MemoryView.py

from Errors import CompileError, error
import ExprNodes
from ExprNodes import IntNode, NameNode, AttributeNode
import Options
from Code import UtilityCode, TempitaUtilityCode
from UtilityCode import CythonUtilityCode
from Cython.Compiler import Buffer, PyrexTypes, ModuleNode, Symtab

START_ERR = "Start must not be given."
STOP_ERR = "Axis specification only allowed in the 'step' slot."
STEP_ERR = "Step must be omitted, 1, or a valid specifier."
BOTH_CF_ERR = "Cannot specify an array that is both C and Fortran contiguous."
INVALID_ERR = "Invalid axis specification."
NOT_CIMPORTED_ERR = "Variable was not cimported from cython.view"
EXPR_ERR = "no expressions allowed in axis spec, only names and literals."
CF_ERR = "Invalid axis specification for a C/Fortran contiguous array."
ERR_UNINITIALIZED = ("Cannot check if memoryview %s is initialized without the "
                     "GIL, consider using initializedcheck(False)")

def concat_flags(*flags):
    return "(%s)" % "|".join(flags)

format_flag = "PyBUF_FORMAT"

memview_c_contiguous = "(PyBUF_C_CONTIGUOUS | PyBUF_FORMAT | PyBUF_WRITABLE)"
memview_f_contiguous = "(PyBUF_F_CONTIGUOUS | PyBUF_FORMAT | PyBUF_WRITABLE)"
memview_any_contiguous = "(PyBUF_ANY_CONTIGUOUS | PyBUF_FORMAT | PyBUF_WRITABLE)"
memview_full_access = "PyBUF_FULL"
#memview_strided_access = "PyBUF_STRIDED"
memview_strided_access = "PyBUF_RECORDS"

MEMVIEW_DIRECT = '__Pyx_MEMVIEW_DIRECT'
MEMVIEW_PTR    = '__Pyx_MEMVIEW_PTR'
MEMVIEW_FULL   = '__Pyx_MEMVIEW_FULL'
MEMVIEW_CONTIG = '__Pyx_MEMVIEW_CONTIG'
MEMVIEW_STRIDED= '__Pyx_MEMVIEW_STRIDED'
MEMVIEW_FOLLOW = '__Pyx_MEMVIEW_FOLLOW'

_spec_to_const = {
        'direct' : MEMVIEW_DIRECT,
        'ptr'    : MEMVIEW_PTR,
        'full'   : MEMVIEW_FULL,
        'contig' : MEMVIEW_CONTIG,
        'strided': MEMVIEW_STRIDED,
        'follow' : MEMVIEW_FOLLOW,
        }

_spec_to_abbrev = {
    'direct'  : 'd',
    'ptr'     : 'p',
    'full'    : 'f',
    'contig'  : 'c',
    'strided' : 's',
    'follow'  : '_',
}

memslice_entry_init = "{ 0, 0, { 0 }, { 0 }, { 0 } }"

memview_name = u'memoryview'
memview_typeptr_cname = '__pyx_memoryview_type'
memview_objstruct_cname = '__pyx_memoryview_obj'
memviewslice_cname = u'__Pyx_memviewslice'

def put_init_entry(mv_cname, code):
    code.putln("%s.data = NULL;" % mv_cname)
    code.putln("%s.memview = NULL;" % mv_cname)

#def axes_to_str(axes):
#    return "".join([access[0].upper()+packing[0] for (access, packing) in axes])

def put_acquire_memoryviewslice(lhs_cname, lhs_type, lhs_pos, rhs, code,
                                have_gil=False, first_assignment=True):
    "We can avoid decreffing the lhs if we know it is the first assignment"
    assert rhs.type.is_memoryviewslice, rhs.type

    pretty_rhs = rhs.result_in_temp() or rhs.is_simple()
    if pretty_rhs:
        rhstmp = rhs.result()
    else:
        rhstmp = code.funcstate.allocate_temp(lhs_type, manage_ref=False)
        code.putln("%s = %s;" % (rhstmp, rhs.result_as(lhs_type)))

    # Allow uninitialized assignment
    #code.putln(code.put_error_if_unbound(lhs_pos, rhs.entry))
    put_assign_to_memviewslice(lhs_cname, rhs, rhstmp, lhs_type, code,
                               have_gil=have_gil, first_assignment=first_assignment)

    if not pretty_rhs:
        code.funcstate.release_temp(rhstmp)

def put_assign_to_memviewslice(lhs_cname, rhs, rhs_cname, memviewslicetype, code,
                               have_gil=False, first_assignment=False):
    if not first_assignment:
        code.put_xdecref_memoryviewslice(lhs_cname, have_gil=have_gil)

    if not rhs.result_in_temp():
        rhs.make_owned_memoryviewslice(code)

    code.putln("%s = %s;" % (lhs_cname, rhs_cname))

def get_buf_flags(specs):
    is_c_contig, is_f_contig = is_cf_contig(specs)

    if is_c_contig:
        return memview_c_contiguous
    elif is_f_contig:
        return memview_f_contiguous

    access, packing = zip(*specs)

    if 'full' in access or 'ptr' in access:
        return memview_full_access
    else:
        return memview_strided_access

def get_best_slice_order(memviewslice):
    return "__pyx_get_best_slice_order(%s, %d)" % (memviewslice.result(),
                                                   memviewslice.type.ndim)

def insert_newaxes(memoryviewtype, n):
    axes = [('direct', 'strided')] * n
    axes.extend(memoryviewtype.axes)
    return PyrexTypes.MemoryViewSliceType(memoryviewtype.dtype, axes)

def broadcast_types(src, dst):
    n = abs(src.ndim - dst.ndim)
    if src.ndim < dst.ndim:
        return insert_newaxes(src, n), dst
    else:
        return src, insert_newaxes(dst, n)

class MemoryViewSliceBufferEntry(Buffer.BufferEntry):
    """
    May be used during code generation time to be queried for
    shape/strides/suboffsets attributes, or to perform indexing or slicing.
    """

    def __init__(self, entry):
        """
        node: the node which this entry wraps. The result of this node
              must be simple
        """
        self.entry = entry
        self.type = entry.type
        self.cname = entry.cname

        self.buf_ptr = "%s.data" % self.cname
        dtype = self.entry.type.dtype
        self.buf_ptr_type = PyrexTypes.CPtrType(dtype)

        self.init_attributes()

    def get_buf_suboffsetvars(self):
        return self._for_all_ndim("%s.suboffsets[%d]")

    def get_buf_stridevars(self):
        return self._for_all_ndim("%s.strides[%d]")

    def get_buf_shapevars(self):
        return self._for_all_ndim("%s.shape[%d]")

    def generate_buffer_lookup_code(self, code, index_cnames):
        axes = [(dim, index_cnames[dim], access, packing)
                    for dim, (access, packing) in enumerate(self.type.axes)]
        return self._generate_buffer_lookup_code(code, axes)

    def _generate_buffer_lookup_code(self, code, axes, cast_result=True):
        """
        Generate a single expression that indexes the memory view slice
        in each dimension.
        """
        bufp = self.buf_ptr
        type_decl = self.type.dtype.declaration_code("")

        for dim, index, access, packing in axes:
            shape = "%s.shape[%d]" % (self.cname, dim)
            stride = "%s.strides[%d]" % (self.cname, dim)
            suboffset = "%s.suboffsets[%d]" % (self.cname, dim)

            flag = get_memoryview_flag(access, packing)

            if flag in ("generic", "generic_contiguous"):
                # Note: we cannot do cast tricks to avoid stride multiplication
                #       for generic_contiguous, as we may have to do (dtype *)
                #       or (dtype **) arithmetic, we won't know which unless
                #       we check suboffsets
                code.globalstate.use_utility_code(memviewslice_index_helpers)
                bufp = ('__pyx_memviewslice_index_full(%s, %s, %s, %s)' %
                                            (bufp, index, stride, suboffset))

            elif flag == "indirect":
                bufp = "(%s + %s * %s)" % (bufp, index, stride)
                bufp = ("(*((char **) %s) + %s)" % (bufp, suboffset))

            elif flag == "indirect_contiguous":
                # Note: we do char ** arithmetic
                bufp = "(*((char **) %s + %s) + %s)" % (bufp, index, suboffset)

            elif flag == "strided":
                bufp = "(%s + %s * %s)" % (bufp, index, stride)

            else:
                assert flag == 'contiguous', flag
                bufp = '((char *) (((%s *) %s) + %s))' % (type_decl, bufp, index)

            bufp = '( /* dim=%d */ %s )' % (dim, bufp)

        if cast_result:
            return "((%s *) %s)" % (type_decl, bufp)

        return bufp

    def generate_buffer_slice_code(self, code, indices, dst, have_gil,
                                   have_slices):
        """
        Slice a memoryviewslice.

        indices     - list of index nodes. If not a SliceNode, or NoneNode,
                      then it must be coercible to Py_ssize_t

        Simply call __pyx_memoryview_slice_memviewslice with the right
        arguments, unless the dimension is omitted or a bare ':', in which
        case we copy over the shape/strides/suboffsets attributes directly
        for that dimension.
        """
        new_ndim = 0
        src = self.cname

        def load_slice_util(name, dict):
            proto, impl = TempitaUtilityCode.load_as_string(
                        name, "MemoryView_C.c", context=dict)
            return impl

        all_dimensions_direct = True
        for access, packing in self.type.axes:
            if access != 'direct':
                all_dimensions_direct = False
                break

        no_suboffset_dim = all_dimensions_direct and not have_slices
        if not no_suboffset_dim:
            suboffset_dim = code.funcstate.allocate_temp(
                             PyrexTypes.c_int_type, False)
            code.putln("%s = -1;" % suboffset_dim)

        code.putln("%(dst)s.data = %(src)s.data;" % locals())
        code.putln("%(dst)s.memview = %(src)s.memview;" % locals())
        code.put_incref_memoryviewslice(dst)

        dim = -1
        for index in indices:
            error_goto = code.error_goto(index.pos)
            if not index.is_none:
                dim += 1
                access, packing = self.type.axes[dim]

            if isinstance(index, ExprNodes.SliceNode):
                # slice, unspecified dimension, or part of ellipsis
                d = locals()
                for s in "start stop step".split():
                    idx = getattr(index, s)
                    have_idx = d['have_' + s] = not idx.is_none
                    if have_idx:
                        d[s] = idx.result()
                    else:
                        d[s] = "0"

                if (not d['have_start'] and
                    not d['have_stop'] and
                    not d['have_step']):
                    # full slice (:), simply copy over the extent, stride
                    # and suboffset. Also update suboffset_dim if needed
                    d['access'] = access
                    code.put(load_slice_util("SimpleSlice", d))
                else:
                    code.put(load_slice_util("ToughSlice", d))

                new_ndim += 1

            elif index.is_none:
                # newaxis
                attribs = [('shape', 1), ('strides', 0), ('suboffsets', -1)]
                for attrib, value in attribs:
                    code.putln("%s.%s[%d] = %d;" % (dst, attrib, new_ndim, value))

                new_ndim += 1

            else:
                # normal index
                idx = index.result()

                if access == 'direct':
                    indirect = False
                else:
                    indirect = True
                    generic = (access == 'full')
                    if new_ndim != 0:
                        return error(index.pos,
                                     "All preceding dimensions must be "
                                     "indexed and not sliced")

                d = locals()
                code.put(load_slice_util("SliceIndex", d))

        if not no_suboffset_dim:
            code.funcstate.release_temp(suboffset_dim)


def empty_slice(pos):
    none = ExprNodes.NoneNode(pos)
    return ExprNodes.SliceNode(pos, start=none,
                               stop=none, step=none)

def unellipsify(indices, ndim):
    result = []
    seen_ellipsis = False
    have_slices = False

    newaxes = [newaxis for newaxis in indices if newaxis.is_none]
    n_indices = len(indices) - len(newaxes)

    for index in indices:
        if isinstance(index, ExprNodes.EllipsisNode):
            have_slices = True
            full_slice = empty_slice(index.pos)

            if seen_ellipsis:
                result.append(full_slice)
            else:
                nslices = ndim - n_indices + 1
                result.extend([full_slice] * nslices)
                seen_ellipsis = True
        else:
            have_slices = (have_slices or
                           isinstance(index, ExprNodes.SliceNode) or
                           index.is_none)
            result.append(index)

    result_length = len(result) - len(newaxes)
    if result_length < ndim:
        have_slices = True
        nslices = ndim - result_length
        result.extend([empty_slice(indices[-1].pos)] * nslices)

    return have_slices, result, newaxes

def get_memoryview_flag(access, packing):
    if access == 'full' and packing in ('strided', 'follow'):
        return 'generic'
    elif access == 'full' and packing == 'contig':
        return 'generic_contiguous'
    elif access == 'ptr' and packing in ('strided', 'follow'):
        return 'indirect'
    elif access == 'ptr' and packing == 'contig':
        return 'indirect_contiguous'
    elif access == 'direct' and packing in ('strided', 'follow'):
        return 'strided'
    else:
        assert (access, packing) == ('direct', 'contig'), (access, packing)
        return 'contiguous'

def get_is_contig_func_name(c_or_f, ndim):
    return "__pyx_memviewslice_is_%s_contig%d" % (c_or_f, ndim)

def get_is_contig_utility(c_contig, ndim):
    C = dict(context, ndim=ndim)
    if c_contig:
        utility = load_memview_c_utility("MemviewSliceIsCContig", C,
                                         requires=[is_contig_utility])
    else:
        utility = load_memview_c_utility("MemviewSliceIsFContig", C,
                                         requires=[is_contig_utility])

    return utility

def slice_iter(slice_type, slice_result, ndim, code):
    if slice_type.is_c_contig or slice_type.is_f_contig:
        return ContigSliceIter(slice_type, slice_result, ndim, code)
    else:
        return StridedSliceIter(slice_type, slice_result, ndim, code)

class SliceIter(object):
    def __init__(self, slice_type, slice_result, ndim, code):
        self.slice_type = slice_type
        self.slice_result = slice_result
        self.code = code
        self.ndim = ndim

class ContigSliceIter(SliceIter):
    def start_loops(self):
        code = self.code
        code.begin_block()

        type_decl = self.slice_type.dtype.declaration_code("")

        total_size = ' * '.join("%s.shape[%d]" % (self.slice_result, i)
                                    for i in range(self.ndim))
        code.putln("Py_ssize_t __pyx_temp_extent = %s;" % total_size)
        code.putln("Py_ssize_t __pyx_temp_idx;")
        code.putln("%s *__pyx_temp_pointer = (%s *) %s.data;" % (
                            type_decl, type_decl, self.slice_result))
        code.putln("for (__pyx_temp_idx = 0; "
                        "__pyx_temp_idx < __pyx_temp_extent; "
                        "__pyx_temp_idx++) {")

        return "__pyx_temp_pointer"

    def end_loops(self):
        self.code.putln("__pyx_temp_pointer += 1;")
        self.code.putln("}")
        self.code.end_block()

class StridedSliceIter(SliceIter):
    def start_loops(self):
        code = self.code
        code.begin_block()

        for i in range(self.ndim):
            t = i, self.slice_result, i
            code.putln("Py_ssize_t __pyx_temp_extent_%d = %s.shape[%d];" % t)
            code.putln("Py_ssize_t __pyx_temp_stride_%d = %s.strides[%d];" % t)
            code.putln("char *__pyx_temp_pointer_%d;" % i)
            code.putln("Py_ssize_t __pyx_temp_idx_%d;" % i)

        code.putln("__pyx_temp_pointer_0 = %s.data;" % self.slice_result)

        for i in range(self.ndim):
            if i > 0:
                code.putln("__pyx_temp_pointer_%d = __pyx_temp_pointer_%d;" % (i, i - 1))

            code.putln("for (__pyx_temp_idx_%d = 0; "
                            "__pyx_temp_idx_%d < __pyx_temp_extent_%d; "
                            "__pyx_temp_idx_%d++) {" % (i, i, i, i))

        return "__pyx_temp_pointer_%d" % (self.ndim - 1)

    def end_loops(self):
        code = self.code
        for i in range(self.ndim - 1, -1, -1):
            code.putln("__pyx_temp_pointer_%d += __pyx_temp_stride_%d;" % (i, i))
            code.putln("}")

        code.end_block()


def copy_c_or_fortran_cname(memview):
    if memview.is_c_contig:
        c_or_f = 'c'
    else:
        c_or_f = 'f'

    return "__pyx_memoryview_copy_slice_%s_%s" % (
            memview.specialization_suffix(), c_or_f)

def get_copy_new_utility(pos, from_memview, to_memview):
    if from_memview.dtype != to_memview.dtype:
        return error(pos, "dtypes must be the same!")
    if len(from_memview.axes) != len(to_memview.axes):
        return error(pos, "number of dimensions must be same")
    if not (to_memview.is_c_contig or to_memview.is_f_contig):
        return error(pos, "to_memview must be c or f contiguous.")

    for (access, packing) in from_memview.axes:
        if access != 'direct':
            return error(
                    pos, "cannot handle 'full' or 'ptr' access at this time.")

    if to_memview.is_c_contig:
        mode = 'c'
        contig_flag = memview_c_contiguous
    elif to_memview.is_f_contig:
        mode = 'fortran'
        contig_flag = memview_f_contiguous

    return load_memview_c_utility(
        "CopyContentsUtility",
        context=dict(
            context,
            mode=mode,
            dtype_decl=to_memview.dtype.declaration_code(''),
            contig_flag=contig_flag,
            ndim=to_memview.ndim,
            func_cname=copy_c_or_fortran_cname(to_memview),
            dtype_is_object=int(to_memview.dtype.is_pyobject)),
        requires=[copy_contents_new_utility])

def get_axes_specs(env, axes):
    '''
    get_axes_specs(env, axes) -> list of (access, packing) specs for each axis.
    access is one of 'full', 'ptr' or 'direct'
    packing is one of 'contig', 'strided' or 'follow'
    '''

    cythonscope = env.global_scope().context.cython_scope
    cythonscope.load_cythonscope()
    viewscope = cythonscope.viewscope

    access_specs = tuple([viewscope.lookup(name)
                    for name in ('full', 'direct', 'ptr')])
    packing_specs = tuple([viewscope.lookup(name)
                    for name in ('contig', 'strided', 'follow')])

    is_f_contig, is_c_contig = False, False
    default_access, default_packing = 'direct', 'strided'
    cf_access, cf_packing = default_access, 'follow'

    axes_specs = []
    # analyse all axes.
    for idx, axis in enumerate(axes):
        if not axis.start.is_none:
            raise CompileError(axis.start.pos,  START_ERR)

        if not axis.stop.is_none:
            raise CompileError(axis.stop.pos, STOP_ERR)

        if axis.step.is_none:
            axes_specs.append((default_access, default_packing))

        elif isinstance(axis.step, IntNode):
            # the packing for the ::1 axis is contiguous,
            # all others are cf_packing.
            if axis.step.compile_time_value(env) != 1:
                raise CompileError(axis.step.pos, STEP_ERR)

            axes_specs.append((cf_access, 'cfcontig'))

        elif isinstance(axis.step, (NameNode, AttributeNode)):
            entry = _get_resolved_spec(env, axis.step)
            if entry.name in view_constant_to_access_packing:
                axes_specs.append(view_constant_to_access_packing[entry.name])
            else:
                raise CompilerError(axis.step.pos, INVALID_ERR)

        else:
            raise CompileError(axis.step.pos, INVALID_ERR)

    # First, find out if we have a ::1 somewhere
    contig_dim = 0
    is_contig = False
    for idx, (access, packing) in enumerate(axes_specs):
        if packing == 'cfcontig':
            if is_contig:
                raise CompileError(axis.step.pos, BOTH_CF_ERR)

            contig_dim = idx
            axes_specs[idx] = (access, 'contig')
            is_contig = True

    if is_contig:
        # We have a ::1 somewhere, see if we're C or Fortran contiguous
        if contig_dim == len(axes) - 1:
            is_c_contig = True
        else:
            is_f_contig = True

            if contig_dim and not axes_specs[contig_dim - 1][0] in ('full', 'ptr'):
                raise CompileError(axes[contig_dim].pos,
                                   "Fortran contiguous specifier must follow an indirect dimension")

        if is_c_contig:
            # Contiguous in the last dimension, find the last indirect dimension
            contig_dim = -1
            for idx, (access, packing) in enumerate(reversed(axes_specs)):
                if access in ('ptr', 'full'):
                    contig_dim = len(axes) - idx - 1

        # Replace 'strided' with 'follow' for any dimension following the last
        # indirect dimension, the first dimension or the dimension following
        # the ::1.
        #               int[::indirect, ::1, :, :]
        #                                    ^  ^
        #               int[::indirect, :, :, ::1]
        #                               ^  ^
        start = contig_dim + 1
        stop = len(axes) - is_c_contig
        for idx, (access, packing) in enumerate(axes_specs[start:stop]):
            idx = contig_dim + 1 + idx
            if access != 'direct':
                raise CompileError(axes[idx].pos,
                                   "Indirect dimension may not follow "
                                   "Fortran contiguous dimension")
            if packing == 'contig':
                raise CompileError(axes[idx].pos,
                                   "Dimension may not be contiguous")
            axes_specs[idx] = (access, cf_packing)

        if is_c_contig:
            # For C contiguity, we need to fix the 'contig' dimension
            # after the loop
            a, p = axes_specs[-1]
            axes_specs[-1] = a, 'contig'

    validate_axes_specs([axis.start.pos for axis in axes],
                        axes_specs,
                        is_c_contig,
                        is_f_contig)

    return axes_specs

def validate_axes(pos, axes):
    if len(axes) >= Options.buffer_max_dims:
        error(pos, "More dimensions than the maximum number"
                   " of buffer dimensions were used.")
        return False

    return True

def all(it):
    for item in it:
        if not item:
            return False
    return True

def is_cf_contig(specs):
    is_c_contig = is_f_contig = False

    if (len(specs) == 1 and specs == [('direct', 'contig')]):
        is_c_contig = True

    elif (specs[-1] == ('direct','contig') and
          all([axis == ('direct','follow') for axis in specs[:-1]])):
        # c_contiguous: 'follow', 'follow', ..., 'follow', 'contig'
        is_c_contig = True

    elif (len(specs) > 1 and
        specs[0] == ('direct','contig') and
        all([axis == ('direct','follow') for axis in specs[1:]])):
        # f_contiguous: 'contig', 'follow', 'follow', ..., 'follow'
        is_f_contig = True

    return is_c_contig, is_f_contig

def get_mode(specs):
    is_c_contig, is_f_contig = is_cf_contig(specs)

    if is_c_contig:
        return 'c'
    elif is_f_contig:
        return 'fortran'

    for access, packing in specs:
        if access in ('ptr', 'full'):
            return 'full'

    return 'strided'

view_constant_to_access_packing = {
    'generic':              ('full',   'strided'),
    'strided':              ('direct', 'strided'),
    'indirect':             ('ptr',    'strided'),
    'generic_contiguous':   ('full',   'contig'),
    'contiguous':           ('direct', 'contig'),
    'indirect_contiguous':  ('ptr',    'contig'),
}

def validate_axes_specs(positions, specs, is_c_contig, is_f_contig):

    packing_specs = ('contig', 'strided', 'follow')
    access_specs = ('direct', 'ptr', 'full')

    # is_c_contig, is_f_contig = is_cf_contig(specs)

    has_contig = has_follow = has_strided = has_generic_contig = False

    last_indirect_dimension = -1
    for idx, (access, packing) in enumerate(specs):
        if access == 'ptr':
            last_indirect_dimension = idx

    for idx, pos, (access, packing) in zip(xrange(len(specs)), positions, specs):

        if not (access in access_specs and
                packing in packing_specs):
            raise CompileError(pos, "Invalid axes specification.")

        if packing == 'strided':
            has_strided = True
        elif packing == 'contig':
            if has_contig:
                raise CompileError(pos, "Only one direct contiguous "
                                        "axis may be specified.")

            valid_contig_dims = last_indirect_dimension + 1, len(specs) - 1
            if idx not in valid_contig_dims and access != 'ptr':
                if last_indirect_dimension + 1 != len(specs) - 1:
                    dims = "dimensions %d and %d" % valid_contig_dims
                else:
                    dims = "dimension %d" % valid_contig_dims[0]

                raise CompileError(pos, "Only %s may be contiguous and direct" % dims)

            has_contig = access != 'ptr'
        elif packing == 'follow':
            if has_strided:
                raise CompileError(pos, "A memoryview cannot have both follow and strided axis specifiers.")
            if not (is_c_contig or is_f_contig):
                raise CompileError(pos, "Invalid use of the follow specifier.")

        if access in ('ptr', 'full'):
            has_strided = False

def _get_resolved_spec(env, spec):
    # spec must be a NameNode or an AttributeNode
    if isinstance(spec, NameNode):
        return _resolve_NameNode(env, spec)
    elif isinstance(spec, AttributeNode):
        return _resolve_AttributeNode(env, spec)
    else:
        raise CompileError(spec.pos, INVALID_ERR)

def _resolve_NameNode(env, node):
    try:
        resolved_name = env.lookup(node.name).name
    except AttributeError:
        raise CompileError(node.pos, INVALID_ERR)

    viewscope = env.global_scope().context.cython_scope.viewscope
    entry = viewscope.lookup(resolved_name)
    if entry is None:
        raise CompileError(node.pos, NOT_CIMPORTED_ERR)

    return entry

def _resolve_AttributeNode(env, node):
    path = []
    while isinstance(node, AttributeNode):
        path.insert(0, node.attribute)
        node = node.obj
    if isinstance(node, NameNode):
        path.insert(0, node.name)
    else:
        raise CompileError(node.pos, EXPR_ERR)
    modnames = path[:-1]
    # must be at least 1 module name, o/w not an AttributeNode.
    assert modnames

    scope = env
    for modname in modnames:
        mod = scope.lookup(modname)
        if not mod or not mod.as_module:
            raise CompileError(
                    node.pos, "undeclared name not builtin: %s" % modname)
        scope = mod.as_module

    entry = scope.lookup(path[-1])
    if not entry:
        raise CompileError(node.pos, "No such attribute '%s'" % path[-1])

    return entry

#
### Utility loading
#

def load_memview_cy_utility(util_code_name, context=None, **kwargs):
    return CythonUtilityCode.load(util_code_name, "MemoryView.pyx",
                                  context=context, **kwargs)

def load_memview_c_utility(util_code_name, context=None, **kwargs):
    if context is None:
        return UtilityCode.load(util_code_name, "MemoryView_C.c", **kwargs)
    else:
        return TempitaUtilityCode.load(util_code_name, "MemoryView_C.c",
                                       context=context, **kwargs)

def use_cython_array_utility_code(env):
    cython_scope = env.global_scope().context.cython_scope
    cython_scope.load_cythonscope()
    cython_scope.viewscope.lookup('array_cwrapper').used = True

context = {
    'memview_struct_name': memview_objstruct_cname,
    'max_dims': Options.buffer_max_dims,
    'memviewslice_name': memviewslice_cname,
    'memslice_init': memslice_entry_init,
}
memviewslice_declare_code = load_memview_c_utility(
        "MemviewSliceStruct",
        proto_block='utility_code_proto_before_types',
        context=context,
        requires=[])

atomic_utility = load_memview_c_utility("Atomics", context,
              proto_block='utility_code_proto_before_types')

memviewslice_init_code = load_memview_c_utility(
    "MemviewSliceInit",
    context=dict(context, BUF_MAX_NDIMS=Options.buffer_max_dims),
    requires=[memviewslice_declare_code,
              Buffer.acquire_utility_code,
              atomic_utility,
              Buffer.typeinfo_compare_code],
)

memviewslice_index_helpers = load_memview_c_utility("MemviewSliceIndex")

typeinfo_to_format_code = load_memview_cy_utility(
        "BufferFormatFromTypeInfo", requires=[Buffer._typeinfo_to_format_code])

is_contig_utility = load_memview_c_utility("MemviewSliceIsContig", context)
overlapping_utility = load_memview_c_utility("OverlappingSlices", context)
read_after_write_utility = load_memview_c_utility("ReadAfterWrite", context)
copy_contents_new_utility = load_memview_c_utility(
    "MemviewSliceCopyTemplate",
    context,
    requires=[], # require cython_array_utility_code
)

view_utility_code = load_memview_cy_utility(
        "View.MemoryView",
        context=context,
        requires=[Buffer.GetAndReleaseBufferUtilityCode(),
                  Buffer.buffer_struct_declare_code,
                  Buffer.empty_bufstruct_utility,
                  memviewslice_init_code,
                  is_contig_utility,
                  overlapping_utility,
                  copy_contents_new_utility,
                  ModuleNode.capsule_utility_code],
)
view_utility_whitelist = ('array', 'memoryview', 'array_cwrapper',
                          'generic', 'strided', 'indirect', 'contiguous',
                          'indirect_contiguous')

memviewslice_declare_code.requires.append(view_utility_code)
copy_contents_new_utility.requires.append(view_utility_code)