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#include <array>
#include "banner.h"
#include "crc16.h"
u16 CalculateCRC16FromBannerData(const u8* banner_data) {
const std::array<u16, 16> crc_table = {
0x0000, 0xCC01, 0xD801, 0x1400,
0xF001, 0x3C00, 0x2800, 0xE401,
0xA001, 0x6C00, 0x7800, 0xB401,
0x5000, 0x9C01, 0x8801, 0x4400,
};
u16 checksum = 0xFFFF;
const std::size_t data_size = sizeof(Banner) - offsetof(Banner, bitmap);
for (std::size_t i = 0; i < data_size; i++) {
u16 lookup_index = crc_table[banner_data[i] & 0xF] ^ (checksum >> 4) ^ crc_table[checksum & 0xF];
checksum = crc_table[banner_data[i] >> 4] ^ (lookup_index >> 4) ^ crc_table[lookup_index & 0xF];
}
return checksum;
}
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