def abn_read(f, opts=None, first=0, last=-1):
"""Read a data block from a .abn file. The file pointer is placed after
the last element read."""
# If f is a file object, fine. Otherwise assume it is a filename, and open the file.
if isinstance(f, file):
filename = f.name
else:
filename = f
f = open(filename, "rb")
if not f:
print >> sys.stderr, "abn_read: could not open '%s'" % filename
return None
# Read .abn header
n = 0
size = 0
endian = ''
fmt = ''
line = f.readline()
while line:
m = re.match(begindata_pattern, line)
if m:
n = int(m.group(1))
size = int(m.group(2))
endian = m.group(3)
fmt = m.group(4)
break
elif opts is not None:
opts.update(cfg_read_line(line))
line = f.readline()
if not line: # reached end of file without finding a data header
print >> sys.stderr, "abn_read: could not read data header from '%s'" % filename
return None
# Check for sensible limits on requested data
if first < 0 or first > n-1:
first = 0
if last < 0 or last > n-1:
last = n-1
# Read binary data
data = []
assert size == struct.calcsize(fmt)
if endian == 'L':
fmt = '<' + fmt
else:
fmt = '>' + fmt
f.seek(first*size, SEEK_CUR) # skip ahead to first requested entry
for i in range(first,last+1):
s = f.read(size)
entry = struct.unpack(fmt, s)
if len(entry) == 1:
data.append(entry[0])
else:
data.append(entry)
return data
def abn_read_numpy(f, opts=None, first=0, last=-1):
"""Read a data block of numbers from a .abn file, and return it as a Numpy
array. The file pointer is placed after the last data element read."""
try:
import numpy as np
except ImportError:
print >> sys.stderr, "abn_read_numpy: could not load numpy module"
return None
# If f is a file object, fine. Otherwise assume it is a filename, and open the file.
if isinstance(f, file):
filename = f.name
else:
filename = f
f = open(filename, "rb")
if not f:
print >> sys.stderr, "abn_read: could not open '%s'" % filename
return None
# Read .abn header
n = 0
size = 0
endian = ''
fmt = ''
line = f.readline()
while line:
m = re.match(begindata_pattern, line)
if m:
n = int(m.group(1))
size = int(m.group(2))
endian = m.group(3)
fmt = m.group(4)
break
elif opts is not None:
opts.update(cfg_read_line(line))
line = f.readline()
if not line: # reached end of file without finding a data header
print >> sys.stderr, "abn_read_numpy: could not find data header in '%s'" % filename
return None
# Check the format: for now we only accept simple formats, since dealing
# with Numpy record types is a little complicated
try:
if endian == 'L':
dt = np.dtype('<' + fmt)
else:
dt = np.dtype('>' + fmt)
except:
print >> sys.stderr, "abn_read_numpy: invalid format '%d'" % fmt
return None
# Check for sensible limits on requested data
if first < 0 or first > n-1:
first = 0
if last < 0 or last > n-1:
last = n-1
# Skip ahead to first requested entry
f.seek(first*size, SEEK_CUR)
# Read binary data
data = np.fromfile(f, dtype=dt, count=last-first+1)
return data
