Issue #14744: Use the new _PyUnicodeWriter internal API to speed up str%args and str.format(args)

 * Formatting string, int, float and complex use the _PyUnicodeWriter API. It
   avoids a temporary buffer in most cases.
 * Add _PyUnicodeWriter_WriteStr() to restore the PyAccu optimization: just
   keep a reference to the string if the output is only composed of one string
 * Disable overallocation when formatting the last argument of str%args and
   str.format(args)
 * Overallocation allocates at least 100 characters: add min_length attribute
   to the _PyUnicodeWriter structure
 * Add new private functions: _PyUnicode_FastCopyCharacters(),
   _PyUnicode_FastFill() and _PyUnicode_FromASCII()

The speed up is around 20% in average.

1 files changed, 6 insertions, 4 deletions

diff --git a/Include/floatobject.h b/Include/floatobject.h
index 0ca4881a32..46ef6e6062 100644
--- a/Include/floatobject.h
+++ b/Include/floatobject.h
@@ -112,10 +112,12 @@ PyAPI_FUNC(int) PyFloat_ClearFreeList(void);
 
 /* Format the object based on the format_spec, as defined in PEP 3101
    (Advanced String Formatting). */
-PyAPI_FUNC(PyObject *) _PyFloat_FormatAdvanced(PyObject *obj,
-                                               PyObject *format_spec,
-                                               Py_ssize_t start,
-                                               Py_ssize_t end);
+PyAPI_FUNC(int) _PyFloat_FormatAdvancedWriter(
+    _PyUnicodeWriter *writer,
+    PyObject *obj,
+    PyObject *format_spec,
+    Py_ssize_t start,
+    Py_ssize_t end);
 #endif /* Py_LIMITED_API */
 
 #ifdef __cplusplus