[EN-1980] exchange code correction in order events

Author: iamishalkin

dxfeed/core/listeners/listener.pyx

@@ -243,7 +243,7 @@ cdef void order_default_listener(int event_type,
                                    count=order[i].count,
                                    scope=order[i].scope,
                                    side=order[i].side,
-                                   exchange_code=unicode_from_dxf_const_string_t(&order[i].exchange_code),
+                                   exchange_code=unicode_from_dxf_const_string_t(&order[i].exchange_code, size=1),
                                    source=unicode_from_dxf_const_string_t(&order[i].source[0]),
                                    market_maker=unicode_from_dxf_const_string_t(order[i].market_maker),
                                    spread_symbol=unicode_from_dxf_const_string_t(order[i].spread_symbol))

dxfeed/core/utils/helpers.pxd

@@ -5,6 +5,6 @@ cdef extern from *:
     PyObject * PyUnicode_FromWideChar(dxf_const_string_t w, Py_ssize_t size)
     dxf_const_string_t PyUnicode_AsWideCharString(object, Py_ssize_t *)
 
-cdef object unicode_from_dxf_const_string_t(dxf_const_string_t wcs)
+cdef object unicode_from_dxf_const_string_t(dxf_const_string_t wcs, int size=*)
 
 cdef dxf_const_string_t dxf_const_string_t_from_unicode(object symbol)

dxfeed/core/utils/helpers.pyx

@@ -5,14 +5,16 @@ from dxfeed.core.pxd_include.DXTypes cimport *
 from pathlib import Path
 import dxfeed
 
-cdef object unicode_from_dxf_const_string_t(dxf_const_string_t wcs):
+cdef object unicode_from_dxf_const_string_t(dxf_const_string_t wcs, int size=-1):
     """
     Cython function, callable from C to convert dxf_const_string_t(wchar_t) to unicode
     
     Parameters
     ----------
     wcs: dxf_const_string_t, wchar_t
         C string
+    size: int
+        Number of characters. By default -1
         
     Returns
     -------
@@ -21,7 +23,7 @@ cdef object unicode_from_dxf_const_string_t(dxf_const_string_t wcs):
     """
     if wcs == NULL:
       return ''
-    ret_val = <object>PyUnicode_FromWideChar(wcs, -1)
+    ret_val = <object>PyUnicode_FromWideChar(wcs, size)
     return ret_val
 
 cdef dxf_const_string_t dxf_const_string_t_from_unicode(object symbol):