Add _PyUnicodeWriter_WriteSubstring() function

Write a function to enable more optimizations:

 * If the substring is the whole string and overallocation is disabled, just
   keep a reference to the string, don't copy characters
 * Avoid a call to the expensive _PyUnicode_FindMaxChar() function when
   possible

1 files changed, 9 insertions, 0 deletions

diff --git a/Include/unicodeobject.h b/Include/unicodeobject.h
index a70585c..0917307 100644
--- a/Include/unicodeobject.h
+++ b/Include/unicodeobject.h
@@ -940,6 +940,15 @@ _PyUnicodeWriter_WriteStr(_PyUnicodeWriter *writer,
     PyObject *str               /* Unicode string */
     );
 
+/* Append a substring of a Unicode string.
+   Return 0 on success, raise an exception and return -1 on error. */
+PyAPI_FUNC(int)
+_PyUnicodeWriter_WriteSubstring(_PyUnicodeWriter *writer,
+    PyObject *str,              /* Unicode string */
+    Py_ssize_t start,
+    Py_ssize_t end
+    );
+
 /* Append a latin1-encoded byte string.
    Return 0 on success, raise an exception and return -1 on error. */
 PyAPI_FUNC(int)