Export Cache::GetCharge (#5476)

Summary:
Exporting GetCharge to cache.hh
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5476

Differential Revision: D15881882

Pulled By: riversand963

fbshipit-source-id: 3d99084d10059b4fcaaaba240606ed50bc23351c

cache/cache_test.cc

@@ -686,6 +686,14 @@ TEST_P(CacheTest, DefaultShardBits) {
   ASSERT_EQ(6, sc->GetNumShardBits());
 }
 
+TEST_P(CacheTest, GetCharge) {
+  Insert(1, 2);
+  Cache::Handle* h1 = cache_->Lookup(EncodeKey(1));
+  ASSERT_EQ(2, DecodeValue(cache_->Value(h1)));
+  ASSERT_EQ(1, cache_->GetCharge(h1));
+  cache_->Release(h1);
+}
+
 #ifdef SUPPORT_CLOCK_CACHE
 std::shared_ptr<Cache> (*new_clock_cache_func)(size_t, int,
                                                bool) = NewClockCache;

cache/sharded_cache.h

@@ -54,7 +54,8 @@ class ShardedCache : public Cache {
   virtual CacheShard* GetShard(int shard) = 0;
   virtual const CacheShard* GetShard(int shard) const = 0;
   virtual void* Value(Handle* handle) override = 0;
-  virtual size_t GetCharge(Handle* handle) const = 0;
+  virtual size_t GetCharge(Handle* handle) const override = 0;
+
   virtual uint32_t GetHash(Handle* handle) const = 0;
   virtual void DisownData() override = 0;
 

include/rocksdb/cache.h

@@ -226,6 +226,9 @@ class Cache {
   // returns the memory size for the entries in use by the system
   virtual size_t GetPinnedUsage() const = 0;
 
+  // returns the charge for the specific entry in the cache.
+  virtual size_t GetCharge(Handle* handle) const = 0;
+
   // Call this on shutdown if you want to speed it up. Cache will disown
   // any underlying data and will not free it on delete. This call will leak
   // memory - call this only if you're shutting down the process.

utilities/simulator_cache/sim_cache.cc

@@ -235,6 +235,8 @@ class SimCacheImpl : public SimCache {
     return cache_->GetUsage(handle);
   }
 
+  size_t GetCharge(Handle* handle) const override { return cache_->GetCharge(handle); }
+
   size_t GetPinnedUsage() const override { return cache_->GetPinnedUsage(); }
 
   void DisownData() override {