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rocksdb/util/vectorrep.cc

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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
#include "rocksdb/memtablerep.h"
#include <unordered_set>
#include <set>
#include <memory>
#include <algorithm>
#include <type_traits>
#include "util/arena.h"
#include "db/memtable.h"
#include "port/port.h"
#include "util/mutexlock.h"
#include "util/stl_wrappers.h"
namespace rocksdb {
namespace {
using namespace stl_wrappers;
class VectorRep : public MemTableRep {
public:
VectorRep(const KeyComparator& compare, Arena* arena, size_t count);
// Insert key into the collection. (The caller will pack key and value into a
// single buffer and pass that in as the parameter to Insert)
// REQUIRES: nothing that compares equal to key is currently in the
// collection.
virtual void Insert(const char* key) override;
// Returns true iff an entry that compares equal to key is in the collection.
virtual bool Contains(const char* key) const override;
virtual void MarkReadOnly() override;
virtual size_t ApproximateMemoryUsage() override;
virtual ~VectorRep() override { }
class Iterator : public MemTableRep::Iterator {
class VectorRep* vrep_;
std::shared_ptr<std::vector<const char*>> bucket_;
typename std::vector<const char*>::const_iterator mutable cit_;
const KeyComparator& compare_;
std::string tmp_; // For passing to EncodeKey
bool mutable sorted_;
void DoSort() const;
public:
explicit Iterator(class VectorRep* vrep,
std::shared_ptr<std::vector<const char*>> bucket,
const KeyComparator& compare);
// Initialize an iterator over the specified collection.
// The returned iterator is not valid.
// explicit Iterator(const MemTableRep* collection);
virtual ~Iterator() override { };
// Returns true iff the iterator is positioned at a valid node.
virtual bool Valid() const override;
// Returns the key at the current position.
// REQUIRES: Valid()
virtual const char* key() const override;
// Advances to the next position.
// REQUIRES: Valid()
virtual void Next() override;
// Advances to the previous position.
// REQUIRES: Valid()
virtual void Prev() override;
// Advance to the first entry with a key >= target
virtual void Seek(const Slice& user_key, const char* memtable_key) override;
// Position at the first entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
virtual void SeekToFirst() override;
// Position at the last entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
virtual void SeekToLast() override;
};
// Unhide default implementations of GetIterator()
using MemTableRep::GetIterator;
// Return an iterator over the keys in this representation.
virtual MemTableRep::Iterator* GetIterator() override;
private:
friend class Iterator;
typedef std::vector<const char*> Bucket;
std::shared_ptr<Bucket> bucket_;
mutable port::RWMutex rwlock_;
bool immutable_;
bool sorted_;
const KeyComparator& compare_;
};
void VectorRep::Insert(const char* key) {
assert(!Contains(key));
WriteLock l(&rwlock_);
assert(!immutable_);
bucket_->push_back(key);
}
// Returns true iff an entry that compares equal to key is in the collection.
bool VectorRep::Contains(const char* key) const {
ReadLock l(&rwlock_);
return std::find(bucket_->begin(), bucket_->end(), key) != bucket_->end();
}
void VectorRep::MarkReadOnly() {
WriteLock l(&rwlock_);
immutable_ = true;
}
size_t VectorRep::ApproximateMemoryUsage() {
return
sizeof(bucket_) + sizeof(*bucket_) +
bucket_->size() *
sizeof(
std::remove_reference<decltype(*bucket_)>::type::value_type
);
}
VectorRep::VectorRep(const KeyComparator& compare, Arena* arena, size_t count)
: bucket_(new Bucket()),
immutable_(false),
sorted_(false),
compare_(compare) { bucket_.get()->reserve(count); }
VectorRep::Iterator::Iterator(class VectorRep* vrep,
std::shared_ptr<std::vector<const char*>> bucket,
const KeyComparator& compare)
: vrep_(vrep),
bucket_(bucket),
cit_(bucket_->end()),
compare_(compare),
sorted_(false) { }
void VectorRep::Iterator::DoSort() const {
// vrep is non-null means that we are working on an immutable memtable
if (!sorted_ && vrep_ != nullptr) {
WriteLock l(&vrep_->rwlock_);
if (!vrep_->sorted_) {
std::sort(bucket_->begin(), bucket_->end(), Compare(compare_));
cit_ = bucket_->begin();
vrep_->sorted_ = true;
}
sorted_ = true;
}
if (!sorted_) {
std::sort(bucket_->begin(), bucket_->end(), Compare(compare_));
cit_ = bucket_->begin();
sorted_ = true;
}
assert(sorted_);
assert(vrep_ == nullptr || vrep_->sorted_);
}
// Returns true iff the iterator is positioned at a valid node.
bool VectorRep::Iterator::Valid() const {
DoSort();
return cit_ != bucket_->end();
}
// Returns the key at the current position.
// REQUIRES: Valid()
const char* VectorRep::Iterator::key() const {
assert(Valid());
return *cit_;
}
// Advances to the next position.
// REQUIRES: Valid()
void VectorRep::Iterator::Next() {
assert(Valid());
if (cit_ == bucket_->end()) {
return;
}
++cit_;
}
// Advances to the previous position.
// REQUIRES: Valid()
void VectorRep::Iterator::Prev() {
assert(Valid());
if (cit_ == bucket_->begin()) {
// If you try to go back from the first element, the iterator should be
// invalidated. So we set it to past-the-end. This means that you can
// treat the container circularly.
cit_ = bucket_->end();
} else {
--cit_;
}
}
// Advance to the first entry with a key >= target
void VectorRep::Iterator::Seek(const Slice& user_key,
const char* memtable_key) {
DoSort();
// Do binary search to find first value not less than the target
const char* encoded_key =
(memtable_key != nullptr) ? memtable_key : EncodeKey(&tmp_, user_key);
cit_ = std::equal_range(bucket_->begin(),
bucket_->end(),
encoded_key,
[this] (const char* a, const char* b) {
return compare_(a, b) < 0;
}).first;
}
// Position at the first entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
void VectorRep::Iterator::SeekToFirst() {
DoSort();
cit_ = bucket_->begin();
}
// Position at the last entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
void VectorRep::Iterator::SeekToLast() {
DoSort();
cit_ = bucket_->end();
if (bucket_->size() != 0) {
--cit_;
}
}
MemTableRep::Iterator* VectorRep::GetIterator() {
ReadLock l(&rwlock_);
// Do not sort here. The sorting would be done the first time
// a Seek is performed on the iterator.
if (immutable_) {
return new Iterator(this, bucket_, compare_);
} else {
std::shared_ptr<Bucket> tmp;
tmp.reset(new Bucket(*bucket_)); // make a copy
return new Iterator(nullptr, tmp, compare_);
}
}
} // anon namespace
MemTableRep* VectorRepFactory::CreateMemTableRep(
MemTableRep::KeyComparator& compare, Arena* arena) {
return new VectorRep(compare, arena, count_);
}
} // namespace rocksdb