From f41959ccb2d9d4c722fe8fc3351401d53bcf4900 Mon Sep 17 00:00:00 2001
From: Manjunath Kudlur <keveman@gmail.com>
Date: Fri, 6 Nov 2015 16:27:58 -0800
Subject: TensorFlow: Initial commit of TensorFlow library. TensorFlow is an
 open source software library for numerical computation using data flow
 graphs.

Base CL: 107276108
---
 tensorflow/core/lib/io/two_level_iterator.cc | 148 +++++++++++++++++++++++++++
 1 file changed, 148 insertions(+)
 create mode 100644 tensorflow/core/lib/io/two_level_iterator.cc

(limited to 'tensorflow/core/lib/io/two_level_iterator.cc')

diff --git a/tensorflow/core/lib/io/two_level_iterator.cc b/tensorflow/core/lib/io/two_level_iterator.cc
new file mode 100644
index 0000000000..409baade6d
--- /dev/null
+++ b/tensorflow/core/lib/io/two_level_iterator.cc
@@ -0,0 +1,148 @@
+// 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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