56 行
1004 B
C++
56 行
1004 B
C++
#pragma once
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#include <nall/hash/hash.hpp>
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namespace nall::Hash {
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struct CRC32 : Hash {
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using Hash::input;
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CRC32(array_view<u8> buffer = {}) {
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reset();
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input(buffer);
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}
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auto reset() -> void override {
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checksum = ~0;
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}
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auto input(u8 value) -> void override {
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checksum = (checksum >> 8) ^ table(checksum ^ value);
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}
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auto output() const -> vector<u8> override {
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vector<u8> result;
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for(auto n : reverse(range(4))) result.append(~checksum >> n * 8);
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return result;
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}
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auto value() const -> u32 {
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return ~checksum;
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}
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private:
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static auto table(u8 index) -> u32 {
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static u32 table[256] = {};
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static bool initialized = false;
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if(!initialized) {
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initialized = true;
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for(auto index : range(256)) {
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u32 crc = index;
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for(auto bit : range(8)) {
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crc = (crc >> 1) ^ (crc & 1 ? 0xedb8'8320 : 0);
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}
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table[index] = crc;
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}
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}
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return table[index];
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}
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u32 checksum = 0;
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};
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}
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