std::hash< SCALED_BITMAP_ID > Struct Template Reference

Public Types
typedef SCALED_BITMAP_ID	argument_type
typedef std::size_t	result_type

Public Member Functions
result_type	operator() (argument_type const &id) const noexcept

Detailed Description

template<>
struct std::hash< SCALED_BITMAP_ID >

Definition at line 65 of file bitmap.cpp.

Member Typedef Documentation

argument_type

typedef SCALED_BITMAP_ID std::hash< SCALED_BITMAP_ID >::argument_type

Definition at line 67 of file bitmap.cpp.

result_type

typedef std::size_t std::hash< SCALED_BITMAP_ID >::result_type

Definition at line 68 of file bitmap.cpp.

Member Function Documentation

operator()()

result_type std::hash< SCALED_BITMAP_ID >::operator() ( argument_type const &  id ) const

inlinenoexcept

Definition at line 70 of file bitmap.cpp.

        {
            static const bool sz64 = sizeof( uintptr_t ) == 8;
            static const size_t mask = sz64 ? 0xF000000000000000uLL : 0xF0000000uL;
            static const size_t offset = sz64 ? 60 : 28;

            // The hash only needs to be fast and simple, not necessarily accurate - a collision
            // only makes things slower, not broken. BITMAPS is a pointer, so the most
            // significant several bits are generally going to be the same for all. Just convert
            // it to an integer and stuff the scale factor into those bits.
            return
                ( (uintptr_t)( id.bitmap ) & ~mask ) |
                ( ( (uintptr_t)( id.scale ) & 0xF ) << offset );
        }

References scale.

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The documentation for this struct was generated from the following file:

• bitmap.cpp