[Delphi]Packed Record和Record的区别
2012-12-07 08:55
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Record的数据各个字节都是对齐的,数据格式比较完整,所以这种格式相对packed占用的内存比较大,但是因为格式比较整齐,所以电脑读取这个类型的数据的时候速度比较快。而Packed Record对数据进行了压缩,节省了内存空间,当然他的速度也变的慢了。
type
//Declare an unpacked record
TDefaultRecord = Record
name1 : string[4];
floater : single;
name2 : char;
int : Integer;
end;
//Declare a packed record
TPackedRecord = Packed Record
name1 : string[4];
floater : single;
name2 : char;
int : Integer;
end;
var defaultRec : TDefaultRecord;
packedRec : TPackedRecord;
begin
ShowMessage('Default record size = '+IntToStr(SizeOf(defaultRec)));
ShowMessage('Packed record size = '+IntToStr(SizeOf(packedRec)));
end;
Default record size = 20
Packed record size = 14
不过,对于现在的操作系统来,packed Record 节省的那些空间已不用考虑他了。除了做DLL(不用packed容易造成内存混乱)和做硬件编程时(比如串口)编程时必须用到packed Record,其它情况都可以用Record
type
//Declare an unpacked record
TDefaultRecord = Record
name1 : string[4];
floater : single;
name2 : char;
int : Integer;
end;
//Declare a packed record
TPackedRecord = Packed Record
name1 : string[4];
floater : single;
name2 : char;
int : Integer;
end;
var defaultRec : TDefaultRecord;
packedRec : TPackedRecord;
begin
ShowMessage('Default record size = '+IntToStr(SizeOf(defaultRec)));
ShowMessage('Packed record size = '+IntToStr(SizeOf(packedRec)));
end;
Default record size = 20
Packed record size = 14
不过,对于现在的操作系统来,packed Record 节省的那些空间已不用考虑他了。除了做DLL(不用packed容易造成内存混乱)和做硬件编程时(比如串口)编程时必须用到packed Record,其它情况都可以用Record
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