Implementation of CuckooTableReader

Summary:
Contains:
- Implementation of TableReader based on Cuckoo Hashing
- Unittests for CuckooTableReader
- Performance test for TableReader

Test Plan:
make cuckoo_table_reader_test
./cuckoo_table_reader_test
make valgrind_check
make asan_check

Reviewers: yhchiang, sdong, igor, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D20511

table/cuckoo_table_reader.cc

@@ -0,0 +1,112 @@
+//  Copyright (c) 2014, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under the BSD-style license found in the
+//  LICENSE file in the root directory of this source tree. An additional grant
+//  of patent rights can be found in the PATENTS file in the same directory.
+//
+// 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.
+
+#ifndef ROCKSDB_LITE
+#include "table/cuckoo_table_reader.h"
+
+#include <string>
+#include "table/meta_blocks.h"
+#include "util/coding.h"
+
+namespace rocksdb {
+
+extern const uint64_t kCuckooTableMagicNumber;
+
+CuckooTableReader::CuckooTableReader(
+    const Options& options,
+    std::unique_ptr<RandomAccessFile>&& file,
+    uint64_t file_size,
+    uint64_t (*GetSliceHashPtr)(const Slice&, uint32_t, uint64_t))
+    : file_(std::move(file)),
+      file_size_(file_size),
+      GetSliceHash(GetSliceHashPtr) {
+  if (!options.allow_mmap_reads) {
+    status_ = Status::InvalidArgument("File is not mmaped");
+  }
+  TableProperties* props = nullptr;
+  status_ = ReadTableProperties(file_.get(), file_size, kCuckooTableMagicNumber,
+      options.env, options.info_log.get(), &props);
+  if (!status_.ok()) {
+    return;
+  }
+  table_props_.reset(props);
+  auto& user_props = props->user_collected_properties;
+  auto hash_funs = user_props.find(CuckooTablePropertyNames::kNumHashTable);
+  if (hash_funs == user_props.end()) {
+    status_ = Status::InvalidArgument("Number of hash functions not found");
+    return;
+  }
+  num_hash_fun_ = *reinterpret_cast<const uint32_t*>(hash_funs->second.data());
+  auto unused_key = user_props.find(CuckooTablePropertyNames::kEmptyKey);
+  if (unused_key == user_props.end()) {
+    status_ = Status::InvalidArgument("Empty bucket value not found");
+    return;
+  }
+  unused_key_ = unused_key->second;
+
+  key_length_ = props->fixed_key_len;
+  auto value_length = user_props.find(CuckooTablePropertyNames::kValueLength);
+  if (value_length == user_props.end()) {
+    status_ = Status::InvalidArgument("Value length not found");
+    return;
+  }
+  value_length_ = *reinterpret_cast<const uint32_t*>(
+      value_length->second.data());
+  bucket_length_ = key_length_ + value_length_;
+
+  auto num_buckets = user_props.find(CuckooTablePropertyNames::kMaxNumBuckets);
+  if (num_buckets == user_props.end()) {
+    status_ = Status::InvalidArgument("Num buckets not found");
+    return;
+  }
+  num_buckets_ = *reinterpret_cast<const uint64_t*>(num_buckets->second.data());
+  auto is_last_level = user_props.find(CuckooTablePropertyNames::kIsLastLevel);
+  if (is_last_level == user_props.end()) {
+    status_ = Status::InvalidArgument("Is last level not found");
+    return;
+  }
+  is_last_level_ = *reinterpret_cast<const bool*>(is_last_level->second.data());
+  status_ = file_->Read(0, file_size, &file_data_, nullptr);
+}
+
+Status CuckooTableReader::Get(
+    const ReadOptions& readOptions, const Slice& key, void* handle_context,
+    bool (*result_handler)(void* arg, const ParsedInternalKey& k,
+                           const Slice& v),
+    void (*mark_key_may_exist_handler)(void* handle_context)) {
+  ParsedInternalKey ikey;
+  if (!ParseInternalKey(key, &ikey)) {
+    return Status::Corruption("Unable to parse key into inernal key.");
+  }
+  for (uint32_t hash_cnt = 0; hash_cnt < num_hash_fun_; ++hash_cnt) {
+    uint64_t hash_val = GetSliceHash(ikey.user_key, hash_cnt, num_buckets_);
+    assert(hash_val < num_buckets_);
+    uint64_t offset = hash_val * bucket_length_;
+    const char* bucket = &file_data_.data()[offset];
+    if (unused_key_.compare(0, key_length_, bucket, key_length_) == 0) {
+      return Status::OK();
+    }
+    // Here, we compare only the user key part as we support only one entry
+    // per user key and we don't support sanpshot.
+    if (ikey.user_key.compare(Slice(bucket, ikey.user_key.size())) == 0) {
+      Slice value = Slice(&bucket[key_length_], value_length_);
+      result_handler(handle_context, ikey, value);
+      // We don't support merge operations. So, we return here.
+      return Status::OK();
+    }
+  }
+  return Status::OK();
+}
+
+Iterator* CuckooTableReader::NewIterator(const ReadOptions&, Arena* arena) {
+  // TODO(rbs): Implement this as this will be used in compaction.
+  return nullptr;
+}
+}  // namespace rocksdb
+#endif