Optimize double-width safe_substr when all double-width.

Author: gitlost

lib/cli/cli.php

@@ -203,15 +203,23 @@ function safe_substr( $str, $start, $length = false, $is_width = false, $encodin
 			$eaw_regex = get_unicode_regexs( 'eaw' );
 			// If there's any East Asian double-width chars...
 			if ( preg_match( $eaw_regex, $substr ) ) {
-				// Explode string into an array of UTF-8 chars. Based on core `_mb_substr()` in "wp-includes/compat.php".
-				$chars = preg_split( '/([\x00-\x7f\xc2-\xf4][^\x00-\x7f\xc2-\xf4]*)/', $substr, $length + 1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY );
-				$cnt = min( count( $chars ), $length );
-				$width = $length;
+				// Note that if the length ends in the middle of a double-width char, the char is included, not excluded.
 
-				for ( $length = 0; $length < $cnt && $width > 0; $length++ ) {
-					$width -= preg_match( $eaw_regex, $chars[ $length ] ) ? 2 : 1;
+				// See if it's all EAW - the most likely case.
+				if ( preg_match_all( $eaw_regex, $substr ) === $length ) {
+					// Just halve the length so (rounded up).
+					$substr = mb_substr( $substr, 0, (int) ( ( $length + 1 ) / 2 ), $encoding );
+				} else {
+					// Explode string into an array of UTF-8 chars. Based on core `_mb_substr()` in "wp-includes/compat.php".
+					$chars = preg_split( '/([\x00-\x7f\xc2-\xf4][^\x00-\x7f\xc2-\xf4]*)/', $substr, $length + 1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY );
+					$cnt = min( count( $chars ), $length );
+					$width = $length;
+
+					for ( $length = 0; $length < $cnt && $width > 0; $length++ ) {
+						$width -= preg_match( $eaw_regex, $chars[ $length ] ) ? 2 : 1;
+					}
+					return join( '', array_slice( $chars, 0, $length ) );
 				}
-				return join( '', array_slice( $chars, 0, $length ) );
 			}
 		}
 	} else {
@@ -279,7 +287,7 @@ function strwidth( $string, $encoding = false ) {
 			return $width;
 		}
 	}
-	return safe_strlen( $string );
+	return safe_strlen( $string, $encoding );
 }
 
 /**