在vc++中通过sqlite3.dll接口对sqlite数据库进行操作，包括打开数据库，插入，查询数据库等，如果操作接口输入参数包含中文字符，会导致操作异常。例如调用sqlite3_open打开数据库文件，如果文件路径出现中文，就会导致打开失败。sqlite3_exec执行sql语句，如果包含中文对应字符就会变成乱码。
这是由于sqlite数据库使用的是utf-8编码方式，而传入的字符串是ascii编码或unicode编码，导致字符串格式错误。解决方案是在调用sqlite接口之前，先将字符串转换成utf-8编码，以下提供各种字符串编码转换函数。
//utf-8转unicode
std::wstring utf82unicode(const std::string& utf8string)
{
int widesize = ::multibytetowidechar(cp_utf8, 0, utf8string.c_str(), -1, null, 0);
if (widesize == error_no_unicode_translation)
{
throw std::exception("invalid utf-8 sequence.");
}
if (widesize == 0)
{
throw std::exception("error in conversion.");
}
std::vector<wchar_t> resultstring(widesize);
int convresult = ::multibytetowidechar(cp_utf8, 0, utf8string.c_str(), -1, &resultstring[0], widesize);
if (convresult != widesize)
{
throw std::exception("la falla!");
}
return std::wstring(&resultstring[0]);
}
//unicode 转为 ascii
string widebyte2acsi(wstring& wstrcode)
{
int asciisize = ::widechartomultibyte(cp_oemcp, 0, wstrcode.c_str(), -1, null, 0, null, null);
if (asciisize == error_no_unicode_translation)
{
throw std::exception("invalid utf-8 sequence.");
}
if (asciisize == 0)
{
throw std::exception("error in conversion.");
}
std::vector<char> resultstring(asciisize);
int convresult =::widechartomultibyte(cp_oemcp, 0, wstrcode.c_str(), -1, &resultstring[0], asciisize, null, null);
if (convresult != asciisize)
{
throw std::exception("la falla!");
}
return std::string(&resultstring[0]);
}
//utf-8 转 ascii
string utf_82ascii(string& strutf8code)
{
string strret("");
//先把 utf8 转为 unicode
wstring wstr = utf82unicode(strutf8code);
//最后把 unicode 转为 ascii
strret = widebyte2acsi(wstr);
return strret;
}
///////////////////////////////////////////////////////////////////////
//ascii 转 unicode
wstring acsi2widebyte(string& strascii)
{
int widesize = multibytetowidechar (cp_acp, 0, (char*)strascii.c_str(), -1, null, 0);
if (widesize == error_no_unicode_translation)
{
throw std::exception("invalid utf-8 sequence.");
}
if (widesize == 0)
{
throw std::exception("error in conversion.");
}
std::vector<wchar_t> resultstring(widesize);
int convresult = multibytetowidechar (cp_acp, 0, (char*)strascii.c_str(), -1, &resultstring[0], widesize);
if (convresult != widesize)
{
throw std::exception("la falla!");
}
return std::wstring(&resultstring[0]);
}
//unicode 转 utf8
std::string unicode2utf8(const std::wstring& widestring)
{
int utf8size = ::widechartomultibyte(cp_utf8, 0, widestring.c_str(), -1, null, 0, null, null);
if (utf8size == 0)
{
throw std::exception("error in conversion.");
}
std::vector<char> resultstring(utf8size);
int convresult = ::widechartomultibyte(cp_utf8, 0, widestring.c_str(), -1, &resultstring[0], utf8size, null, null);
if (convresult != utf8size)
{
throw std::exception("la falla!");
}
return std::string(&resultstring[0]);
}
//ascii 转 utf8
string ascii2utf_8(string& strasciicode)
{
string strret("");
//先把 ascii 转为 unicode
wstring wstr = acsi2widebyte(strasciicode);
//最后把 unicode 转为 utf8
strret = unicode2utf8(wstr);
return strret;
}
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