# http://pyrocko.org - GPLv3
#
# The Pyrocko Developers, 21st Century
# ---|P------/S----------~Lg----------
from __future__ import division, absolute_import
import sys
import struct
import re
import numpy as num
from io import StringIO
from collections import namedtuple
from pyrocko import util, trace
from .io_common import FileLoadError
guralp_zero = util.str_to_time('1989-11-17 00:00:00')
[docs]class GCFLoadError(FileLoadError):
pass
[docs]class EOF(Exception):
pass
Header = namedtuple(
'Header',
'''
block_type
system_id
stream_id
instrument_type
time
gain
ttl
sample_rate
compression
nrecords
'''.split())
def read(f, n, eof_ok=False):
data = f.read(n)
if eof_ok and len(data) == 0:
raise EOF()
if len(data) != n:
raise GCFLoadError('Unexpected end of file')
return data
def read_header(f, endianness='>'):
e = endianness
data = read(f, 16, eof_ok=True)
isystem_id, istream_id = struct.unpack(e+'II', data[:8])
ex = isystem_id & 0x80000000
if ex:
ex2 = isystem_id & (1 << 30)
if ex2:
system_id = util.base36encode(isystem_id & (2**21 - 1))
else:
system_id = util.base36encode(isystem_id & (2**26 - 1))
instrument_type = (isystem_id >> 26) & 0b1
gain = [None, 1, 2, 4, 8, 16, 32, 64][(isystem_id >> 27) & 0b111]
else:
system_id = util.base36encode(isystem_id)
instrument_type = None
gain = None
stream_id = util.base36encode(istream_id)
i_day_second = struct.unpack(e+'I', data[8:12])[0]
iday = i_day_second >> 17
isecond = i_day_second & 0x1ffff
time = (iday*24*60*60) + guralp_zero + isecond
ittl, israte, compression, nrecords = struct.unpack(e+'BBBB', data[12:])
if nrecords > 250:
raise FileLoadError('Header indicates too many records in block.')
if israte == 0:
if compression == 4 and stream_id[-2:] == '00':
block_type = 'status_block'
elif compression == 4 and stream_id[-2:] == '01':
block_type = 'unified_status_block'
elif compression == 4 and stream_id[-2:] == 'SM':
block_type = 'strong_motion_block'
elif stream_id[-2:] == 'CD':
block_type = 'cd_status_block'
elif compression == 4 and stream_id[-2:] == 'BP':
block_type = 'byte_pipe_block'
elif stream_id[-2:] == 'IB':
block_type = 'information_block'
else:
raise FileLoadError('Unexpected block type found.')
return Header(block_type, system_id, stream_id, instrument_type,
time, gain, ittl, 0.0, compression, nrecords)
else:
block_type = 'data_block'
if not re.match(r'^([ZNEXC][0-9A-CG-S]|M[0-9A-F])$', stream_id[-2:]):
raise FileLoadError('Unexpected data stream ID')
sample_rate_tab = {
157: (0.1, None),
161: (0.125, None),
162: (0.2, None),
164: (0.25, None),
167: (0.5, None),
171: (400., 8),
174: (500., 2),
176: (1000., 4),
179: (2000., 8),
181: (4000., 16)}
if israte in sample_rate_tab:
sample_rate, tfod = sample_rate_tab[israte]
else:
sample_rate = float(israte)
tfod = None
if tfod is not None:
toff = (compression >> 4) // tfod
compression = compression & 0b1111
time += toff
if compression not in (1, 2, 4):
raise GCFLoadError(
'Unsupported compression code: %i' % compression)
return Header(block_type, system_id, stream_id, instrument_type,
time, gain, ittl, sample_rate, compression, nrecords)
def read_data(f, h, endianness='>'):
e = endianness
data = read(f, 1024 - 16)
first = struct.unpack(e+'i', data[0:4])[0]
dtype = {1: e+'i4', 2: e+'i2', 4: e+'i1'}
if h.compression not in dtype:
raise GCFLoadError('Unsupported compression code: %i' % h.compression)
nsamples = h.compression * h.nrecords
difs = num.fromstring(data[4:4+h.nrecords*4], dtype=dtype[h.compression],
count=nsamples)
samples = difs.astype(num.int32)
samples[0] += first
samples = num.cumsum(samples, dtype=num.int32)
last = struct.unpack(e+'i', data[4+h.nrecords*4:4+h.nrecords*4+4])[0]
if last != samples[-1]:
raise GCFLoadError('Checksum error occured')
return samples
def read_status(f, h):
data = read(f, 1024 - 16)
return data[:h.nrecords*4]
def iload(filename, load_data=True):
traces = {}
with open(filename, 'rb') as f:
try:
while True:
h = read_header(f)
if h.block_type == 'data_block':
deltat = 1.0 / h.sample_rate
if load_data:
samples = read_data(f, h)
tmax = None
else:
f.seek(1024 - 16, 1)
samples = None
tmax = h.time + (
h.nrecords * h.compression - 1) * deltat
nslc = ('', h.system_id, '', h.stream_id)
if nslc in traces:
tr = traces[nslc]
if abs((tr.tmax + tr.deltat) - h.time) < deltat*0.0001:
if samples is not None:
tr.append(samples)
else:
tr.tmax = tmax
else:
del traces[nslc]
yield tr
if nslc not in traces:
traces[nslc] = trace.Trace(
*nslc,
tmin=h.time,
deltat=deltat,
ydata=samples,
tmax=tmax)
else:
f.seek(1024 - 16, 1)
except EOF:
for tr in traces.values():
yield tr
def detect(first512):
# does not work properly, produces too many false positives
# difficult to improve due to the very compact GCF header
try:
if len(first512) < 512:
return False
f = StringIO(first512)
read_header(f)
return True
except Exception:
return False
if __name__ == '__main__':
from pyrocko import util
util.setup_logging('warn')
all_traces = []
for fn in sys.argv[1:]:
if detect(open(fn, 'rb').read(512)):
print(fn)
all_traces.extend(iload(fn))
trace.snuffle(all_traces)
