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// 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 "tensorflow/core/lib/io/two_level_iterator.h"
#include "tensorflow/core/lib/io/table.h"
#include "tensorflow/core/lib/io/block.h"
#include "tensorflow/core/lib/io/format.h"
#include "tensorflow/core/lib/io/iterator.h"
namespace tensorflow {
namespace table {
namespace {
typedef Iterator* (*BlockFunction)(void*, const StringPiece&);
class TwoLevelIterator : public Iterator {
public:
TwoLevelIterator(Iterator* index_iter, BlockFunction block_function,
void* arg);
virtual ~TwoLevelIterator();
virtual void Seek(const StringPiece& target);
virtual void SeekToFirst();
virtual void Next();
virtual bool Valid() const {
return (data_iter_ == nullptr) ? false : data_iter_->Valid();
}
virtual StringPiece key() const {
assert(Valid());
return data_iter_->key();
}
virtual StringPiece 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_ != 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 SetDataIterator(Iterator* data_iter);
void InitDataBlock();
BlockFunction block_function_;
void* arg_;
Status status_;
Iterator* index_iter_;
Iterator* 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_.
string data_block_handle_;
};
TwoLevelIterator::TwoLevelIterator(Iterator* index_iter,
BlockFunction block_function, void* arg)
: block_function_(block_function),
arg_(arg),
index_iter_(index_iter),
data_iter_(NULL) {}
TwoLevelIterator::~TwoLevelIterator() {
delete index_iter_;
delete data_iter_;
}
void TwoLevelIterator::Seek(const StringPiece& target) {
index_iter_->Seek(target);
InitDataBlock();
if (data_iter_ != NULL) data_iter_->Seek(target);
SkipEmptyDataBlocksForward();
}
void TwoLevelIterator::SeekToFirst() {
index_iter_->SeekToFirst();
InitDataBlock();
if (data_iter_ != NULL) data_iter_->SeekToFirst();
SkipEmptyDataBlocksForward();
}
void TwoLevelIterator::Next() {
assert(Valid());
data_iter_->Next();
SkipEmptyDataBlocksForward();
}
void TwoLevelIterator::SkipEmptyDataBlocksForward() {
while (data_iter_ == NULL || !data_iter_->Valid()) {
// Move to next block
if (!index_iter_->Valid()) {
SetDataIterator(NULL);
return;
}
index_iter_->Next();
InitDataBlock();
if (data_iter_ != NULL) data_iter_->SeekToFirst();
}
}
void TwoLevelIterator::SetDataIterator(Iterator* data_iter) {
if (data_iter_ != NULL) {
SaveError(data_iter_->status());
delete data_iter_;
}
data_iter_ = data_iter;
}
void TwoLevelIterator::InitDataBlock() {
if (!index_iter_->Valid()) {
SetDataIterator(NULL);
} else {
StringPiece handle = index_iter_->value();
if (data_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_, handle);
data_block_handle_.assign(handle.data(), handle.size());
SetDataIterator(iter);
}
}
}
} // namespace
Iterator* NewTwoLevelIterator(Iterator* index_iter,
BlockFunction block_function, void* arg) {
return new TwoLevelIterator(index_iter, block_function, arg);
}
} // namespace table
} // namespace tensorflow
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