選択できるのは25トピックまでです。
トピックは、先頭が英数字で、英数字とダッシュ('-')を使用した35文字以内のものにしてください。
182 行
4.6 KiB
182 行
4.6 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 "table/two_level_iterator.h"
|
|
|
|
#include "leveldb/table.h"
|
|
#include "table/block.h"
|
|
#include "table/format.h"
|
|
#include "table/iterator_wrapper.h"
|
|
|
|
namespace leveldb {
|
|
|
|
namespace {
|
|
|
|
typedef Iterator* (*BlockFunction)(void*, const ReadOptions&, const Slice&);
|
|
|
|
class TwoLevelIterator: public Iterator {
|
|
public:
|
|
TwoLevelIterator(
|
|
Iterator* index_iter,
|
|
BlockFunction block_function,
|
|
void* arg,
|
|
const ReadOptions& options);
|
|
|
|
virtual ~TwoLevelIterator();
|
|
|
|
virtual void Seek(const Slice& target);
|
|
virtual void SeekToFirst();
|
|
virtual void SeekToLast();
|
|
virtual void Next();
|
|
virtual void Prev();
|
|
|
|
virtual bool Valid() const {
|
|
return data_iter_.Valid();
|
|
}
|
|
virtual Slice key() const {
|
|
assert(Valid());
|
|
return data_iter_.key();
|
|
}
|
|
virtual Slice value() const {
|
|
assert(Valid());
|
|
return data_iter_.value();
|
|
}
|
|
virtual Status status() const {
|
|
// It'd be nice if status() returned a const Status& instead of a Status
|
|
if (!index_iter_.status().ok()) {
|
|
return index_iter_.status();
|
|
} else if (data_iter_.iter() != NULL && !data_iter_.status().ok()) {
|
|
return data_iter_.status();
|
|
} else {
|
|
return status_;
|
|
}
|
|
}
|
|
|
|
private:
|
|
void SaveError(const Status& s) {
|
|
if (status_.ok() && !s.ok()) status_ = s;
|
|
}
|
|
void SkipEmptyDataBlocksForward();
|
|
void SkipEmptyDataBlocksBackward();
|
|
void SetDataIterator(Iterator* data_iter);
|
|
void InitDataBlock();
|
|
|
|
BlockFunction block_function_;
|
|
void* arg_;
|
|
const ReadOptions options_;
|
|
Status status_;
|
|
IteratorWrapper index_iter_;
|
|
IteratorWrapper data_iter_; // May be NULL
|
|
// If data_iter_ is non-NULL, then "data_block_handle_" holds the
|
|
// "index_value" passed to block_function_ to create the data_iter_.
|
|
std::string data_block_handle_;
|
|
};
|
|
|
|
TwoLevelIterator::TwoLevelIterator(
|
|
Iterator* index_iter,
|
|
BlockFunction block_function,
|
|
void* arg,
|
|
const ReadOptions& options)
|
|
: block_function_(block_function),
|
|
arg_(arg),
|
|
options_(options),
|
|
index_iter_(index_iter),
|
|
data_iter_(NULL) {
|
|
}
|
|
|
|
TwoLevelIterator::~TwoLevelIterator() {
|
|
}
|
|
|
|
void TwoLevelIterator::Seek(const Slice& target) {
|
|
index_iter_.Seek(target);
|
|
InitDataBlock();
|
|
if (data_iter_.iter() != NULL) data_iter_.Seek(target);
|
|
SkipEmptyDataBlocksForward();
|
|
}
|
|
|
|
void TwoLevelIterator::SeekToFirst() {
|
|
index_iter_.SeekToFirst();
|
|
InitDataBlock();
|
|
if (data_iter_.iter() != NULL) data_iter_.SeekToFirst();
|
|
SkipEmptyDataBlocksForward();
|
|
}
|
|
|
|
void TwoLevelIterator::SeekToLast() {
|
|
index_iter_.SeekToLast();
|
|
InitDataBlock();
|
|
if (data_iter_.iter() != NULL) data_iter_.SeekToLast();
|
|
SkipEmptyDataBlocksBackward();
|
|
}
|
|
|
|
void TwoLevelIterator::Next() {
|
|
assert(Valid());
|
|
data_iter_.Next();
|
|
SkipEmptyDataBlocksForward();
|
|
}
|
|
|
|
void TwoLevelIterator::Prev() {
|
|
assert(Valid());
|
|
data_iter_.Prev();
|
|
SkipEmptyDataBlocksBackward();
|
|
}
|
|
|
|
|
|
void TwoLevelIterator::SkipEmptyDataBlocksForward() {
|
|
while (data_iter_.iter() == NULL || !data_iter_.Valid()) {
|
|
// Move to next block
|
|
if (!index_iter_.Valid()) {
|
|
SetDataIterator(NULL);
|
|
return;
|
|
}
|
|
index_iter_.Next();
|
|
InitDataBlock();
|
|
if (data_iter_.iter() != NULL) data_iter_.SeekToFirst();
|
|
}
|
|
}
|
|
|
|
void TwoLevelIterator::SkipEmptyDataBlocksBackward() {
|
|
while (data_iter_.iter() == NULL || !data_iter_.Valid()) {
|
|
// Move to next block
|
|
if (!index_iter_.Valid()) {
|
|
SetDataIterator(NULL);
|
|
return;
|
|
}
|
|
index_iter_.Prev();
|
|
InitDataBlock();
|
|
if (data_iter_.iter() != NULL) data_iter_.SeekToLast();
|
|
}
|
|
}
|
|
|
|
void TwoLevelIterator::SetDataIterator(Iterator* data_iter) {
|
|
if (data_iter_.iter() != NULL) SaveError(data_iter_.status());
|
|
data_iter_.Set(data_iter);
|
|
}
|
|
|
|
void TwoLevelIterator::InitDataBlock() {
|
|
if (!index_iter_.Valid()) {
|
|
SetDataIterator(NULL);
|
|
} else {
|
|
Slice handle = index_iter_.value();
|
|
if (data_iter_.iter() != NULL && handle.compare(data_block_handle_) == 0) {
|
|
// data_iter_ is already constructed with this iterator, so
|
|
// no need to change anything
|
|
} else {
|
|
Iterator* iter = (*block_function_)(arg_, options_, handle);
|
|
data_block_handle_.assign(handle.data(), handle.size());
|
|
SetDataIterator(iter);
|
|
}
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
Iterator* NewTwoLevelIterator(
|
|
Iterator* index_iter,
|
|
BlockFunction block_function,
|
|
void* arg,
|
|
const ReadOptions& options) {
|
|
return new TwoLevelIterator(index_iter, block_function, arg, options);
|
|
}
|
|
|
|
}
|