bsnes/nall/hash/crc64.hpp

51 lines
977 B
C++

#pragma once
#include <nall/hash/hash.hpp>
namespace nall { namespace Hash {
struct CRC64 : Hash {
nallHash(CRC64)
auto reset() -> void override {
checksum = ~0;
}
auto input(uint8_t value) -> void override {
checksum = (checksum >> 8) ^ table(checksum ^ value);
}
auto output() const -> vector<uint8_t> {
vector<uint8_t> result;
for(auto n : rrange(8)) result.append(~checksum >> n * 8);
return result;
}
auto value() const -> uint64_t {
return ~checksum;
}
private:
static auto table(uint8_t index) -> uint64_t {
static uint64_t table[256] = {0};
static bool initialized = false;
if(!initialized) {
initialized = true;
for(auto index : range(256)) {
uint64_t crc = index;
for(auto bit : range(8)) {
crc = (crc >> 1) ^ (crc & 1 ? 0xc96c'5795'd787'0f42 : 0);
}
table[index] = crc;
}
}
return table[index];
}
uint64_t checksum = 0;
};
}}