Reduce memory allocated by var_export, json_encode, serialize, and other

Author: arnaud-lb

Zend/zend_smart_str.h

@@ -25,6 +25,8 @@
 	smart_str_appendl_ex((dest), (src), strlen(src), (what))
 #define smart_str_appends(dest, src) \
 	smart_str_appendl((dest), (src), strlen(src))
+#define smart_str_finalize(dest) \
+	smart_str_finalize_ex((dest), 0)
 #define smart_str_extend(dest, len) \
 	smart_str_extend_ex((dest), (len), 0)
 #define smart_str_appendc(dest, c) \
@@ -76,6 +78,29 @@ static zend_always_inline size_t smart_str_alloc(smart_str *str, size_t len, boo
 	return len;
 }
 
+static zend_always_inline void smart_str_trim_to_len(smart_str *str, bool persistent)
+{
+	if (str->s && str->a > ZSTR_LEN(str->s)) {
+		str->s = zend_string_realloc(str->s, ZSTR_LEN(str->s), persistent);
+		str->a = ZSTR_LEN(str->s);
+	}
+}
+
+static zend_always_inline zend_string* smart_str_finalize_ex(smart_str *str, bool persistent)
+{
+	if (UNEXPECTED(!str->s)) {
+		return ZSTR_EMPTY_ALLOC();
+	}
+
+	smart_str_trim_to_len(str, persistent);
+	zend_string *retval = str->s;
+
+	str->s = NULL;
+	str->a = 0;
+
+	return retval;
+}
+
 static zend_always_inline char* smart_str_extend_ex(smart_str *dest, size_t len, bool persistent) {
 	size_t new_len = smart_str_alloc(dest, len, persistent);
 	char *ret = ZSTR_VAL(dest->s) + ZSTR_LEN(dest->s);

ext/dom/documenttype.c

@@ -189,7 +189,7 @@ int dom_documenttype_internal_subset_read(dom_object *obj, zval *retval)
 
 		if (ret_buf.s) {
 			smart_str_0(&ret_buf);
-			ZVAL_NEW_STR(retval, ret_buf.s);
+			ZVAL_STR(retval, smart_str_finalize(&ret_buf));
 			return SUCCESS;
 		}
 	}

ext/filter/sanitizing_filters.c

@@ -48,7 +48,7 @@ static void php_filter_encode_html(zval *value, const unsigned char *chars)
 
 	smart_str_0(&str);
 	zval_ptr_dtor(value);
-	ZVAL_NEW_STR(value, str.s);
+	ZVAL_STR(value, smart_str_finalize(&str));
 }
 
 static const unsigned char hexchars[] = "0123456789ABCDEF";

ext/iconv/iconv.c

@@ -1845,7 +1845,7 @@ PHP_FUNCTION(iconv_substr)
 	_php_iconv_show_error(err, GENERIC_SUPERSET_NAME, charset);
 
 	if (err == PHP_ICONV_ERR_SUCCESS && retval.s != NULL) {
-		RETURN_NEW_STR(retval.s);
+		RETURN_STR(smart_str_finalize(&retval));
 	}
 	smart_str_free(&retval);
 	RETURN_FALSE;
@@ -2038,11 +2038,7 @@ PHP_FUNCTION(iconv_mime_encode)
 	_php_iconv_show_error(err, out_charset, in_charset);
 
 	if (err == PHP_ICONV_ERR_SUCCESS) {
-		if (retval.s != NULL) {
-			RETVAL_STR(retval.s);
-		} else {
-			RETVAL_EMPTY_STRING();
-		}
+		RETVAL_STR(smart_str_finalize(&retval));
 	} else {
 		smart_str_free(&retval);
 		RETVAL_FALSE;
@@ -2083,11 +2079,7 @@ PHP_FUNCTION(iconv_mime_decode)
 	_php_iconv_show_error(err, charset, "???");
 
 	if (err == PHP_ICONV_ERR_SUCCESS) {
-		if (retval.s != NULL) {
-			RETVAL_STR(retval.s);
-		} else {
-			RETVAL_EMPTY_STRING();
-		}
+		RETVAL_STR(smart_str_finalize(&retval));
 	} else {
 		smart_str_free(&retval);
 		RETVAL_FALSE;

ext/json/json.c

@@ -212,11 +212,8 @@ PHP_FUNCTION(json_encode)
 		}
 	}
 
-	smart_str_0(&buf); /* copy? */
-	if (buf.s) {
-		RETURN_NEW_STR(buf.s);
-	}
-	RETURN_EMPTY_STRING();
+	smart_str_0(&buf);
+	RETURN_STR(smart_str_finalize(&buf));
 }
 /* }}} */
 

ext/mbstring/php_mbregex.c

@@ -1145,12 +1145,10 @@ static void _php_mb_regex_ereg_replace_exec(INTERNAL_FUNCTION_PARAMETERS, OnigOp
 	if (err <= -2) {
 		smart_str_free(&out_buf);
 		RETVAL_FALSE;
-	} else if (out_buf.s) {
-		smart_str_0(&out_buf);
-		RETVAL_STR(out_buf.s);
-	} else {
-		RETVAL_EMPTY_STRING();
 	}
+
+	smart_str_0(&out_buf);
+	RETVAL_STR(smart_str_finalize(&out_buf));
 }
 /* }}} */
 

ext/session/session.c

@@ -1464,7 +1464,7 @@ PHPAPI zend_result php_session_reset_id(void) /* {{{ */
 		smart_str_0(&var);
 		if (sid) {
 			zval_ptr_dtor_str(sid);
-			ZVAL_NEW_STR(sid, var.s);
+			ZVAL_STR(sid, smart_str_finalize(&var));
 		} else {
 			REGISTER_STRINGL_CONSTANT("SID", ZSTR_VAL(var.s), ZSTR_LEN(var.s), 0);
 			smart_str_free(&var);
@@ -2363,7 +2363,7 @@ PHP_FUNCTION(session_create_id)
 		RETURN_FALSE;
 	}
 	smart_str_0(&id);
-	RETVAL_NEW_STR(id.s);
+	RETVAL_STR(smart_str_finalize(&id));
 }
 /* }}} */
 

ext/soap/php_sdl.c

@@ -3262,7 +3262,7 @@ sdlPtr get_sdl(zval *this_ptr, char *uri, zend_long cache_wsdl)
 			smart_str_appends(&proxy,":");
 			smart_str_append_long(&proxy,Z_LVAL_P(proxy_port));
 			smart_str_0(&proxy);
-			ZVAL_NEW_STR(&str_proxy, proxy.s);
+			ZVAL_STR(&str_proxy, smart_str_finalize(&proxy));
 
 			if (!context) {
 				context = php_stream_context_alloc();
@@ -3305,7 +3305,7 @@ sdlPtr get_sdl(zval *this_ptr, char *uri, zend_long cache_wsdl)
 		}
 
 		smart_str_0(&headers);
-		ZVAL_NEW_STR(&str_headers, headers.s);
+		ZVAL_STR(&str_headers, smart_str_finalize(&headers));
 		php_stream_context_set_option(context, "http", "header", &str_headers);
 		zval_ptr_dtor(&str_headers);
 	}

ext/spl/spl_array.c

@@ -1554,7 +1554,7 @@ PHP_METHOD(ArrayObject, serialize)
 	/* done */
 	PHP_VAR_SERIALIZE_DESTROY(var_hash);
 
-	RETURN_NEW_STR(buf.s);
+	RETURN_STR(smart_str_finalize(&buf));
 } /* }}} */
 
 /* {{{ unserialize the object */

ext/spl/spl_dllist.c

@@ -1037,7 +1037,7 @@ PHP_METHOD(SplDoublyLinkedList, serialize)
 	/* done */
 	PHP_VAR_SERIALIZE_DESTROY(var_hash);
 
-	RETURN_NEW_STR(buf.s);
+	RETURN_STR(smart_str_finalize(&buf));
 } /* }}} */
 
 /* {{{ Unserializes storage */

ext/spl/spl_observer.c

@@ -808,7 +808,7 @@ PHP_METHOD(SplObjectStorage, serialize)
 	/* done */
 	PHP_VAR_SERIALIZE_DESTROY(var_hash);
 
-	RETURN_NEW_STR(buf.s);
+	RETURN_STR(smart_str_finalize(&buf));
 } /* }}} */
 
 /* {{{ Unserializes storage */

ext/standard/http.c

@@ -238,12 +238,7 @@ PHP_FUNCTION(http_build_query)
 
 	php_url_encode_hash_ex(HASH_OF(formdata), &formstr, prefix, prefix_len, NULL, 0, NULL, 0, (Z_TYPE_P(formdata) == IS_OBJECT ? formdata : NULL), arg_sep, (int)enc_type);
 
-	if (!formstr.s) {
-		RETURN_EMPTY_STRING();
-	}
-
 	smart_str_0(&formstr);
-
-	RETURN_NEW_STR(formstr.s);
+	RETURN_STR(smart_str_finalize(&formstr));
 }
 /* }}} */

ext/standard/string.c

@@ -2892,7 +2892,7 @@ static void php_strtr_array(zval *return_value, zend_string *input, HashTable *p
 	if (result.s) {
 		smart_str_appendl(&result, str + old_pos, slen - old_pos);
 		smart_str_0(&result);
-		RETVAL_NEW_STR(result.s);
+		RETVAL_STR(smart_str_finalize(&result));
 	} else {
 		smart_str_free(&result);
 		RETVAL_STR_COPY(input);

ext/standard/var.c

@@ -645,7 +645,7 @@ PHP_FUNCTION(var_export)
 	smart_str_0 (&buf);
 
 	if (return_output) {
-		RETURN_NEW_STR(buf.s);
+		RETURN_STR(smart_str_finalize(&buf));
 	} else {
 		PHPWRITE(ZSTR_VAL(buf.s), ZSTR_LEN(buf.s));
 		smart_str_free(&buf);
@@ -1318,11 +1318,7 @@ PHP_FUNCTION(serialize)
 		RETURN_THROWS();
 	}
 
-	if (buf.s) {
-		RETURN_NEW_STR(buf.s);
-	} else {
-		RETURN_EMPTY_STRING();
-	}
+	RETURN_STR(smart_str_finalize(&buf));
 }
 /* }}} */