宽字节UTF-8、多字节互转

　　在进行windows编程时，常常遇到不同字符编码之间的转换以对应不同的输出格式，本文介绍宽字节utf-8编码格式和多字节之间的项目转换。分别调用windows底层函数multibytetowidechar和  widechartomultibyte实现。

1.utf-8转多字节

　　

std::string u82mb(const char* cont)
{
    if (null == cont)
    {
        return "";
    }

    int num = multibytetowidechar(cp_utf8, null, cont, -1, null, null);
    if (num <= 0)
    {
        return "";
    }
    wchar_t* buffw = new (std::nothrow) wchar_t[num];
    if (null == buffw)
    {
        return "";
    }
    multibytetowidechar(cp_utf8, null, cont, -1, buffw, num);
    int len = widechartomultibyte(cp_acp, 0, buffw, num - 1, null, null, null, null);
    if (len <= 0)
    {
        delete[] buffw;
        return "";
    }
    char* lpsz = new (std::nothrow) char[len + 1]; 
    if (null == lpsz)
    {
        delete[] buffw;
        return "";
    }
    widechartomultibyte(cp_acp, 0, buffw, num - 1, lpsz, len, null, null);
    lpsz[len]='\0';
    delete[] buffw;
    std::string rtn(lpsz);
    delete[] lpsz;
    return rtn;
}

2.多字节转utf-8

std::string mb2u8(const char* cont)
{
    if (null == cont)
    {
        return "";
    }
    int num = multibytetowidechar(cp_acp, null, cont, -1, null, null);
    if (num <= 0)
    {
        return "";
    }
    wchar_t* buffw = new (std::nothrow) wchar_t[num];
    if (null == buffw)
    {
        return "";
    }
    multibytetowidechar(cp_acp, null, cont, -1, buffw, num);
    int len = widechartomultibyte(cp_utf8, 0, buffw, num - 1, null, null, null, null); 
    if (len <= 0)
    {
        delete[] buffw;
        return "";
    }
    char* lpsz = new (std::nothrow) char[len + 1]; 
    if (null == lpsz)
    {
        delete[] buffw;
        return "";
    }
    widechartomultibyte(cp_utf8, 0, buffw, num - 1, lpsz, len, null, null);
    lpsz[len]='\0';
    delete[] buffw;
    std::string rtn(lpsz);
    delete[] lpsz;
    return rtn ;
}