bpo-40334: PEP 617 implementation: New PEG parser for CPython (GH-19503)

Co-authored-by: Guido van Rossum <guido@python.org>
Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com>

Tools/peg_generator/peg_extension/peg_extension.c

@@ -0,0 +1,153 @@
+#include "pegen.h"
+
+PyObject *
+_build_return_object(mod_ty module, int mode, PyObject *filename_ob, PyArena *arena)
+{
+    PyObject *result = NULL;
+
+    if (mode == 2) {
+        result = (PyObject *)PyAST_CompileObject(module, filename_ob, NULL, -1, arena);
+    } else if (mode == 1) {
+        result = PyAST_mod2obj(module);
+    } else {
+        result = Py_None;
+        Py_INCREF(result);
+        
+    }
+
+    return result;
+}
+
+static PyObject *
+parse_file(PyObject *self, PyObject *args, PyObject *kwds)
+{
+    static char *keywords[] = {"file", "mode", NULL};
+    const char *filename;
+    int mode = 2;
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "s|i", keywords, &filename, &mode)) {
+        return NULL;
+    }
+    if (mode < 0 || mode > 2) {
+        return PyErr_Format(PyExc_ValueError, "Bad mode, must be 0 <= mode <= 2");
+    }
+
+    PyArena *arena = PyArena_New();
+    if (arena == NULL) {
+        return NULL;
+    }
+
+    PyObject *result = NULL;
+
+    PyObject *filename_ob = PyUnicode_FromString(filename);
+    if (filename_ob == NULL) {
+        goto error;
+    }
+
+    mod_ty res = _PyPegen_run_parser_from_file(filename, Py_file_input, filename_ob, arena);
+    if (res == NULL) {
+        goto error;
+    }
+
+    result = _build_return_object(res, mode, filename_ob, arena);
+
+error:
+    Py_XDECREF(filename_ob);
+    PyArena_Free(arena);
+    return result;
+}
+
+static PyObject *
+parse_string(PyObject *self, PyObject *args, PyObject *kwds)
+{
+    static char *keywords[] = {"str", "mode", NULL};
+    const char *the_string;
+    int mode = 2;
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "s|i", keywords, &the_string, &mode)) {
+        return NULL;
+    }
+    if (mode < 0 || mode > 2) {
+        return PyErr_Format(PyExc_ValueError, "Bad mode, must be 0 <= mode <= 2");
+    }
+
+    PyArena *arena = PyArena_New();
+    if (arena == NULL) {
+        return NULL;
+    }
+
+    PyObject *result = NULL;
+
+    PyObject *filename_ob = PyUnicode_FromString("<string>");
+    if (filename_ob == NULL) {
+        goto error;
+    }
+
+    mod_ty res = _PyPegen_run_parser_from_string(the_string, Py_file_input, filename_ob,
+                                        PyCF_IGNORE_COOKIE, arena);
+    if (res == NULL) {
+        goto error;
+    }
+    result = _build_return_object(res, mode, filename_ob, arena);
+
+error:
+    Py_XDECREF(filename_ob);
+    PyArena_Free(arena);
+    return result;
+}
+
+static PyObject *
+clear_memo_stats()
+{
+    _PyPegen_clear_memo_statistics();
+    Py_RETURN_NONE;
+}
+
+static PyObject *
+get_memo_stats()
+{
+    return _PyPegen_get_memo_statistics();
+}
+
+// TODO: Write to Python's sys.stdout instead of C's stdout.
+static PyObject *
+dump_memo_stats()
+{
+    PyObject *list = _PyPegen_get_memo_statistics();
+    if (list == NULL) {
+        return NULL;
+    }
+    Py_ssize_t len = PyList_Size(list);
+    for (Py_ssize_t i = 0; i < len; i++) {
+        PyObject *value = PyList_GetItem(list, i);  // Borrowed reference.
+        long count = PyLong_AsLong(value);
+        if (count < 0) {
+            break;
+        }
+        if (count > 0) {
+            printf("%4ld %9ld\n", i, count);
+        }
+    }
+    Py_DECREF(list);
+    Py_RETURN_NONE;
+}
+
+static PyMethodDef ParseMethods[] = {
+    {"parse_file", (PyCFunction)(void(*)(void))parse_file, METH_VARARGS|METH_KEYWORDS, "Parse a file."},
+    {"parse_string", (PyCFunction)(void(*)(void))parse_string, METH_VARARGS|METH_KEYWORDS, "Parse a string."},
+    {"clear_memo_stats", clear_memo_stats, METH_NOARGS},
+    {"dump_memo_stats", dump_memo_stats, METH_NOARGS},
+    {"get_memo_stats", get_memo_stats, METH_NOARGS},
+    {NULL, NULL, 0, NULL}        /* Sentinel */
+};
+
+static struct PyModuleDef parsemodule = {
+    PyModuleDef_HEAD_INIT,
+    .m_name = "parse",
+    .m_doc = "A parser.",
+    .m_methods = ParseMethods,
+};
+
+PyMODINIT_FUNC
+PyInit_parse(void)
+{
+    return PyModule_Create(&parsemodule);
+}