"""
Boxing and unboxing of native Numba values to / from CPython objects.
"""

from llvmlite import ir

from numba.core import types, cgutils
from numba.core.pythonapi import box, unbox, reflect, NativeValue

from numba.cpython import setobj, listobj
from numba.np import numpy_support

#
# Scalar types
#

@box(types.Boolean)
def box_bool(typ, val, c):
    return c.pyapi.bool_from_bool(val)

@unbox(types.Boolean)
def unbox_boolean(typ, obj, c):
    istrue = c.pyapi.object_istrue(obj)
    zero = ir.Constant(istrue.type, 0)
    val = c.builder.icmp_signed('!=', istrue, zero)
    return NativeValue(val, is_error=c.pyapi.c_api_error())


@box(types.IntegerLiteral)
@box(types.BooleanLiteral)
def box_literal_integer(typ, val, c):
    val = c.context.cast(c.builder, val, typ, typ.literal_type)
    return c.box(typ.literal_type, val)


@box(types.Integer)
def box_integer(typ, val, c):
    if typ.signed:
        ival = c.builder.sext(val, c.pyapi.longlong)
        return c.pyapi.long_from_longlong(ival)
    else:
        ullval = c.builder.zext(val, c.pyapi.ulonglong)
        return c.pyapi.long_from_ulonglong(ullval)

@unbox(types.Integer)
def unbox_integer(typ, obj, c):
    ll_type = c.context.get_argument_type(typ)
    val = cgutils.alloca_once(c.builder, ll_type)
    longobj = c.pyapi.number_long(obj)
    with c.pyapi.if_object_ok(longobj):
        if typ.signed:
            llval = c.pyapi.long_as_longlong(longobj)
        else:
            llval = c.pyapi.long_as_ulonglong(longobj)
        c.pyapi.decref(longobj)
        c.builder.store(c.builder.trunc(llval, ll_type), val)
    return NativeValue(c.builder.load(val),
                       is_error=c.pyapi.c_api_error())


@box(types.Float)
def box_float(typ, val, c):
    if typ == types.float32:
        dbval = c.builder.fpext(val, c.pyapi.double)
    else:
        assert typ == types.float64
        dbval = val
    return c.pyapi.float_from_double(dbval)

@unbox(types.Float)
def unbox_float(typ, obj, c):
    fobj = c.pyapi.number_float(obj)
    dbval = c.pyapi.float_as_double(fobj)
    c.pyapi.decref(fobj)
    if typ == types.float32:
        val = c.builder.fptrunc(dbval,
                                c.context.get_argument_type(typ))
    else:
        assert typ == types.float64
        val = dbval
    return NativeValue(val, is_error=c.pyapi.c_api_error())


@box(types.Complex)
def box_complex(typ, val, c):
    cval = c.context.make_complex(c.builder, typ, value=val)

    if typ == types.complex64:
        freal = c.builder.fpext(cval.real, c.pyapi.double)
        fimag = c.builder.fpext(cval.imag, c.pyapi.double)
    else:
        assert typ == types.complex128
        freal, fimag = cval.real, cval.imag
    return c.pyapi.complex_from_doubles(freal, fimag)

@unbox(types.Complex)
def unbox_complex(typ, obj, c):
    # First unbox to complex128, since that's what CPython gives us
    c128 = c.context.make_complex(c.builder, types.complex128)
    ok = c.pyapi.complex_adaptor(obj, c128._getpointer())
    failed = cgutils.is_false(c.builder, ok)

    with cgutils.if_unlikely(c.builder, failed):
        c.pyapi.err_set_string("PyExc_TypeError",
                               "conversion to %s failed" % (typ,))

    if typ == types.complex64:
        # Downcast to complex64 if necessary
        cplx = c.context.make_complex(c.builder, typ)
        cplx.real = c.context.cast(c.builder, c128.real,
                                   types.float64, types.float32)
        cplx.imag = c.context.cast(c.builder, c128.imag,
                                   types.float64, types.float32)
    else:
        assert typ == types.complex128
        cplx = c128
    return NativeValue(cplx._getvalue(), is_error=failed)


@box(types.NoneType)
def box_none(typ, val, c):
    return c.pyapi.make_none()

@unbox(types.NoneType)
@unbox(types.EllipsisType)
def unbox_none(typ, val, c):
    return NativeValue(c.context.get_dummy_value())


@box(types.NPDatetime)
def box_npdatetime(typ, val, c):
    return c.pyapi.create_np_datetime(val, typ.unit_code)

@unbox(types.NPDatetime)
def unbox_npdatetime(typ, obj, c):
    val = c.pyapi.extract_np_datetime(obj)
    return NativeValue(val, is_error=c.pyapi.c_api_error())


@box(types.NPTimedelta)
def box_nptimedelta(typ, val, c):
    return c.pyapi.create_np_timedelta(val, typ.unit_code)

@unbox(types.NPTimedelta)
def unbox_nptimedelta(typ, obj, c):
    val = c.pyapi.extract_np_timedelta(obj)
    return NativeValue(val, is_error=c.pyapi.c_api_error())


@box(types.RawPointer)
def box_raw_pointer(typ, val, c):
    """
    Convert a raw pointer to a Python int.
    """
    ll_intp = c.context.get_value_type(types.uintp)
    addr = c.builder.ptrtoint(val, ll_intp)
    return c.box(types.uintp, addr)


@box(types.EnumMember)
def box_enum(typ, val, c):
    """
    Fetch an enum member given its native value.
    """
    valobj = c.box(typ.dtype, val)
    # Call the enum class with the value object
    cls_obj = c.pyapi.unserialize(c.pyapi.serialize_object(typ.instance_class))
    return c.pyapi.call_function_objargs(cls_obj, (valobj,))


@unbox(types.EnumMember)
def unbox_enum(typ, obj, c):
    """
    Convert an enum member's value to its native value.
    """
    valobj = c.pyapi.object_getattr_string(obj, "value")
    return c.unbox(typ.dtype, valobj)

#
# Composite types
#

@box(types.Record)
def box_record(typ, val, c):
    # Note we will create a copy of the record
    # This is the only safe way.
    size = ir.Constant(ir.IntType(32), val.type.pointee.count)
    ptr = c.builder.bitcast(val, ir.PointerType(ir.IntType(8)))
    return c.pyapi.recreate_record(ptr, size, typ.dtype, c.env_manager)


@unbox(types.Record)
def unbox_record(typ, obj, c):
    buf = c.pyapi.alloca_buffer()
    ptr = c.pyapi.extract_record_data(obj, buf)
    is_error = cgutils.is_null(c.builder, ptr)

    ltyp = c.context.get_value_type(typ)
    val = c.builder.bitcast(ptr, ltyp)

    def cleanup():
        c.pyapi.release_buffer(buf)
    return NativeValue(val, cleanup=cleanup, is_error=is_error)


@box(types.UnicodeCharSeq)
def box_unicodecharseq(typ, val, c):
    # XXX could kind be determined from strptr?
    unicode_kind = {
        1: c.pyapi.py_unicode_1byte_kind,
        2: c.pyapi.py_unicode_2byte_kind,
        4: c.pyapi.py_unicode_4byte_kind}[numpy_support.sizeof_unicode_char]
    kind = c.context.get_constant(types.int32, unicode_kind)
    rawptr = cgutils.alloca_once_value(c.builder, value=val)
    strptr = c.builder.bitcast(rawptr, c.pyapi.cstring)

    fullsize = c.context.get_constant(types.intp, typ.count)
    zero = fullsize.type(0)
    one = fullsize.type(1)
    step = fullsize.type(numpy_support.sizeof_unicode_char)
    count = cgutils.alloca_once_value(c.builder, zero)
    with cgutils.loop_nest(c.builder, [fullsize], fullsize.type) as [idx]:
        # Get char at idx
        ch = c.builder.load(c.builder.gep(strptr, [c.builder.mul(idx, step)]))
        # If the char is a non-null-byte, store the next index as count
        with c.builder.if_then(cgutils.is_not_null(c.builder, ch)):
            c.builder.store(c.builder.add(idx, one), count)
    strlen = c.builder.load(count)
    return c.pyapi.string_from_kind_and_data(kind, strptr, strlen)


@unbox(types.UnicodeCharSeq)
def unbox_unicodecharseq(typ, obj, c):
    lty = c.context.get_value_type(typ)

    ok, buffer, size, kind, is_ascii, hashv = \
        c.pyapi.string_as_string_size_and_kind(obj)

    # If conversion is ok, copy the buffer to the output storage.
    with cgutils.if_likely(c.builder, ok):
        # Check if the returned string size fits in the charseq
        storage_size = ir.Constant(size.type, typ.count)
        size_fits = c.builder.icmp_unsigned("<=", size, storage_size)

        # Allow truncation of string
        size = c.builder.select(size_fits, size, storage_size)

        # Initialize output to zero bytes
        null_string = ir.Constant(lty, None)
        outspace  = cgutils.alloca_once_value(c.builder, null_string)

        # We don't need to set the NULL-terminator because the storage
        # is already zero-filled.
        cgutils.memcpy(c.builder,
                        c.builder.bitcast(outspace, buffer.type),
                        buffer, size)

    ret = c.builder.load(outspace)
    return NativeValue(ret, is_error=c.builder.not_(ok))


@box(types.Bytes)
def box_bytes(typ, val, c):
    obj = c.context.make_helper(c.builder, typ, val)
    return c.pyapi.bytes_from_string_and_size(obj.data, obj.nitems)


@box(types.CharSeq)
def box_charseq(typ, val, c):
    rawptr = cgutils.alloca_once_value(c.builder, value=val)
    strptr = c.builder.bitcast(rawptr, c.pyapi.cstring)
    fullsize = c.context.get_constant(types.intp, typ.count)
    zero = fullsize.type(0)
    one = fullsize.type(1)
    count = cgutils.alloca_once_value(c.builder, zero)

    # Find the length of the string, mimicking Numpy's behaviour:
    # search for the last non-null byte in the underlying storage
    # (e.g. b'A\0\0B\0\0\0' will return the logical string b'A\0\0B')
    with cgutils.loop_nest(c.builder, [fullsize], fullsize.type) as [idx]:
        # Get char at idx
        ch = c.builder.load(c.builder.gep(strptr, [idx]))
        # If the char is a non-null-byte, store the next index as count
        with c.builder.if_then(cgutils.is_not_null(c.builder, ch)):
            c.builder.store(c.builder.add(idx, one), count)

    strlen = c.builder.load(count)
    return c.pyapi.bytes_from_string_and_size(strptr, strlen)


@unbox(types.CharSeq)
def unbox_charseq(typ, obj, c):
    lty = c.context.get_value_type(typ)
    ok, buffer, size = c.pyapi.string_as_string_and_size(obj)

    # If conversion is ok, copy the buffer to the output storage.
    with cgutils.if_likely(c.builder, ok):
        # Check if the returned string size fits in the charseq
        storage_size = ir.Constant(size.type, typ.count)
        size_fits = c.builder.icmp_unsigned("<=", size, storage_size)

        # Allow truncation of string
        size = c.builder.select(size_fits, size, storage_size)

        # Initialize output to zero bytes
        null_string = ir.Constant(lty, None)
        outspace  = cgutils.alloca_once_value(c.builder, null_string)

        # We don't need to set the NULL-terminator because the storage
        # is already zero-filled.
        cgutils.memcpy(c.builder,
                       c.builder.bitcast(outspace, buffer.type),
                       buffer, size)

    ret = c.builder.load(outspace)
    return NativeValue(ret, is_error=c.builder.not_(ok))


@box(types.Optional)
def box_optional(typ, val, c):
    optval = c.context.make_helper(c.builder, typ, val)
    ret = cgutils.alloca_once_value(c.builder, c.pyapi.borrow_none())
    with c.builder.if_else(optval.valid) as (then, otherwise):
        with then:
            validres = c.box(typ.type, optval.data)
            c.builder.store(validres, ret)
        with otherwise:
            c.builder.store(c.pyapi.make_none(), ret)
    return c.builder.load(ret)


@unbox(types.Optional)
def unbox_optional(typ, obj, c):
    """
    Convert object *obj* to a native optional structure.
    """
    noneval = c.context.make_optional_none(c.builder, typ.type)
    is_not_none = c.builder.icmp_signed('!=', obj, c.pyapi.borrow_none())

    retptr = cgutils.alloca_once(c.builder, noneval.type)
    errptr = cgutils.alloca_once_value(c.builder, cgutils.false_bit)

    with c.builder.if_else(is_not_none) as (then, orelse):
        with then:
            native = c.unbox(typ.type, obj)
            just = c.context.make_optional_value(c.builder,
                                                 typ.type, native.value)
            c.builder.store(just, retptr)
            c.builder.store(native.is_error, errptr)

        with orelse:
            c.builder.store(noneval, retptr)

    if native.cleanup is not None:
        def cleanup():
            with c.builder.if_then(is_not_none):
                native.cleanup()
    else:
        cleanup = None

    ret = c.builder.load(retptr)
    return NativeValue(ret, is_error=c.builder.load(errptr),
                       cleanup=cleanup)


@unbox(types.SliceType)
def unbox_slice(typ, obj, c):
    """
    Convert object *obj* to a native slice structure.
    """
    from numba.cpython import slicing
    ok, start, stop, step = c.pyapi.slice_as_ints(obj)
    sli = c.context.make_helper(c.builder, typ)
    sli.start = start
    sli.stop = stop
    sli.step = step
    return NativeValue(sli._getvalue(), is_error=c.builder.not_(ok))


@unbox(types.StringLiteral)
def unbox_string_literal(typ, obj, c):
    # A string literal is a dummy value
    return NativeValue(c.context.get_dummy_value())

#
# Collections
#

# NOTE: boxing functions are supposed to steal any NRT references in
# the given native value.

@box(types.Array)
def box_array(typ, val, c):
    nativearycls = c.context.make_array(typ)
    nativeary = nativearycls(c.context, c.builder, value=val)
    if c.context.enable_nrt:
        np_dtype = numpy_support.as_dtype(typ.dtype)
        dtypeptr = c.env_manager.read_const(c.env_manager.add_const(np_dtype))
        newary = c.pyapi.nrt_adapt_ndarray_to_python(typ, val, dtypeptr)
        # Steals NRT ref
        c.context.nrt.decref(c.builder, typ, val)
        return newary
    else:
        parent = nativeary.parent
        c.pyapi.incref(parent)
        return parent


@unbox(types.Buffer)
def unbox_buffer(typ, obj, c):
    """
    Convert a Py_buffer-providing object to a native array structure.
    """
    buf = c.pyapi.alloca_buffer()
    res = c.pyapi.get_buffer(obj, buf)
    is_error = cgutils.is_not_null(c.builder, res)

    nativearycls = c.context.make_array(typ)
    nativeary = nativearycls(c.context, c.builder)
    aryptr = nativeary._getpointer()

    with cgutils.if_likely(c.builder, c.builder.not_(is_error)):
        ptr = c.builder.bitcast(aryptr, c.pyapi.voidptr)
        if c.context.enable_nrt:
            c.pyapi.nrt_adapt_buffer_from_python(buf, ptr)
        else:
            c.pyapi.numba_buffer_adaptor(buf, ptr)

    def cleanup():
        c.pyapi.release_buffer(buf)

    return NativeValue(c.builder.load(aryptr), is_error=is_error,
                       cleanup=cleanup)

@unbox(types.Array)
def unbox_array(typ, obj, c):
    """
    Convert a Numpy array object to a native array structure.
    """
    # This is necessary because unbox_buffer() does not work on some
    # dtypes, e.g. datetime64 and timedelta64.
    # TODO check matching dtype.
    #      currently, mismatching dtype will still work and causes
    #      potential memory corruption
    nativearycls = c.context.make_array(typ)
    nativeary = nativearycls(c.context, c.builder)
    aryptr = nativeary._getpointer()

    ptr = c.builder.bitcast(aryptr, c.pyapi.voidptr)
    if c.context.enable_nrt:
        errcode = c.pyapi.nrt_adapt_ndarray_from_python(obj, ptr)
    else:
        errcode = c.pyapi.numba_array_adaptor(obj, ptr)

    # TODO: here we have minimal typechecking by the itemsize.
    #       need to do better
    try:
        expected_itemsize = numpy_support.as_dtype(typ.dtype).itemsize
    except NotImplementedError:
        # Don't check types that can't be `as_dtype()`-ed
        itemsize_mismatch = cgutils.false_bit
    else:
        expected_itemsize = nativeary.itemsize.type(expected_itemsize)
        itemsize_mismatch = c.builder.icmp_unsigned(
            '!=',
            nativeary.itemsize,
            expected_itemsize,
            )

    failed = c.builder.or_(
        cgutils.is_not_null(c.builder, errcode),
        itemsize_mismatch,
    )
    # Handle error
    with c.builder.if_then(failed, likely=False):
        c.pyapi.err_set_string("PyExc_TypeError",
                               "can't unbox array from PyObject into "
                               "native value.  The object maybe of a "
                               "different type")
    return NativeValue(c.builder.load(aryptr), is_error=failed)


@box(types.Tuple)
@box(types.UniTuple)
def box_tuple(typ, val, c):
    """
    Convert native array or structure *val* to a tuple object.
    """
    tuple_val = c.pyapi.tuple_new(typ.count)

    for i, dtype in enumerate(typ):
        item = c.builder.extract_value(val, i)
        obj = c.box(dtype, item)
        c.pyapi.tuple_setitem(tuple_val, i, obj)

    return tuple_val

@box(types.NamedTuple)
@box(types.NamedUniTuple)
def box_namedtuple(typ, val, c):
    """
    Convert native array or structure *val* to a namedtuple object.
    """
    cls_obj = c.pyapi.unserialize(c.pyapi.serialize_object(typ.instance_class))
    tuple_obj = box_tuple(typ, val, c)
    obj = c.pyapi.call(cls_obj, tuple_obj)
    c.pyapi.decref(cls_obj)
    c.pyapi.decref(tuple_obj)
    return obj


@unbox(types.BaseTuple)
def unbox_tuple(typ, obj, c):
    """
    Convert tuple *obj* to a native array (if homogeneous) or structure.
    """
    n = len(typ)
    values = []
    cleanups = []
    lty = c.context.get_value_type(typ)

    is_error_ptr = cgutils.alloca_once_value(c.builder, cgutils.false_bit)
    value_ptr = cgutils.alloca_once(c.builder, lty)

    # Issue #1638: need to check the tuple size
    actual_size = c.pyapi.tuple_size(obj)
    size_matches = c.builder.icmp_unsigned('==', actual_size,
                                            ir.Constant(actual_size.type, n))
    with c.builder.if_then(c.builder.not_(size_matches), likely=False):
        c.pyapi.err_format(
            "PyExc_ValueError",
            "size mismatch for tuple, expected %d element(s) but got %%zd" % (n,),
            actual_size)
        c.builder.store(cgutils.true_bit, is_error_ptr)

    # We unbox the items even if not `size_matches`, to avoid issues with
    # the generated IR (instruction doesn't dominate all uses)
    for i, eltype in enumerate(typ):
        elem = c.pyapi.tuple_getitem(obj, i)
        native = c.unbox(eltype, elem)
        values.append(native.value)
        with c.builder.if_then(native.is_error, likely=False):
            c.builder.store(cgutils.true_bit, is_error_ptr)
        if native.cleanup is not None:
            cleanups.append(native.cleanup)

    value = c.context.make_tuple(c.builder, typ, values)
    c.builder.store(value, value_ptr)

    if cleanups:
        with c.builder.if_then(size_matches, likely=True):
            def cleanup():
                for func in reversed(cleanups):
                    func()
    else:
        cleanup = None

    return NativeValue(c.builder.load(value_ptr), cleanup=cleanup,
                       is_error=c.builder.load(is_error_ptr))


@box(types.List)
def box_list(typ, val, c):
    """
    Convert native list *val* to a list object.
    """
    list = listobj.ListInstance(c.context, c.builder, typ, val)
    obj = list.parent
    res = cgutils.alloca_once_value(c.builder, obj)
    with c.builder.if_else(cgutils.is_not_null(c.builder, obj)) as (has_parent, otherwise):
        with has_parent:
            # List is actually reflected => return the original object
            # (note not all list instances whose *type* is reflected are
            #  actually reflected; see numba.tests.test_lists for an example)
            c.pyapi.incref(obj)

        with otherwise:
            # Build a new Python list
            nitems = list.size
            obj = c.pyapi.list_new(nitems)
            with c.builder.if_then(cgutils.is_not_null(c.builder, obj),
                                   likely=True):
                with cgutils.for_range(c.builder, nitems) as loop:
                    item = list.getitem(loop.index)
                    list.incref_value(item)
                    itemobj = c.box(typ.dtype, item)
                    c.pyapi.list_setitem(obj, loop.index, itemobj)

            c.builder.store(obj, res)

    # Steal NRT ref
    c.context.nrt.decref(c.builder, typ, val)
    return c.builder.load(res)


class _NumbaTypeHelper(object):
    """A helper for acquiring `numba.typeof` for type checking.

    Usage
    -----

        # `c` is the boxing context.
        with _NumbaTypeHelper(c) as nth:
            # This contextmanager maintains the lifetime of the `numba.typeof`
            # function.
            the_numba_type = nth.typeof(some_object)
            # Do work on the type object
            do_checks(the_numba_type)
            # Cleanup
            c.pyapi.decref(the_numba_type)
        # At this point *nth* should not be used.
    """
    def __init__(self, c):
        self.c = c

    def __enter__(self):
        c = self.c
        numba_name = c.context.insert_const_string(c.builder.module, 'numba')
        numba_mod = c.pyapi.import_module_noblock(numba_name)
        typeof_fn = c.pyapi.object_getattr_string(numba_mod, 'typeof')
        self.typeof_fn = typeof_fn
        c.pyapi.decref(numba_mod)
        return self

    def __exit__(self, *args, **kwargs):
        c = self.c
        c.pyapi.decref(self.typeof_fn)

    def typeof(self, obj):
        res = self.c.pyapi.call_function_objargs(self.typeof_fn, [obj])
        return res


def _python_list_to_native(typ, obj, c, size, listptr, errorptr):
    """
    Construct a new native list from a Python list.
    """
    def check_element_type(nth, itemobj, expected_typobj):
        typobj = nth.typeof(itemobj)
        # Check if *typobj* is NULL
        with c.builder.if_then(
                cgutils.is_null(c.builder, typobj),
                likely=False,
                ):
            c.builder.store(cgutils.true_bit, errorptr)
            loop.do_break()
        # Mandate that objects all have the same exact type
        type_mismatch = c.builder.icmp_signed('!=', typobj, expected_typobj)

        with c.builder.if_then(type_mismatch, likely=False):
            c.builder.store(cgutils.true_bit, errorptr)
            c.pyapi.err_format(
                "PyExc_TypeError",
                "can't unbox heterogeneous list: %S != %S",
                expected_typobj, typobj,
                )
            c.pyapi.decref(typobj)
            loop.do_break()
        c.pyapi.decref(typobj)

    # Allocate a new native list
    ok, list = listobj.ListInstance.allocate_ex(c.context, c.builder, typ, size)
    with c.builder.if_else(ok, likely=True) as (if_ok, if_not_ok):
        with if_ok:
            list.size = size
            zero = ir.Constant(size.type, 0)
            with c.builder.if_then(c.builder.icmp_signed('>', size, zero),
                                   likely=True):
                # Traverse Python list and unbox objects into native list
                with _NumbaTypeHelper(c) as nth:
                    # Note: *expected_typobj* can't be NULL
                    expected_typobj = nth.typeof(c.pyapi.list_getitem(obj, zero))
                    with cgutils.for_range(c.builder, size) as loop:
                        itemobj = c.pyapi.list_getitem(obj, loop.index)
                        check_element_type(nth, itemobj, expected_typobj)
                        # XXX we don't call native cleanup for each
                        # list element, since that would require keeping
                        # of which unboxings have been successful.
                        native = c.unbox(typ.dtype, itemobj)
                        with c.builder.if_then(native.is_error, likely=False):
                            c.builder.store(cgutils.true_bit, errorptr)
                            loop.do_break()
                        # The reference is borrowed so incref=False
                        list.setitem(loop.index, native.value, incref=False)
                    c.pyapi.decref(expected_typobj)
            if typ.reflected:
                list.parent = obj
            # Stuff meminfo pointer into the Python object for
            # later reuse.
            with c.builder.if_then(c.builder.not_(c.builder.load(errorptr)),
                                                  likely=False):
                c.pyapi.object_set_private_data(obj, list.meminfo)
            list.set_dirty(False)
            c.builder.store(list.value, listptr)

        with if_not_ok:
            c.builder.store(cgutils.true_bit, errorptr)

    # If an error occurred, drop the whole native list
    with c.builder.if_then(c.builder.load(errorptr)):
        c.context.nrt.decref(c.builder, typ, list.value)


@unbox(types.List)
def unbox_list(typ, obj, c):
    """
    Convert list *obj* to a native list.

    If list was previously unboxed, we reuse the existing native list
    to ensure consistency.
    """
    size = c.pyapi.list_size(obj)

    errorptr = cgutils.alloca_once_value(c.builder, cgutils.false_bit)
    listptr = cgutils.alloca_once(c.builder, c.context.get_value_type(typ))

    # See if the list was previously unboxed, if so, re-use the meminfo.
    ptr = c.pyapi.object_get_private_data(obj)

    with c.builder.if_else(cgutils.is_not_null(c.builder, ptr)) \
        as (has_meminfo, otherwise):

        with has_meminfo:
            # List was previously unboxed => reuse meminfo
            list = listobj.ListInstance.from_meminfo(c.context, c.builder, typ, ptr)
            list.size = size
            if typ.reflected:
                list.parent = obj
            c.builder.store(list.value, listptr)

        with otherwise:
            _python_list_to_native(typ, obj, c, size, listptr, errorptr)

    def cleanup():
        # Clean up the associated pointer, as the meminfo is now invalid.
        c.pyapi.object_reset_private_data(obj)

    return NativeValue(c.builder.load(listptr),
                       is_error=c.builder.load(errorptr),
                       cleanup=cleanup)


@reflect(types.List)
def reflect_list(typ, val, c):
    """
    Reflect the native list's contents into the Python object.
    """
    if not typ.reflected:
        return
    if typ.dtype.reflected:
        msg = "cannot reflect element of reflected container: {}\n".format(typ)
        raise TypeError(msg)

    list = listobj.ListInstance(c.context, c.builder, typ, val)
    with c.builder.if_then(list.dirty, likely=False):
        obj = list.parent
        size = c.pyapi.list_size(obj)
        new_size = list.size
        diff = c.builder.sub(new_size, size)
        diff_gt_0 = c.builder.icmp_signed('>=', diff,
                                          ir.Constant(diff.type, 0))
        with c.builder.if_else(diff_gt_0) as (if_grow, if_shrink):
            # XXX no error checking below
            with if_grow:
                # First overwrite existing items
                with cgutils.for_range(c.builder, size) as loop:
                    item = list.getitem(loop.index)
                    list.incref_value(item)
                    itemobj = c.box(typ.dtype, item)
                    c.pyapi.list_setitem(obj, loop.index, itemobj)
                # Then add missing items
                with cgutils.for_range(c.builder, diff) as loop:
                    idx = c.builder.add(size, loop.index)
                    item = list.getitem(idx)
                    list.incref_value(item)
                    itemobj = c.box(typ.dtype, item)
                    c.pyapi.list_append(obj, itemobj)
                    c.pyapi.decref(itemobj)

            with if_shrink:
                # First delete list tail
                c.pyapi.list_setslice(obj, new_size, size, None)
                # Then overwrite remaining items
                with cgutils.for_range(c.builder, new_size) as loop:
                    item = list.getitem(loop.index)
                    list.incref_value(item)
                    itemobj = c.box(typ.dtype, item)
                    c.pyapi.list_setitem(obj, loop.index, itemobj)

        # Mark the list clean, in case it is reflected twice
        list.set_dirty(False)


def _python_set_to_native(typ, obj, c, size, setptr, errorptr):
    """
    Construct a new native set from a Python set.
    """
    # Allocate a new native set
    ok, inst = setobj.SetInstance.allocate_ex(c.context, c.builder, typ, size)
    with c.builder.if_else(ok, likely=True) as (if_ok, if_not_ok):
        with if_ok:
            # Traverse Python set and unbox objects into native set
            typobjptr = cgutils.alloca_once_value(c.builder,
                                                  ir.Constant(c.pyapi.pyobj, None))

            with c.pyapi.set_iterate(obj) as loop:
                itemobj = loop.value
                # Mandate that objects all have the same exact type
                typobj = c.pyapi.get_type(itemobj)
                expected_typobj = c.builder.load(typobjptr)

                with c.builder.if_else(
                    cgutils.is_null(c.builder, expected_typobj),
                    likely=False) as (if_first, if_not_first):
                    with if_first:
                        # First iteration => store item type
                        c.builder.store(typobj, typobjptr)
                    with if_not_first:
                        # Otherwise, check item type
                        type_mismatch = c.builder.icmp_signed('!=', typobj,
                                                              expected_typobj)
                        with c.builder.if_then(type_mismatch, likely=False):
                            c.builder.store(cgutils.true_bit, errorptr)
                            c.pyapi.err_set_string("PyExc_TypeError",
                                                   "can't unbox heterogeneous set")
                            loop.do_break()

                # XXX we don't call native cleanup for each set element,
                # since that would require keeping track
                # of which unboxings have been successful.
                native = c.unbox(typ.dtype, itemobj)
                with c.builder.if_then(native.is_error, likely=False):
                    c.builder.store(cgutils.true_bit, errorptr)
                inst.add_pyapi(c.pyapi, native.value, do_resize=False)

            if typ.reflected:
                inst.parent = obj
            # Associate meminfo pointer with the Python object for later reuse.
            with c.builder.if_then(c.builder.not_(c.builder.load(errorptr)),
                                   likely=False):
                c.pyapi.object_set_private_data(obj, inst.meminfo)
            inst.set_dirty(False)
            c.builder.store(inst.value, setptr)

        with if_not_ok:
            c.builder.store(cgutils.true_bit, errorptr)

    # If an error occurred, drop the whole native set
    with c.builder.if_then(c.builder.load(errorptr)):
        c.context.nrt.decref(c.builder, typ, inst.value)


@unbox(types.Set)
def unbox_set(typ, obj, c):
    """
    Convert set *obj* to a native set.

    If set was previously unboxed, we reuse the existing native set
    to ensure consistency.
    """
    size = c.pyapi.set_size(obj)

    errorptr = cgutils.alloca_once_value(c.builder, cgutils.false_bit)
    setptr = cgutils.alloca_once(c.builder, c.context.get_value_type(typ))

    # See if the set was previously unboxed, if so, re-use the meminfo.
    ptr = c.pyapi.object_get_private_data(obj)

    with c.builder.if_else(cgutils.is_not_null(c.builder, ptr)) \
        as (has_meminfo, otherwise):

        with has_meminfo:
            # Set was previously unboxed => reuse meminfo
            inst = setobj.SetInstance.from_meminfo(c.context, c.builder, typ, ptr)
            if typ.reflected:
                inst.parent = obj
            c.builder.store(inst.value, setptr)

        with otherwise:
            _python_set_to_native(typ, obj, c, size, setptr, errorptr)

    def cleanup():
        # Clean up the associated pointer, as the meminfo is now invalid.
        c.pyapi.object_reset_private_data(obj)

    return NativeValue(c.builder.load(setptr),
                       is_error=c.builder.load(errorptr),
                       cleanup=cleanup)


def _native_set_to_python_list(typ, payload, c):
    """
    Create a Python list from a native set's items.
    """
    nitems = payload.used
    listobj = c.pyapi.list_new(nitems)
    ok = cgutils.is_not_null(c.builder, listobj)
    with c.builder.if_then(ok, likely=True):
        index = cgutils.alloca_once_value(c.builder,
                                          ir.Constant(nitems.type, 0))
        with payload._iterate() as loop:
            i = c.builder.load(index)
            item = loop.entry.key
            itemobj = c.box(typ.dtype, item)
            c.pyapi.list_setitem(listobj, i, itemobj)
            i = c.builder.add(i, ir.Constant(i.type, 1))
            c.builder.store(i, index)

    return ok, listobj


@box(types.Set)
def box_set(typ, val, c):
    """
    Convert native set *val* to a set object.
    """
    inst = setobj.SetInstance(c.context, c.builder, typ, val)
    obj = inst.parent
    res = cgutils.alloca_once_value(c.builder, obj)

    with c.builder.if_else(cgutils.is_not_null(c.builder, obj)) as (has_parent, otherwise):
        with has_parent:
            # Set is actually reflected => return the original object
            # (note not all set instances whose *type* is reflected are
            #  actually reflected; see numba.tests.test_sets for an example)
            c.pyapi.incref(obj)

        with otherwise:
            # Build a new Python list and then create a set from that
            payload = inst.payload
            ok, listobj = _native_set_to_python_list(typ, payload, c)
            with c.builder.if_then(ok, likely=True):
                obj = c.pyapi.set_new(listobj)
                c.pyapi.decref(listobj)
                c.builder.store(obj, res)

    # Steal NRT ref
    c.context.nrt.decref(c.builder, typ, val)
    return c.builder.load(res)

@reflect(types.Set)
def reflect_set(typ, val, c):
    """
    Reflect the native set's contents into the Python object.
    """
    if not typ.reflected:
        return
    inst = setobj.SetInstance(c.context, c.builder, typ, val)
    payload = inst.payload

    with c.builder.if_then(payload.dirty, likely=False):
        obj = inst.parent
        # XXX errors are not dealt with below
        c.pyapi.set_clear(obj)

        # Build a new Python list and then update the set with that
        ok, listobj = _native_set_to_python_list(typ, payload, c)
        with c.builder.if_then(ok, likely=True):
            c.pyapi.set_update(obj, listobj)
            c.pyapi.decref(listobj)

        # Mark the set clean, in case it is reflected twice
        inst.set_dirty(False)


#
# Other types
#

@box(types.Generator)
def box_generator(typ, val, c):
    return c.pyapi.from_native_generator(val, typ, c.env_manager.env_ptr)

@unbox(types.Generator)
def unbox_generator(typ, obj, c):
    return c.pyapi.to_native_generator(obj, typ)


@box(types.DType)
def box_dtype(typ, val, c):
    np_dtype = numpy_support.as_dtype(typ.dtype)
    return c.pyapi.unserialize(c.pyapi.serialize_object(np_dtype))

@unbox(types.DType)
def unbox_dtype(typ, val, c):
    return NativeValue(c.context.get_dummy_value())


@box(types.NumberClass)
def box_number_class(typ, val, c):
    np_dtype = numpy_support.as_dtype(typ.dtype)
    return c.pyapi.unserialize(c.pyapi.serialize_object(np_dtype))

@unbox(types.NumberClass)
def unbox_number_class(typ, val, c):
    return NativeValue(c.context.get_dummy_value())


@box(types.PyObject)
@box(types.Object)
def box_pyobject(typ, val, c):
    return val

@unbox(types.PyObject)
@unbox(types.Object)
def unbox_pyobject(typ, obj, c):
    return NativeValue(obj)


@unbox(types.ExternalFunctionPointer)
def unbox_funcptr(typ, obj, c):
    if typ.get_pointer is None:
        raise NotImplementedError(typ)

    # Call get_pointer() on the object to get the raw pointer value
    ptrty = c.context.get_function_pointer_type(typ)
    ret = cgutils.alloca_once_value(c.builder,
                                    ir.Constant(ptrty, None),
                                    name='fnptr')
    ser = c.pyapi.serialize_object(typ.get_pointer)
    get_pointer = c.pyapi.unserialize(ser)
    with cgutils.if_likely(c.builder,
                           cgutils.is_not_null(c.builder, get_pointer)):
        intobj = c.pyapi.call_function_objargs(get_pointer, (obj,))
        c.pyapi.decref(get_pointer)
        with cgutils.if_likely(c.builder,
                               cgutils.is_not_null(c.builder, intobj)):
            ptr = c.pyapi.long_as_voidptr(intobj)
            c.pyapi.decref(intobj)
            c.builder.store(c.builder.bitcast(ptr, ptrty), ret)
    return NativeValue(c.builder.load(ret), is_error=c.pyapi.c_api_error())

@box(types.DeferredType)
def box_deferred(typ, val, c):
    out = c.pyapi.from_native_value(typ.get(),
                                    c.builder.extract_value(val, [0]),
                                    env_manager=c.env_manager)
    return out


@unbox(types.DeferredType)
def unbox_deferred(typ, obj, c):
    native_value = c.pyapi.to_native_value(typ.get(), obj)
    model = c.context.data_model_manager[typ]
    res = model.set(c.builder, model.make_uninitialized(), native_value.value)
    return NativeValue(res, is_error=native_value.is_error,
                       cleanup=native_value.cleanup)


@unbox(types.Dispatcher)
def unbox_dispatcher(typ, obj, c):
    # In native code, Dispatcher types can be casted to FunctionType.
    return NativeValue(obj)


@box(types.Dispatcher)
def box_pyobject(typ, val, c):
    c.pyapi.incref(val)
    return val


def unbox_unsupported(typ, obj, c):
    c.pyapi.err_set_string("PyExc_TypeError",
                           "can't unbox {!r} type".format(typ))
    res = c.context.get_constant_null(typ)
    return NativeValue(res, is_error=cgutils.true_bit)


def box_unsupported(typ, val, c):
    msg = "cannot convert native %s to Python object" % (typ,)
    c.pyapi.err_set_string("PyExc_TypeError", msg)
    res = c.pyapi.get_null_object()
    return res


@box(types.Literal)
def box_literal(typ, val, c):
    # Const type contains the python object of the constant value,
    # which we can directly return.
    retval = typ.literal_value
    # Serialize the value into the IR
    return c.pyapi.unserialize(c.pyapi.serialize_object(retval))


@box(types.MemInfoPointer)
def box_meminfo_pointer(typ, val, c):
    return c.pyapi.nrt_meminfo_as_pyobject(val)


@unbox(types.MemInfoPointer)
def unbox_meminfo_pointer(typ, obj, c):
    res = c.pyapi.nrt_meminfo_from_pyobject(obj)
    errored = cgutils.is_null(c.builder, res)
    return NativeValue(res, is_error=errored)

@unbox(types.TypeRef)
def unbox_typeref(typ, val, c):
    return NativeValue(c.context.get_dummy_value(), is_error=cgutils.false_bit)


@box(types.LiteralStrKeyDict)
def box_LiteralStrKeyDict(typ, val, c):
    return box_unsupported(typ, val, c)
