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gh-95382: Use cache for indentations in the JSON encoder #118636

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Merged
merged 8 commits into from
Nov 12, 2024
Merged

gh-95382: Use cache for indentations in the JSON encoder #118636

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2e915fd
gh-95382: Use cache for indentations in the JSON encoder
serhiy-storchaka May 6, 2024
2a7b274
Apply suggestions from code review
serhiy-storchaka May 6, 2024
86c7797
Merge branch 'main' into json-encode-indent-cache
serhiy-storchaka May 6, 2024
a108c34
Merge branch 'main' into json-encode-indent-cache
serhiy-storchaka May 7, 2024
86586a5
Refactoring.
serhiy-storchaka May 7, 2024
5778e86
Merge branch 'main' into json-encode-indent-cache
serhiy-storchaka Jun 29, 2024
21681c5
Merge branch 'main' into json-encode-indent-cache
serhiy-storchaka Sep 28, 2024
0f835d9
Merge branch 'main' into json-encode-indent-cache
serhiy-storchaka Nov 12, 2024
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182 changes: 118 additions & 64 deletions Modules/_json.c
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Original file line number Diff line number Diff line change
Expand Up @@ -86,11 +86,11 @@ encoder_dealloc(PyObject *self);
static int
encoder_clear(PyEncoderObject *self);
static int
encoder_listencode_list(PyEncoderObject *s, PyUnicodeWriter *writer, PyObject *seq, PyObject *newline_indent);
encoder_listencode_list(PyEncoderObject *s, PyUnicodeWriter *writer, PyObject *seq, Py_ssize_t indent_level, PyObject *indent_cache);
static int
encoder_listencode_obj(PyEncoderObject *s, PyUnicodeWriter *writer, PyObject *obj, PyObject *newline_indent);
encoder_listencode_obj(PyEncoderObject *s, PyUnicodeWriter *writer, PyObject *obj, Py_ssize_t indent_level, PyObject *indent_cache);
static int
encoder_listencode_dict(PyEncoderObject *s, PyUnicodeWriter *writer, PyObject *dct, PyObject *newline_indent);
encoder_listencode_dict(PyEncoderObject *s, PyUnicodeWriter *writer, PyObject *dct, Py_ssize_t indent_level, PyObject *indent_cache);
static PyObject *
_encoded_const(PyObject *obj);
static void
Expand Down Expand Up @@ -1252,17 +1252,92 @@ encoder_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
return (PyObject *)s;
}


/* indent_cache is a list that contains intermixed values at even and odd
* positions:
*
* 2*k : '\n' + indent * (k + initial_indent_level)
* strings written after opening and before closing brackets
* 2*k-1 : item_separator + '\n' + indent * (k + initial_indent_level)
* strings written between items
*
* Its size is always an odd number.
*/
static PyObject *
_create_newline_indent(PyObject *indent, Py_ssize_t indent_level)
create_indent_cache(PyEncoderObject *s, Py_ssize_t indent_level)
{
PyObject *newline_indent = PyUnicode_FromOrdinal('\n');
if (newline_indent != NULL && indent_level) {
PyUnicode_AppendAndDel(&newline_indent,
PySequence_Repeat(indent, indent_level));
PySequence_Repeat(s->indent, indent_level));
}
if (newline_indent == NULL) {
return NULL;
}
PyObject *indent_cache = PyList_New(1);
if (indent_cache == NULL) {
Py_DECREF(newline_indent);
return NULL;
}
return newline_indent;
PyList_SET_ITEM(indent_cache, 0, newline_indent);
return indent_cache;
}

/* Extend indent_cache by adding values for the next level.
* It should have values for the indent_level-1 level before the call.
*/
static int
update_indent_cache(PyEncoderObject *s,
Py_ssize_t indent_level, PyObject *indent_cache)
{
assert(indent_level * 2 == PyList_GET_SIZE(indent_cache) + 1);
assert(indent_level > 0);
PyObject *newline_indent = PyList_GET_ITEM(indent_cache, (indent_level - 1)*2);
newline_indent = PyUnicode_Concat(newline_indent, s->indent);
if (newline_indent == NULL) {
return -1;
}
PyObject *separator_indent = PyUnicode_Concat(s->item_separator, newline_indent);
if (separator_indent == NULL) {
Py_DECREF(newline_indent);
return -1;
}

if (PyList_Append(indent_cache, separator_indent) < 0 ||
PyList_Append(indent_cache, newline_indent) < 0)
{
Py_DECREF(separator_indent);
Py_DECREF(newline_indent);
return -1;
}
Py_DECREF(separator_indent);
Py_DECREF(newline_indent);
return 0;
}

static PyObject *
get_item_separator(PyEncoderObject *s,
Py_ssize_t indent_level, PyObject *indent_cache)
{
assert(indent_level > 0);
if (indent_level * 2 > PyList_GET_SIZE(indent_cache)) {
if (update_indent_cache(s, indent_level, indent_cache) < 0) {
return NULL;
}
}
assert(indent_level * 2 < PyList_GET_SIZE(indent_cache));
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Suggested change
assert(indent_level * 2 < PyList_GET_SIZE(indent_cache));
assert(indent_level * 2 - 1 < PyList_GET_SIZE(indent_cache));

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indent_level * 2 < PyList_GET_SIZE(indent_cache) is more strong condition.

return PyList_GET_ITEM(indent_cache, indent_level * 2 - 1);
}

static int
write_newline_indent(PyUnicodeWriter *writer,
Py_ssize_t indent_level, PyObject *indent_cache)
{
PyObject *newline_indent = PyList_GET_ITEM(indent_cache, indent_level * 2);
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Suggested change
PyObject *newline_indent = PyList_GET_ITEM(indent_cache, indent_level * 2);
assert(indent_level * 2 < PyList_GET_SIZE(indent_cache));
PyObject *newline_indent = PyList_GET_ITEM(indent_cache, indent_level * 2);

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The assert above is placed after conditional resizing the cache. It is useful to check that we always get the right cache size, independently from conditions. But here we do not change the cache.

return PyUnicodeWriter_WriteStr(writer, newline_indent);
}


static PyObject *
encoder_call(PyEncoderObject *self, PyObject *args, PyObject *kwds)
{
Expand All @@ -1280,20 +1355,20 @@ encoder_call(PyEncoderObject *self, PyObject *args, PyObject *kwds)
return NULL;
}

PyObject *newline_indent = NULL;
PyObject *indent_cache = NULL;
if (self->indent != Py_None) {
newline_indent = _create_newline_indent(self->indent, indent_level);
if (newline_indent == NULL) {
indent_cache = create_indent_cache(self, indent_level);
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When called via the public interface indent_level is always zero. By removing the argument indent_level in the internal implementation this call and some other bits of the code can be a bit simplified.

(this is probably not worth creating a separate PR for, I leave it up to you)

if (indent_cache == NULL) {
PyUnicodeWriter_Discard(writer);
return NULL;
}
}
if (encoder_listencode_obj(self, writer, obj, newline_indent)) {
if (encoder_listencode_obj(self, writer, obj, indent_level, indent_cache)) {
PyUnicodeWriter_Discard(writer);
Py_XDECREF(newline_indent);
Py_XDECREF(indent_cache);
return NULL;
}
Py_XDECREF(newline_indent);
Py_XDECREF(indent_cache);

PyObject *str = PyUnicodeWriter_Finish(writer);
if (str == NULL) {
Expand Down Expand Up @@ -1381,7 +1456,8 @@ _steal_accumulate(PyUnicodeWriter *writer, PyObject *stolen)

static int
encoder_listencode_obj(PyEncoderObject *s, PyUnicodeWriter *writer,
PyObject *obj, PyObject *newline_indent)
PyObject *obj,
Py_ssize_t indent_level, PyObject *indent_cache)
{
/* Encode Python object obj to a JSON term */
PyObject *newobj;
Expand Down Expand Up @@ -1421,14 +1497,14 @@ encoder_listencode_obj(PyEncoderObject *s, PyUnicodeWriter *writer,
else if (PyList_Check(obj) || PyTuple_Check(obj)) {
if (_Py_EnterRecursiveCall(" while encoding a JSON object"))
return -1;
rv = encoder_listencode_list(s, writer, obj, newline_indent);
rv = encoder_listencode_list(s, writer, obj, indent_level, indent_cache);
_Py_LeaveRecursiveCall();
return rv;
}
else if (PyDict_Check(obj)) {
if (_Py_EnterRecursiveCall(" while encoding a JSON object"))
return -1;
rv = encoder_listencode_dict(s, writer, obj, newline_indent);
rv = encoder_listencode_dict(s, writer, obj, indent_level, indent_cache);
_Py_LeaveRecursiveCall();
return rv;
}
Expand Down Expand Up @@ -1462,7 +1538,7 @@ encoder_listencode_obj(PyEncoderObject *s, PyUnicodeWriter *writer,
Py_XDECREF(ident);
return -1;
}
rv = encoder_listencode_obj(s, writer, newobj, newline_indent);
rv = encoder_listencode_obj(s, writer, newobj, indent_level, indent_cache);
_Py_LeaveRecursiveCall();

Py_DECREF(newobj);
Expand All @@ -1485,7 +1561,7 @@ encoder_listencode_obj(PyEncoderObject *s, PyUnicodeWriter *writer,
static int
encoder_encode_key_value(PyEncoderObject *s, PyUnicodeWriter *writer, bool *first,
PyObject *dct, PyObject *key, PyObject *value,
PyObject *newline_indent,
Py_ssize_t indent_level, PyObject *indent_cache,
PyObject *item_separator)
{
PyObject *keystr = NULL;
Expand Down Expand Up @@ -1541,7 +1617,7 @@ encoder_encode_key_value(PyEncoderObject *s, PyUnicodeWriter *writer, bool *firs
if (PyUnicodeWriter_WriteStr(writer, s->key_separator) < 0) {
return -1;
}
if (encoder_listencode_obj(s, writer, value, newline_indent) < 0) {
if (encoder_listencode_obj(s, writer, value, indent_level, indent_cache) < 0) {
_PyErr_FormatNote("when serializing %T item %R", dct, key);
return -1;
}
Expand All @@ -1550,15 +1626,14 @@ encoder_encode_key_value(PyEncoderObject *s, PyUnicodeWriter *writer, bool *firs

static int
encoder_listencode_dict(PyEncoderObject *s, PyUnicodeWriter *writer,
PyObject *dct, PyObject *newline_indent)
PyObject *dct,
Py_ssize_t indent_level, PyObject *indent_cache)
{
/* Encode Python dict dct a JSON term */
PyObject *ident = NULL;
PyObject *items = NULL;
PyObject *key, *value;
bool first = true;
PyObject *new_newline_indent = NULL;
PyObject *separator_indent = NULL;

if (PyDict_GET_SIZE(dct) == 0) {
/* Fast path */
Expand All @@ -1585,19 +1660,13 @@ encoder_listencode_dict(PyEncoderObject *s, PyUnicodeWriter *writer,
goto bail;
}

PyObject *current_item_separator = s->item_separator; // borrowed reference
PyObject *separator = s->item_separator; // borrowed reference
if (s->indent != Py_None) {
new_newline_indent = PyUnicode_Concat(newline_indent, s->indent);
if (new_newline_indent == NULL) {
goto bail;
}
separator_indent = PyUnicode_Concat(current_item_separator, new_newline_indent);
if (separator_indent == NULL) {
goto bail;
}
// update item separator with a borrowed reference
current_item_separator = separator_indent;
if (PyUnicodeWriter_WriteStr(writer, new_newline_indent) < 0) {
indent_level++;
separator = get_item_separator(s, indent_level, indent_cache);
if (separator == NULL ||
write_newline_indent(writer, indent_level, indent_cache) < 0)
{
goto bail;
}
}
Expand All @@ -1618,8 +1687,8 @@ encoder_listencode_dict(PyEncoderObject *s, PyUnicodeWriter *writer,
key = PyTuple_GET_ITEM(item, 0);
value = PyTuple_GET_ITEM(item, 1);
if (encoder_encode_key_value(s, writer, &first, dct, key, value,
new_newline_indent,
current_item_separator) < 0)
indent_level, indent_cache,
separator) < 0)
goto bail;
}
Py_CLEAR(items);
Expand All @@ -1628,8 +1697,8 @@ encoder_listencode_dict(PyEncoderObject *s, PyUnicodeWriter *writer,
Py_ssize_t pos = 0;
while (PyDict_Next(dct, &pos, &key, &value)) {
if (encoder_encode_key_value(s, writer, &first, dct, key, value,
new_newline_indent,
current_item_separator) < 0)
indent_level, indent_cache,
separator) < 0)
goto bail;
}
}
Expand All @@ -1640,10 +1709,8 @@ encoder_listencode_dict(PyEncoderObject *s, PyUnicodeWriter *writer,
Py_CLEAR(ident);
}
if (s->indent != Py_None) {
Py_CLEAR(new_newline_indent);
Py_CLEAR(separator_indent);

if (PyUnicodeWriter_WriteStr(writer, newline_indent) < 0) {
indent_level--;
if (write_newline_indent(writer, indent_level, indent_cache) < 0) {
goto bail;
}
}
Expand All @@ -1656,20 +1723,17 @@ encoder_listencode_dict(PyEncoderObject *s, PyUnicodeWriter *writer,
bail:
Py_XDECREF(items);
Py_XDECREF(ident);
Py_XDECREF(separator_indent);
Py_XDECREF(new_newline_indent);
return -1;
}

static int
encoder_listencode_list(PyEncoderObject *s, PyUnicodeWriter *writer,
PyObject *seq, PyObject *newline_indent)
PyObject *seq,
Py_ssize_t indent_level, PyObject *indent_cache)
{
PyObject *ident = NULL;
PyObject *s_fast = NULL;
Py_ssize_t i;
PyObject *new_newline_indent = NULL;
PyObject *separator_indent = NULL;

ident = NULL;
s_fast = PySequence_Fast(seq, "_iterencode_list needs a sequence");
Expand Down Expand Up @@ -1702,28 +1766,21 @@ encoder_listencode_list(PyEncoderObject *s, PyUnicodeWriter *writer,

PyObject *separator = s->item_separator; // borrowed reference
if (s->indent != Py_None) {
new_newline_indent = PyUnicode_Concat(newline_indent, s->indent);
if (new_newline_indent == NULL) {
goto bail;
}

if (PyUnicodeWriter_WriteStr(writer, new_newline_indent) < 0) {
goto bail;
}

separator_indent = PyUnicode_Concat(separator, new_newline_indent);
if (separator_indent == NULL) {
indent_level++;
separator = get_item_separator(s, indent_level, indent_cache);
if (separator == NULL ||
write_newline_indent(writer, indent_level, indent_cache) < 0)
{
goto bail;
}
separator = separator_indent; // assign separator with borrowed reference
}
for (i = 0; i < PySequence_Fast_GET_SIZE(s_fast); i++) {
PyObject *obj = PySequence_Fast_GET_ITEM(s_fast, i);
if (i) {
if (PyUnicodeWriter_WriteStr(writer, separator) < 0)
goto bail;
}
if (encoder_listencode_obj(s, writer, obj, new_newline_indent)) {
if (encoder_listencode_obj(s, writer, obj, indent_level, indent_cache)) {
_PyErr_FormatNote("when serializing %T item %zd", seq, i);
goto bail;
}
Expand All @@ -1735,9 +1792,8 @@ encoder_listencode_list(PyEncoderObject *s, PyUnicodeWriter *writer,
}

if (s->indent != Py_None) {
Py_CLEAR(new_newline_indent);
Py_CLEAR(separator_indent);
if (PyUnicodeWriter_WriteStr(writer, newline_indent) < 0) {
indent_level--;
if (write_newline_indent(writer, indent_level, indent_cache) < 0) {
goto bail;
}
}
Expand All @@ -1751,8 +1807,6 @@ encoder_listencode_list(PyEncoderObject *s, PyUnicodeWriter *writer,
bail:
Py_XDECREF(ident);
Py_DECREF(s_fast);
Py_XDECREF(separator_indent);
Py_XDECREF(new_newline_indent);
return -1;
}

Expand Down
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