File size: 1,315 Bytes
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import os
import struct
def read_index(filename):
index = []
with open(filename) as index_file:
while True:
offset = index_file.read(8)
if not offset:
break
offset, = struct.unpack('<Q', offset)
index.append(offset)
return index
class IndexedFileWriter(object):
def __init__(self, path):
self.f = open(path, 'wb')
self.index_f = open(path + '.index', 'wb')
def append(self, record):
offset = self.f.tell()
self.f.write(record)
self.index_f.write(struct.pack('<Q', offset))
def close(self):
self.f.close()
self.index_f.close()
class IndexedFileReader(object):
def __init__(self, path):
self.f = open(path, 'rb')
self.index = read_index(path + '.index')
self.lengths = [
end - start
for start, end in zip([0] + self.index, self.index +
[os.path.getsize(path)])
]
def __len__(self):
return len(self.index)
def __getitem__(self, idx):
# TODO: support slices
if not isinstance(idx, int):
return TypeError('index must be integer')
self.file.seek(self.index[idx])
return self.file.read(self.lengths[idx])
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