add prioritized cache wrapper

Signed-off-by: haoxiang47 <[email protected]>

src/prioritized_cache.cc

@@ -0,0 +1,26 @@
+#include "prioritized_cache.h"
+
+namespace rocksdb {
+namespace titandb {
+
+PrioritizedCache::PrioritizedCache(std::shared_ptr<Cache> cache) : 
+                                                    cache_(cache) {}
+
+std::shared_ptr<Cache> PrioritizedCache::GetPrioritizedCache() {
+    return cache_;
+}
+
+Status PrioritizedCache::HighPriCacheInsert(const Slice& key, void* value, size_t charge,
+                                            void (*deleter)(const Slice& key, void* value),
+                                            Cache::Handle** handle) {
+    return cache_->Insert(key, value, charge, deleter, handle, Cache::Priority::HIGH);
+}
+
+Status PrioritizedCache::LowPriCacheInsert(const Slice& key, void* value, size_t charge,
+                                           void (*deleter)(const Slice& key, void* value),
+                                           Cache::Handle** handle) {
+    return cache_->Insert(key, value, charge, deleter, handle, Cache::Priority::LOW);
+}
+
+}  // namespace titandb
+}  // namespace rocksdb

src/prioritized_cache.h

@@ -0,0 +1,37 @@
+#pragma once
+#include "rocksdb/cache.h"
+#include "rocksdb/env.h"
+
+namespace rocksdb {
+namespace titandb {
+
+class PrioritizedCache {
+public:
+
+    // Constructs a PrioritizedCache, which is a wrapper
+    // of rocksdb Cache
+    PrioritizedCache(std::shared_ptr<Cache> cache);
+    ~PrioritizedCache();
+
+    // Get the Cache ptr
+    std::shared_ptr<Cache> GetPrioritizedCache();
+
+    // always insert into the cache with high-priority, 
+    // regardless of user provided option
+    Status HighPriCacheInsert(const Slice& key, void* value, size_t charge,
+                              void (*deleter)(const Slice& key, void* value),
+                              Cache::Handle** handle = nullptr);
+
+    // always insert into the cache with low-priority, 
+    // regardless of user provided option
+    Status LowPriCacheInsert(const Slice& key, void* value, size_t charge,
+                             void (*deleter)(const Slice& key, void* value),
+                             Cache::Handle** handle = nullptr);
+
+private:
+    std::shared_ptr<Cache> cache_;
+};
+
+
+}  // namespace titandb
+}  // namespace rocksdb