用一维数组实现变长字符串
经常看到在结构中定一个1维的数组，估计大多数人初看这种定义都要蒙一下，其实这是用结构实现变长字符串，是程序设计中一个很有意思的技巧
使用结构实现变长字符串可以很容易的控制字符串的结构，方便对字符串数据的操作。
试想一下，如果不用结构那么需要一位一位的计算每一个字符所在位置，不把你搞死才怪
废话少说，下面是一个例子，很简单的。
#pragma pach(push, 1)
struct SHORT_STRING
{
BYTE byStrLen;
char sString[1];
};
struct STRUCT_HEAD
{
BYTE byRelation;
bool bNotify;
};
struct STRUCT_HEAD_SAVE : STRUCT_HEAD
{
SHORT_STRING PartnerName;
};
struct STRUCT_SAVE_HEAD
{
WORD wCount;
BYTE byMsgTransmit;
};
#pragma pack(pop)
#define LOGIN_ROLE_NAME_MAX_LEN 32
#define SHORT_STRING_LEN(n) ((n) + 1)
#define STRUCT_HEAD_SAVE_LEN(n) (sizeof(STRUCT_HEAD) + SHORT_STRING_LEN(n))
int main()
{
int nCount = 10;
STRUCT_SAVE_HEAD* pSaveHead;
int nSize = sizeof(STRUCT_SAVE_HEAD) + (sizeof(STRUCT_HEAD_SAVE) + LOGIN_ROLE_NAME_MAX_LEN) * nCount;
pSaveHead = (STRUCT_SAVE_HEAD*)malloc(nSize);
int nOffset = sizeof(STRUCT_SAVE_HEAD);
pSaveHead->wCount = 0;
STRUCT_HEAD_SAVE* pRelation = (STRUCT_HEAD_SAVE*)(((char*)pSaveHead) + nOffset);
static char szName[][12] = {
"1",
"22",
"333",
"4444",
"55555",
"666666",
"7777777",
"88888888",
"999999999",
"0000000000"
};
for (int i=0; i<10; i++)
{
pRelation->byRelation = 1;
pRelation->bNotify = 1;
pRelation->PartnerName.byStrLen = strlen(szName[i]);
memcpy(pRelation->PartnerName.sString, szName[i], pRelation->PartnerName.byStrLen);
nOffset += STRUCT_HEAD_SAVE_LEN(pRelation->PartnerName.byStrLen);
pRelation = (STRUCT_HEAD_SAVE*)(((BYTE*)pSaveHead) + nOffset);
pSaveHead->wCount++;
}
STRUCT_SAVE_HEAD *head = (STRUCT_SAVE_HEAD*)pSaveHead;
nOffset = sizeof(STRUCT_SAVE_HEAD);
pRelation = (STRUCT_HEAD_SAVE*)(((char*)pSaveHead) + nOffset);
pRelation = (STRUCT_HEAD_SAVE*)&(pRelation->PartnerName.sString[pRelation->PartnerName.byStrLen]);
pRelation = (STRUCT_HEAD_SAVE*)&(pRelation->PartnerName.sString[pRelation->PartnerName.byStrLen]);
pRelation = (STRUCT_HEAD_SAVE*)&(pRelation->PartnerName.sString[pRelation->PartnerName.byStrLen]);
}
