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bpo-37348: optimize decoding ASCII string #14291

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bpo-37348: optimize decoding ASCII string #14291

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46 changes: 35 additions & 11 deletions Objects/unicodeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -265,6 +265,9 @@ unicode_fill(enum PyUnicode_Kind kind, void *data, Py_UCS4 value,
/* Forward declaration */
static inline int
_PyUnicodeWriter_WriteCharInline(_PyUnicodeWriter *writer, Py_UCS4 ch);
static inline int
_PyUnicodeWriter_InitPrepare(_PyUnicodeWriter *writer,
Py_ssize_t length, Py_UCS4 maxchar);
static PyObject *
unicode_encode_utf8(PyObject *unicode, _Py_error_handler error_handler,
const char *errors);
Expand Down Expand Up @@ -4900,10 +4903,9 @@ unicode_decode_utf8(const char *s, Py_ssize_t size,
return get_latin1_char((unsigned char)s[0]);
}

_PyUnicodeWriter_Init(&writer);
writer.min_length = size;
if (_PyUnicodeWriter_Prepare(&writer, writer.min_length, 127) == -1)
if (_PyUnicodeWriter_InitPrepare(&writer, size, 127) == -1) {
goto onError;
}

writer.pos = ascii_decode(s, end, writer.data);
s += writer.pos;
Expand Down Expand Up @@ -6993,10 +6995,9 @@ PyUnicode_DecodeASCII(const char *s,
if (size == 1 && (unsigned char)s[0] < 128)
return get_latin1_char((unsigned char)s[0]);

_PyUnicodeWriter_Init(&writer);
writer.min_length = size;
if (_PyUnicodeWriter_Prepare(&writer, writer.min_length, 127) < 0)
if (_PyUnicodeWriter_InitPrepare(&writer, size, 127) < 0) {
return NULL;
}

e = s + size;
data = writer.data;
Expand Down Expand Up @@ -8056,9 +8057,7 @@ PyUnicode_DecodeCharmap(const char *s,

if (size == 0)
_Py_RETURN_UNICODE_EMPTY();
_PyUnicodeWriter_Init(&writer);
writer.min_length = size;
if (_PyUnicodeWriter_Prepare(&writer, writer.min_length, 127) == -1)
if (_PyUnicodeWriter_InitPrepare(&writer, size, 127) == -1)
goto onError;

if (PyUnicode_CheckExact(mapping)) {
Expand Down Expand Up @@ -8979,8 +8978,7 @@ _PyUnicode_TranslateCharmap(PyObject *input,

/* allocate enough for a simple 1:1 translation without
replacements, if we need more, we'll resize */
_PyUnicodeWriter_Init(&writer);
if (_PyUnicodeWriter_Prepare(&writer, size, 127) == -1)
if (_PyUnicodeWriter_InitPrepare(&writer, size, 127) == -1)
goto onError;

ignore = (errors != NULL && strcmp(errors, "ignore") == 0);
Expand Down Expand Up @@ -13506,6 +13504,32 @@ _PyUnicodeWriter_Init(_PyUnicodeWriter *writer)
assert(writer->kind <= PyUnicode_1BYTE_KIND);
}

static inline int
_PyUnicodeWriter_InitPrepare(_PyUnicodeWriter *writer,
Py_ssize_t length, Py_UCS4 maxchar)
{
assert(maxchar <= MAX_UNICODE);
maxchar = Py_MAX(maxchar, 127);

memset(writer, 0, sizeof(*writer));
writer->min_length = length;

writer->buffer = PyUnicode_New(length, maxchar);
if (writer->buffer == NULL) {
return -1;
}
_PyUnicodeWriter_Update(writer);
return 0;
}

/* Initialize and prepare the writer.
*
* This is same to following code, but faster:
*
* _PyUnicodeWriter_Init(&writer);
* writer.min_length = size;
* _PyUnicodeWriter_Prepare(&writer, size, maxchar);
*/
int
_PyUnicodeWriter_PrepareInternal(_PyUnicodeWriter *writer,
Py_ssize_t length, Py_UCS4 maxchar)
Expand Down