151 lines
4.7 KiB
Python
151 lines
4.7 KiB
Python
# Authors: The MNE-Python contributors.
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# License: BSD-3-Clause
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# Copyright the MNE-Python contributors.
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from collections import namedtuple
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from datetime import datetime
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from math import modf
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from os import SEEK_END
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from struct import Struct
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import numpy as np
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from ...utils import warn
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def _read_teeg(f, teeg_offset):
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"""
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Read TEEG structure from an open CNT file.
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# from TEEG structure in http://paulbourke.net/dataformats/eeg/
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typedef struct {
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char Teeg; /* Either 1 or 2 */
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long Size; /* Total length of all the events */
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long Offset; /* Hopefully always 0 */
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} TEEG;
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"""
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# we use a more descriptive names based on TEEG doc comments
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Teeg = namedtuple("Teeg", "event_type total_length offset")
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teeg_parser = Struct("<Bll")
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f.seek(teeg_offset)
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return Teeg(*teeg_parser.unpack(f.read(teeg_parser.size)))
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CNTEventType1 = namedtuple("CNTEventType1", ("StimType KeyBoard KeyPad_Accept Offset"))
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# typedef struct {
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# unsigned short StimType; /* range 0-65535 */
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# unsigned char KeyBoard; /* range 0-11 corresponding to fcn keys +1 */
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# char KeyPad_Accept; /* 0->3 range 0-15 bit coded response pad */
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# /* 4->7 values 0xd=Accept 0xc=Reject */
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# long Offset; /* file offset of event */
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# } EVENT1;
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CNTEventType2 = namedtuple(
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"CNTEventType2",
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(
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"StimType KeyBoard KeyPad_Accept Offset Type "
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"Code Latency EpochEvent Accept2 Accuracy"
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),
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)
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# unsigned short StimType; /* range 0-65535 */
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# unsigned char KeyBoard; /* range 0-11 corresponding to fcn keys +1 */
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# char KeyPad_Accept; /* 0->3 range 0-15 bit coded response pad */
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# /* 4->7 values 0xd=Accept 0xc=Reject */
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# long Offset; /* file offset of event */
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# short Type;
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# short Code;
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# float Latency;
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# char EpochEvent;
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# char Accept2;
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# char Accuracy;
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# needed for backward compat: EVENT type 3 has the same structure as type 2
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CNTEventType3 = namedtuple(
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"CNTEventType3",
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(
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"StimType KeyBoard KeyPad_Accept Offset Type "
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"Code Latency EpochEvent Accept2 Accuracy"
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),
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)
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def _get_event_parser(event_type):
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if event_type == 1:
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event_maker = CNTEventType1
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struct_pattern = "<HBcl"
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elif event_type == 2:
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event_maker = CNTEventType2
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struct_pattern = "<HBclhhfccc"
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elif event_type == 3:
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event_maker = CNTEventType3
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struct_pattern = "<HBclhhfccc" # Same as event type 2
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else:
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raise ValueError(f"unknown CNT even type {event_type}")
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def parser(buffer):
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struct = Struct(struct_pattern)
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for chunk in struct.iter_unpack(buffer):
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yield event_maker(*chunk)
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return parser
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def _session_date_2_meas_date(session_date, date_format):
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try:
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frac_part, int_part = modf(
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datetime.strptime(session_date, date_format).timestamp()
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)
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except ValueError:
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warn(" Could not parse meas date from the header. Setting to None.")
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return None
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else:
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return (int_part, frac_part)
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def _compute_robust_event_table_position(fid, data_format="int32"):
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"""Compute `event_table_position`.
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When recording event_table_position is computed (as accomulation). If the
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file recording is large then this value overflows and ends up pointing
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somewhere else. (SEE #gh-6535)
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If the file is smaller than 2G the value in the SETUP is returned.
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Otherwise, the address of the table position is computed from:
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n_samples, n_channels, and the bytes size.
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"""
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SETUP_NCHANNELS_OFFSET = 370
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SETUP_NSAMPLES_OFFSET = 864
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SETUP_EVENTTABLEPOS_OFFSET = 886
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fid_origin = fid.tell() # save the state
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if fid.seek(0, SEEK_END) < 2e9:
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fid.seek(SETUP_EVENTTABLEPOS_OFFSET)
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(event_table_pos,) = np.frombuffer(fid.read(4), dtype="<i4")
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else:
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if data_format == "auto":
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warn(
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"Using `data_format='auto' for a CNT file larger"
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" than 2Gb is not granted to work. Please pass"
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" 'int16' or 'int32'.` (assuming int32)"
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)
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n_bytes = 2 if data_format == "int16" else 4
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fid.seek(SETUP_NSAMPLES_OFFSET)
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(n_samples,) = np.frombuffer(fid.read(4), dtype="<i4")
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fid.seek(SETUP_NCHANNELS_OFFSET)
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(n_channels,) = np.frombuffer(fid.read(2), dtype="<u2")
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event_table_pos = (
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900 + 75 * int(n_channels) + n_bytes * int(n_channels) * int(n_samples)
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)
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fid.seek(fid_origin) # restore the state
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return event_table_pos
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