| // Copyright 2014 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef V8_BASE_FUNCTIONAL_H_ |
| #define V8_BASE_FUNCTIONAL_H_ |
| |
| #include <stddef.h> |
| #include <stdint.h> |
| |
| #include <cstddef> |
| #include <cstring> |
| #include <functional> |
| #include <utility> |
| |
| #include "src/base/base-export.h" |
| #include "src/base/macros.h" |
| |
| namespace v8 { |
| namespace base { |
| |
| // base::hash is an implementation of the hash function object specified by |
| // C++11. It was designed to be compatible with std::hash (in C++11) and |
| // boost:hash (which in turn is based on the hash function object specified by |
| // the Draft Technical Report on C++ Library Extensions (TR1)). |
| // |
| // base::hash is implemented by calling the hash_value function. The namespace |
| // isn't specified so that it can detect overloads via argument dependent |
| // lookup. So if there is a free function hash_value in the same namespace as a |
| // custom type, it will get called. |
| // |
| // If users are asked to implement a hash function for their own types with no |
| // guidance, they generally write bad hash functions. Instead, we provide a |
| // simple function base::hash_combine to pass hash-relevant member variables |
| // into, in order to define a decent hash function. base::hash_combine is |
| // declared as: |
| // |
| // template<typename T, typename... Ts> |
| // size_t hash_combine(const T& v, const Ts& ...vs); |
| // |
| // Consider the following example: |
| // |
| // namespace v8 { |
| // namespace bar { |
| // struct Point { int x; int y; }; |
| // size_t hash_value(Point const& p) { |
| // return base::hash_combine(p.x, p.y); |
| // } |
| // } |
| // |
| // namespace foo { |
| // void DoSomeWork(bar::Point const& p) { |
| // base::hash<bar::Point> h; |
| // ... |
| // size_t hash_code = h(p); // calls bar::hash_value(Point const&) |
| // ... |
| // } |
| // } |
| // } |
| // |
| // Based on the "Hashing User-Defined Types in C++1y" proposal from Jeffrey |
| // Yasskin and Chandler Carruth, see |
| // http://www.open-std.org/Jtc1/sc22/wg21/docs/papers/2012/n3333.html. |
| |
| template <typename> |
| struct hash; |
| |
| |
| V8_INLINE size_t hash_combine() { return 0u; } |
| V8_INLINE size_t hash_combine(size_t seed) { return seed; } |
| V8_BASE_EXPORT size_t hash_combine(size_t seed, size_t value); |
| template <typename T, typename... Ts> |
| V8_INLINE size_t hash_combine(T const& v, Ts const&... vs) { |
| return hash_combine(hash_combine(vs...), hash<T>()(v)); |
| } |
| |
| |
| template <typename Iterator> |
| V8_INLINE size_t hash_range(Iterator first, Iterator last) { |
| size_t seed = 0; |
| for (; first != last; ++first) { |
| seed = hash_combine(seed, *first); |
| } |
| return seed; |
| } |
| |
| template <typename Iterator> |
| V8_INLINE size_t hash_range(size_t seed, Iterator first, Iterator last) { |
| for (; first != last; ++first) { |
| seed = hash_combine(seed, *first); |
| } |
| return seed; |
| } |
| |
| #define V8_BASE_HASH_VALUE_TRIVIAL(type) \ |
| V8_INLINE size_t hash_value(type v) { return static_cast<size_t>(v); } |
| V8_BASE_HASH_VALUE_TRIVIAL(bool) |
| V8_BASE_HASH_VALUE_TRIVIAL(unsigned char) |
| V8_BASE_HASH_VALUE_TRIVIAL(unsigned short) // NOLINT(runtime/int) |
| #undef V8_BASE_HASH_VALUE_TRIVIAL |
| |
| V8_BASE_EXPORT size_t hash_value(unsigned int); |
| V8_BASE_EXPORT size_t hash_value(unsigned long); // NOLINT(runtime/int) |
| V8_BASE_EXPORT size_t hash_value(unsigned long long); // NOLINT(runtime/int) |
| |
| #define V8_BASE_HASH_VALUE_SIGNED(type) \ |
| V8_INLINE size_t hash_value(signed type v) { \ |
| return hash_value(bit_cast<unsigned type>(v)); \ |
| } |
| V8_BASE_HASH_VALUE_SIGNED(char) |
| V8_BASE_HASH_VALUE_SIGNED(short) // NOLINT(runtime/int) |
| V8_BASE_HASH_VALUE_SIGNED(int) // NOLINT(runtime/int) |
| V8_BASE_HASH_VALUE_SIGNED(long) // NOLINT(runtime/int) |
| V8_BASE_HASH_VALUE_SIGNED(long long) // NOLINT(runtime/int) |
| #undef V8_BASE_HASH_VALUE_SIGNED |
| |
| V8_INLINE size_t hash_value(float v) { |
| // 0 and -0 both hash to zero. |
| return v != 0.0f ? hash_value(bit_cast<uint32_t>(v)) : 0; |
| } |
| |
| V8_INLINE size_t hash_value(double v) { |
| // 0 and -0 both hash to zero. |
| return v != 0.0 ? hash_value(bit_cast<uint64_t>(v)) : 0; |
| } |
| |
| template <typename T, size_t N> |
| V8_INLINE size_t hash_value(const T (&v)[N]) { |
| return hash_range(v, v + N); |
| } |
| |
| template <typename T, size_t N> |
| V8_INLINE size_t hash_value(T (&v)[N]) { |
| return hash_range(v, v + N); |
| } |
| |
| template <typename T> |
| V8_INLINE size_t hash_value(T* const& v) { |
| return hash_value(bit_cast<uintptr_t>(v)); |
| } |
| |
| template <typename T1, typename T2> |
| V8_INLINE size_t hash_value(std::pair<T1, T2> const& v) { |
| return hash_combine(v.first, v.second); |
| } |
| |
| template <typename T> |
| struct hash { |
| V8_INLINE size_t operator()(T const& v) const { return hash_value(v); } |
| }; |
| |
| #define V8_BASE_HASH_SPECIALIZE(type) \ |
| template <> \ |
| struct hash<type> { \ |
| V8_INLINE size_t operator()(type const v) const { \ |
| return ::v8::base::hash_value(v); \ |
| } \ |
| }; |
| V8_BASE_HASH_SPECIALIZE(bool) |
| V8_BASE_HASH_SPECIALIZE(signed char) |
| V8_BASE_HASH_SPECIALIZE(unsigned char) |
| V8_BASE_HASH_SPECIALIZE(short) // NOLINT(runtime/int) |
| V8_BASE_HASH_SPECIALIZE(unsigned short) // NOLINT(runtime/int) |
| V8_BASE_HASH_SPECIALIZE(int) |
| V8_BASE_HASH_SPECIALIZE(unsigned int) |
| V8_BASE_HASH_SPECIALIZE(long) // NOLINT(runtime/int) |
| V8_BASE_HASH_SPECIALIZE(unsigned long) // NOLINT(runtime/int) |
| V8_BASE_HASH_SPECIALIZE(long long) // NOLINT(runtime/int) |
| V8_BASE_HASH_SPECIALIZE(unsigned long long) // NOLINT(runtime/int) |
| V8_BASE_HASH_SPECIALIZE(float) |
| V8_BASE_HASH_SPECIALIZE(double) |
| #undef V8_BASE_HASH_SPECIALIZE |
| |
| template <typename T> |
| struct hash<T*> { |
| V8_INLINE size_t operator()(T* const v) const { |
| return ::v8::base::hash_value(v); |
| } |
| }; |
| |
| // base::bit_equal_to is a function object class for bitwise equality |
| // comparison, similar to std::equal_to, except that the comparison is performed |
| // on the bit representation of the operands. |
| // |
| // base::bit_hash is a function object class for bitwise hashing, similar to |
| // base::hash. It can be used together with base::bit_equal_to to implement a |
| // hash data structure based on the bitwise representation of types. |
| |
| template <typename T> |
| struct bit_equal_to {}; |
| |
| template <typename T> |
| struct bit_hash {}; |
| |
| #define V8_BASE_BIT_SPECIALIZE_TRIVIAL(type) \ |
| template <> \ |
| struct bit_equal_to<type> : public std::equal_to<type> {}; \ |
| template <> \ |
| struct bit_hash<type> : public hash<type> {}; |
| V8_BASE_BIT_SPECIALIZE_TRIVIAL(signed char) |
| V8_BASE_BIT_SPECIALIZE_TRIVIAL(unsigned char) |
| V8_BASE_BIT_SPECIALIZE_TRIVIAL(short) // NOLINT(runtime/int) |
| V8_BASE_BIT_SPECIALIZE_TRIVIAL(unsigned short) // NOLINT(runtime/int) |
| V8_BASE_BIT_SPECIALIZE_TRIVIAL(int) |
| V8_BASE_BIT_SPECIALIZE_TRIVIAL(unsigned int) |
| V8_BASE_BIT_SPECIALIZE_TRIVIAL(long) // NOLINT(runtime/int) |
| V8_BASE_BIT_SPECIALIZE_TRIVIAL(unsigned long) // NOLINT(runtime/int) |
| V8_BASE_BIT_SPECIALIZE_TRIVIAL(long long) // NOLINT(runtime/int) |
| V8_BASE_BIT_SPECIALIZE_TRIVIAL(unsigned long long) // NOLINT(runtime/int) |
| #undef V8_BASE_BIT_SPECIALIZE_TRIVIAL |
| |
| #define V8_BASE_BIT_SPECIALIZE_BIT_CAST(type, btype) \ |
| template <> \ |
| struct bit_equal_to<type> { \ |
| V8_INLINE bool operator()(type lhs, type rhs) const { \ |
| return bit_cast<btype>(lhs) == bit_cast<btype>(rhs); \ |
| } \ |
| }; \ |
| template <> \ |
| struct bit_hash<type> { \ |
| V8_INLINE size_t operator()(type v) const { \ |
| hash<btype> h; \ |
| return h(bit_cast<btype>(v)); \ |
| } \ |
| }; |
| V8_BASE_BIT_SPECIALIZE_BIT_CAST(float, uint32_t) |
| V8_BASE_BIT_SPECIALIZE_BIT_CAST(double, uint64_t) |
| #undef V8_BASE_BIT_SPECIALIZE_BIT_CAST |
| |
| } // namespace base |
| } // namespace v8 |
| |
| #endif // V8_BASE_FUNCTIONAL_H_ |