/*
 * Simple PyMemoryView'ish object for Python 2.6 compatibility.
 *
 * On Python >= 2.7, we can use the actual PyMemoryView objects.
 *
 * Some code copied from the CPython implementation.
 */

#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include "structmember.h"

#define NPY_NO_DEPRECATED_API NPY_API_VERSION
#define _MULTIARRAYMODULE
#include "numpy/arrayobject.h"
#include "numpy/arrayscalars.h"

#include "npy_config.h"
#include "npy_pycompat.h"

#include "numpymemoryview.h"


#if PY_VERSION_HEX < 0x02070000

/*
 * Memory allocation
 */

static int
memorysimpleview_traverse(PyMemorySimpleViewObject *self,
                          visitproc visit, void *arg)
{
    if (self->base != NULL)
        Py_VISIT(self->base);
    if (self->view.obj != NULL)
        Py_VISIT(self->view.obj);
    return 0;
}

static int
memorysimpleview_clear(PyMemorySimpleViewObject *self)
{
    Py_CLEAR(self->base);
    PyBuffer_Release(&self->view);
    self->view.obj = NULL;
    return 0;
}

static void
memorysimpleview_dealloc(PyMemorySimpleViewObject *self)
{
    PyObject_GC_UnTrack(self);
    Py_CLEAR(self->base);
    if (self->view.obj != NULL) {
        PyBuffer_Release(&self->view);
        self->view.obj = NULL;
    }
    PyObject_GC_Del(self);
}

static PyObject *
memorysimpleview_new(PyTypeObject *subtype, PyObject *args, PyObject *kwds)
{
    PyObject *obj;
    static char *kwlist[] = {"object", 0};
    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O:memorysimpleview", kwlist,
                                     &obj)) {
        return NULL;
    }
    return PyMemorySimpleView_FromObject(obj);
}


/*
 * Buffer interface
 */

static int
memorysimpleview_getbuffer(PyMemorySimpleViewObject *self,
                           Py_buffer *view, int flags)
{
    return PyObject_GetBuffer(self->base, view, flags);
}

static void
memorysimpleview_releasebuffer(PyMemorySimpleViewObject *self,
                               Py_buffer *view)
{
    PyBuffer_Release(view);
}

static PyBufferProcs memorysimpleview_as_buffer = {
    (readbufferproc)0,       /*bf_getreadbuffer*/
    (writebufferproc)0,     /*bf_getwritebuffer*/
    (segcountproc)0,        /*bf_getsegcount*/
    (charbufferproc)0,       /*bf_getcharbuffer*/
    (getbufferproc)memorysimpleview_getbuffer, /* bf_getbuffer */
    (releasebufferproc)memorysimpleview_releasebuffer, /* bf_releasebuffer */
};


/*
 * Getters
 */

static PyObject *
_IntTupleFromSsizet(int len, Py_ssize_t *vals)
{
    int i;
    PyObject *o;
    PyObject *intTuple;

    if (vals == NULL) {
        Py_INCREF(Py_None);
        return Py_None;
    }
    intTuple = PyTuple_New(len);
    if (!intTuple) return NULL;
    for(i=0; i<len; i++) {
        o = PyInt_FromSsize_t(vals[i]);
        if (!o) {
            Py_DECREF(intTuple);
            return NULL;
        }
        PyTuple_SET_ITEM(intTuple, i, o);
    }
    return intTuple;
}

static PyObject *
memorysimpleview_format_get(PyMemorySimpleViewObject *self)
{
    return PyUString_FromString(self->view.format);
}

static PyObject *
memorysimpleview_itemsize_get(PyMemorySimpleViewObject *self)
{
    return PyLong_FromSsize_t(self->view.itemsize);
}

static PyObject *
memorysimpleview_shape_get(PyMemorySimpleViewObject *self)
{
    return _IntTupleFromSsizet(self->view.ndim, self->view.shape);
}

static PyObject *
memorysimpleview_strides_get(PyMemorySimpleViewObject *self)
{
    return _IntTupleFromSsizet(self->view.ndim, self->view.strides);
}

static PyObject *
memorysimpleview_suboffsets_get(PyMemorySimpleViewObject *self)
{
    return _IntTupleFromSsizet(self->view.ndim, self->view.suboffsets);
}

static PyObject *
memorysimpleview_readonly_get(PyMemorySimpleViewObject *self)
{
    return PyBool_FromLong(self->view.readonly);
}

static PyObject *
memorysimpleview_ndim_get(PyMemorySimpleViewObject *self)
{
    return PyLong_FromLong(self->view.ndim);
}


static PyGetSetDef memorysimpleview_getsets[] =
{
    {"format", (getter)memorysimpleview_format_get, NULL, NULL, NULL},
    {"itemsize", (getter)memorysimpleview_itemsize_get, NULL, NULL, NULL},
    {"shape", (getter)memorysimpleview_shape_get, NULL, NULL, NULL},
    {"strides", (getter)memorysimpleview_strides_get, NULL, NULL, NULL},
    {"suboffsets", (getter)memorysimpleview_suboffsets_get, NULL, NULL, NULL},
    {"readonly", (getter)memorysimpleview_readonly_get, NULL, NULL, NULL},
    {"ndim", (getter)memorysimpleview_ndim_get, NULL, NULL, NULL},
    {NULL, NULL, NULL, NULL}
};

NPY_NO_EXPORT PyTypeObject PyMemorySimpleView_Type = {
#if defined(NPY_PY3K)
    PyVarObject_HEAD_INIT(NULL, 0)
#else
    PyObject_HEAD_INIT(NULL)
    0,                                          /* ob_size */
#endif
    "numpy.memorysimpleview",
    sizeof(PyMemorySimpleViewObject),
    0,                                          /* tp_itemsize */
    /* methods */
    (destructor)memorysimpleview_dealloc,       /* tp_dealloc */
    0,                                          /* tp_print */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
#if defined(NPY_PY3K)
    0,                                          /* tp_reserved */
#else
    (cmpfunc)0,                                 /* tp_compare */
#endif
    (reprfunc)0,                                /* tp_repr */
    0,                                          /* tp_as_number */
    0,                                          /* tp_as_sequence */
    0,                                          /* tp_as_mapping */
    0,                                          /* tp_hash */
    0,                                          /* tp_call */
    (reprfunc)0,                                /* tp_str */
    0,                                          /* tp_getattro */
    0,                                          /* tp_setattro */
    &memorysimpleview_as_buffer,                /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC
    | Py_TPFLAGS_HAVE_NEWBUFFER,                /* tp_flags */
    0,                                          /* tp_doc */
    (traverseproc)memorysimpleview_traverse,    /* tp_traverse */
    (inquiry)memorysimpleview_clear,            /* tp_clear */
    0,                                          /* tp_richcompare */
    0,                                          /* tp_weaklistoffset */
    0,                                          /* tp_iter */
    0,                                          /* tp_iternext */
    0,                                          /* tp_methods */
    0,                                          /* tp_members */
    memorysimpleview_getsets,                   /* 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 */
    memorysimpleview_new,                       /* tp_new */
    0,                                          /* tp_free */
    0,                                          /* tp_is_gc */
    0,                                          /* tp_bases */
    0,                                          /* tp_mro */
    0,                                          /* tp_cache */
    0,                                          /* tp_subclasses */
    0,                                          /* tp_weaklist */
    0,                                          /* tp_del */
    0,                                          /* tp_version_tag */
};


/*
 * Factory
 */
NPY_NO_EXPORT PyObject *
PyMemorySimpleView_FromObject(PyObject *base)
{
    PyMemorySimpleViewObject *mview = NULL;
    Py_buffer view;

    if (Py_TYPE(base)->tp_as_buffer == NULL ||
        Py_TYPE(base)->tp_as_buffer->bf_getbuffer == NULL) {

        PyErr_SetString(PyExc_TypeError,
            "cannot make memory view because object does "
            "not have the buffer interface");
        return NULL;
    }

    memset(&view, 0, sizeof(Py_buffer));
    if (PyObject_GetBuffer(base, &view, PyBUF_FULL_RO) < 0)
        return NULL;

    mview = (PyMemorySimpleViewObject *)
        PyObject_GC_New(PyMemorySimpleViewObject, &PyMemorySimpleView_Type);
    if (mview == NULL) {
        PyBuffer_Release(&view);
        return NULL;
    }
    memcpy(&mview->view, &view, sizeof(Py_buffer));
    mview->base = base;
    Py_INCREF(base);

    PyObject_GC_Track(mview);
    return (PyObject *)mview;
}


/*
 * Module initialization
 */

NPY_NO_EXPORT int
_numpymemoryview_init(PyObject **typeobject)
{
    if (PyType_Ready(&PyMemorySimpleView_Type) < 0) {
        return -1;
    }
    *typeobject = (PyObject*)&PyMemorySimpleView_Type;
    return 0;
}

#else

NPY_NO_EXPORT int
_numpymemoryview_init(PyObject **typeobject)
{
    *typeobject = NULL;
    return 0;
}

#endif
