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Issue #16147: Rewrite PyUnicode_FromFormatV() to use _PyUnicodeWriter API

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* 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.
This commit is contained in:
Victor Stinner 2012-10-06 23:03:36 +02:00
parent 2a09b6e849
commit e215d960be
3 changed files with 380 additions and 500 deletions
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18
Include/unicodeobject.h
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@ -933,12 +933,28 @@ PyAPI_FUNC(int)
_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