I have ported spreadtrum PAC file extraction code to java.

References are:-
https://spdflashtool.com/source/spd-tool-source-code
https://github.com/unisoc/dloader/blob/master/include/BinPack.h
https://github.com/unisoc/dloader/blob/master/src/BinPack.cpp
https://github.com/yonglongliu/vendor/blob/master/sprd/build/buildpac/tools/unpac_perl/unpac.pl
https://github.com/newsfh/sprd_tool/blob/master/parse_pac.pl
https://github.com/Transsion-CI/7.SPRD_Compile/blob/master/Scripts/pac_via_conf.pl
https://github.com/yulinwang79/sprd-ap/blob/master/auto-pac/crc16.c

