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Turn rapidjson.Decoder into heap type #227

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Turn rapidjson.Decoder into heap type #227

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123 changes: 78 additions & 45 deletions rapidjson.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@

#include <algorithm>
#include <cmath>
#include <memory>
#include <string>
#include <vector>

Expand All @@ -28,6 +29,53 @@
using namespace rapidjson;


#if PY_VERSION_HEX < 0x030A0000
// Fallback for Py_TPFLAGS_IMMUTABLETYPE which is added in 3.10
#define Py_TPFLAGS_IMMUTABLETYPE 0
#endif


static uint32_t
py_version_hex() noexcept {
#if PY_VERSION_HEX < 0x030B0000
static const uint32_t once_fetched_ver = [] {
constexpr uint32_t ver_fallback = 0x03000000;

auto* ver_tuple = PySys_GetObject("version_info");
if (!ver_tuple)
return ver_fallback;

long major, minor, micro, serial;
const char* releaselevel;
if (!PyArg_ParseTuple(ver_tuple, "lllsl", &major, &minor, &micro, &releaselevel, &serial))
return ver_fallback;

return uint32_t(((major & 0xFF) << 24) | ((minor & 0xFF) << 16) | ((micro & 0xFF) << 8));
}();
return once_fetched_ver;
#else
return Py_Version;
#endif
}


struct PyDerefer {
void operator() (PyObject* obj) const noexcept {Py_DecRef(obj);}
};
using PyStrongRef = std::unique_ptr<PyObject, PyDerefer>;


static PyStrongRef
inline from_module_and_spec(PyObject& module, PyType_Spec& spec) noexcept {
#if PY_VERSION_HEX >= 0x03090000
PyStrongRef type{PyType_FromModuleAndSpec(&module, &spec, NULL)};
#else
PyStrongRef type{PyType_FromSpec(&spec)};
#endif
return type;
}


/* On some MacOS combo, using Py_IS_XXX() macros does not work (see
https://github.com/python-rapidjson/python-rapidjson/issues/78).
OTOH, MSVC < 2015 does not have std::isxxx() (see
Expand Down Expand Up @@ -208,6 +256,7 @@ static PyObject* do_decode(PyObject* decoder,
unsigned uuidMode, unsigned parseMode);
static PyObject* decoder_call(PyObject* self, PyObject* args, PyObject* kwargs);
static PyObject* decoder_new(PyTypeObject* type, PyObject* args, PyObject* kwargs);
static int decoder_traverse(PyObject *op, visitproc visit, void *arg);


static PyObject* do_encode(PyObject* value, PyObject* defaultFn, bool ensureAscii,
Expand Down Expand Up @@ -1890,46 +1939,22 @@ static PyMemberDef decoder_members[] = {
};


static PyTypeObject Decoder_Type = {
PyVarObject_HEAD_INIT(NULL, 0)
"rapidjson.Decoder", /* tp_name */
sizeof(DecoderObject), /* tp_basicsize */
0, /* tp_itemsize */
0, /* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_compare */
0, /* tp_repr */
0, /* tp_as_number */
0, /* tp_as_sequence */
0, /* tp_as_mapping */
0, /* tp_hash */
(ternaryfunc) decoder_call, /* tp_call */
0, /* tp_str */
0, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /* tp_flags */
decoder_doc, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
0, /* tp_methods */
decoder_members, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
0, /* tp_alloc */
decoder_new, /* tp_new */
PyObject_Del, /* tp_free */
static PyType_Slot Decoder_Type_Slot[] = {
{Py_tp_doc, const_cast<char*>(decoder_doc)},
{Py_tp_call, reinterpret_cast<void*>(decoder_call)},
{Py_tp_members, decoder_members},
{Py_tp_new, reinterpret_cast<void*>(decoder_new)},
{Py_tp_traverse, reinterpret_cast<void*>(decoder_traverse)},
{0, NULL}
};


static PyType_Spec Decoder_Type_Spec = {
"rapidjson.Decoder", /* name */
sizeof(DecoderObject), /* basicsize */
0, /* itemsize */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_IMMUTABLETYPE, /* flags */
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@VestniK VestniK Sep 3, 2025

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The type is flagged as Py_TPFLAGS_IMMUTABLETYPE to make this change more "noop-like". All static types are immutable. Decoder type remains immutable after it's transformation into heap-type. This flag can be dropped if it's ok to make Decoder to be closer to regular types defined in python.

Decoder_Type_Slot /* slots */
};


Expand Down Expand Up @@ -2291,6 +2316,16 @@ decoder_new(PyTypeObject* type, PyObject* args, PyObject* kwargs)
}


static int
decoder_traverse(PyObject *op, visitproc visit, void *arg)
{
if (py_version_hex() >= 0x03090000)
Py_VISIT(Py_TYPE(op));
return 0;
}



/////////////
// Encoder //
/////////////
Expand Down Expand Up @@ -3884,7 +3919,8 @@ module_exec(PyObject* m)
PyObject* decimalModule;
PyObject* uuidModule;

if (PyType_Ready(&Decoder_Type) < 0)
auto decoder_type = from_module_and_spec(*m, Decoder_Type_Spec);
if (!decoder_type)
return -1;

if (PyType_Ready(&Encoder_Type) < 0)
Expand Down Expand Up @@ -4067,11 +4103,8 @@ module_exec(PyObject* m)
)
return -1;

Py_INCREF(&Decoder_Type);
if (PyModule_AddObject(m, "Decoder", (PyObject*) &Decoder_Type) < 0) {
Py_DECREF(&Decoder_Type);
if (PyModule_AddObject(m, "Decoder", decoder_type.get()) < 0)
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@VestniK VestniK Sep 3, 2025

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Using RAII here prolongates lifetime of a strong reference to decoder type to the end of the module exec function. It shouldn't affect type object lifetime since there are other strong references to it. But using RAII make the code smaller and less error prone.

return -1;
}

Py_INCREF(&Encoder_Type);
if (PyModule_AddObject(m, "Encoder", (PyObject*) &Encoder_Type) < 0) {
Expand Down