# -*- coding: utf-8 -*-
"""
SAC bindings to ObsPy core module.
:copyright:
The ObsPy Development Team (devs@obspy.org) & C. J. Ammon & J. MacCarthy
:license:
GNU Lesser General Public License, Version 3
(https://www.gnu.org/copyleft/lesser.html)
"""
import io
import os
import struct
from obspy import Stream
from .sactrace import SACTrace
[docs]def _is_sac(filename):
"""
Checks whether a file is a SAC file or not.
:param filename: SAC file to be checked.
:type filename: str, open file, or file-like object
:rtype: bool
:return: ``True`` if a SAC file.
.. rubric:: Example
>>> from obspy.core.util import get_example_file
>>> _is_sac(get_example_file('test.sac'))
True
>>> _is_sac(get_example_file('test.mseed'))
False
"""
if isinstance(filename, io.BufferedIOBase):
return _internal_is_sac(filename)
elif isinstance(filename, (str, bytes)):
with open(filename, "rb") as fh:
return _internal_is_sac(fh)
else:
raise ValueError("Cannot open '%s'." % filename)
[docs]def _internal_is_sac(buf):
"""
Checks whether a file-like object contains a SAC file or not.
:param buf: SAC file to be checked.
:type buf: file-like object or open file
:rtype: bool
:return: ``True`` if a SAC file.
"""
starting_pos = buf.tell()
try:
# read delta (first header float)
delta_bin = buf.read(4)
delta = struct.unpack('<f', delta_bin)[0]
# read nvhdr (70 header floats, 6 position in header integers)
buf.seek(starting_pos + 4 * 70 + 4 * 6, 0)
nvhdr_bin = buf.read(4)
nvhdr = struct.unpack('<i', nvhdr_bin)[0]
# read leven (70 header floats, 35 header integers, 0 position in
# header bool)
buf.seek(starting_pos + 4 * 70 + 4 * 35, 0)
leven_bin = buf.read(4)
leven = struct.unpack('<i', leven_bin)[0]
# read lpspol (70 header floats, 35 header integers, 1 position in
# header bool)
buf.seek(starting_pos + 4 * 70 + 4 * 35 + 4 * 1, 0)
lpspol_bin = buf.read(4)
lpspol = struct.unpack('<i', lpspol_bin)[0]
# read lovrok (70 header floats, 35 header integers, 2 position in
# header bool)
buf.seek(starting_pos + 4 * 70 + 4 * 35 + 4 * 2, 0)
lovrok_bin = buf.read(4)
lovrok = struct.unpack('<i', lovrok_bin)[0]
# read lcalda (70 header floats, 35 header integers, 3 position in
# header bool)
buf.seek(starting_pos + 4 * 70 + 4 * 35 + 4 * 3, 0)
lcalda_bin = buf.read(4)
lcalda = struct.unpack('<i', lcalda_bin)[0]
# check if file is big-endian
if nvhdr < 0 or nvhdr > 20:
nvhdr = struct.unpack('>i', nvhdr_bin)[0]
delta = struct.unpack('>f', delta_bin)[0]
leven = struct.unpack('>i', leven_bin)[0]
lpspol = struct.unpack('>i', lpspol_bin)[0]
lovrok = struct.unpack('>i', lovrok_bin)[0]
lcalda = struct.unpack('>i', lcalda_bin)[0]
# check again nvhdr
if nvhdr < 1 or nvhdr > 20:
return False
if delta <= 0:
return False
if leven != 0 and leven != 1 and leven != -12345:
return False
if lpspol != 0 and lpspol != 1 and lpspol != -12345:
return False
if lovrok != 0 and lovrok != 1 and lovrok != -12345:
return False
if lcalda != 0 and lcalda != 1 and lcalda != -12345:
return False
except Exception:
return False
finally:
# Reset buffer head position after reading.
buf.seek(starting_pos, 0)
return True
[docs]def _is_sac_xy(filename):
"""
Checks whether a file is alphanumeric SAC file or not.
:param filename: Alphanumeric SAC file to be checked.
:type filename: str, open file, or file-like object
:rtype: bool
:return: ``True`` if a alphanumeric SAC file.
.. rubric:: Example
>>> from obspy.core.util import get_example_file
>>> _is_sac_xy(get_example_file('testxy.sac'))
True
>>> _is_sac_xy(get_example_file('test.sac'))
False
"""
if isinstance(filename, io.BufferedIOBase):
return _internal_is_sac_xy(filename)
elif isinstance(filename, (str, bytes)):
with open(filename, "rb") as fh:
return _internal_is_sac_xy(fh)
else:
raise ValueError("Cannot open '%s'." % filename)
[docs]def _internal_is_sac_xy(buf):
"""
Checks whether a file is alphanumeric SAC file or not.
:param buf: Alphanumeric SAC file to be checked.
:type buf: file-like object or open file
:rtype: bool
:return: ``True`` if a alphanumeric SAC file.
"""
cur_pos = buf.tell()
try:
try:
hdcards = []
# read in the header cards
for _i in range(30):
hdcards.append(buf.readline())
npts = int(hdcards[15].split()[-1])
# read in the seismogram
seis = buf.read(-1).split()
except Exception:
return False
# check that npts header value and seismogram length are consistent
if npts != len(seis):
return False
return True
finally:
buf.seek(cur_pos, 0)
[docs]def _read_sac_xy(filename, headonly=False, debug_headers=False,
**kwargs): # @UnusedVariable
"""
Reads an alphanumeric SAC 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.
:param filename: Alphanumeric SAC file to be read.
:type filename: str, open file, or file-like object
:param headonly: If set to True, read only the head. This is most useful
for scanning available data in huge (temporary) data sets.
:type headonly: bool
:param debug_headers: Extracts also the SAC headers ``'nzyear', 'nzjday',
'nzhour', 'nzmin', 'nzsec', 'nzmsec', 'delta', 'scale', 'npts',
'knetwk', 'kstnm', 'kcmpnm'`` which are usually directly mapped to the
:class:`~obspy.core.stream.Stream` object if set to ``True``. Those
values are not synchronized with the Stream object itself and won't
be used during writing of a SAC file! Defaults to ``False``.
:type debug_headers: bool
:rtype: :class:`~obspy.core.stream.Stream`
:return: A ObsPy Stream object.
.. rubric:: Example
>>> from obspy import read
>>> st = read("/path/to/testxy.sac")
"""
if isinstance(filename, io.BufferedIOBase):
return _internal_read_sac_xy(buf=filename, headonly=headonly,
debug_headers=debug_headers, **kwargs)
else:
with open(filename, "rb") as fh:
return _internal_read_sac_xy(buf=fh, headonly=headonly,
debug_headers=debug_headers, **kwargs)
[docs]def _internal_read_sac_xy(buf, headonly=False, debug_headers=False,
**kwargs): # @UnusedVariable
"""
Reads an alphanumeric SAC 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.
:param buf: Alphanumeric SAC file to be read.
:type buf: file or file-like object
:param headonly: If set to True, read only the head. This is most useful
for scanning available data in huge (temporary) data sets.
:type headonly: bool
:param debug_headers: Extracts also the SAC headers ``'nzyear', 'nzjday',
'nzhour', 'nzmin', 'nzsec', 'nzmsec', 'delta', 'scale', 'npts',
'knetwk', 'kstnm', 'kcmpnm'`` which are usually directly mapped to the
:class:`~obspy.core.stream.Stream` object if set to ``True``. Those
values are not synchronized with the Stream object itself and won't
be used during writing of a SAC file! Defaults to ``False``.
:type debug_headers: bool
:rtype: :class:`~obspy.core.stream.Stream`
:return: A ObsPy Stream object.
.. rubric:: Example
>>> from obspy import read
>>> st = read("/path/to/testxy.sac")
"""
sac = SACTrace.read(buf, headonly=headonly, ascii=True)
# assign all header entries to a new dictionary compatible with ObsPy
tr = sac.to_obspy_trace(debug_headers=debug_headers)
return Stream([tr])
[docs]def _write_sac_xy(stream, filename, **kwargs): # @UnusedVariable
"""
Writes a alphanumeric SAC file.
.. warning::
This function should NOT be called directly, it registers via the
the :meth:`~obspy.core.stream.Stream.write` method of an
ObsPy :class:`~obspy.core.stream.Stream` object, call this instead.
:param stream: The ObsPy Stream object to write.
:type stream: :class:`~obspy.core.stream.Stream`
:param filename: Name of file to write. In case an open file or
file-like object is passed, this function only supports writing
Stream objects containing a single Trace. This is a limitation of
the SAC file format. An exception will be raised in case it's
necessary.
:type filename: str, open file, or file-like object
.. rubric:: Example
>>> from obspy import read
>>> st = read()
>>> st.write("testxy.sac", format="SACXY") #doctest: +SKIP
"""
# SAC can only store one Trace per file.
if isinstance(filename, io.BufferedIOBase):
if len(stream) > 1:
raise ValueError("If writing to a file-like object in the SAC "
"format, the Stream object can only contain "
"one Trace.")
_internal_write_sac_xy(stream[0], filename, **kwargs)
return
elif isinstance(filename, (str, bytes)):
# Otherwise treat it as a filename
# Translate the common (renamed) entries
base, ext = os.path.splitext(filename)
for i, trace in enumerate(stream):
if len(stream) != 1:
filename = "%s%02d%s" % (base, i + 1, ext)
with open(filename, "wb") as fh:
_internal_write_sac_xy(trace, fh, **kwargs)
else:
raise ValueError("Cannot open '%s'." % filename)
[docs]def _internal_write_sac_xy(trace, buf, **kwargs): # @UnusedVariable
"""
Writes a single trace to alphanumeric SAC file.
.. warning::
This function should NOT be called directly, it registers via the
the :meth:`~obspy.core.stream.Stream.write` method of an
ObsPy :class:`~obspy.core.stream.Stream` object, call this instead.
:param trace: The ObsPy Trace object to write.
:type trace: :class:`~obspy.core.trace.Trace`
:param buf: Object to write to.
:type buf: file-like object
"""
sac = SACTrace.from_obspy_trace(trace, keep_sac_header=True)
sac.write(buf, ascii=True, flush_headers=False)
[docs]def _read_sac(filename, headonly=False, debug_headers=False, fsize=True,
**kwargs): # @UnusedVariable
"""
Reads an SAC 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.
:param filename: SAC file to be read.
:type filename: str, open file, or file-like object
:param headonly: If set to True, read only the head. This is most useful
for scanning available data in huge (temporary) data sets.
:type headonly: bool
:param debug_headers: Extracts also the SAC headers ``'nzyear', 'nzjday',
'nzhour', 'nzmin', 'nzsec', 'nzmsec', 'delta', 'scale', 'npts',
'knetwk', 'kstnm', 'kcmpnm'`` which are usually directly mapped to the
:class:`~obspy.core.stream.Stream` object if set to ``True``. Those
values are not synchronized with the Stream object itself and won't
be used during writing of a SAC file! Defaults to ``False``.
:type debug_headers: bool
:param fsize: Check if file size is consistent with theoretical size
from header. Defaults to ``True``.
:type fsize: bool
:rtype: :class:`~obspy.core.stream.Stream`
:return: A ObsPy Stream object.
.. rubric:: Example
>>> from obspy import read
>>> st = read("/path/to/test.sac")
"""
# Only byte buffers for binary SAC.
if isinstance(filename, io.BufferedIOBase):
return _internal_read_sac(buf=filename, headonly=headonly,
debug_headers=debug_headers, fsize=fsize,
**kwargs)
elif isinstance(filename, (str, bytes)):
with open(filename, "rb") as fh:
return _internal_read_sac(buf=fh, headonly=headonly,
debug_headers=debug_headers, fsize=fsize,
**kwargs)
else:
raise ValueError("Cannot open '%s'." % filename)
[docs]def _internal_read_sac(buf, headonly=False, debug_headers=False, fsize=True,
byteorder=None, **kwargs): # @UnusedVariable
"""
Reads an SAC 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.
:param buf: SAC file to be read.
:type buf: file or file-like object
:param headonly: If set to True, read only the head. This is most useful
for scanning available data in huge (temporary) data sets.
:type headonly: bool
:param debug_headers: Extracts also the SAC headers ``'nzyear', 'nzjday',
'nzhour', 'nzmin', 'nzsec', 'nzmsec', 'delta', 'scale', 'npts',
'knetwk', 'kstnm', 'kcmpnm'`` which are usually directly mapped to the
:class:`~obspy.core.stream.Stream` object if set to ``True``. Those
values are not synchronized with the Stream object itself and won't
be used during writing of a SAC file! Defaults to ``False``.
:type debug_headers: bool
:param fsize: Check if file size is consistent with theoretical size
from header. Defaults to ``True``.
:type fsize: bool
:param byteorder: If omitted or None, automatic byte-order checking is
done, starting with native order. If byteorder is specified,
{'little', 'big'}, and incorrect, a
:class:`obspy.io.sac.util.SacIOError` is raised. Only valid for binary
files.
:type byteorder: str, optional
:rtype: :class:`~obspy.core.stream.Stream`
:return: A ObsPy Stream object.
"""
# Extract encoding flag (default to ascii)
encoding_str = kwargs.get('encoding', 'ascii')
# read SAC file
sac = SACTrace.read(buf, headonly=headonly, ascii=False,
byteorder=byteorder, checksize=fsize,
encoding=encoding_str)
# assign all header entries to a new dictionary compatible with an ObsPy
tr = sac.to_obspy_trace(debug_headers=debug_headers, encoding=encoding_str)
return Stream([tr])
[docs]def _write_sac(stream, filename, byteorder="<", **kwargs): # @UnusedVariable
"""
Writes a SAC file.
.. warning::
This function should NOT be called directly, it registers via the
the :meth:`~obspy.core.stream.Stream.write` method of an
ObsPy :class:`~obspy.core.stream.Stream` object, call this instead.
:param stream: The ObsPy Stream object to write.
:type stream: :class:`~obspy.core.stream.Stream`
:param filename: Name of file to write. In case an open file or
file-like object is passed, this function only supports writing
Stream objects containing a single Trace. This is a limitation of
the SAC file format. An exception will be raised in case it's
necessary.
:type filename: str, open file, or file-like object
:param byteorder: Must be either ``0`` or ``'<'`` for LSBF or
little-endian, ``1`` or ``'>'`` for MSBF or big-endian.
Defaults to little endian.
:type byteorder: int or str
.. rubric:: Example
>>> from obspy import read
>>> st = read()
>>> st.write("test.sac", format="SAC") #doctest: +SKIP
"""
# Bytes buffer are ok, but only if the Stream object contains only one
# Trace. SAC can only store one Trace per file.
if isinstance(filename, io.BufferedIOBase):
if len(stream) > 1:
raise ValueError("If writing to a file-like object in the SAC "
"format, the Stream object can only contain "
"one Trace.")
_internal_write_sac(stream[0], filename, byteorder=byteorder, **kwargs)
return
elif isinstance(filename, (str, bytes)):
# Otherwise treat it as a filename
# Translate the common (renamed) entries
base, ext = os.path.splitext(filename)
for i, trace in enumerate(stream):
if len(stream) != 1:
filename = "%s%02d%s" % (base, i + 1, ext)
with open(filename, "wb") as fh:
_internal_write_sac(trace, fh, byteorder=byteorder, **kwargs)
else:
raise ValueError("Cannot open '%s'." % filename)
[docs]def _internal_write_sac(trace, buf, byteorder="<", **kwargs):
"""
Writes a single trace to an open file or file-like object
.. warning::
This function should NOT be called directly, it registers via the
the :meth:`~obspy.core.stream.Stream.write` method of an
ObsPy :class:`~obspy.core.stream.Stream` object, call this instead.
:param trace: The ObsPy Trace object to write.
:type trace: :class:`~obspy.core.trace.Trace`
:param buf: Object to write to.
:type buf: open file or file-like object
:param byteorder: Must be either ``0`` or ``'<'`` for LSBF or
little-endian, ``1`` or ``'>'`` for MSBF or big-endian.
Defaults to little endian.
:type byteorder: int or str
"""
if byteorder in ("<", 0, "0"):
byteorder = 'little'
elif byteorder in (">", 1, "1"):
byteorder = 'big'
else:
msg = "Invalid byte order. It must be either '<', '>', 0 or 1"
raise ValueError(msg)
sac = SACTrace.from_obspy_trace(trace)
sac.write(buf, ascii=False, byteorder=byteorder)