class HashState
Defined at line 315 of file ../../third_party/abseil-cpp/absl/hash/hash.h
HashState
A type erased version of the hash state concept, for use in user-defined
`AbslHashValue` implementations that can't use templates (such as PImpl
classes, virtual functions, etc.). The type erasure adds overhead so it
should be avoided unless necessary.
Note: This wrapper will only erase calls to
combine_contiguous(H, const unsigned char*, size_t)
RunCombineUnordered(H, CombinerF)
All other calls will be handled internally and will not invoke overloads
provided by the wrapped class.
Users of this class should still define a template `AbslHashValue` function,
but can use `absl::HashState::Create(
&state
)` to erase the type of the hash
state and dispatch to their private hashing logic.
This state can be used like any other hash state. In particular, you can call
`HashState::combine()` and `HashState::combine_contiguous()` on it.
Example:
class Interface {
public:
template
<typename
H>
friend H AbslHashValue(H state, const Interface
&
value) {
state = H::combine(std::move(state), std::type_index(typeid(*this)));
value.HashValue(absl::HashState::Create(
&state
));
return state;
}
private:
virtual void HashValue(absl::HashState state) const = 0;
};
class Impl : Interface {
private:
void HashValue(absl::HashState state) const override {
absl::HashState::combine(std::move(state), v1_, v2_);
}
int v1_;
std::string v2_;
};
Public Methods
template <typename T>HashState Create (T * state)HashState::Create()
Create a new `HashState` instance that wraps `state`. All calls to
`combine()` and `combine_contiguous()` on the new instance will be
redirected to the original `state` object. The `state` object must outlive
the `HashState` instance.
Defined at line 324 of file ../../third_party/abseil-cpp/absl/hash/hash.h
void HashState (const HashState & )Defined at line 330 of file ../../third_party/abseil-cpp/absl/hash/hash.h
HashState & operator= (const HashState & )Defined at line 331 of file ../../third_party/abseil-cpp/absl/hash/hash.h
void HashState (HashState && )Defined at line 332 of file ../../third_party/abseil-cpp/absl/hash/hash.h
HashState & operator= (HashState && )Defined at line 333 of file ../../third_party/abseil-cpp/absl/hash/hash.h
HashState combine_contiguous (HashState hash_state, const unsigned char * first, size_t size)HashState::combine_contiguous()
Combines a contiguous array of `size` elements into a hash state, returning
the updated state.
Defined at line 345 of file ../../third_party/abseil-cpp/absl/hash/hash.h
Records
Friends
class HashStateBase