Optimize performances of str_pad()

Author: alexandre-daubois

ext/standard/string.c

@@ -5737,6 +5737,29 @@ PHP_FUNCTION(substr_count)
 }
 /* }}} */
 
+static zend_always_inline void php_str_pad_fill(zend_string *result, size_t pad_chars, const char *pad_str, size_t pad_str_len) {
+	char *dest = ZSTR_VAL(result) + ZSTR_LEN(result);
+	
+	if (pad_str_len == 1) {
+		memset(dest, pad_str[0], pad_chars);
+
+		return;
+	}
+
+	size_t full_copies = pad_chars / pad_str_len;
+	size_t remainder = pad_chars % pad_str_len;
+	char *p = dest;
+
+	for (size_t j = 0; j < full_copies; ++j) {
+		memcpy(p, pad_str, pad_str_len);
+		p += pad_str_len;
+	}
+
+	if (remainder > 0) {
+		memcpy(p, pad_str, remainder);
+	}
+}
+
 /* {{{ Returns input string padded on the left or right to specified length with pad_string */
 PHP_FUNCTION(str_pad)
 {
@@ -5749,7 +5772,7 @@ PHP_FUNCTION(str_pad)
 	char *pad_str = " "; /* Pointer to padding string */
 	size_t pad_str_len = 1;
 	zend_long   pad_type_val = PHP_STR_PAD_RIGHT; /* The padding type value */
-	size_t	   i, left_pad=0, right_pad=0;
+	size_t left_pad=0, right_pad=0;
 	zend_string *result = NULL;	/* Resulting string */
 
 	ZEND_PARSE_PARAMETERS_START(2, 4)
@@ -5799,16 +5822,20 @@ PHP_FUNCTION(str_pad)
 	}
 
 	/* First we pad on the left. */
-	for (i = 0; i < left_pad; i++)
-		ZSTR_VAL(result)[ZSTR_LEN(result)++] = pad_str[i % pad_str_len];
+	if (left_pad > 0) {
+		php_str_pad_fill(result, left_pad, pad_str, pad_str_len);
+		ZSTR_LEN(result) += left_pad;
+	}
 
 	/* Then we copy the input string. */
 	memcpy(ZSTR_VAL(result) + ZSTR_LEN(result), ZSTR_VAL(input), ZSTR_LEN(input));
 	ZSTR_LEN(result) += ZSTR_LEN(input);
 
 	/* Finally, we pad on the right. */
-	for (i = 0; i < right_pad; i++)
-		ZSTR_VAL(result)[ZSTR_LEN(result)++] = pad_str[i % pad_str_len];
+	if (right_pad > 0) {
+		php_str_pad_fill(result, right_pad, pad_str, pad_str_len);
+		ZSTR_LEN(result) += right_pad;
+	}
 
 	ZSTR_VAL(result)[ZSTR_LEN(result)] = '\0';