在一个字符串中找到一个子字符串

char* FindSubString(char* pStr, char* pSubStr)
{
unsigned int iMainStrLen = 0;
unsigned int iSubStrLen  = 0;
unsigned int i,j;
unsigned int ii,jj;

if(pStr==NULL || pSubStr==NULL)
return NULL;

iMainStrLen = strlen(pStr);
iSubStrLen  = strlen(pSubStr);

if(iMainStrLen < iSubStrLen)
return NULL;

i = 0;
j = 0;

while (i<iMainStrLen && j<iSubStrLen)
{
if(pStr[i] == pSubStr[j])
{
ii = i;
jj = j;

while (1)
{
ii++;
jj++;

if (jj == iSubStrLen)
{
return (pStr+i);
}

if (ii == iMainStrLen)
{
return NULL;
}

if (pStr[ii] != pSubStr[jj])
{
break;
}
}
}
i++;
}
return NULL;
}