将 4 个 Byte 合成 1 个 Integer 的五种方法 - 回复 "三足乌" 的问题

问题来源: http://www.cnblogs.com/del/archive/2010/04/21/1717584.html#1809298
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//方法 1: 共用内存
procedure TForm1.Button1Click(Sender: TObject);
var
bf: record b1,b2,b3,b4: Byte end;
i: Integer absolute bf;
begin
bf.b1 := $CC;
bf.b2 := $DD;
bf.b3 := $EE;
bf.b4 := $FF;
ShowMessageFmt('%x', [i]); //FFEEDDCC
end;

//方法 2: 位运算
procedure TForm1.Button2Click(Sender: TObject);
var
i: Integer;
begin
i := $CC or ($DD shl 8) or ($EE shl 16) or ($FF shl 24); //不用括号也可
ShowMessageFmt('%x', [i]); //FFEEDDCC
end;

//方法 3: 使用函数
procedure TForm1.Button3Click(Sender: TObject);
var
i: Integer;
begin
i := MakeLong(MakeWord($CC,$DD), MakeWord($EE,$FF));
ShowMessageFmt('%x', [i]); //FFEEDDCC
end;

//方法 4: 从静态数组...
procedure TForm1.Button4Click(Sender: TObject);
var
bs: array[0..3] of Byte;
P: PInteger;
begin
bs[0] := $CC;
bs[1] := $DD;
bs[2] := $EE;
bs[3] := $FF;
P := @bs;
ShowMessageFmt('%x', [P^]); //FFEEDDCC
end;

//方法 5: 从动态数组...
procedure TForm1.Button5Click(Sender: TObject);
var
bs: array of Byte;
P: PInteger;
begin
SetLength(bs, 4);
bs[0] := $CC;
bs[1] := $DD;
bs[2] := $EE;
bs[3] := $FF;
P := @bs[0];
ShowMessageFmt('%x', [P^]); //FFEEDDCC
end;