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Henrik RydgårdandClaude Opus 5.5
3cc61d3f8e
- A failed final flush (a full disk) or a failed rename into place was reported as "Saved State". A failed load undo rename still pointed load undo at the current game, while the file was another game's state. - Refusing a save or load for being online didn't call the callback, unlike every other refusal. - A rewind dropped after its decode started stayed active, and stopped rewind snapshots until the next clear. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
113 lines
4.0 KiB
C++
113 lines
4.0 KiB
C++
#pragma once
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#include <atomic>
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#include "Common/Serialize/Serializer.h"
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#include "Common/CommonTypes.h"
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#include "Common/TimeUtil.h"
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namespace SaveState {
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// This ring buffer of states is for rewind save states, which are kept in RAM.
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// Save states are compressed against one of two reference saves (bases_), and the reference
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// is switched to a fresh save every N saves, where N is BASE_USAGE_INTERVAL.
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// The compression is a simple block based scheme where 0 means to copy a block from the base,
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// and 1 means that the following bytes are the next block, then zstd on top. See Compress/ApplyDelta.
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//
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// The emu thread owns the ring itself (which slots hold what). Compressing and decoding run as jobs
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// on the savestate worker, and the emu thread leaves the buffers a job uses alone until it's done.
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class StateRingbuffer {
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public:
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StateRingbuffer() {
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size_ = REWIND_NUM_STATES;
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states_.resize(size_);
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baseMapping_.resize(size_);
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}
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CChunkFileReader::Error Save();
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// A rewind in two halves: StartRestore picks the state and has the worker decode it (false if
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// there's nothing to rewind to), and once RestoreDecoded, FinishRestore applies it.
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bool StartRestore();
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bool RestoreDecoded() const { return restoreDecoded_; }
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CChunkFileReader::Error FinishRestore(std::string *errorString, std::string *metadata);
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// Both halves, waiting for the worker in between.
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CChunkFileReader::Error Restore(std::string *errorString, std::string *metadata);
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// For a rewind that was started and then dropped.
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void CancelRestore();
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void Clear();
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bool Empty() const {
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return count_ == 0;
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}
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void Process();
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void NotifyState();
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double NextStateTimestamp() const;
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private:
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bool BaseAlive(int generation) const;
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void DropNewest();
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void Compress(std::vector<u8> &result, const std::vector<u8> &state, const std::vector<u8> &base);
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bool Decompress(std::vector<u8> &result, const std::vector<u8> &compressed, const std::vector<u8> &base);
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void ApplyDelta(std::vector<u8> &result, const std::vector<u8> &delta, const std::vector<u8> &base);
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const int BLOCK_SIZE = 8192;
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const int REWIND_NUM_STATES = 20;
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// TODO: Instead, based on size of compressed state?
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const int BASE_USAGE_INTERVAL = 15;
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// A rewind this soon after the last one steps back past the state that one restored.
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const double STEP_BACK_SECONDS = 0.8;
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// Fast. Higher levels shrink the deltas a little more for a lot more time.
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const int ZSTD_COMPRESSION_LEVEL = 1;
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typedef std::vector<u8> StateBuffer;
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struct RewindState {
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StateBuffer stateBuffer;
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// CoreTiming's clock when the state was taken, in seconds.
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double emuTime = 0.0;
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bool empty() const { return stateBuffer.empty(); }
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void clear() { stateBuffer.clear(); emuTime = 0.0; }
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};
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// The slot the next save goes in, and how many slots before it hold states we can restore.
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int next_ = 0;
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int count_ = 0;
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int size_;
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std::vector<RewindState> states_;
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StateBuffer bases_[2];
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// Which generation each base slot currently holds, and which generation each state was
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// compressed against. There are more states than bases, so states do go stale.
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int baseGeneration_[2] = {-1, -1};
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int nextBaseGeneration_ = 0;
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std::vector<int> baseMapping_;
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std::vector<u8> buffer_;
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int base_ = -1;
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int baseUsage_ = 0;
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double rewindLastTime_ = 0.0f;
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// A snapshot being compressed on the worker, from buffer_ or a base.
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std::atomic<bool> compressPending_{ false };
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// The rewind under way: its slot, when it started, and the state the worker decodes it into.
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bool restoreActive_ = false;
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int restoreSlot_ = -1;
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double restoreTime_ = 0.0;
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std::atomic<bool> restoreDecoded_{ false };
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CChunkFileReader::Error restoreError_ = CChunkFileReader::ERROR_NONE;
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std::vector<u8> restoreBuffer_;
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// Whether the newest state is the one the last rewind restored, and when that was.
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bool newestRestored_ = false;
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double lastRestoreTime_ = 0.0;
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// CoreTiming's clock when the current run of rewinds started, for "seconds ago".
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double rewindFromEmuTime_ = 0.0;
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bool retryingAfterFailure_ = false;
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};
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} // namespace SaveState
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