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# This file is part of h5py, a Python interface to the HDF5 library.
#
# http://www.h5py.org
#
# Copyright 2008-2013 Andrew Collette and contributors
#
# License: Standard 3-clause BSD; see "license.txt" for full license terms
# and contributor agreement.
"""
Implements a portion of the selection operations.
"""
import numpy as np
from .. import h5s
def read_dtypes(dataset_dtype, names):
""" Returns a 2-tuple containing:
1. Output dataset dtype
2. Dtype containing HDF5-appropriate description of destination
"""
if len(names) == 0: # Not compound, or all fields needed
format_dtype = dataset_dtype
elif dataset_dtype.names is None:
raise ValueError("Field names only allowed for compound types")
elif any(x not in dataset_dtype.names for x in names):
raise ValueError("Field does not appear in this type.")
else:
format_dtype = np.dtype([(name, dataset_dtype.fields[name][0]) for name in names])
if len(names) == 1:
# We don't preserve the field information if only one explicitly selected.
output_dtype = format_dtype.fields[names[0]][0]
else:
output_dtype = format_dtype
return output_dtype, format_dtype
def read_selections_scalar(dsid, args):
""" Returns a 2-tuple containing:
1. Output dataset shape
2. HDF5 dataspace containing source selection.
Works for scalar datasets.
"""
if dsid.shape != ():
raise RuntimeError("Illegal selection function for non-scalar dataset")
if args == ():
# This is a signal that an array scalar should be returned instead
# of an ndarray with shape ()
out_shape = None
elif args == (Ellipsis,):
out_shape = ()
else:
raise ValueError("Illegal slicing argument for scalar dataspace")
source_space = dsid.get_space()
source_space.select_all()
return out_shape, source_space
class ScalarReadSelection(object):
"""
Implements slicing for scalar datasets.
"""
def __init__(self, fspace, args):
if args == ():
self.mshape = None
elif args == (Ellipsis,):
self.mshape = ()
else:
raise ValueError("Illegal slicing argument for scalar dataspace")
self.mspace = h5s.create(h5s.SCALAR)
self.fspace = fspace
def __iter__(self):
self.mspace.select_all()
yield self.fspace, self.mspace
def select_read(fspace, args):
""" Top-level dispatch function for reading.
At the moment, only supports reading from scalar datasets.
"""
if fspace.shape == ():
return ScalarReadSelection(fspace, args)
raise NotImplementedError()
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