1# Copyright 2014 Google Inc. All rights reserved.
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7#     http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
14
15from . import number_types as N
16from . import packer
17from .compat import memoryview_type
18from .compat import import_numpy, NumpyRequiredForThisFeature
19
20np = import_numpy()
21
22FILE_IDENTIFIER_LENGTH=4
23
24def Get(packer_type, buf, head):
25    """ Get decodes a value at buf[head] using `packer_type`. """
26    return packer_type.unpack_from(memoryview_type(buf), head)[0]
27
28
29def GetVectorAsNumpy(numpy_type, buf, count, offset):
30    """ GetVecAsNumpy decodes values starting at buf[head] as
31    `numpy_type`, where `numpy_type` is a numpy dtype. """
32    if np is not None:
33        # TODO: could set .flags.writeable = False to make users jump through
34        #       hoops before modifying...
35        return np.frombuffer(buf, dtype=numpy_type, count=count, offset=offset)
36    else:
37        raise NumpyRequiredForThisFeature('Numpy was not found.')
38
39
40def Write(packer_type, buf, head, n):
41    """ Write encodes `n` at buf[head] using `packer_type`. """
42    packer_type.pack_into(buf, head, n)
43