intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 858 insertions, 0 deletions

diff --git a/contrib/tools/cython/Cython/Compiler/MemoryView.py b/contrib/tools/cython/Cython/Compiler/MemoryView.py
new file mode 100644
index 0000000000..0406d6c716
--- /dev/null
+++ b/contrib/tools/cython/Cython/Compiler/MemoryView.py
@@ -0,0 +1,858 @@
+from __future__ import absolute_import
+
+from .Errors import CompileError, error
+from . import ExprNodes
+from .ExprNodes import IntNode, NameNode, AttributeNode
+from . import Options
+from .Code import UtilityCode, TempitaUtilityCode
+from .UtilityCode import CythonUtilityCode
+from . import Buffer
+from . import PyrexTypes
+from . import ModuleNode
+
+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)"
+memview_f_contiguous = "(PyBUF_F_CONTIGUOUS | PyBUF_FORMAT)"
+memview_any_contiguous = "(PyBUF_ANY_CONTIGUOUS | PyBUF_FORMAT)"
+memview_full_access = "PyBUF_FULL_RO"
+#memview_strided_access = "PyBUF_STRIDED_RO"
+memview_strided_access = "PyBUF_RECORDS_RO"
+
+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
+
+    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 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)
+
+
+def valid_memslice_dtype(dtype, i=0):
+    """
+    Return whether type dtype can be used as the base type of a
+    memoryview slice.
+
+    We support structs, numeric types and objects
+    """
+    if dtype.is_complex and dtype.real_type.is_int:
+        return False
+
+    if dtype is PyrexTypes.c_bint_type:
+        return False
+
+    if dtype.is_struct and dtype.kind == 'struct':
+        for member in dtype.scope.var_entries:
+            if not valid_memslice_dtype(member.type):
+                return False
+
+        return True
+
+    return (
+        dtype.is_error or
+        # Pointers are not valid (yet)
+        # (dtype.is_ptr and valid_memslice_dtype(dtype.base_type)) or
+        (dtype.is_array and i < 8 and
+         valid_memslice_dtype(dtype.base_type, i + 1)) or
+        dtype.is_numeric or
+        dtype.is_pyobject or
+        dtype.is_fused or # accept this as it will be replaced by specializations later
+        (dtype.is_typedef and valid_memslice_dtype(dtype.typedef_base_type))
+    )
+
+
+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):
+        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.empty_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, directives):
+        """
+        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.
+        """
+        src = self.cname
+
+        code.putln("%(dst)s.data = %(src)s.data;" % locals())
+        code.putln("%(dst)s.memview = %(src)s.memview;" % locals())
+        code.put_incref_memoryviewslice(dst)
+
+        all_dimensions_direct = all(access == 'direct' for access, packing in self.type.axes)
+        suboffset_dim_temp = []
+
+        def get_suboffset_dim():
+            # create global temp variable at request
+            if not suboffset_dim_temp:
+                suboffset_dim = code.funcstate.allocate_temp(PyrexTypes.c_int_type, manage_ref=False)
+                code.putln("%s = -1;" % suboffset_dim)
+                suboffset_dim_temp.append(suboffset_dim)
+            return suboffset_dim_temp[0]
+
+        dim = -1
+        new_ndim = 0
+        for index in indices:
+            if index.is_none:
+                # newaxis
+                for attrib, value in [('shape', 1), ('strides', 0), ('suboffsets', -1)]:
+                    code.putln("%s.%s[%d] = %d;" % (dst, attrib, new_ndim, value))
+
+                new_ndim += 1
+                continue
+
+            dim += 1
+            access, packing = self.type.axes[dim]
+
+            if isinstance(index, ExprNodes.SliceNode):
+                # slice, unspecified dimension, or part of ellipsis
+                d = dict(locals())
+                for s in "start stop step".split():
+                    idx = getattr(index, s)
+                    have_idx = d['have_' + s] = not idx.is_none
+                    d[s] = idx.result() if have_idx else "0"
+
+                if not (d['have_start'] or d['have_stop'] or d['have_step']):
+                    # full slice (:), simply copy over the extent, stride
+                    # and suboffset. Also update suboffset_dim if needed
+                    d['access'] = access
+                    util_name = "SimpleSlice"
+                else:
+                    util_name = "ToughSlice"
+                    d['error_goto'] = code.error_goto(index.pos)
+
+                new_ndim += 1
+            else:
+                # normal index
+                idx = index.result()
+
+                indirect = access != 'direct'
+                if indirect:
+                    generic = access == 'full'
+                    if new_ndim != 0:
+                        return error(index.pos,
+                                     "All preceding dimensions must be "
+                                     "indexed and not sliced")
+
+                d = dict(
+                    locals(),
+                    wraparound=int(directives['wraparound']),
+                    boundscheck=int(directives['boundscheck']),
+                )
+                if d['boundscheck']:
+                    d['error_goto'] = code.error_goto(index.pos)
+                util_name = "SliceIndex"
+
+            _, impl = TempitaUtilityCode.load_as_string(util_name, "MemoryView_C.c", context=d)
+            code.put(impl)
+
+        if suboffset_dim_temp:
+            code.funcstate.release_temp(suboffset_dim_temp[0])
+
+
+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 index.is_slice 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(contig_type, ndim):
+    assert contig_type in ('C', 'F')
+    return "__pyx_memviewslice_is_contig_%s%d" % (contig_type, ndim)
+
+
+def get_is_contig_utility(contig_type, ndim):
+    assert contig_type in ('C', 'F')
+    C = dict(context, ndim=ndim, contig_type=contig_type)
+    utility = load_memview_c_utility("MemviewSliceCheckContig", 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.empty_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 and
+            not (from_memview.dtype.is_const and from_memview.dtype.const_base_type == to_memview.dtype)):
+        error(pos, "dtypes must be the same!")
+        return
+    if len(from_memview.axes) != len(to_memview.axes):
+        error(pos, "number of dimensions must be same")
+        return
+    if not (to_memview.is_c_contig or to_memview.is_f_contig):
+        error(pos, "to_memview must be c or f contiguous.")
+        return
+
+    for (access, packing) in from_memview.axes:
+        if access != 'direct':
+            error(pos, "cannot handle 'full' or 'ptr' access at this time.")
+            return
+
+    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.empty_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 CompileError(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 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 enumerate(zip(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",
+        context=context,
+        requires=[])
+
+atomic_utility = load_memview_c_utility("Atomics", context)
+
+memviewslice_init_code = load_memview_c_utility(
+    "MemviewSliceInit",
+    context=dict(context, BUF_MAX_NDIMS=Options.buffer_max_dims),
+    requires=[memviewslice_declare_code,
+              atomic_utility],
+)
+
+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)
+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.buffer_formats_declare_code,
+                  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)