c++ utf8与std::string字符编码转换

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本文介绍如何在UTF-8编码与标准C++字符串之间进行转换。具体包括从UTF-8转换到标准字符串的过程，及反之亦然的方法。转换过程中涉及到使用Windows API函数MultiByteToWideChar和WideCharToMultiByte。

转自：http://blog.youkuaiyun.com/henren555/article/details/9295907

1. utf8转std::string

转换过程：先将utf8转双字节Unicode编码，再通过WideCharToMultiByte将宽字符转换为多字节。
//-----------------------------------------------------------------------
std::string UTF8_To_string(const std::string & str)
{
int nwLen = MultiByteToWideChar(CP_UTF8, 0, str.c_str(), -1, NULL, 0);

wchar_t * pwBuf = new wchar_t[nwLen + 1];//一定要加1，不然会出现尾巴
memset(pwBuf, 0, nwLen * 2 + 2);

MultiByteToWideChar(CP_UTF8, 0, str.c_str(), str.length(), pwBuf, nwLen);

int nLen = WideCharToMultiByte(CP_ACP, 0, pwBuf, -1, NULL, NULL, NULL, NULL);

char * pBuf = new char[nLen + 1];
memset(pBuf, 0, nLen + 1);

WideCharToMultiByte(CP_ACP, 0, pwBuf, nwLen, pBuf, nLen, NULL, NULL);

std::string retStr = pBuf;

delete []pBuf;
delete []pwBuf;

pBuf = NULL;
pwBuf = NULL;

return retStr;
}
//////////////////////////////////////////////////////////////////////////

//////////////////////////////////////////////////////////////////////////
// [8/19/2009 Leezhm]
// translate ascii characters to utf-8 characters

2.std::string转utf8字符串

转换过程：与1过程相反
//------------------------------------------------------------------------
std::string string_To_UTF8(const std::string & str)
{
int nwLen = ::MultiByteToWideChar(CP_ACP, 0, str.c_str(), -1, NULL, 0);

wchar_t * pwBuf = new wchar_t[nwLen + 1];//一定要加1，不然会出现尾巴
ZeroMemory(pwBuf, nwLen * 2 + 2);

::MultiByteToWideChar(CP_ACP, 0, str.c_str(), str.length(), pwBuf, nwLen);

int nLen = ::WideCharToMultiByte(CP_UTF8, 0, pwBuf, -1, NULL, NULL, NULL, NULL);

char * pBuf = new char[nLen + 1];
ZeroMemory(pBuf, nLen + 1);

::WideCharToMultiByte(CP_UTF8, 0, pwBuf, nwLen, pBuf, nLen, NULL, NULL);

std::string retStr(pBuf);

delete []pwBuf;
delete []pBuf;

pwBuf = NULL;
pBuf = NULL;

return retStr;
}