Nelze vybrat více než 25 témat
Téma musí začínat písmenem nebo číslem, může obsahovat pomlčky („-“) a může být dlouhé až 35 znaků.
117 řádky
3.6 KiB
117 řádky
3.6 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
|
|
|
#include "db/memtable.h"
|
|
#include "db/dbformat.h"
|
|
#include "leveldb/comparator.h"
|
|
#include "leveldb/env.h"
|
|
#include "leveldb/iterator.h"
|
|
#include "util/coding.h"
|
|
|
|
namespace leveldb {
|
|
|
|
static Slice GetLengthPrefixedSlice(const char* data) {
|
|
uint32_t len;
|
|
const char* p = data;
|
|
p = GetVarint32Ptr(p, p + 5, &len); // +5: we assume "p" is not corrupted
|
|
return Slice(p, len);
|
|
}
|
|
|
|
MemTable::MemTable(const InternalKeyComparator& cmp)
|
|
: comparator_(cmp),
|
|
refs_(0),
|
|
table_(comparator_, &arena_) {
|
|
}
|
|
|
|
MemTable::~MemTable() {
|
|
assert(refs_ == 0);
|
|
}
|
|
|
|
size_t MemTable::ApproximateMemoryUsage() { return arena_.MemoryUsage(); }
|
|
|
|
int MemTable::KeyComparator::operator()(const char* aptr, const char* bptr)
|
|
const {
|
|
// Internal keys are encoded as length-prefixed strings.
|
|
Slice a = GetLengthPrefixedSlice(aptr);
|
|
Slice b = GetLengthPrefixedSlice(bptr);
|
|
return comparator.Compare(a, b);
|
|
}
|
|
|
|
// Encode a suitable internal key target for "target" and return it.
|
|
// Uses *scratch as scratch space, and the returned pointer will point
|
|
// into this scratch space.
|
|
static const char* EncodeKey(std::string* scratch, const Slice& target) {
|
|
scratch->clear();
|
|
PutVarint32(scratch, target.size());
|
|
scratch->append(target.data(), target.size());
|
|
return scratch->data();
|
|
}
|
|
|
|
class MemTableIterator: public Iterator {
|
|
public:
|
|
explicit MemTableIterator(MemTable* mem, MemTable::Table* table) {
|
|
mem_ = mem;
|
|
iter_ = new MemTable::Table::Iterator(table);
|
|
mem->Ref();
|
|
}
|
|
virtual ~MemTableIterator() {
|
|
delete iter_;
|
|
mem_->Unref();
|
|
}
|
|
|
|
virtual bool Valid() const { return iter_->Valid(); }
|
|
virtual void Seek(const Slice& k) { iter_->Seek(EncodeKey(&tmp_, k)); }
|
|
virtual void SeekToFirst() { iter_->SeekToFirst(); }
|
|
virtual void SeekToLast() { iter_->SeekToLast(); }
|
|
virtual void Next() { iter_->Next(); }
|
|
virtual void Prev() { iter_->Prev(); }
|
|
virtual Slice key() const { return GetLengthPrefixedSlice(iter_->key()); }
|
|
virtual Slice value() const {
|
|
Slice key_slice = GetLengthPrefixedSlice(iter_->key());
|
|
return GetLengthPrefixedSlice(key_slice.data() + key_slice.size());
|
|
}
|
|
|
|
virtual Status status() const { return Status::OK(); }
|
|
|
|
private:
|
|
MemTable* mem_;
|
|
MemTable::Table::Iterator* iter_;
|
|
std::string tmp_; // For passing to EncodeKey
|
|
|
|
// No copying allowed
|
|
MemTableIterator(const MemTableIterator&);
|
|
void operator=(const MemTableIterator&);
|
|
};
|
|
|
|
Iterator* MemTable::NewIterator() {
|
|
return new MemTableIterator(this, &table_);
|
|
}
|
|
|
|
void MemTable::Add(SequenceNumber s, ValueType type,
|
|
const Slice& key,
|
|
const Slice& value) {
|
|
// Format of an entry is concatenation of:
|
|
// key_size : varint32 of internal_key.size()
|
|
// key bytes : char[internal_key.size()]
|
|
// value_size : varint32 of value.size()
|
|
// value bytes : char[value.size()]
|
|
size_t key_size = key.size();
|
|
size_t val_size = value.size();
|
|
size_t internal_key_size = key_size + 8;
|
|
const size_t encoded_len =
|
|
VarintLength(internal_key_size) + internal_key_size +
|
|
VarintLength(val_size) + val_size;
|
|
char* buf = arena_.Allocate(encoded_len);
|
|
char* p = EncodeVarint32(buf, internal_key_size);
|
|
memcpy(p, key.data(), key_size);
|
|
p += key_size;
|
|
EncodeFixed64(p, (s << 8) | type);
|
|
p += 8;
|
|
p = EncodeVarint32(p, val_size);
|
|
memcpy(p, value.data(), val_size);
|
|
assert((p + val_size) - buf == encoded_len);
|
|
table_.Insert(buf);
|
|
}
|
|
|
|
}
|