89 行
2.7 KiB
C++
89 行
2.7 KiB
C++
#pragma once
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namespace nall::Beat::Single {
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inline auto apply(array_view<u8> source, array_view<u8> beat, maybe<string&> manifest = {}, maybe<string&> result = {}) -> maybe<vector<u8>> {
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#define error(text) { if(result) *result = {"error: ", text}; return {}; }
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#define warning(text) { if(result) *result = {"warning: ", text}; return target; }
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#define success() { if(result) *result = ""; return target; }
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if(beat.size() < 19) error("beat size mismatch");
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vector<u8> target;
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u32 beatOffset = 0;
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auto read = [&]() -> u8 {
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return beat[beatOffset++];
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};
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auto decode = [&]() -> u64 {
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u64 data = 0, shift = 1;
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while(true) {
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u8 x = read();
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data += (x & 0x7f) * shift;
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if(x & 0x80) break;
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shift <<= 7;
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data += shift;
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}
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return data;
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};
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auto write = [&](u8 data) {
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target.append(data);
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};
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if(read() != 'B') error("beat header invalid");
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if(read() != 'P') error("beat header invalid");
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if(read() != 'S') error("beat header invalid");
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if(read() != '1') error("beat version mismatch");
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if(decode() != source.size()) error("source size mismatch");
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u32 targetSize = decode();
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target.reserve(targetSize);
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u32 metadataSize = decode();
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for(u32 n : range(metadataSize)) {
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auto data = read();
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if(manifest) manifest->append((char)data);
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}
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enum : u32 { SourceRead, TargetRead, SourceCopy, TargetCopy };
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u32 sourceRelativeOffset = 0, targetRelativeOffset = 0;
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while(beatOffset < beat.size() - 12) {
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u32 length = decode();
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u32 mode = length & 3;
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length = (length >> 2) + 1;
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if(mode == SourceRead) {
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while(length--) write(source[target.size()]);
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} else if(mode == TargetRead) {
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while(length--) write(read());
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} else {
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s32 offset = decode();
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offset = offset & 1 ? -(offset >> 1) : (offset >> 1);
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if(mode == SourceCopy) {
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sourceRelativeOffset += offset;
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while(length--) write(source[sourceRelativeOffset++]);
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} else {
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targetRelativeOffset += offset;
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while(length--) write(target[targetRelativeOffset++]);
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}
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}
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}
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u32 sourceHash = 0, targetHash = 0, beatHash = 0;
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for(u32 shift : range(0, 32, 8)) sourceHash |= read() << shift;
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for(u32 shift : range(0, 32, 8)) targetHash |= read() << shift;
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for(u32 shift : range(0, 32, 8)) beatHash |= read() << shift;
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if(target.size() != targetSize) warning("target size mismatch");
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if(sourceHash != Hash::CRC32(source).value()) warning("source hash mismatch");
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if(targetHash != Hash::CRC32(target).value()) warning("target hash mismatch");
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if(beatHash != Hash::CRC32({beat.data(), beat.size() - 4}).value()) warning("beat hash mismatch");
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success();
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#undef error
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#undef warning
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#undef success
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}
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}
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