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decode 8 byte real according to Calma official GDSII format documenta… #1

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decode 8 byte real according to Calma official GDSII format documenta… #1

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20 changes: 19 additions & 1 deletion gds2ascii.py
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,19 @@ def appendName(record):
}
return name_list[record[1][0]]

def unpack_8byte_real(data):
e = (data[0] & 0x7F) - 64
s = (data[0] & 0x80) >> 7

m = 0
for i in range(7):
m |= (data[i + 1] & 0xFF) << ((6 - i) * 8)

d = m
d = d * (16.0 ** (e - 14))
d = -d if s == 1 else d
return d

# Extracting Hex Data to readable ASCii
#
# input : (list) [ record length, [record type, data type], [data1, data2, ...] ]
Expand Down Expand Up @@ -117,7 +130,12 @@ def extractData(record):

elif record[1][1] == 0x05:
for i in list(range(0, (record[0]-4)//8)):
data.append( struct.unpack('>d', record[2][i])[0] )
# note that we cant just pack into a 8 byte python double
# because gdsii 8-byte real number has the form of
# SEEEEEEE MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM MMMMMMMM
# that's different than the IEEE 754 binary64 double format that python "struct" uses
# data.append( struct.unpack('>d', record[2][i])[0] )
data.append(unpack_8byte_real(record[2][i]))
return data

else:
Expand Down