#include <windows.h>
#include <crtdbg.h>

/*
UTF-8 编码规则
1字节 0BBBBBBB 
2字节 110BBBBB 10BBBBBB 
3字节 1110BBBB 10BBBBBB 10BBBBBB 
4字节 11110BBB 10BBBBBB 10BBBBBB 10BBBBBB 
5字节 111110BB 10BBBBBB 10BBBBBB 10BBBBBB 10BBBBBB 
6字节 1111110B 10BBBBBB 10BBBBBB 10BBBBBB 10BBBBBB 10BBBBBB 
*/

//探测输入字符串是否是UTF8字符串
bool IsUtf8String(const char *pString)
{
  bool bRet = true;

  //输入长度
  int iStrLen = pString ? strlen(pString):0;

  //临时变量
  int m,n, iBLen;  BYTE b0;

  for(m=0; bRet && m<iStrLen; )
  {
    //根据第一个字节计算长度
    b0 = (BYTE)pString[m]; 
    iBLen = 0;
    if((b0 & 0x80) == 0x00)      { iBLen = 1; } //1字节
    else if((b0 & 0xE0) == 0xC0) { iBLen = 2; } //2字节
    else if((b0 & 0xF0) == 0xE0) { iBLen = 3; } //3字节
    else if((b0 & 0xF8) == 0xF0) { iBLen = 4; } //4字节
    else if((b0 & 0xFC) == 0xF8) { iBLen = 5; } //5字节
    else if((b0 & 0xFE) == 0xFC) { iBLen = 6; } //6字节
    else {} //非法

    //非法长度或超出缓冲区范围
    if(iBLen <= 0 || m+iBLen > iStrLen)
    {
      bRet = false;
      break;
    }
   
    //判断后续字节需 10xxxxxx
    for(n=1; n<iBLen; n++)
    {
      if((pString[m+n] & 0xC0) == 0x80)
        continue;

      bRet = false;
      break;
    }

    //对齐到下一个长度
    m += iBLen;
  }

  return bRet;
}

int _tmain(int argc, _TCHAR* argv[])
{
  LPCWSTR strW = L"中国";
  CHAR chBuff[16]={0};
  WideCharToMultiByte(CP_UTF8, 0, strW, -1, chBuff, sizeof(chBuff), NULL, NULL);

  _ASSERT(!IsUtf8String((CHAR*)strW));
  _ASSERT(IsUtf8String(chBuff));

	return 0;
}