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Line 90:
Line 90: − + Line 96:
Line 96: − + − This implementation uses 0x0000 as the starting value, which is different + − from what CRC16-CCITT specifies. − + − # note: a correct implementation of CRC16-CCITT − # would initialize this to 0xffff
→Checksum: The implementation is not wrong it's just a different one called CRC-16/XMODEM
==Checksum==
==Checksum==
The algorithm used to verify the integrity of the database is based on [http://srecord.sourceforge.net/crc16-ccitt.html CRC16-CCITT], though it's an incorrect implementation. It is the same algorithm used to verify [http://wiibrew.org/wiki/Mii_Data#Block_format Mii Data on the Wii].
The algorithm used to verify the integrity of the database is based on CRC-16/XMODEM. It is the same algorithm used to verify [http://wiibrew.org/wiki/Mii_Data#Block_format Mii Data on the Wii].
To obtain the correct value for the checksum, apply the algorithm to the first 0xC81E bytes of the database. This can be done using [https://gbatemp.net/threads/tutorial-give-your-mii-gold-pants-and-use-it-for-streetpass.379146/page-24#post-6569186 FixCRC]; alternativly a pseudocode implementation of the checksum algorithm is given below:
To obtain the correct value for the checksum, apply the algorithm to the first 0xC81E bytes of the database. This can be done using [https://gbatemp.net/threads/tutorial-give-your-mii-gold-pants-and-use-it-for-streetpass.379146/page-24#post-6569186 FixCRC]; alternativly a pseudocode implementation of the checksum algorithm is given below:
<source lang="python">
<source lang="python">
def crc16_CCITTWii(u8[]: data) -> u16:
def crc16_CCITTWii(u8[]: data) -> u16:
"""Calculate a checksum of data using the CRC16-CCITT implementation of the Wii
"""Calculate a checksum of data using the CRC-16/XMODEM implementation
CRC-16/XMODEM implementation uses 0x0000 as the starting value
"""
"""
u32 crc := 0x0
u32 crc := 0x0