【高手求助】小字节序转为大字节序函数

[Barbiegirl2010]

昨天的一道笔试题，编写如下结构的小字节序转大字节序的转换函数：void ConvertLToB(T_Sample*ptIn),结构的定义如下

#pragma pack(4)
typedef struct tagT_Sample{
BYTE ucA   :3;
BYTE ucB   :3;
BYTE ucC   :3;
BYTE ucD   :3;
BYTE ucE   :3;
DWORD dwF   :24;
}T_Sample;

自己对大小端也有点了解，但是也只是限于判断和求个输出什么的，哎，怪自己学艺不精，求高手来解答！

[Barbiegirl2010]

顶一下！求高手相助！

[qq120848369]

#pragma pack(4)
typedef struct tagT_Sample{
////1字节//////
BYTE ucA :3;
BYTE ucB :3;
//////////////

////1字节/////
BYTE ucC :3;
BYTE ucD :3;
//////////////

///1字节//////
BYTE ucE :3;
//////////////

//填充1字节///
/////////////

/////4字节////
DWORD dwF :24;
/////////////

}T_Sample;


就这么8个字节, SB面试官是打算让你把整个结构体的字节颠倒一下还是把DWORD字节的字节序颠倒一下(唯一的多字节),还是把每个域里的位颠倒一下?

[mymtom]

出题的就是个半桶水！

按照标准sizeof(T_Sample)都是不确定的！

对于位字段来说，几乎所有的描述都是不确定的[B]implementation-defined[/B]或者[B]unspecified[/B].

A bit-field may have type int, unsigned int, or signed int. Whether the high-order bit position of a “plain” int bit-field is treated as a sign bit is [B]implementation-defined[/B]. A bit-field is interpreted as an integral type consisting of the specified number of bits.

An implementation may allocate any addressable storage unit large enough to hold a bit-field. If enough space remains, a bit-field that immediately follows another bit-field in a structure shall be packed into adjacent bits of the same unit. If insufficient space remains, whether a bit-field that does not fit is put into the next unit or overlaps adjacent units is [B]implementation-defined[/B]. The order of allocation of bit-fields within a unit (high-order to low-order or low-order to high-order) is [B]implementation-defined[/B]. The alignment of the addressable storage unit is [B]unspecified[/B].

[Barbiegirl2010]

[Quote=引用 2 楼 的回复:]
#pragma pack(4)
typedef struct tagT_Sample{
////1字节//////
BYTE ucA :3;
BYTE ucB :3;
//////////////

////1字节/////
BYTE ucC :3;
BYTE ucD :3;
//////////////

///1字节//////
BYTE ucE :3;
/////……
[/Quote]我也不清楚额。。。题目我拍照原封不动的抄过来的额，不过网上相关的都进行移位操作什么的，没看明白额

[Barbiegirl2010]

#pragma pack(4)
这个不是说了按四字节对齐么，可以求出大小的么
[Quote=引用 3 楼 的回复:]
出题的就是个半桶水！

按照标准sizeof(T_Sample)都是不确定的！

对于位字段来说，几乎所有的描述都是不确定的implementation-defined或者unspecified.

A bit-field may have type int, unsigned int, or signed int. Whether the high-order bit positio……
[/Quote]

[mymtom]

C标准里没有#pragma pack吧！

[Barbiegirl2010]

嗯，是vc里面的。。。人家写了估计就得按他的来吧。。。好苦逼啊[Quote=引用 6 楼 的回复:]
C标准里没有#pragma pack吧！
[/Quote]

[Barbiegirl2010]

有人帮助小弟解决下么。。。