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| Current File : //proc/thread-self/root/usr/local/lib/python3.8/dist-packages/pdfminer/runlength.py |
#!/usr/bin/env python
#
# RunLength decoder (Adobe version) implementation based on PDF Reference
# version 1.4 section 3.3.4.
#
# * public domain *
#
def rldecode(data):
r"""
RunLength decoder (Adobe version) implementation based on PDF Reference
version 1.4 section 3.3.4:
The RunLengthDecode filter decodes data that has been encoded in a
simple byte-oriented format based on run length. The encoded data
is a sequence of runs, where each run consists of a length byte
followed by 1 to 128 bytes of data. If the length byte is in the
range 0 to 127, the following length + 1 (1 to 128) bytes are
copied literally during decompression. If length is in the range
129 to 255, the following single byte is to be copied 257 - length
(2 to 128) times during decompression. A length value of 128
denotes EOD.
>>> s = b'\x05123456\xfa7\x04abcde\x80junk'
>>> rldecode(s)
b'1234567777777abcde'
"""
decoded = b''
i = 0
while i < len(data):
#print('data[%d]=:%d:' % (i,ord(data[i])))
length = data[i]
if length == 128:
break
if length >= 0 and length < 128:
run = data[i+1:(i+1)+(length+1)]
#print('length=%d, run=%s' % (length+1,run))
decoded += run
i = (i+1) + (length+1)
if length > 128:
run = data[i+1:i+2]*(257-length)
#print('length=%d, run=%s' % (257-length,run))
decoded += run
i = (i+1) + 1
return decoded
if __name__ == '__main__':
import doctest
print('pdfminer.runlength', doctest.testmod())