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Edit File: CacheNameSpaceTrait.php

<?php

namespace Automattic\WooCommerce\Caching;

/**
 * Implements namespacing algorithm to simulate grouping and namespacing for wp_cache, memcache and other caching engines that don't support grouping natively.
 *
 * See the algorithm details here: https://github.com/memcached/memcached/wiki/ProgrammingTricks#namespacing.
 *
 * To use the namespacing algorithm in the CacheEngine class:
 * 1. Use a group string to identify all objects of a type.
 * 2. Before setting cache, prefix the cache key by using the `get_cache_prefix`.
 * 3. Use `invalidate_cache_group` function to invalidate all caches in entire group at once.
 */
trait CacheNameSpaceTrait {

/**
	 * Get prefix for use with wp_cache_set. Allows all cache in a group to be invalidated at once.
	 *
	 * @param  string $group Group of cache to get.
	 * @return string Prefix.
	 */
	public static function get_cache_prefix( $group ) {
		// Get cache key - uses cache key wc_orders_cache_prefix to invalidate when needed.
		$prefix = wp_cache_get( 'wc_' . $group . '_cache_prefix', $group );

if ( false === $prefix ) {
			$prefix = microtime();
			wp_cache_set( 'wc_' . $group . '_cache_prefix', $prefix, $group );
		}

return 'wc_cache_' . $prefix . '_';
	}

/**
	 * Increment group cache prefix (invalidates cache).
	 *
	 * @param string $group Group of cache to clear.
	 */
	public static function incr_cache_prefix( $group ) {
		wc_deprecated_function( 'WC_Cache_Helper::incr_cache_prefix', '3.9.0', 'WC_Cache_Helper::invalidate_cache_group' );
		self::invalidate_cache_group( $group );
	}

/**
	 * Invalidate cache group.
	 *
	 * @param string $group Group of cache to clear.
	 * @since 3.9.0
	 */
	public static function invalidate_cache_group( $group ) {
		return wp_cache_set( 'wc_' . $group . '_cache_prefix', microtime(), $group );
	}

/**
	 * Helper method to get prefixed key.
	 *
	 * @param  string $key   Key to prefix.
	 * @param  string $group Group of cache to get.
	 *
	 * @return string Prefixed key.
	 */
	public static function get_prefixed_key( $key, $group ) {
		return self::get_cache_prefix( $group ) . $key;
	}
}