diff options
author | costan <costan@google.com> | 2018-04-30 15:11:03 -0700 |
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committer | Victor Costan <pwnall@chromium.org> | 2018-04-30 16:01:39 -0700 |
commit | 18683981505dc374ce29211c80a9552f8f2f4571 (patch) | |
tree | 539de50e1d72a1c2df017e6f531058cc7cbb80c4 /db/snapshot.h | |
parent | e7840de9f3db1a5eddedfecbbbc1ff72a4c2631a (diff) | |
download | leveldb-18683981505dc374ce29211c80a9552f8f2f4571.tar.gz |
Clean up SnapshotImpl.
* Omit SnapshotImpl::list_ when assert() isn't on
* Make SnapshotImpl::number_ const and set it in the constructor
* Make SnapshotImpl::number_ private and access it via a getter
* Rename SnapshotImpl::number_ to SnapshotImpl::sequence_number_
* Rename SnapshotList::list_ to SnapshotList::head_
* Wrap casting from Snapshot* to SnapshotImpl* in ToSnapshotImpl()
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=194852828
Diffstat (limited to 'db/snapshot.h')
-rw-r--r-- | db/snapshot.h | 72 |
1 files changed, 47 insertions, 25 deletions
diff --git a/db/snapshot.h b/db/snapshot.h index 6ed413c..c43d9f9 100644 --- a/db/snapshot.h +++ b/db/snapshot.h @@ -16,50 +16,72 @@ class SnapshotList; // Each SnapshotImpl corresponds to a particular sequence number. class SnapshotImpl : public Snapshot { public: - SequenceNumber number_; // const after creation + SnapshotImpl(SequenceNumber sequence_number) + : sequence_number_(sequence_number) {} + + SequenceNumber sequence_number() const { return sequence_number_; } private: friend class SnapshotList; - // SnapshotImpl is kept in a doubly-linked circular list + // SnapshotImpl is kept in a doubly-linked circular list. The SnapshotList + // implementation operates on the next/previous fields direcly. SnapshotImpl* prev_; SnapshotImpl* next_; - SnapshotList* list_; // just for sanity checks + const SequenceNumber sequence_number_; + +#if !defined(NDEBUG) + SnapshotList* list_ = nullptr; +#endif // !defined(NDEBUG) }; class SnapshotList { public: - SnapshotList() { - list_.prev_ = &list_; - list_.next_ = &list_; + SnapshotList() : head_(0) { + head_.prev_ = &head_; + head_.next_ = &head_; } - bool empty() const { return list_.next_ == &list_; } - SnapshotImpl* oldest() const { assert(!empty()); return list_.next_; } - SnapshotImpl* newest() const { assert(!empty()); return list_.prev_; } - - const SnapshotImpl* New(SequenceNumber seq) { - SnapshotImpl* s = new SnapshotImpl; - s->number_ = seq; - s->list_ = this; - s->next_ = &list_; - s->prev_ = list_.prev_; - s->prev_->next_ = s; - s->next_->prev_ = s; - return s; + bool empty() const { return head_.next_ == &head_; } + SnapshotImpl* oldest() const { assert(!empty()); return head_.next_; } + SnapshotImpl* newest() const { assert(!empty()); return head_.prev_; } + + // Creates a SnapshotImpl and appends it to the end of the list. + SnapshotImpl* New(SequenceNumber sequence_number) { + assert(empty() || newest()->sequence_number_ <= sequence_number); + + SnapshotImpl* snapshot = new SnapshotImpl(sequence_number); + +#if !defined(NDEBUG) + snapshot->list_ = this; +#endif // !defined(NDEBUG) + snapshot->next_ = &head_; + snapshot->prev_ = head_.prev_; + snapshot->prev_->next_ = snapshot; + snapshot->next_->prev_ = snapshot; + return snapshot; } - void Delete(const SnapshotImpl* s) { - assert(s->list_ == this); - s->prev_->next_ = s->next_; - s->next_->prev_ = s->prev_; - delete s; + // Removes a SnapshotImpl from this list. + // + // The snapshot must have been created by calling New() on this list. + // + // The snapshot pointer should not be const, because its memory is + // deallocated. However, that would force us to change DB::ReleaseSnapshot(), + // which is in the API, and currently takes a const Snapshot. + void Delete(const SnapshotImpl* snapshot) { +#if !defined(NDEBUG) + assert(snapshot->list_ == this); +#endif // !defined(NDEBUG) + snapshot->prev_->next_ = snapshot->next_; + snapshot->next_->prev_ = snapshot->prev_; + delete snapshot; } private: // Dummy head of doubly-linked list of snapshots - SnapshotImpl list_; + SnapshotImpl head_; }; } // namespace leveldb |