
+	/**
 	 * Hydrate the input data for the request.
 	 *
 	 * @return void

system/validation/rules/upload_of.php

+<?php namespace System\Validation\Rules;
+
+use System\Input;
+use System\Validation\Rule;
+
+class Upload_Of extends Rule {
+
+	/**
+	 * The acceptable file extensions.
+	 *
+	 * @var array
+	 */
+	public $extensions;
+
+	/**
+	 * The maximum file size in bytes.
+	 *
+	 * @var int
+	 */
+	public $maximum;
+
+	/**
+	 * Evaluate the validity of an attribute.
+	 *
+	 * @param  string  $attribute
+	 * @param  array   $attributes
+	 * @return void
+	 */
+	public function check($attribute, $attributes)
+	{
+		if ( ! array_key_exists($attribute, Input::file()))
+		{
+			return true;
+		}
+
+		$file = Input::file($attribute);
+
+		if ( ! is_null($this->maximum) and $file['size'] > $this->maximum)
+		{
+			return false;
+		}
+
+		if ( ! is_null($this->extensions) and ! in_array(File::extension($file['name']), $this->extensions))
+		{
+			return false;
+		}
+
+		return true;
+	}	
+
+}
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