| /* |
| * Copyright 2016 gRPC authors. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef GRPC_CORE_LIB_SLICE_SLICE_WEAK_HASH_TABLE_H |
| #define GRPC_CORE_LIB_SLICE_SLICE_WEAK_HASH_TABLE_H |
| |
| #include <grpc/support/port_platform.h> |
| |
| #include "src/core/lib/gprpp/memory.h" |
| #include "src/core/lib/gprpp/ref_counted.h" |
| #include "src/core/lib/gprpp/ref_counted_ptr.h" |
| #include "src/core/lib/slice/slice_internal.h" |
| |
| /// Weak hash table implementation. |
| /// |
| /// This entries in this table are weak: an entry may be removed at any time due |
| /// to a number of reasons: memory pressure, hash collisions, etc. |
| /// |
| /// The keys are \a grpc_slice objects. The values are of arbitrary type. |
| /// |
| /// This class is thread unsafe. It's the caller's responsibility to ensure |
| /// proper locking when accessing its methods. |
| |
| namespace grpc_core { |
| |
| template <typename T, size_t Size> |
| class SliceWeakHashTable : public RefCounted<SliceWeakHashTable<T, Size>> { |
| public: |
| /// Creates a new table of at most \a size entries. |
| static RefCountedPtr<SliceWeakHashTable> Create() { |
| return MakeRefCounted<SliceWeakHashTable<T, Size>>(); |
| } |
| |
| /// Add a mapping from \a key to \a value, taking ownership of \a key. This |
| /// operation will always succeed. It may discard older entries. |
| void Add(grpc_slice key, T value) { |
| const size_t idx = grpc_slice_hash(key) % Size; |
| entries_[idx].Set(key, std::move(value)); |
| return; |
| } |
| |
| /// Returns the value from the table associated with / \a key or null if not |
| /// found. |
| const T* Get(const grpc_slice key) const { |
| const size_t idx = grpc_slice_hash(key) % Size; |
| const auto& entry = entries_[idx]; |
| return grpc_slice_eq(entry.key(), key) ? entry.value() : nullptr; |
| } |
| |
| private: |
| // So New() can call our private ctor. |
| template <typename T2, typename... Args> |
| friend T2* New(Args&&... args); |
| |
| // So Delete() can call our private dtor. |
| template <typename T2> |
| friend void Delete(T2*); |
| |
| SliceWeakHashTable() = default; |
| ~SliceWeakHashTable() = default; |
| |
| /// The type of the table "rows". |
| class Entry { |
| public: |
| Entry() = default; |
| ~Entry() { |
| if (is_set_) grpc_slice_unref_internal(key_); |
| } |
| grpc_slice key() const { return key_; } |
| |
| /// Return the entry's value, or null if unset. |
| const T* value() const { |
| if (!is_set_) return nullptr; |
| return &value_; |
| } |
| |
| /// Set the \a key and \a value (which is moved) for the entry. |
| void Set(grpc_slice key, T&& value) { |
| if (is_set_) grpc_slice_unref_internal(key_); |
| key_ = key; |
| value_ = std::move(value); |
| is_set_ = true; |
| } |
| |
| private: |
| grpc_slice key_; |
| T value_; |
| bool is_set_ = false; |
| }; |
| |
| Entry entries_[Size]; |
| }; |
| |
| } // namespace grpc_core |
| |
| #endif /* GRPC_CORE_LIB_SLICE_SLICE_WEAK_HASH_TABLE_H */ |