大小端交换

大小端交换

{$IF RTLVersion<25}
  IntPtr = Integer;
  {$IFEND IntPtr}

　　

function swap16(const v): Word;
begin
  // FF, EE : EE->1, FF->2
  PByte(@result)^ := PByte(IntPtr(@v) + 1)^;
  PByte(IntPtr(@result) + 1)^ := PByte(@v)^;
end;

function swap32(const v): Cardinal;
begin
  // FF, EE, DD, CC : CC->1, DD->2, EE->3, FF->4
  PByte(@result)^ := PByte(IntPtr(@v) + 3)^;
  PByte(IntPtr(@result) + 1)^ := PByte(IntPtr(@v) + 2)^;
  PByte(IntPtr(@result) + 2)^ := PByte(IntPtr(@v) + 1)^;
  PByte(IntPtr(@result) + 3)^ := PByte(@v)^;
end;

function swap64(const v): Int64;
begin
  // FF, EE, DD, CC, BB, AA, 99, 88 : 88->1 ,99->2 ....
  PByte(@result)^ := PByte(IntPtr(@v) + 7)^;
  PByte(IntPtr(@result) + 1)^ := PByte(IntPtr(@v) + 6)^;
  PByte(IntPtr(@result) + 2)^ := PByte(IntPtr(@v) + 5)^;
  PByte(IntPtr(@result) + 3)^ := PByte(IntPtr(@v) + 4)^;
  PByte(IntPtr(@result) + 4)^ := PByte(IntPtr(@v) + 3)^;
  PByte(IntPtr(@result) + 5)^ := PByte(IntPtr(@v) + 2)^;
  PByte(IntPtr(@result) + 6)^ := PByte(IntPtr(@v) + 1)^;
  PByte(IntPtr(@result) + 7)^ := PByte(@v)^;
end;

// v and outVal is can't the same value
procedure swap64Ex(const v; out outVal);
begin
  // FF, EE, DD, CC, BB, AA, 99, 88 : 88->1 ,99->2 ....
  PByte(@outVal)^ := PByte(IntPtr(@v) + 7)^;
  PByte(IntPtr(@outVal) + 1)^ := PByte(IntPtr(@v) + 6)^;
  PByte(IntPtr(@outVal) + 2)^ := PByte(IntPtr(@v) + 5)^;
  PByte(IntPtr(@outVal) + 3)^ := PByte(IntPtr(@v) + 4)^;
  PByte(IntPtr(@outVal) + 4)^ := PByte(IntPtr(@v) + 3)^;
  PByte(IntPtr(@outVal) + 5)^ := PByte(IntPtr(@v) + 2)^;
  PByte(IntPtr(@outVal) + 6)^ := PByte(IntPtr(@v) + 1)^;
  PByte(IntPtr(@outVal) + 7)^ := PByte(@v)^;
end;

// v and outVal is can't the same value
procedure swap32Ex(const v; out outVal);
begin
  // FF, EE, DD, CC : CC->1, DD->2, EE->3, FF->4
  PByte(@outVal)^ := PByte(IntPtr(@v) + 3)^;
  PByte(IntPtr(@outVal) + 1)^ := PByte(IntPtr(@v) + 2)^;
  PByte(IntPtr(@outVal) + 2)^ := PByte(IntPtr(@v) + 1)^;
  PByte(IntPtr(@outVal) + 3)^ := PByte(@v)^;
end;

// v and outVal is can't the same value
procedure swap16Ex(const v; out outVal);
begin
  // FF, EE : EE->1, FF->2
  PByte(@outVal)^ := PByte(IntPtr(@v) + 1)^;
  PByte(IntPtr(@outVal) + 1)^ := PByte(@v)^;
end;

// overload swap, result type is integer, because single maybe NaN
function swap(v: Single): Integer; overload;
begin
  swap32Ex(v, Result);
end;

// overload swap
function swap(v: word): Word; overload;
begin
  swap16Ex(v, Result);
end;

// overload swap
function swap(v: Cardinal): Cardinal; overload;
begin
  swap32Ex(v, Result);
end;

// swap , result type is Int64, because Double maybe NaN
function swap(v: Double): Int64; overload;
begin
  swap64Ex(v, Result);
end;