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reader.py
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reader.py
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"""
File: reader.py
Author: Damien Riquet
Email: d.riquet@gmail.com
Description: Describe how to read a binary file
"""
import struct
import binascii
type_names = {
'byte' : '<b',
'short' : '<h',
'ushort' : '<H',
'int' : '<i',
'uint' : '<I',
'long' : '<q',
'double' : '<d',
}
class GWCReaderEOFException(Exception):
def __str__(self):
return 'Not enough bytes in gwc file to satisfy read request'
class GWCReader:
def __init__(self, filename):
self.file = open(filename, 'rb')
def __del__(self):
self.file.close()
def read(self, type_name):
if type_name == 'string':
return self.read_string()
type_format = type_names[type_name]
type_size = struct.calcsize(type_format)
print('read(%s) expected size: %d' % (type_name, type_size))
value = self.file.read(type_size)
if type_size != len(value):
raise GWCReaderEOFException
return struct.unpack(type_format, value)[0]
def read_string(self):
ascii_str = ""
char = self.read_one_char()
while char != 0:
ascii_str += chr(char)
char = self.read_one_char()
return ascii_str
def seek(self, position):
self.file.seek(position, 0)
def read_raw(self, size):
return self.file.read(size)
def read_one_char(self):
byte = self.file.read(1)
if len(byte) != 1:
raise GWCReaderEOFException
return int(binascii.hexlify(byte), 16)