1 files changed, 113 insertions, 0 deletions
diff --git a/src/rocksdb/table/persistent_cache_helper.cc b/src/rocksdb/table/persistent_cache_helper.cc
new file mode 100644
index 00000000..4e90697a
--- /dev/null
+++ b/src/rocksdb/table/persistent_cache_helper.cc
@@ -0,0 +1,113 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include "table/persistent_cache_helper.h"
+#include "table/block_based_table_reader.h"
+#include "table/format.h"
+
+namespace rocksdb {
+
+void PersistentCacheHelper::InsertRawPage(
+    const PersistentCacheOptions& cache_options, const BlockHandle& handle,
+    const char* data, const size_t size) {
+  assert(cache_options.persistent_cache);
+  assert(cache_options.persistent_cache->IsCompressed());
+
+  // construct the page key
+  char cache_key[BlockBasedTable::kMaxCacheKeyPrefixSize + kMaxVarint64Length];
+  auto key = BlockBasedTable::GetCacheKey(cache_options.key_prefix.c_str(),
+                                          cache_options.key_prefix.size(),
+                                          handle, cache_key);
+  // insert content to cache
+  cache_options.persistent_cache->Insert(key, data, size);
+}
+
+void PersistentCacheHelper::InsertUncompressedPage(
+    const PersistentCacheOptions& cache_options, const BlockHandle& handle,
+    const BlockContents& contents) {
+  assert(cache_options.persistent_cache);
+  assert(!cache_options.persistent_cache->IsCompressed());
+  // Precondition:
+  // (1) content is cacheable
+  // (2) content is not compressed
+
+  // construct the page key
+  char cache_key[BlockBasedTable::kMaxCacheKeyPrefixSize + kMaxVarint64Length];
+  auto key = BlockBasedTable::GetCacheKey(cache_options.key_prefix.c_str(),
+                                          cache_options.key_prefix.size(),
+                                          handle, cache_key);
+  // insert block contents to page cache
+  cache_options.persistent_cache->Insert(key, contents.data.data(),
+                                         contents.data.size());
+}
+
+Status PersistentCacheHelper::LookupRawPage(
+    const PersistentCacheOptions& cache_options, const BlockHandle& handle,
+    std::unique_ptr<char[]>* raw_data, const size_t raw_data_size) {
+#ifdef NDEBUG
+  (void)raw_data_size;
+#endif
+  assert(cache_options.persistent_cache);
+  assert(cache_options.persistent_cache->IsCompressed());
+
+  // construct the page key
+  char cache_key[BlockBasedTable::kMaxCacheKeyPrefixSize + kMaxVarint64Length];
+  auto key = BlockBasedTable::GetCacheKey(cache_options.key_prefix.c_str(),
+                                          cache_options.key_prefix.size(),
+                                          handle, cache_key);
+  // Lookup page
+  size_t size;
+  Status s = cache_options.persistent_cache->Lookup(key, raw_data, &size);
+  if (!s.ok()) {
+    // cache miss
+    RecordTick(cache_options.statistics, PERSISTENT_CACHE_MISS);
+    return s;
+  }
+
+  // cache hit
+  assert(raw_data_size == handle.size() + kBlockTrailerSize);
+  assert(size == raw_data_size);
+  RecordTick(cache_options.statistics, PERSISTENT_CACHE_HIT);
+  return Status::OK();
+}
+
+Status PersistentCacheHelper::LookupUncompressedPage(
+    const PersistentCacheOptions& cache_options, const BlockHandle& handle,
+    BlockContents* contents) {
+  assert(cache_options.persistent_cache);
+  assert(!cache_options.persistent_cache->IsCompressed());
+  if (!contents) {
+    // We shouldn't lookup in the cache. Either
+    // (1) Nowhere to store
+    return Status::NotFound();
+  }
+
+  // construct the page key
+  char cache_key[BlockBasedTable::kMaxCacheKeyPrefixSize + kMaxVarint64Length];
+  auto key = BlockBasedTable::GetCacheKey(cache_options.key_prefix.c_str(),
+                                          cache_options.key_prefix.size(),
+                                          handle, cache_key);
+  // Lookup page
+  std::unique_ptr<char[]> data;
+  size_t size;
+  Status s = cache_options.persistent_cache->Lookup(key, &data, &size);
+  if (!s.ok()) {
+    // cache miss
+    RecordTick(cache_options.statistics, PERSISTENT_CACHE_MISS);
+    return s;
+  }
+
+  // please note we are potentially comparing compressed data size with
+  // uncompressed data size
+  assert(handle.size() <= size);
+
+  // update stats
+  RecordTick(cache_options.statistics, PERSISTENT_CACHE_HIT);
+  // construct result and return
+  *contents = BlockContents(std::move(data), size);
+  return Status::OK();
+}
+
+}  // namespace rocksdb