how to decode the cross-reference stream?

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<</DecodeParms<</Columns 4/Predictor 12>>/Filter/FlateDecode/ID[<275EB65AA3259D4FB5B288864AD5DDFC><3476ED2 4B8B8844D840F1CF1600D5665>]/Info 23 0 R/Length 59/Root 25 0 R/Size 24/Type/XRef/W[1 2 1]>>stream

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I try to develp a pdf parser,but i'm in real trouble now.

First,I inflate the cross-reference stream by ZLIB.

I read the pdf reference 1.6 and  find that I need to use predictor function.

please help me,i don't konw how to do use predictor function to parse cross-reference stream in pdf?