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Add checksum section: explain the checksum algorithm using pseudo code.
| 0xC81E
| 0xC81E
| 0x2
| 0x2
| Checksum of all of the above. Can be calculated with [https://www.dropbox.com/s/863idp5wmh50c1v/Gold_Mii_Tools.zip?dl=0 FixCRC for Windows].
| Checksum of all of the above (the first 0xC81E byte). See section [[#Checksum|below]].
|-
|-
| 0xC820
| 0xC820
Alternative interpretation: FFFF FFFF 0000 0000 0000 0000 0000 is the 1st item; FF7F FF7F 0000 [...] the 2nd, etc;
Alternative interpretation: FFFF FFFF 0000 0000 0000 0000 0000 is the 1st item; FF7F FF7F 0000 [...] the 2nd, etc;
==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].
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://www.dropbox.com/s/863idp5wmh50c1v/Gold_Mii_Tools.zip?dl=0 FixCRC for Windows]; alternativly a pseudocode implementation of the checksum algorithm is given below:
<source lang="python">
def crc16_CCITTWii(u8[]: data) -> u16:
"""Calculate a checksum of data using the CRC16-CCITT implementation of the Wii
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
u32 crc := 0x0
for byte in data:
# Iterate over every of the 8 bits in byte.
# Begin with the most significant bit. (7, 6, ... , 1, 0)
for bit in 7..0:
# & - binary `and'; <</>> - bitshift left/right; ^ - binary `xor'
crc := (
(crc << 1) | ((byte >> bit) & 0x1)
^ (0x1021 if crc & 0x8000 else 0)
)
for _ in 0..15:
crc := (crc << 1) ^ (0x1021 if crc & 0x8000 else 0)
# only return the lowest 16 bit of crc
return (u16) (crc & 0xffff)
checksum := crc16_CCITTWii(miidb[0:0xc81e]) # checksum over the first 0xc81e bytes
</source>
==Mii format==
==Mii format==