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.

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

bitmap.cpp

Public Types

Public Member Functions