为何这样一个Record.用SizeOf返回的是84字节

Question

  TItemSDataInfo = record
    nType: ShortInt;
    nTypeID: ShortInt;
    n1: SmallInt;
    nReqlevel: SmallInt;
    nCountry: ShortInt;
    nAttackfighter: ShortInt;
    nDefensefighter: ShortInt;
    nPatrolrogue: ShortInt;
    nShootrogue: ShortInt;
    nAttackmage: ShortInt;
    nDefensemage: ShortInt;
    nGrow: ShortInt;
    //n2: SmallInt;
    nReqStr: SmallInt;
    nReqDex: SmallInt;
    nReqRec: SmallInt;
    nReqInt: SmallInt;
    nReqWis: SmallInt;
    nReqluc: SmallInt;
    nReqVg: SmallInt;
    nReqOg: ShortInt;
    nReqIg: ShortInt;
    //nRange: SmallInt;
    nRange: ShortInt;
    nAttackTime: ShortInt;
    nAttrib: ShortInt;
    nSpecial: ShortInt;
    nSlot: ShortInt;
    nQuality: SmallInt;
    nEffect: SmallInt;
    nEffect2: SmallInt;
    nEffect3: SmallInt;
    nEffect4: SmallInt;
    nConstHP: SmallInt;
    nConstSP: SmallInt;
    nConstMP: SmallInt;
    nConstStr: SmallInt;
    nConstDex: SmallInt;
    nConstRec: SmallInt;
    nConstInt: SmallInt;
    nConstWis: SmallInt;
    nConstLuc: SmallInt;
    nSpeed: ShortInt;
    nExp: ShortInt;
    nBuy: Integer;
    nSell: Integer;
    nGrade: SmallInt;
    nDrop: SmallInt;
    nServer: ShortInt;
    nCount: ShortInt;
  end;
被纳闷一下午了..........

Answer 1

 memo1.Lines.Append(INttostr(Sizeof(ShortInt)));
  memo1.Lines.Append(INttostr(Sizeof(SmallInt)));
   memo1.Lines.Append(INttostr(Sizeof(Integer)));這樣算下吧，看得眼都花了。

Answer 2

 TItemSDataInfo = packed record
    nType: ShortInt;
    nTypeID: ShortInt;
    n1: SmallInt;
    nReqlevel: SmallInt;
    nCountry: ShortInt;
    nAttackfighter: ShortInt;
    nDefensefighter: ShortInt;
    nPatrolrogue: ShortInt;
    nShootrogue: ShortInt;
    nAttackmage: ShortInt;
    nDefensemage: ShortInt;
    nGrow: ShortInt;
    //n2: SmallInt;
    nReqStr: SmallInt;
    nReqDex: SmallInt;
    nReqRec: SmallInt;
    nReqInt: SmallInt;
    nReqWis: SmallInt;
    nReqluc: SmallInt;
    nReqVg: SmallInt;
    nReqOg: ShortInt;
    nReqIg: ShortInt;
    //nRange: SmallInt;
    nRange: ShortInt;
    nAttackTime: ShortInt;
    nAttrib: ShortInt;
    nSpecial: ShortInt;
    nSlot: ShortInt;
    nQuality: SmallInt;
    nEffect: SmallInt;
    nEffect2: SmallInt;
    nEffect3: SmallInt;
    nEffect4: SmallInt;
    nConstHP: SmallInt;
    nConstSP: SmallInt;
    nConstMP: SmallInt;
    nConstStr: SmallInt;
    nConstDex: SmallInt;
    nConstRec: SmallInt;
    nConstInt: SmallInt;
    nConstWis: SmallInt;
    nConstLuc: SmallInt;
    nSpeed: ShortInt;
    nExp: ShortInt;
    nBuy: Integer;
    nSell: Integer;
    nGrade: SmallInt;
    nDrop: SmallInt;
    nServer: ShortInt;
    nCount: ShortInt;
  end; 這樣再來讀讀看。

Answer 3

type
 TItemSDataInfo = record
    nType: ShortInt;
    nTypeID: ShortInt;
    n1: SmallInt;
    nReqlevel: SmallInt;
    nCountry: ShortInt;
    nAttackfighter: ShortInt;
    nDefensefighter: ShortInt;
    nPatrolrogue: ShortInt;
    nShootrogue: ShortInt;
    nAttackmage: ShortInt;
    nDefensemage: ShortInt;
    nGrow: ShortInt;
    //n2: SmallInt;
    nReqStr: SmallInt;
    nReqDex: SmallInt;
    nReqRec: SmallInt;
    nReqInt: SmallInt;
    nReqWis: SmallInt;
    nReqluc: SmallInt;
    nReqVg: SmallInt;
    nReqOg: ShortInt;
    nReqIg: ShortInt;
    //nRange: SmallInt;
    nRange: ShortInt;
    nAttackTime: ShortInt;    nAttrib: ShortInt;
    nSpecial: ShortInt;
    nSlot: ShortInt;
     //浪費 1 個
    nQuality: SmallInt;
    nEffect: SmallInt;
    nEffect2: SmallInt;
    nEffect3: SmallInt;
    nEffect4: SmallInt;
    nConstHP: SmallInt;
    nConstSP: SmallInt;
    nConstMP: SmallInt;
    nConstStr: SmallInt;
    nConstDex: SmallInt;
    nConstRec: SmallInt;
    nConstInt: SmallInt;
    nConstWis: SmallInt;
    nConstLuc: SmallInt;
    nSpeed: ShortInt;
    nExp: ShortInt;
     //浪費 2個
    nBuy: Integer;
    nSell: Integer;
    nGrade: SmallInt;
    nDrop: SmallInt;
    nServer: ShortInt;
    nCount: ShortInt;
    //浪費2個
  end;
 幫你區分了下，呵呵

Answer 4

按ShortInt 1字节 SmallInt 2字节 Integer 4字节来算.应该是81个字节
但是返回总是84字节

Answer 5

  TItemSDataInfo = record
    nSpeed: ShortInt;
    nExp: ShortInt;
    nBuy: Integer;
    nSell: Integer;
    nGrade: SmallInt;
    nDrop: SmallInt;
    nServer: ShortInt;
    nCount: ShortInt;
  end;
我试着一段一段SizeOf  这段返回是20字节
但是我又单独把这段一行一行SizeOf 返回的是对的
是什么原因呢?

Answer 6

上面的區分還不明白嗎？而且你手工去算都算錯了。這是因為數據對齊的問題。上面我寫的一個  packet record  就會是要要的結果。
不然 Type Recprd   的話，按4個字節分配的話，就會出現你上面的情況。

Answer 7

说句题外话，你的record设计有问题

Answer 8

因为一直是自学.所以之前一直没注意record还有个同胞packed record

Answer 9

這裏我寫的：type
TItemSDataInfo = record
    nSpeed: ShortInt;
    nExp: ShortInt;
    nGrade: SmallInt;    nBuy: Integer;
    nSell: Integer;    nDrop: SmallInt;
    nServer: ShortInt;
    nCount: ShortInt;
  end;
這是你寫的：
 TItemSDataInfo = record
    nSpeed: ShortInt;
    nExp: ShortInt;
    nBuy: Integer;
    nSell: Integer;
    nGrade: SmallInt;
    nDrop: SmallInt;
    nServer: ShortInt;
    nCount: ShortInt;
  end;
看下各個變量的位置，要按4個字節去數據對齊明白了嗎？？   
如果你用 type Packet Record   則會按各個字段的類型占用字節數去申請內存，就不會出現上面的問題。

Answer 10

shortint 理论上占用2个字节，实际上呢？ 一个shortint站4个字节，2个shortint站4个字节，3个占8个，4个占8个 
懂了吧，
如果不这样 声明是加上packed  TItemSDataInfo = packed record
  
end;

Answer 11

size of 确定返回的就是字节个数么？