# Source code for obspy.io.y.core

    # -*- coding: utf-8 -*-
    """
    Y bindings to ObsPy core module.

    :copyright:
        The ObsPy Development Team (devs@obspy.org)
    :license:
        GNU Lesser General Public License, Version 3
        (https://www.gnu.org/copyleft/lesser.html)
    """
    from __future__ import (absolute_import, division, print_function,
                            unicode_literals)
    from future.builtins import *  # NOQA

    import re
    import warnings
    from struct import unpack

    import numpy as np

    from obspy import Stream
    from obspy.core.compatibility import from_buffer
    from obspy.core.trace import Trace
    from obspy.core.utcdatetime import UTCDateTime
    from obspy.core.util import AttribDict

    INVALID_CHAR_MSG = (
        "Invalid non-ASCII characters in Y file header detected (%s). "
        "These were ignored.")

    def _unpack_with_asciiz_and_decode(fmt, data):
        """
        Unpack binary data and decode ASCII bytestrings, stripping ASCIIZ
        bytestrings correctly as specified by Y format definition. In addition to
        format flags defined by :py:func:`struct.unpack`, "z" can be used to denote
        ASCIIZ fields.

        :param fmt: see :py:func:`struct.unpack`
        :param data: see :py:func:`struct.unpack`
        :returns: see :py:func:`struct.unpack` but with bytestrings being decoded
        """
        fmt_list = re.findall(b'[a-zA-Z]', fmt)
        z_positions = [pos for pos, fmt_ in enumerate(fmt_list) if fmt_ == b"z"]
        s_positions = [pos for pos, fmt_ in enumerate(fmt_list) if fmt_ == b"s"]

        parts = list(unpack(fmt.replace(b"z", b"s"), data))

        # special handling for ASCIIZ fields:
        # strip everything after first (if any) ASCII NULL character *before*
        # decoding (those need not be valid encoded ASCII bytes and should be
        # ignored)
        for i in z_positions:
            part = parts[i]
            terminal_index = part.find(b"\x00")
            if terminal_index != -1:
                parts[i] = part[:terminal_index]
        # decode all bytestrings from ASCII
        for i in z_positions + s_positions:
            part = parts[i]
            try:
                part = part.decode('ascii', errors="strict")
            except UnicodeError as e:
                warnings.warn(INVALID_CHAR_MSG % str(e), UserWarning)
                part = part.decode('ascii', errors="ignore")
            parts[i] = part
        # right-strip all BLANKPADDED fields
        for i in s_positions:
            parts[i] = parts[i].rstrip()

        return tuple(parts)

    def _parse_tag(fh):
        """
        Reads and parses a single tag.

        returns endian, tag_type, next_tag, next_same
        """
        data = fh.read(16)
        # byte order format for this data. Uses letter “I” for Intel format
        # data (little endian) or letter “M” for Motorola (big endian) format
        format = unpack(b'=c', data[0:1])[0]
        if format == b'I':
            endian = b'<'
        elif format == b'M':
            endian = b'>'
        else:
            raise ValueError('Invalid tag: missing byte order information')
        # magic: check for magic number "31"
        magic = unpack(endian + b'B', data[1:2])[0]
        if magic != 31:
            raise ValueError('Invalid tag: missing magic number')
        # tag type: the type of data attached to this tag.
        tag_type = unpack(endian + b'H', data[2:4])[0]
        # NextTag is the offset in bytes from the end of this tag to the start of
        # the next tag. That means, the offset is the size of the data attached
        # to this tag.
        next_tag = unpack(endian + b'i', data[4:8])[0]
        # NextSame is the offset in bytes from the end of this tag to the start
        # of the next tag with the same type. If zero, there is no next tag with
        # the same type.
        next_same = unpack(endian + b'i', data[8:12])[0]
        return endian, tag_type, next_tag, next_same

    def _is_y(filename):
        """
        Checks whether a file is a Nanometrics Y file or not.

        :type filename: str
        :param filename: Name of the Nanometrics Y file to be checked.
        :rtype: bool
        :return: ``True`` if a Nanometrics Y file.

        .. rubric:: Example

        >>> _is_y("/path/to/YAYT_BHZ_20021223.124800")  #doctest: +SKIP
        True
        """
        try:
            # get first tag (16 bytes)
            with open(filename, 'rb') as fh:
                _, tag_type, _, _ = _parse_tag(fh)
        except Exception:
            return False
        # The first tag in a Y-file must be the TAG_Y_FILE tag (tag type 0)
        if tag_type != 0:
            return False
        return True

    def _read_y(filename, headonly=False, **kwargs):  # @UnusedVariable
        """
        Reads a Nanometrics Y file and returns an ObsPy Stream object.

        .. warning::
            This function should NOT be called directly, it registers via the
            ObsPy :func:`~obspy.core.stream.read` function, call this instead.

        :type filename: str
        :param filename: Nanometrics Y file to be read.
        :type headonly: bool, optional
        :param headonly: If set to True, read only the head. This is most useful
            for scanning available data in huge (temporary) data sets.
        :rtype: :class:`~obspy.core.stream.Stream`
        :return: A ObsPy Stream object.

        .. rubric:: Example

        >>> from obspy import read
        >>> st = read("/path/to/YAYT_BHZ_20021223.124800")
        >>> st  # doctest: +ELLIPSIS
        <obspy.core.stream.Stream object at 0x...>
        >>> print(st)  # doctest: +ELLIPSIS
        1 Trace(s) in Stream:
        .AYT..BHZ | 2002-12-23T12:48:00.000100Z - ... | 100.0 Hz, 18000 samples
        """
        # The first tag in a Y-file must be the TAG_Y_FILE (0) tag. This must be
        # followed by the following tags, in any order:
        #   TAG_STATION_INFO (1)
        #   TAG_STATION_LOCATION (2)
        #   TAG_STATION_PARAMETERS (3)
        #   TAG_STATION_DATABASE (4)
        #   TAG_SERIES_INFO (5)
        #   TAG_SERIES_DATABASE (6)
        # The following tag is optional:
        #   TAG_STATION_RESPONSE (26)
        # The last tag in the file must be a TAG_DATA_INT32 (7) tag. This tag must
        # be followed by an array of LONG's. The number of entries in the array
        # must agree with what was described in the TAG_SERIES_INFO data.
        with open(filename, 'rb') as fh:
            trace = Trace()
            trace.stats.y = AttribDict()
            count = -1
            while True:
                endian, tag_type, next_tag, _next_same = _parse_tag(fh)
                if tag_type == 1:
                    # TAG_STATION_INFO
                    # UCHAR Update[8]
                    #   This field is only used internally for administrative
                    #   purposes.  It should always be set to zeroes.
                    # UCHAR Station[5] (BLANKPAD)
                    #   Station is the five letter SEED format station
                    #   identification.
                    # UCHAR Location[2] (BLANKPAD)
                    #   Location Location is the two letter SEED format location
                    #   identification.
                    # UCHAR Channel[3] (BLANKPAD)
                    #   Channel Channel is the three letter SEED format channel
                    #   identification.
                    # UCHAR NetworkID[51] (ASCIIZ)
                    #   This is some descriptive text identifying the network.
                    # UCHAR SiteName[61] (ASCIIZ)
                    #   SiteName is some text identifying the site.
                    # UCHAR Comment[31] (ASCIIZ)
                    #   Comment is any comment for this station.
                    # UCHAR SensorType[51] (ASCIIZ)
                    #   SensorType is some text describing the type of sensor used
                    #   at the station.
                    # UCHAR DataFormat[7] (ASCIIZ)
                    #   DataFormat is some text describing the data format recorded
                    #   at the station.
                    data = fh.read(next_tag)
                    parts = _unpack_with_asciiz_and_decode(
                        b'5s2s3s51z61z31z51z7z', data[8:])
                    trace.stats.station = parts[0]
                    trace.stats.location = parts[1]
                    trace.stats.channel = parts[2]
                    # extra
                    params = AttribDict()
                    params.network_id = parts[3]
                    params.site_name = parts[4]
                    params.comment = parts[5]
                    params.sensor_type = parts[6]
                    params.data_format = parts[7]
                    trace.stats.y.tag_station_info = params
                elif tag_type == 2:
                    # TAG_STATION_LOCATION
                    # UCHAR Update[8]
                    #   This field is only used internally for administrative
                    #   purposes.  It should always be set to zeroes.
                    # FLOAT Latitude
                    #   Latitude in degrees of the location of the station. The
                    #   latitude should be between -90 (South) and +90 (North).
                    # FLOAT Longitude
                    #   Longitude in degrees of the location of the station. The
                    #   longitude should be between -180 (West) and +180 (East).
                    # FLOAT Elevation
                    #   Elevation in meters above sea level of the station.
                    # FLOAT Depth
                    #   Depth is the depth in meters of the sensor.
                    # FLOAT Azimuth
                    #   Azimuth of the sensor in degrees clockwise.
                    # FLOAT Dip
                    #   Dip is the dip of the sensor. 90 degrees is defined as
                    #   vertical right way up.
                    data = fh.read(next_tag)
                    parts = _unpack_with_asciiz_and_decode(
                        endian + b'ffffff', data[8:])
                    params = AttribDict()
                    params.latitude = parts[0]
                    params.longitude = parts[1]
                    params.elevation = parts[2]
                    params.depth = parts[3]
                    params.azimuth = parts[4]
                    params.dip = parts[5]
                    trace.stats.y.tag_station_location = params
                elif tag_type == 3:
                    # TAG_STATION_PARAMETERS
                    # UCHAR Update[16]
                    #   This field is only used internally for administrative
                    #   purposes.  It should always be set to zeroes.
                    # REALTIME StartValidTime
                    #   Time that the information in these records became valid.
                    # REALTIME EndValidTime
                    #   Time that the information in these records became invalid.
                    # FLOAT Sensitivity
                    #   Sensitivity of the sensor in nanometers per bit.
                    # FLOAT SensFreq
                    #   Frequency at which the sensitivity was measured.
                    # FLOAT SampleRate
                    #   This is the number of samples per second. This value can be
                    #   less than 1.0. (i.e. 0.1)
                    # FLOAT MaxClkDrift
                    #   Maximum drift rate of the clock in seconds per sample.
                    # UCHAR SensUnits[24] (ASCIIZ)
                    #   Some text indicating the units in which the sensitivity was
                    #   measured.
                    # UCHAR CalibUnits[24] (ASCIIZ)
                    #   Some text indicating the units in which calibration input
                    #   was measured.
                    # UCHAR ChanFlags[27] (BLANKPAD)
                    #   Text indicating the channel flags according to the SEED
                    #   definition.
                    # UCHAR UpdateFlag
                    #   This flag must be “N” or “U” according to the SEED
                    #   definition.
                    # UCHAR Filler[4]
                    #   Filler Pads out the record to satisfy the alignment
                    #   restrictions for reading data on a SPARC processor.
                    data = fh.read(next_tag)
                    parts = _unpack_with_asciiz_and_decode(
                        endian + b'ddffff24z24z27sc4s', data[16:])
                    trace.stats.sampling_rate = parts[4]
                    # extra
                    params = AttribDict()
                    params.start_valid_time = parts[0]
                    params.end_valid_time = parts[1]
                    params.sensitivity = parts[2]
                    params.sens_freq = parts[3]
                    params.sample_rate = parts[4]
                    params.max_clk_drift = parts[5]
                    params.sens_units = parts[6]
                    params.calib_units = parts[7]
                    params.chan_flags = parts[8]
                    params.update_flag = parts[9]
                    trace.stats.y.tag_station_parameters = params
                elif tag_type == 4:
                    # TAG_STATION_DATABASE
                    # UCHAR Update[8]
                    #   This field is only used internally for administrative
                    #   purposes.  It should always be set to zeroes.
                    # REALTIME LoadDate
                    #   Date the information was loaded into the database.
                    # UCHAR Key[16]
                    #   Unique key that identifies this record in the database.
                    data = fh.read(next_tag)
                    parts = _unpack_with_asciiz_and_decode(
                        endian + b'd16s', data[8:])
                    params = AttribDict()
                    params.load_date = parts[0]
                    params.key = parts[1]
                    trace.stats.y.tag_station_database = params
                elif tag_type == 5:
                    # TAG_SERIES_INFO
                    # UCHAR Update[16]
                    #   This field is only used internally for administrative
                    #   purposes.  It should always be set to zeroes.
                    # REALTIME StartTime
                    #   This is start time of the data in this series.
                    # REALTIME EndTime
                    #   This is end time of the data in this series.
                    # ULONG NumSamples
                    #   This is the number of samples of data in this series.
                    # LONG DCOffset
                    #   DCOffset is the DC offset of the data.
                    # LONG MaxAmplitude
                    #   MaxAmplitude is the maximum amplitude of the data.
                    # LONG MinAmplitude
                    #   MinAmplitude is the minimum amplitude of the data.
                    # UCHAR Format[8] (ASCIIZ)
                    #   This is the format of the data. This should always be
                    #   “YFILE”.
                    # UCHAR FormatVersion[8] (ASCIIZ)
                    #   FormatVersion is the version of the format of the data.
                    #   This should always be “5.0”
                    data = fh.read(next_tag)
                    parts = _unpack_with_asciiz_and_decode(
                        endian + b'ddLlll8z8z', data[16:])
                    trace.stats.starttime = UTCDateTime(parts[0])
                    count = parts[2]
                    # extra
                    params = AttribDict()
                    params.endtime = UTCDateTime(parts[1])
                    params.num_samples = parts[2]
                    params.dc_offset = parts[3]
                    params.max_amplitude = parts[4]
                    params.min_amplitude = parts[5]
                    params.format = parts[6]
                    params.format_version = parts[7]
                    trace.stats.y.tag_series_info = params
                elif tag_type == 6:
                    # TAG_SERIES_DATABASE
                    # UCHAR Update[8]
                    #   This field is only used internally for administrative
                    #   purposes.  It should always be set to zeroes.
                    # REALTIME LoadDate
                    #   Date the information was loaded into the database.
                    # UCHAR Key[16]
                    #   Unique key that identifies this record in the database.
                    data = fh.read(next_tag)
                    parts = _unpack_with_asciiz_and_decode(
                        endian + b'd16s', data[8:])
                    params = AttribDict()
                    params.load_date = parts[0]
                    params.key = parts[1]
                    trace.stats.y.tag_series_database = params
                elif tag_type == 26:
                    # TAG_STATION_RESPONSE
                    # UCHAR Update[8]
                    #   This field is only used internally for administrative
                    #   purposes.  It should always be set to zeroes.
                    # UCHAR PathName[260]
                    #  PathName is the full name of the file which contains the
                    #  response information for this station.
                    data = fh.read(next_tag)
                    parts = _unpack_with_asciiz_and_decode(b'260s', data[8:])
                    params = AttribDict()
                    params.path_name = parts[0]
                    trace.stats.y.tag_station_response = params
                elif tag_type == 7:
                    # TAG_DATA_INT32
                    trace.data = from_buffer(
                        fh.read(np.dtype(np.int32).itemsize * count),
                        dtype=np.int32)
                    # break loop as TAG_DATA_INT32 should be the last tag in file
                    break
                else:
                    fh.seek(next_tag, 1)
        return Stream([trace])

    if __name__ == '__main__':
        import doctest
        doctest.testmod(exclude_empty=True)

### Thank you!

We would like to thank our contributors, whose efforts make this software what it is. These people have helped by writing code and documentation, and by testing. They have created and maintained this product, its associated libraries and applications, our build tools and our web sites.

#### Contributors

- Ackerley, Nick
- Allgeyer, Sebastien
- Ammon, Charles J.
- Antunes, Emanuel
- Arnarsson, Ólafur St.
- Bank, Markus
- Barsch, Robert
- Behr, Yannik
- Bernardi, Fabrizio
- Bernauer, Felix
- Bes de Berc, Maxime
- Beyreuther, Moritz
- Boltz, Shawn
- Bonaimé, Sébastien
- Carothers, Lloyd
- Chamberlain, Calum
- Chambers, Derrick
- Chen, Zhao
- Clark, Adam
- Danecek, Peter
- Egdorf, Sven
- Engels, Fabian
- Ermert, Laura
- Eulenfeld, Tom

- Fabbri, Tommaso
- Falco, Nicholas
- Fee, Jeremy
- Grellier, Clément
- Grunberg, Marc
- Hammer, Conny
- Heimann, Sebastian
- Heiniger, Lukas
- Hope, Gaute
- Igel, Heiner
- Inza, Adolfo
- Isken, Marius
- Ketchum, David
- Koymans, Mathijs
- Kremers, Simon
- Kress, Victor
- Krieger, Lars
- Krischer, Lion
- Kula, Damian
- Käufl, Paul
- Köhler, Andreas
- Lecocq, Thomas
- Leeman, John
- Legovini, Paride

- Lesage, Philippe
- Li, Yulin
- Lomax, Anthony
- Lopes, Rui L.
- MacCarthy, Jonathan
- Maggi, Alessia
- Martin, Henri
- Medlin, Andrew
- Megies, Tobias
- Meschede, Matthias
- Michelini, Alberto
- Miller, Nathaniel C.
- Morgenstern, Bernhard
- Nof, Ran Novitsky
- Panning, Mark P.
- Parker, Tom
- Pestourie, Romain
- Rapagnani, Giovanni
- Reyes, Celso
- Ringler, Adam
- Rothenhäusler, Nicolas
- Russo, Emiliano
- Sales de Andrade, Elliott

- Satriano, Claudio
- Saul, Joachim
- Scheingraber, Chris
- Schneider, Simon
- Sippl, Christian
- Snoke, Arthur
- Stange, Stefan
- Stähler, Simon C.
- Sullivan, Benjamin
- Tian, Dongdong
- Trabant, Chad
- Trani, Luca
- Uieda, Leonardo
- Walker, Andrew
- Walther, Marcus
- Wassermann, Joachim
- Williams, Mark C.
- Winkelman, Andrew
- Zaccarelli, Riccardo
- Zad, Seyed Kasra Hosseini
- Zhu, Lijun
- van Driel, Martin
- van Wijk, Kasper

#### Funds

ObsPy was partially funded by the

- German Science Foundation (DFG) via grant DFG IG 16/9-1
- German Ministry for Education and Research (BMBF), GEOTECHNOLOGIEN grant 03G0646H.
- NERA project (Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation) under the European Community's Seventh Framework Programme (FP7/2007-2013) grant agreement n° 262330
- Leibniz Institute for Applied Geophysics (LIAG)
- VERCE EU-FP7 project (no. 283543)