aboutsummaryrefslogtreecommitdiff
path: root/src/leveldb/table/two_level_iterator.cc
diff options
context:
space:
mode:
Diffstat (limited to 'src/leveldb/table/two_level_iterator.cc')
-rw-r--r--src/leveldb/table/two_level_iterator.cc182
1 files changed, 182 insertions, 0 deletions
diff --git a/src/leveldb/table/two_level_iterator.cc b/src/leveldb/table/two_level_iterator.cc
new file mode 100644
index 0000000000..7822ebab9c
--- /dev/null
+++ b/src/leveldb/table/two_level_iterator.cc
@@ -0,0 +1,182 @@
+// 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);
+ }
+ }
+}
+
+} // namespace
+
+Iterator* NewTwoLevelIterator(
+ Iterator* index_iter,
+ BlockFunction block_function,
+ void* arg,
+ const ReadOptions& options) {
+ return new TwoLevelIterator(index_iter, block_function, arg, options);
+}
+
+} // namespace leveldb