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gh-95385 Fastpath for encoding dict to JSON (gh-95374)
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@aivarsk
aivarsk authored Aug 6, 2022
1 parent 56d16e8 commit 15f4a35
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2022-07-28-17-14-38.gh-issue-95385.6YlsDI.rst
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@@ -0,0 +1 @@
Faster ``json.dumps()`` when sorting of keys is not requested (default).
166 changes: 88 additions & 78 deletions Modules/_json.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
#include "Python.h"
#include "pycore_ceval.h" // _Py_EnterRecursiveCall()
#include "structmember.h" // PyMemberDef
#include <stdbool.h> // bool


typedef struct _PyScannerObject {
Expand Down Expand Up @@ -1491,17 +1492,79 @@ encoder_listencode_obj(PyEncoderObject *s, _PyUnicodeWriter *writer,
}
}

static int
encoder_encode_key_value(PyEncoderObject *s, _PyUnicodeWriter *writer, bool *first,
PyObject *key, PyObject *value, Py_ssize_t indent_level)
{
PyObject *keystr = NULL;
PyObject *encoded;

if (PyUnicode_Check(key)) {
Py_INCREF(key);
keystr = key;
}
else if (PyFloat_Check(key)) {
keystr = encoder_encode_float(s, key);
}
else if (key == Py_True || key == Py_False || key == Py_None) {
/* This must come before the PyLong_Check because
True and False are also 1 and 0.*/
keystr = _encoded_const(key);
}
else if (PyLong_Check(key)) {
keystr = PyLong_Type.tp_repr(key);
}
else if (s->skipkeys) {
return 0;
}
else {
PyErr_Format(PyExc_TypeError,
"keys must be str, int, float, bool or None, "
"not %.100s", Py_TYPE(key)->tp_name);
return -1;
}

if (keystr == NULL) {
return -1;
}

if (*first) {
*first = false;
}
else {
if (_PyUnicodeWriter_WriteStr(writer, s->item_separator) < 0) {
Py_DECREF(keystr);
return -1;
}
}

encoded = encoder_encode_string(s, keystr);
Py_DECREF(keystr);
if (encoded == NULL) {
return -1;
}

if (_steal_accumulate(writer, encoded) < 0) {
return -1;
}
if (_PyUnicodeWriter_WriteStr(writer, s->key_separator) < 0) {
return -1;
}
if (encoder_listencode_obj(s, writer, value, indent_level) < 0) {
return -1;
}
return 0;
}

static int
encoder_listencode_dict(PyEncoderObject *s, _PyUnicodeWriter *writer,
PyObject *dct, Py_ssize_t indent_level)
{
/* Encode Python dict dct a JSON term */
PyObject *kstr = NULL;
PyObject *ident = NULL;
PyObject *it = NULL;
PyObject *items;
PyObject *item = NULL;
Py_ssize_t idx;
PyObject *items = NULL;
PyObject *key, *value;
bool first = true;

if (PyDict_GET_SIZE(dct) == 0) /* Fast path */
return _PyUnicodeWriter_WriteASCIIString(writer, "{}", 2);
Expand Down Expand Up @@ -1535,84 +1598,34 @@ encoder_listencode_dict(PyEncoderObject *s, _PyUnicodeWriter *writer,
*/
}

items = PyMapping_Items(dct);
if (items == NULL)
goto bail;
if (s->sort_keys && PyList_Sort(items) < 0) {
Py_DECREF(items);
goto bail;
}
it = PyObject_GetIter(items);
Py_DECREF(items);
if (it == NULL)
goto bail;
idx = 0;
while ((item = PyIter_Next(it)) != NULL) {
PyObject *encoded, *key, *value;
if (!PyTuple_Check(item) || PyTuple_GET_SIZE(item) != 2) {
PyErr_SetString(PyExc_ValueError, "items must return 2-tuples");
if (s->sort_keys) {

items = PyDict_Items(dct);
if (items == NULL || PyList_Sort(items) < 0)
goto bail;
}
key = PyTuple_GET_ITEM(item, 0);
if (PyUnicode_Check(key)) {
Py_INCREF(key);
kstr = key;
}
else if (PyFloat_Check(key)) {
kstr = encoder_encode_float(s, key);
if (kstr == NULL)
goto bail;
}
else if (key == Py_True || key == Py_False || key == Py_None) {
/* This must come before the PyLong_Check because
True and False are also 1 and 0.*/
kstr = _encoded_const(key);
if (kstr == NULL)
goto bail;
}
else if (PyLong_Check(key)) {
kstr = PyLong_Type.tp_repr(key);
if (kstr == NULL) {

for (Py_ssize_t i = 0; i < PyList_GET_SIZE(items); i++) {
PyObject *item = PyList_GET_ITEM(items, i);

if (!PyTuple_Check(item) || PyTuple_GET_SIZE(item) != 2) {
PyErr_SetString(PyExc_ValueError, "items must return 2-tuples");
goto bail;
}
}
else if (s->skipkeys) {
Py_DECREF(item);
continue;
}
else {
PyErr_Format(PyExc_TypeError,
"keys must be str, int, float, bool or None, "
"not %.100s", Py_TYPE(key)->tp_name);
goto bail;
}

if (idx) {
if (_PyUnicodeWriter_WriteStr(writer, s->item_separator))
key = PyTuple_GET_ITEM(item, 0);
value = PyTuple_GET_ITEM(item, 1);
if (encoder_encode_key_value(s, writer, &first, key, value, indent_level) < 0)
goto bail;
}
Py_CLEAR(items);

encoded = encoder_encode_string(s, kstr);
Py_CLEAR(kstr);
if (encoded == NULL)
goto bail;
if (_PyUnicodeWriter_WriteStr(writer, encoded)) {
Py_DECREF(encoded);
goto bail;
} else {
Py_ssize_t pos = 0;
while (PyDict_Next(dct, &pos, &key, &value)) {
if (encoder_encode_key_value(s, writer, &first, key, value, indent_level) < 0)
goto bail;
}
Py_DECREF(encoded);
if (_PyUnicodeWriter_WriteStr(writer, s->key_separator))
goto bail;

value = PyTuple_GET_ITEM(item, 1);
if (encoder_listencode_obj(s, writer, value, indent_level))
goto bail;
idx += 1;
Py_DECREF(item);
}
if (PyErr_Occurred())
goto bail;
Py_CLEAR(it);

if (ident != NULL) {
if (PyDict_DelItem(s->markers, ident))
Expand All @@ -1630,14 +1643,11 @@ encoder_listencode_dict(PyEncoderObject *s, _PyUnicodeWriter *writer,
return 0;

bail:
Py_XDECREF(it);
Py_XDECREF(item);
Py_XDECREF(kstr);
Py_XDECREF(items);
Py_XDECREF(ident);
return -1;
}


static int
encoder_listencode_list(PyEncoderObject *s, _PyUnicodeWriter *writer,
PyObject *seq, Py_ssize_t indent_level)
Expand Down

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