mirror of https://github.com/bsnes-emu/bsnes.git
50 lines
1.2 KiB
C++
50 lines
1.2 KiB
C++
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#pragma once
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//burrows-wheeler transform
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#include <nall/suffix-array.hpp>
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namespace nall { namespace Encode {
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inline auto BWT(const void* data, uint size) -> vector<uint8_t> {
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auto input = (const uint8_t*)data;
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vector<uint8_t> output;
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output.reserve(8 + 8 + size);
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for(uint byte : range(8)) output.append(size >> byte * 8);
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for(uint byte : range(8)) output.append(0x00);
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auto suffixes = new int[size];
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//suffix_array(suffixes, input, size);
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for(uint n : range(size)) suffixes[n] = n;
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sort(suffixes, size, [&](int lhs, int rhs) -> bool {
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uint l = size;
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while(l--) {
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auto x = input[lhs++];
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auto y = input[rhs++];
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if(x != y) return x - y < 0;
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if(lhs >= size) lhs = 0;
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if(rhs >= size) rhs = 0;
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}
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return 0;
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});
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uint64_t root = 0;
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for(uint offset : range(size)) {
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if(suffixes[offset] == 0) root = offset;
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uint suffix = suffixes[offset];
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if(suffix == 0) suffix = size;
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output.append(input[--suffix]);
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}
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for(uint byte : range(8)) output[8 + byte] = root >> byte * 8;
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delete[] suffixes;
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return output;
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}
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template<typename T>
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inline auto BWT(const vector<T>& buffer) -> vector<uint8_t> {
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return move(BWT(buffer.data(), buffer.size() * sizeof(T)));
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}
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}}
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