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/*
* 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 */
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