Make the compression_level at settable option and expand it to zlib (#540)

Make it possible to use setOption to set Memcached::OPT_COMPRESSION_LEVEL which
was missed in the original zstd PR #539

zlib compression was using the default zlib compression level of 6. With this PR
it is now possible to choose other levels for zlib as well. The default remains
at 6 so nothing will change for people upgrading unless they explicitly set a
different level.

Here is some more benchmarking data using php serialized data
https://gist.github.com/rlerdorf/b9bae385446d5a30b65e6e241e34d0a8

fastlz is not really useful at any value size anymore. Anybody looking for
lightning quick compression and decompression should use zstd at level 1.

compression_level is not applied to fastlz because it only has 2 levels and
php-memcached already switches from level 1 to 2 automatically for values larger
than 65535 bytes. Forcing it to one or the other doesn't seem useful.

Author: rlerdorf

Diff for: php_memcached.c

@@ -884,7 +884,7 @@ zend_bool s_invoke_cache_callback(zval *zobject, zend_fcall_info *fci, zend_fcal
 ****************************************/
 
 static
-zend_bool s_compress_value (php_memc_compression_type compression_type, zend_string **payload_in, uint32_t *flags)
+zend_bool s_compress_value (php_memc_compression_type compression_type, zend_long compression_level, zend_string **payload_in, uint32_t *flags)
 {
 	/* status */
 	zend_bool compress_status = 0;
@@ -915,7 +915,13 @@ zend_bool s_compress_value (php_memc_compression_type compression_type, zend_str
 #ifdef HAVE_ZSTD_H
 		case COMPRESSION_TYPE_ZSTD:
 		{
-			compressed_size = ZSTD_compress((void *)buffer, buffer_size, ZSTR_VAL(payload), ZSTR_LEN(payload), MEMC_G(compression_level));
+			compressed_size = ZSTD_compress((void *)buffer, buffer_size, ZSTR_VAL(payload), ZSTR_LEN(payload), compression_level);
+
+			if (compression_level < -22) {
+				compression_level = -22;
+			} else if (compression_level > 22) {
+				compression_level = 22;
+			}
 
 			if (!ZSTD_isError(compressed_size)) {
 				compress_status = 1;
@@ -928,7 +934,14 @@ zend_bool s_compress_value (php_memc_compression_type compression_type, zend_str
 		case COMPRESSION_TYPE_ZLIB:
 		{
 			compressed_size = buffer_size;
-			int status = compress((Bytef *) buffer, &compressed_size, (Bytef *) ZSTR_VAL(payload), ZSTR_LEN(payload));
+
+			if (compression_level < 0) {
+				compression_level = 0;
+			} else if (compression_level > 9) {
+				compression_level = 9;
+			}
+
+			int status = compress2((Bytef *) buffer, &compressed_size, (Bytef *) ZSTR_VAL(payload), ZSTR_LEN(payload), compression_level);
 
 			if (status == Z_OK) {
 				compress_status = 1;
@@ -1120,7 +1133,7 @@ zend_string *s_zval_to_payload(php_memc_object_t *intern, zval *value, uint32_t
 		 *
 		 * No need to check the return value because the payload is always valid.
 		 */
-		(void)s_compress_value (memc_user_data->compression_type, &payload, flags);
+		(void)s_compress_value (memc_user_data->compression_type, memc_user_data->compression_level, &payload, flags);
 	}
 
 	if (memc_user_data->set_udf_flags >= 0) {
@@ -1325,6 +1338,7 @@ static PHP_METHOD(Memcached, __construct)
 	memc_user_data                    = pecalloc (1, sizeof(*memc_user_data), is_persistent);
 	memc_user_data->serializer        = MEMC_G(serializer_type);
 	memc_user_data->compression_type  = MEMC_G(compression_type);
+	memc_user_data->compression_level = MEMC_G(compression_level);
 	memc_user_data->compression_enabled = 1;
 	memc_user_data->encoding_enabled  = 0;
 	memc_user_data->store_retry_count = MEMC_G(store_retry_count);
@@ -3075,6 +3089,11 @@ int php_memc_set_option(php_memc_object_t *intern, long option, zval *value)
 			}
 			break;
 
+		case MEMC_OPT_COMPRESSION_LEVEL:
+			lval = zval_get_long(value);
+			memc_user_data->compression_level = lval;
+			break;
+
 		case MEMC_OPT_ITEM_SIZE_LIMIT:
 			lval = zval_get_long(value);
 			if (lval < 0) {
@@ -4054,7 +4073,7 @@ PHP_GINIT_FUNCTION(php_memcached)
 	php_memcached_globals->memc.compression_threshold = 2000;
 	php_memcached_globals->memc.compression_type = COMPRESSION_TYPE_FASTLZ;
 	php_memcached_globals->memc.compression_factor = 1.30;
-	php_memcached_globals->memc.compression_level = 3;
+	php_memcached_globals->memc.compression_level = 6;
 	php_memcached_globals->memc.store_retry_count = 2;
 	php_memcached_globals->memc.item_size_limit = 0;