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pythongh-119182: Use public PyUnicodeWriter API in ga_repr() (python#…
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…120799)

The public PyUnicodeWriter API enables overallocation by default and
so is more efficient.

Benchmark:

python -m pyperf timeit \
    -s 't = list[int, float, complex, str, bytes, bytearray, ' \
                 'memoryview, list, dict]' \
    'str(t)'

Result:

1.49 us +- 0.03 us -> 1.10 us +- 0.02 us: 1.35x faster
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vstinner authored and mrahtz committed Jun 30, 2024
1 parent f8061a7 commit c0cd6da
Showing 1 changed file with 35 additions and 33 deletions.
68 changes: 35 additions & 33 deletions Objects/genericaliasobject.c
Original file line number Diff line number Diff line change
Expand Up @@ -51,16 +51,15 @@ ga_traverse(PyObject *self, visitproc visit, void *arg)
}

static int
ga_repr_item(_PyUnicodeWriter *writer, PyObject *p)
ga_repr_item(PyUnicodeWriter *writer, PyObject *p)
{
PyObject *qualname = NULL;
PyObject *module = NULL;
PyObject *r = NULL;
int rc;

if (p == Py_Ellipsis) {
// The Ellipsis object
r = PyUnicode_FromString("...");
rc = PyUnicodeWriter_WriteUTF8(writer, "...", 3);
goto done;
}

Expand All @@ -71,17 +70,17 @@ ga_repr_item(_PyUnicodeWriter *writer, PyObject *p)
goto use_repr;
}
if (rc < 0) {
goto done;
goto error;
}

if (PyObject_GetOptionalAttr(p, &_Py_ID(__qualname__), &qualname) < 0) {
goto done;
goto error;
}
if (qualname == NULL) {
goto use_repr;
}
if (PyObject_GetOptionalAttr(p, &_Py_ID(__module__), &module) < 0) {
goto done;
goto error;
}
if (module == NULL || module == Py_None) {
goto use_repr;
Expand All @@ -92,45 +91,42 @@ ga_repr_item(_PyUnicodeWriter *writer, PyObject *p)
_PyUnicode_EqualToASCIIString(module, "builtins"))
{
// builtins don't need a module name
r = PyObject_Str(qualname);
rc = PyUnicodeWriter_WriteStr(writer, qualname);
goto done;
}
else {
r = PyUnicode_FromFormat("%S.%S", module, qualname);
rc = PyUnicodeWriter_Format(writer, "%S.%S", module, qualname);
goto done;
}

error:
rc = -1;
goto done;

use_repr:
r = PyObject_Repr(p);
rc = PyUnicodeWriter_WriteRepr(writer, p);
goto done;

done:
Py_XDECREF(qualname);
Py_XDECREF(module);
if (r == NULL) {
// error if any of the above PyObject_Repr/PyUnicode_From* fail
rc = -1;
}
else {
rc = _PyUnicodeWriter_WriteStr(writer, r);
Py_DECREF(r);
}
return rc;
}

static int
ga_repr_items_list(_PyUnicodeWriter *writer, PyObject *p)
ga_repr_items_list(PyUnicodeWriter *writer, PyObject *p)
{
assert(PyList_CheckExact(p));

Py_ssize_t len = PyList_GET_SIZE(p);

if (_PyUnicodeWriter_WriteASCIIString(writer, "[", 1) < 0) {
if (PyUnicodeWriter_WriteChar(writer, '[') < 0) {
return -1;
}

for (Py_ssize_t i = 0; i < len; i++) {
if (i > 0) {
if (_PyUnicodeWriter_WriteASCIIString(writer, ", ", 2) < 0) {
if (PyUnicodeWriter_WriteUTF8(writer, ", ", 2) < 0) {
return -1;
}
}
Expand All @@ -140,7 +136,7 @@ ga_repr_items_list(_PyUnicodeWriter *writer, PyObject *p)
}
}

if (_PyUnicodeWriter_WriteASCIIString(writer, "]", 1) < 0) {
if (PyUnicodeWriter_WriteChar(writer, ']') < 0) {
return -1;
}

Expand All @@ -153,49 +149,55 @@ ga_repr(PyObject *self)
gaobject *alias = (gaobject *)self;
Py_ssize_t len = PyTuple_GET_SIZE(alias->args);

_PyUnicodeWriter writer;
_PyUnicodeWriter_Init(&writer);
// Estimation based on the shortest format: "int[int, int, int]"
Py_ssize_t estimate = (len <= PY_SSIZE_T_MAX / 5) ? len * 5 : len;
estimate = 3 + 1 + estimate + 1;
PyUnicodeWriter *writer = PyUnicodeWriter_Create(estimate);
if (writer == NULL) {
return NULL;
}

if (alias->starred) {
if (_PyUnicodeWriter_WriteASCIIString(&writer, "*", 1) < 0) {
if (PyUnicodeWriter_WriteChar(writer, '*') < 0) {
goto error;
}
}
if (ga_repr_item(&writer, alias->origin) < 0) {
if (ga_repr_item(writer, alias->origin) < 0) {
goto error;
}
if (_PyUnicodeWriter_WriteASCIIString(&writer, "[", 1) < 0) {
if (PyUnicodeWriter_WriteChar(writer, '[') < 0) {
goto error;
}
for (Py_ssize_t i = 0; i < len; i++) {
if (i > 0) {
if (_PyUnicodeWriter_WriteASCIIString(&writer, ", ", 2) < 0) {
if (PyUnicodeWriter_WriteUTF8(writer, ", ", 2) < 0) {
goto error;
}
}
PyObject *p = PyTuple_GET_ITEM(alias->args, i);
if (PyList_CheckExact(p)) {
// Looks like we are working with ParamSpec's list of type args:
if (ga_repr_items_list(&writer, p) < 0) {
if (ga_repr_items_list(writer, p) < 0) {
goto error;
}
}
else if (ga_repr_item(&writer, p) < 0) {
else if (ga_repr_item(writer, p) < 0) {
goto error;
}
}
if (len == 0) {
// for something like tuple[()] we should print a "()"
if (_PyUnicodeWriter_WriteASCIIString(&writer, "()", 2) < 0) {
if (PyUnicodeWriter_WriteUTF8(writer, "()", 2) < 0) {
goto error;
}
}
if (_PyUnicodeWriter_WriteASCIIString(&writer, "]", 1) < 0) {
if (PyUnicodeWriter_WriteChar(writer, ']') < 0) {
goto error;
}
return _PyUnicodeWriter_Finish(&writer);
return PyUnicodeWriter_Finish(writer);

error:
_PyUnicodeWriter_Dealloc(&writer);
PyUnicodeWriter_Discard(writer);
return NULL;
}

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