added zstd as compress option

Author: mklooss

Cm/Cache/Backend/Redis.php

@@ -309,6 +309,15 @@ public function __construct($options = array())
             }
             $this->_compressionLib = 'l4z';
         }
+        else if ( function_exists('zstd_compress')) {
+            $version = phpversion("zstd");
+            if (version_compare($version, "0.4.13") < 0)
+            {
+                $this->_compressTags = $this->_compressTags > 1 ? true : false;
+                $this->_compressData = $this->_compressData > 1 ? true : false;
+            }
+            $this->_compressionLib = 'zstd';
+        }
         else if ( function_exists('lzf_compress') ) {
             $this->_compressionLib = 'lzf';
         }
@@ -1171,6 +1180,7 @@ protected function _encodeData($data, $level)
                 case 'snappy': $data = snappy_compress($data); break;
                 case 'lzf':    $data = lzf_compress($data); break;
                 case 'l4z':    $data = lz4_compress($data, $level); break;
+                case 'zstd':   $data = zstd_compress($data, $level); break;
                 case 'gzip':   $data = gzcompress($data, $level); break;
                 default:       throw new CredisException("Unrecognized 'compression_lib'.");
             }
@@ -1193,6 +1203,7 @@ protected function _decodeData($data)
                 case 'sn': return snappy_uncompress(substr($data,5));
                 case 'lz': return lzf_decompress(substr($data,5));
                 case 'l4': return lz4_uncompress(substr($data,5));
+                case 'zs': return zstd_uncompress(substr($data,5));
                 case 'gz': case 'zc': return gzuncompress(substr($data,5));
             }
         }

README.md

@@ -48,7 +48,7 @@ Works with any Zend Framework project including all versions of Magento!
             <compress_data>1</compress_data>  <!-- 0-9 for compression level, recommended: 0 or 1 -->
             <compress_tags>1</compress_tags>  <!-- 0-9 for compression level, recommended: 0 or 1 -->
             <compress_threshold>20480</compress_threshold>  <!-- Strings below this size will not be compressed -->
-            <compression_lib>gzip</compression_lib> <!-- Supports gzip, lzf, lz4 (as l4z) and snappy -->
+            <compression_lib>gzip</compression_lib> <!-- Supports gzip, lzf, lz4 (as l4z), snappy and zstd -->
             <use_lua>0</use_lua> <!-- Set to 1 if Lua scripts should be used for some operations (recommended) -->
             <load_from_slave>tcp://redis-slave:6379</load_from_slave> <!-- Perform reads from a different server --> 
           </backend_options>