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https://github.com/patchzyy/wiicompiled
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patchzyy
60 lines
2.5 KiB
C++
60 lines
2.5 KiB
C++
#pragma once
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#include <filesystem>
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#include <fstream>
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#include <istream>
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namespace RuntimeNandSave {
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enum class Contents { Missing, Blank, Nonzero, Error };
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enum class ReadAction { Proceed, Missing, Error, RecoveryNeeded };
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// A failed read is not evidence that a save is blank. Check badbit before EOF:
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// an I/O failure may set both, whereas a successful short final read sets EOF.
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inline Contents InspectStream(std::istream& input) {
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if (!input) return Contents::Error;
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char block[4096];
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for (;;) {
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input.read(block, sizeof(block));
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if (input.bad() || (input.fail() && !input.eof())) return Contents::Error;
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for (std::streamsize i = 0; i < input.gcount(); ++i) {
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if (block[i] != 0) return Contents::Nonzero;
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}
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if (input.eof()) return Contents::Blank;
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}
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}
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inline Contents InspectFile(const std::filesystem::path& path) {
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std::error_code ec;
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const auto status = std::filesystem::symlink_status(path, ec);
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if (ec && ec != std::errc::no_such_file_or_directory) return Contents::Error;
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if (!std::filesystem::exists(status)) return Contents::Missing;
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if (!std::filesystem::is_regular_file(path, ec) || ec) return Contents::Error;
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std::ifstream input(path, std::ios::binary);
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return InspectStream(input);
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}
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// Probe only read-only opens of the actual save and its exact write shadow.
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// No probe writes, removes, or repairs data, and backups are not save aliases.
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inline ReadAction CheckRead(const std::filesystem::path& path, int mode) {
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const auto name = path.filename();
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const bool isMain = name == "rksys.dat";
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if (mode != 1 || (!isMain && name != "rksys.dat.nandsafe.tmp")) return ReadAction::Proceed;
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const auto contents = InspectFile(path);
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if (contents == Contents::Error) return ReadAction::Error;
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if (contents == Contents::Nonzero) return ReadAction::Proceed;
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if (isMain) {
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auto shadow = path;
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shadow += ".nandsafe.tmp";
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const auto shadowContents = InspectFile(shadow);
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if (shadowContents == Contents::Error) return ReadAction::Error;
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// The next write normally discards an old shadow. Preserve a possible
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// recovery source when there is no usable original, without promoting
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// an uncommitted (and potentially incomplete) shadow to the real save.
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if (shadowContents == Contents::Nonzero) return ReadAction::RecoveryNeeded;
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}
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return contents == Contents::Blank ? ReadAction::Missing : ReadAction::Proceed;
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}
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} // namespace RuntimeNandSave
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