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Merged
merged 2 commits into from
Apr 18, 2019
Merged

Select formats based on index #2

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5c81869
Select formats based on index, use np.frombuffer instead of struct.un…
tstenner Apr 13, 2019
ba8edbd
Remove unused fmtindex, OrderedDict
tstenner Apr 18, 2019
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26 changes: 17 additions & 9 deletions pyxdf/pyxdf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -170,10 +170,15 @@ class StreamData:
"""Temporary per-stream data."""
def __init__(self, xml):
"""Init a new StreamData object from a stream header."""
fmt2char = {'int8': 'b', 'int16': 'h', 'int32': 'i', 'int64': 'q',
'float32': 'f', 'double64': 'd'}
fmt2nbytes = {'int8': 1, 'int16': 2, 'int32': 4, 'int64': 8,
'float32': 4, 'double64': 8}
fmts = dict([
('double64', np.float64),
('float32', np.float32),
('string', np.object),
('int32', np.int32),
('int16', np.int16),
('int8', np.int8),
('int64', np.int64)
])
# number of channels
self.nchns = int(xml['info']['channel_count'][0])
# nominal sampling rate in Hz
Expand All @@ -194,10 +199,9 @@ def __init__(self, xml):
self.tdiff = 1.0 / self.srate if self.srate > 0 else 0.0
# pre-calc some parsing parameters for efficiency
if self.fmt != 'string':
self.dtype = np.dtype(fmts[self.fmt])
# number of bytes to read from stream to handle one sample
self.samplebytes = self.nchns * fmt2nbytes[self.fmt]
# format string to pass to struct.unpack() to handle one sample
self.structfmt = '<%s%s' % (self.nchns, fmt2char[self.fmt])
self.samplebytes = self.nchns * self.dtype.itemsize

logger.info('Importing XDF file %s...' % filename)
if not os.path.exists(filename):
Expand Down Expand Up @@ -288,7 +292,7 @@ def __init__(self, xml):
values[k][ch] = raw.decode(errors='replace')
else:
# read a sample comprised of numeric values
values = np.zeros((nsamples, temp[StreamId].nchns))
values = np.zeros((nsamples, temp[StreamId].nchns), dtype=temp[StreamId].dtype)
# for each sample...
for k in range(nsamples):
# read or deduce time stamp
Expand All @@ -300,7 +304,11 @@ def __init__(self, xml):
temp[StreamId].last_timestamp = stamps[k]
# read the values
raw = f.read(temp[StreamId].samplebytes)
values[k, :] = struct.unpack(temp[StreamId].structfmt, raw)
# no fromfile(), see
# https://github.com/numpy/numpy/issues/13319
values[k, :] = np.frombuffer(raw,
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frombuffer doesn't need a character format string and is about 30% faster in one of my tests

dtype=temp[StreamId].dtype,
count=temp[StreamId].nchns)
logger.debug(' reading [%s,%s]' % (temp[StreamId].nchns,
nsamples))
# optionally send through the on_chunk function
Expand Down