Issue #16147: Rewrite PyUnicode_FromFormatV() to use _PyUnicodeWriter API
* Simplify the code: replace 4 steps with one unique step using the
_PyUnicodeWriter API. PyUnicode_Format() has the same design. It avoids to
store intermediate results which require to allocate an array of pointers on
the heap.
* Use the _PyUnicodeWriter API for speed (and its convinient API):
overallocate the buffer to reduce the number of "realloc()"
* Implement "width" and "precision" in Python, don't rely on sprintf(). It
avoids to need of a temporary buffer allocated on the heap: only use a small
buffer allocated in the stack.
* Add _PyUnicodeWriter_WriteCstr() function
* Split PyUnicode_FromFormatV() into two functions: add
unicode_fromformat_arg().
* Inline parse_format_flags(): the format of an argument is now only parsed
once, it's no more needed to have a subfunction.
* Optimize PyUnicode_FromFormatV() for characters between two "%" arguments:
search the next "%" and copy the substring in one chunk, instead of copying
character per character.
diff --git a/Include/unicodeobject.h b/Include/unicodeobject.h
index 4152dd7..fa21c1c 100644
--- a/Include/unicodeobject.h
+++ b/Include/unicodeobject.h
@@ -933,12 +933,28 @@
_PyUnicodeWriter_PrepareInternal(_PyUnicodeWriter *writer,
Py_ssize_t length, Py_UCS4 maxchar);
+/* Append a Unicode string.
+ Return 0 on success, raise an exception and return -1 on error. */
PyAPI_FUNC(int)
-_PyUnicodeWriter_WriteStr(_PyUnicodeWriter *writer, PyObject *str);
+_PyUnicodeWriter_WriteStr(_PyUnicodeWriter *writer,
+ PyObject *str /* Unicode string */
+ );
+/* Append a latin1-encoded byte string.
+ Return 0 on success, raise an exception and return -1 on error. */
+PyAPI_FUNC(int)
+_PyUnicodeWriter_WriteCstr(_PyUnicodeWriter *writer,
+ const char *str, /* latin1-encoded byte string */
+ Py_ssize_t len /* length in bytes */
+ );
+
+/* Get the value of the write as an Unicode string. Clear the
+ buffer of the writer. Raise an exception and return NULL
+ on error. */
PyAPI_FUNC(PyObject *)
_PyUnicodeWriter_Finish(_PyUnicodeWriter *writer);
+/* Deallocate memory of a writer (clear its internal buffer). */
PyAPI_FUNC(void)
_PyUnicodeWriter_Dealloc(_PyUnicodeWriter *writer);
#endif