silverstripe-framework/control/injector/SilverStripeServiceConfigurationLocator.php

<?php

/**
 * Use the SilverStripe configuration system to lookup config for a
 * particular service.
 *
 * @package framework
 * @subpackage injector
 */
class SilverStripeServiceConfigurationLocator extends ServiceConfigurationLocator {

	/**
	 * List of Injector configurations cached from Config in class => config format.
	 * If any config is false, this denotes that this class and all its parents
	 * have no configuration specified.
	 *
	 * @var array
	 */
	protected $configs = array();

	public function locateConfigFor($name) {
		// Check direct or cached result
		$config = $this->configFor($name);
		if(!$config) {
			return null;
		}

		// If config is in `%$Source` format then inherit from the named config
		if(is_string($config) && stripos($config, '%$') === 0) {
			$name = substr($config, 2);
			return $this->locateConfigFor($name);
		}

		// Return the located config
		return $config;
	}

	/**
	 * Retrieves the config for a named service without performing a hierarchy walk
	 *
	 * @param string $name Name of service
	 * @return mixed Get config for this service
	 */
	protected function configFor($name) {
		// Return cached result
		if (array_key_exists($name, $this->configs)) {
			return $this->configs[$name];
		}

		$config = Config::inst()->get('Injector', $name);
		$this->configs[$name] = $config;
		return $config;
	}
}