mwparserfromhell/mwparserfromhell/parser/tokenizer.c

/*
Tokenizer for MWParserFromHell
Copyright (C) 2012 Ben Kurtovic <ben.kurtovic@verizon.net>

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

#ifndef PY_SSIZE_T_CLEAN
#define PY_SSIZE_T_CLEAN
#endif

#include <Python.h>
#include "setjmp.h"
#include "structmember.h"

static PyObject* EMPTY;

#define PU (Py_UNICODE*)
static const Py_UNICODE* MARKERS[] = {PU"{", PU"}", PU"[", PU"]", PU"<", PU">",
                                      PU"|", PU"=", PU"&", PU"#", PU"*", PU";",
                                      PU":", PU"/", PU"-", PU"!", PU"\n", PU""};
#undef PU

static jmp_buf exception_env;
static const int BAD_ROUTE = 1;

static PyObject* contexts;
static PyObject* tokens;

static PyMethodDef
module_methods[] = {
    {NULL}
};

typedef struct {
    PyObject_HEAD
    PyObject* text;        /* text to tokenize */
    PyObject* stacks;      /* token stacks */
    PyObject* topstack;    /* topmost stack */
    Py_ssize_t head;       /* current position in text */
    Py_ssize_t length;     /* length of text */
    Py_ssize_t global;     /* global context */
} Tokenizer;

static PyObject*
Tokenizer_new(PyTypeObject* type, PyObject* args, PyObject* kwds)
{
    Tokenizer *self;

    self = (Tokenizer*) type->tp_alloc(type, 0);
    if (self != NULL) {

        self->text = Py_None;
        Py_INCREF(Py_None);

        self->stacks = PyList_New(0);
        if (!self->stacks) {
            Py_DECREF(self);
            return NULL;
        }

        self->head = 0;
        self->length = 0;
        self->global = 0;
    }

    return (PyObject*) self;
}

static void
Tokenizer_dealloc(Tokenizer* self)
{
    Py_XDECREF(self->text);
    Py_XDECREF(self->stacks);
    Py_XDECREF(self->topstack);
    self->ob_type->tp_free((PyObject*) self);
}

static int
Tokenizer_init(Tokenizer* self, PyObject* args, PyObject* kwds)
{
    static char* kwlist[] = {NULL};
    if (!PyArg_ParseTupleAndKeywords(args, kwds, "", kwlist))
        return -1;
    return 0;
}

#define Tokenizer_STACK(self) PySequence_Fast_GET_ITEM(self->topstack, 0)
#define Tokenizer_CONTEXT(self) PySequence_Fast_GET_ITEM(self->topstack, 1)
#define Tokenizer_TEXTBUFFER(self) PySequence_Fast_GET_ITEM(self->topstack, 2)

static int
Tokenizer_set_context(Tokenizer* self, Py_ssize_t value)
{
    if (PyList_SetItem(self->topstack, 1, PyInt_FromSsize_t(value)))
        return -1;
    return 0;
}

static int
Tokenizer_set_textbuffer(Tokenizer* self, PyObject* value)
{
    if (PyList_SetItem(self->topstack, 2, value))
        return -1;
    return 0;
}

/*
    Add a new token stack, context, and textbuffer to the list.
*/
static int
Tokenizer_push(Tokenizer* self, int context)
{
    PyObject* top = PyList_New(3);
    PyList_SET_ITEM(top, 0, PyList_New(0));
    PyList_SET_ITEM(top, 1, PyInt_FromSsize_t(0));
    PyList_SET_ITEM(top, 2, PyList_New(0));

    Py_XDECREF(self->topstack);
    self->topstack = top;

    if (PyList_Append(self->stacks, top))
        return -1;
    return 0;
}

/*
    Push the textbuffer onto the stack as a Text node and clear it.
*/
static int
Tokenizer_push_textbuffer(Tokenizer* self)
{
    if (PySequence_Fast_GET_SIZE(Tokenizer_TEXTBUFFER(self)) > 0) {
        PyObject* text = PyUnicode_Join(EMPTY, Tokenizer_TEXTBUFFER(self));
        if (!text) return -1;

        PyObject* klass = PyObject_GetAttrString(tokens, "Text");
        if (!klass) return -1;
        PyObject* args = PyTuple_New(0);
        if (!args) return -1;
        PyObject* kwargs = PyDict_New();
        if (!kwargs) return -1;
        PyDict_SetItemString(kwargs, "text", text);
        Py_DECREF(text);

        PyObject* token = PyInstance_New(klass, args, kwargs);
        if (!token) {
            Py_DECREF(klass);
            Py_DECREF(args);
            Py_DECREF(kwargs);
            return -1;
        }

        Py_DECREF(klass);
        Py_DECREF(args);
        Py_DECREF(kwargs);

        if (PyList_Append(Tokenizer_STACK(self), token)) {
            Py_XDECREF(token);
            return -1;
        }

        Py_DECREF(token);

        if (Tokenizer_set_textbuffer(self, PyList_New(0)))
            return -1;
    }
    return 0;
}

static int
Tokenizer_delete_top_of_stack(Tokenizer* self)
{
    if (PySequence_DelItem(self->stacks, -1))
        return -1;
    Py_DECREF(self->topstack);

    Py_ssize_t size = PySequence_Fast_GET_SIZE(self->stacks);
    if (size > 0) {
        PyObject* top = PySequence_Fast_GET_ITEM(self->stacks, size - 1);
        self->topstack = top;
        Py_INCREF(top);
    }
    else {
        self->topstack = NULL;
    }

    return 0;
}

/*
    Pop the current stack/context/textbuffer, returing the stack.
*/
static PyObject*
Tokenizer_pop(Tokenizer* self)
{
    if (Tokenizer_push_textbuffer(self))
        return NULL;

    PyObject* stack = Tokenizer_STACK(self);
    Py_INCREF(stack);

    if (Tokenizer_delete_top_of_stack(self))
        return NULL;

    return stack;
}

/*
    Pop the current stack/context/textbuffer, returing the stack. We will also
    replace the underlying stack's context with the current stack's.
*/
static PyObject*
Tokenizer_pop_keeping_context(Tokenizer* self)
{
    if (Tokenizer_push_textbuffer(self))
        return NULL;

    PyObject* stack = Tokenizer_STACK(self);
    PyObject* context = Tokenizer_CONTEXT(self);
    Py_INCREF(stack);
    Py_INCREF(context);

    if (Tokenizer_delete_top_of_stack(self))
        return NULL;

    if (PyList_SetItem(self->topstack, 1, context))
        return NULL;

    return stack;
}

/*
    Fail the current tokenization route. Discards the current
    stack/context/textbuffer and "raises a BAD_ROUTE exception", which is
    implemented using longjmp().
*/
static void
Tokenizer_fail_route(Tokenizer* self)
{
    Tokenizer_pop(self);
    longjmp(exception_env, BAD_ROUTE);
}

/*
    Write a token to the end of the current token stack.
*/
static int
Tokenizer_write(Tokenizer* self, PyObject* token)
{
    if (Tokenizer_push_textbuffer(self))
        return -1;

    if (PyList_Append(Tokenizer_STACK(self), token))
        return -1;

    return 0;
}

/*
    Write a token to the beginning of the current token stack.
*/
static int
Tokenizer_write_first(Tokenizer* self, PyObject* token)
{
    if (Tokenizer_push_textbuffer(self))
        return -1;

    if (PyList_Insert(Tokenizer_STACK(self), 0, token))
        return -1;

    return 0;
}

/*
    Write text to the current textbuffer.
*/
static int
Tokenizer_write_text(Tokenizer* self, PyObject* text)
{
    if (PyList_Append(Tokenizer_TEXTBUFFER(self), text))
        return -1;

    return 0;
}

/*
    Write a series of tokens to the current stack at once.
*/
static int
Tokenizer_write_all(Tokenizer* self, PyObject* tokenlist)
{
    if (Tokenizer_push_textbuffer(self))
        return -1;

    PyObject* stack = Tokenizer_STACK(self);
    Py_ssize_t size = PySequence_Fast_GET_SIZE(stack);

    if (PyList_SetSlice(stack, size, size, tokenlist))
        return -1;

    return 0;
}

/*
    Pop the current stack, write text, and then write the stack.
*/
static int
Tokenizer_write_text_then_stack(Tokenizer* self, PyObject* text)
{
    PyObject* stack = Tokenizer_pop(self);
    if (Tokenizer_write_text(self, text)) {
        Py_XDECREF(stack);
        return -1;
    }

    if (stack) {
        if (PySequence_Fast_GET_SIZE(stack) > 0) {
            if (Tokenizer_write_all(self, stack)) {
                Py_DECREF(stack);
                return -1;
            }
        }
        Py_DECREF(stack);
    }

    self->head--;
    return 0;
}

/*
    Read the value at a relative point in the wikicode.
*/
static PyObject*
Tokenizer_read(Tokenizer* self, Py_ssize_t delta)
{
    Py_ssize_t index = self->head + delta;

    if (index >= self->length) {
        return EMPTY;
    }

    return PySequence_Fast_GET_ITEM(self->text, index);
}

/*
    Parse the wikicode string, using *context* for when to stop.
*/
static PyObject*
Tokenizer_parse(Tokenizer* self, int context)
{
    PyObject* this;

    Tokenizer_push(self, context);

    while (1) {
        this = Tokenizer_read(self, 0);
     /*   if (this not in MARKERS) {
            WRITE TEXT
        } */
        if (this == EMPTY) {
            return Tokenizer_pop(self);
        }
        self->head++;
    }
}

/*
    Build a list of tokens from a string of wikicode and return it.
*/
static PyObject*
Tokenizer_tokenize(Tokenizer* self, PyObject *args)
{
    PyObject* text;

    if (!PyArg_ParseTuple(args, "U", &text)) {
        /* Failed to parse a Unicode object; try a string instead. */
        PyErr_Clear();
        const char* encoded;
        Py_ssize_t size;

        if (!PyArg_ParseTuple(args, "s#", &encoded, &size)) {
            return NULL;
        }

        PyObject* temp;
        temp = PyUnicode_FromStringAndSize(encoded, size);
        if (!text)
            return NULL;

        Py_XDECREF(self->text);
        text = PySequence_Fast(temp, "expected a sequence");
        Py_XDECREF(temp);
        self->text = text;
    }
    else {
        Py_XDECREF(self->text);
        self->text = PySequence_Fast(text, "expected a sequence");
    }

    self->length = PySequence_Length(self->text);

    return Tokenizer_parse(self, 0);
}

static PyMethodDef
Tokenizer_methods[] = {
    {"tokenize", (PyCFunction) Tokenizer_tokenize, METH_VARARGS,
    "Build a list of tokens from a string of wikicode and return it."},
    {NULL}
};

static PyMemberDef
Tokenizer_members[] = {
    {NULL}
};

static PyTypeObject
TokenizerType = {
    PyObject_HEAD_INIT(NULL)
    0,                                                      /* ob_size */
    "_tokenizer.CTokenizer",                                /* tp_name */
    sizeof(Tokenizer),                                      /* tp_basicsize */
    0,                                                      /* tp_itemsize */
    (destructor) Tokenizer_dealloc,                         /* 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  */
    0,                                                      /* tp_call */
    0,                                                      /* tp_str */
    0,                                                      /* tp_getattro */
    0,                                                      /* tp_setattro */
    0,                                                      /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT,                                     /* tp_flags */
    "Creates a list of tokens from a string of wikicode.",  /* tp_doc */
    0,                                                      /* tp_traverse */
    0,                                                      /* tp_clear */
    0,                                                      /* tp_richcompare */
    0,                                                      /* tp_weaklistoffset */
    0,                                                      /* tp_iter */
    0,                                                      /* tp_iternext */
    Tokenizer_methods,                                      /* tp_methods */
    Tokenizer_members,                                      /* tp_members */
    0,                                                      /* tp_getset */
    0,                                                      /* tp_base */
    0,                                                      /* tp_dict */
    0,                                                      /* tp_descr_get */
    0,                                                      /* tp_descr_set */
    0,                                                      /* tp_dictoffset */
    (initproc) Tokenizer_init,                              /* tp_init */
    0,                                                      /* tp_alloc */
    Tokenizer_new,                                          /* tp_new */
};

PyMODINIT_FUNC
init_tokenizer(void)
{
    PyObject* module;

    TokenizerType.tp_new = PyType_GenericNew;
    if (PyType_Ready(&TokenizerType) < 0)
        return;

    module = Py_InitModule("_tokenizer", module_methods);

    Py_INCREF(&TokenizerType);
    PyModule_AddObject(module, "CTokenizer", (PyObject*) &TokenizerType);

    EMPTY = PyUnicode_FromString("");

    PyObject* globals = PyEval_GetGlobals();
    PyObject* locals = PyEval_GetLocals();
    PyObject* fromlist = PyList_New(0);

    contexts = PyImport_ImportModuleLevel("contexts", globals, locals, fromlist, 1);
    tokens = PyImport_ImportModuleLevel("tokens", globals, locals, fromlist, 1);
    Py_DECREF(fromlist);
}