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352605c1b5
This tool was made from reverse-engineering the Nitro SDK's makebanner, and is intended to replace that program. It has been tested to match the Diamond/Pearl banners as well as the HeartGold/SoulSilver banners.
23 lines
723 B
C++
23 lines
723 B
C++
#include <array>
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#include "banner.h"
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#include "crc16.h"
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u16 CalculateCRC16FromBannerData(const u8* banner_data) {
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const std::array<u16, 16> crc_table = {
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0x0000, 0xCC01, 0xD801, 0x1400,
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0xF001, 0x3C00, 0x2800, 0xE401,
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0xA001, 0x6C00, 0x7800, 0xB401,
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0x5000, 0x9C01, 0x8801, 0x4400,
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};
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u16 checksum = 0xFFFF;
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const std::size_t data_size = sizeof(Banner) - offsetof(Banner, bitmap);
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for (std::size_t i = 0; i < data_size; i++) {
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u16 lookup_index = crc_table[banner_data[i] & 0xF] ^ (checksum >> 4) ^ crc_table[checksum & 0xF];
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checksum = crc_table[banner_data[i] >> 4] ^ (lookup_index >> 4) ^ crc_table[lookup_index & 0xF];
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}
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return checksum;
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}
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