mirror of
https://github.com/facebook/sapling.git
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072e6b3e43
Summary: Adding a nullptr check for the case when the journal is empty and removing the use of default parameters. Reviewed By: strager Differential Revision: D15907329 fbshipit-source-id: 787b4a44f835fd8d128496ee6655e02987db98a7
154 lines
5.1 KiB
C++
154 lines
5.1 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This software may be used and distributed according to the terms of the
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* GNU General Public License version 2.
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*/
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#pragma once
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#include <folly/Function.h>
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#include <folly/Synchronized.h>
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#include <algorithm>
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#include <cstdint>
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#include <memory>
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#include <optional>
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#include <unordered_map>
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#include "eden/fs/journal/JournalDelta.h"
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namespace facebook {
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namespace eden {
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/** Contains statistics about the current state of the journal */
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struct JournalStats {
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size_t entryCount = 0;
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size_t memoryUsage = 0;
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std::chrono::steady_clock::time_point earliestTimestamp;
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std::chrono::steady_clock::time_point latestTimestamp;
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};
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/** The Journal exists to answer questions about how files are changing
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* over time.
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*
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* It contains metadata only; it is not a full snapshot of the state of
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* the filesystem at a particular point in time.
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* The intent is to be able query things like "which set of files changed
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* between time A and time B?".
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*
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* In the initial implementation we are recording file names from the overlay
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* but will expand this to record things like checking out different
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* revisions (the prior and new revision hash) from which we can derive
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* the larger list of files.
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*
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* The Journal class is thread-safe. Subscribers are called on the thread
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* that called addDelta.
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*/
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class Journal {
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public:
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Journal() = default;
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/// It is almost always a mistake to copy a Journal.
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Journal(const Journal&) = delete;
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Journal& operator=(const Journal&) = delete;
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using SequenceNumber = JournalDelta::SequenceNumber;
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using SubscriberId = uint64_t;
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using SubscriberCallback = std::function<void()>;
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void recordCreated(RelativePathPiece fileName);
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void recordRemoved(RelativePathPiece fileName);
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void recordChanged(RelativePathPiece fileName);
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/**
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* "Renamed" means that that newName was created as a result of the mv(1).
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*/
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void recordRenamed(RelativePathPiece oldName, RelativePathPiece newName);
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/**
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* "Replaced" means that that newName was overwritten by oldName as a result
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* of the mv(1).
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*/
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void recordReplaced(RelativePathPiece oldName, RelativePathPiece newName);
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/**
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* Creates a journal delta that updates the hash to this new hash
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*/
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void recordHashUpdate(Hash toHash);
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/**
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* Creates a journal delta that updates the hash from fromHash to toHash
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*/
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void recordHashUpdate(Hash fromHash, Hash toHash);
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/**
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* Creates a journal delta that updates the hash from fromHash to toHash and
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* also sets uncleanPaths
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*/
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void recordUncleanPaths(
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Hash fromHash,
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Hash toHash,
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std::unordered_set<RelativePath>&& uncleanPaths);
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/** Get a shared, immutable reference to the tip of the journal.
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* May return nullptr if there have been no changes */
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JournalDeltaPtr getLatest() const;
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/** Register a subscriber.
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* A subscriber is just a callback that is called whenever the
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* journal has changed.
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* It is recommended that the subscriber callback do the minimal
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* amount of work needed to schedule the real work to happen in
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* some other context because journal updates are likely to happen
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* in awkward contexts or in the middle of some batch of mutations
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* where it is not appropriate to do any heavy lifting.
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* The return value of registerSubscriber is an identifier than
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* can be passed to cancelSubscriber to later remove the registration.
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*/
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SubscriberId registerSubscriber(SubscriberCallback&& callback);
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void cancelSubscriber(SubscriberId id);
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void cancelAllSubscribers();
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bool isSubscriberValid(SubscriberId id) const;
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/** Returns an option that is nullopt if the Journal is empty or an option
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* that contains valid JournalStats if the Journal is non-empty*/
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std::optional<JournalStats> getStats();
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/** Gets the sum of the modifications done by the deltas with Sequence
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* Numbers >= limitSequence, if the limitSequence is further back than the
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* Journal remembers isTruncated will be set on the JournalDeltaSum
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* The default limit value is 0 which is never assigned by the Journal
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* and thus indicates that all deltas should be summed.
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* If the limitSequence means that no deltas will match, returns nullptr.
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* */
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std::unique_ptr<JournalDeltaRange> accumulateRange(
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SequenceNumber limitSequence) const;
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std::unique_ptr<JournalDeltaRange> accumulateRange() const;
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private:
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/** Add a delta to the journal.
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* The delta will have a new sequence number and timestamp
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* applied.
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*/
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void addDelta(std::unique_ptr<JournalDelta>&& delta);
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struct DeltaState {
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/** The sequence number that we'll use for the next entry
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* that we link into the chain */
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SequenceNumber nextSequence{1};
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/** The most recently recorded entry */
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JournalDeltaPtr latest;
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/** The stats about this Journal up to the latest delta */
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std::optional<JournalStats> stats;
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};
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folly::Synchronized<DeltaState> deltaState_;
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struct SubscriberState {
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SubscriberId nextSubscriberId{1};
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std::unordered_map<SubscriberId, SubscriberCallback> subscribers;
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};
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folly::Synchronized<SubscriberState> subscriberState_;
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};
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} // namespace eden
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} // namespace facebook
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