关于宽字符转多字节的问题，求解

[rushdown2012]

代码如下
其中MChar 定义为 char

wchar_t* szTempPath = L“sdmc:/中文.mp4”;
UrlTmpsize= wstrlen((const wchar_t*)szTempPath);	  
UrlTmppath = (MChar*)MMemAlloc(MNull, sizeof(MChar) * (2*UrlTmpsize + 1));
wcstombs(UrlTmppath,(const wchar_t*)szTempPath, (2*UrlTmpsize + 1)*sizeof(MChar));

宽字符转多字节的结果 UrlTmppath = “sdmc:/”
转换出问题，中文以及后面的字符没有了，请问大家这是什么原因？急！应该不是内存申请大小有问题

[derekrose]

wchar_t和char字节数不同，转换要注意

[rushdown2012]

引用 1 楼 derekrose 的回复:

wchar_t和char字节数不同，转换要注意

你看代码 字节数有问题么？

[jimette]

WideCharToMultiByte http://bbs.csdn.net/topics/390346355

[jimette]

http://wenku.baidu.com/view/14de725c804d2b160b4ec0ff.html

[rushdown2012]

引用 4 楼 sha_jinhao 的回复:

http://wenku.baidu.com/view/14de725c804d2b160b4ec0ff.html

我这个环境比较特殊，不能用win32的这个函数。。也就是说 c标准的转换会出问题么？

[rushdown2012]

没有人能看出代码中的问题么？？？

[derekrose]

引用 2 楼 rushdown2012 的回复:

引用 1 楼 derekrose 的回复:wchar_t和char字节数不同，转换要注意 你看代码 字节数有问题么？

你是任务wchar的字节数是char的2倍么？ 那你试试4倍的情况，char是8字节，wchar是16或32，你试试32字节的，你的机器是64位的？

[derekrose]

wchar_t* szTempPath = L“sdmc:/中文.mp4”;
UrlTmpsize= wstrlen((const wchar_t*)szTempPath);	  
UrlTmppath = (MChar*)MMemAlloc(MNull, sizeof(MChar) * (4*UrlTmpsize + 1));
wcstombs(UrlTmppath,(const wchar_t*)szTempPath, (2*UrlTmpsize + 1)*sizeof(MChar));

你怀疑申请内存不够，那么你就申请足够大的内存，看看是不是发生在内存不够用这个问题上不就行了，如果你申请了一个足够大的内存还有问题那就说明不是发生在malloc中，而是其他地方，要学会自己调试，聪明地调试和找bug

[赵4老师]

仅供参考，尽管是VB6

Private Declare Function MultiByteToWideChar Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByRef lpMultiByteStr As Any, ByVal cchMultiByte As Long, ByVal lpWideCharStr As Long, ByVal cchWideChar As Long) As Long
Private Declare Function WideCharToMultiByte Lib "kernel32" (ByVal CodePage As Long, ByVal dwFlags As Long, ByVal lpWideCharStr As Long, ByVal cchWideChar As Long, ByRef lpMultiByteStr As Any, ByVal cchMultiByte As Long, ByVal lpDefaultChar As Long, ByVal lpUsedDefaultChar As Long) As Long
'常用的代码页：
const cpUTF8   =65001
const cpGB2312 =  936
const cpGB18030=54936
const cpUTF7   =65000
Function MultiByteToUTF16(UTF8() As Byte, CodePage As Long) As String
    Dim bufSize As Long
    bufSize = MultiByteToWideChar(CodePage, 0&, UTF8(0), UBound(UTF8) + 1, 0, 0)
    MultiByteToUTF16 = Space(bufSize)
    MultiByteToWideChar CodePage, 0&, UTF8(0), UBound(UTF8) + 1, StrPtr(MultiByteToUTF16), bufSize
End Function

Function UTF16ToMultiByte(UTF16 As String, CodePage As Long) As Byte()
    Dim bufSize As Long
    Dim arr() As Byte
    bufSize = WideCharToMultiByte(CodePage, 0&, StrPtr(UTF16), Len(UTF16), 0, 0, 0, 0)
    ReDim arr(bufSize - 1)
    WideCharToMultiByte CodePage, 0&, StrPtr(UTF16), Len(UTF16), arr(0), bufSize, 0, 0
    UTF16ToMultiByte = arr
End Function

Private Sub Command1_Click()
    MsgBox MultiByteToUTF16(UTF16ToMultiByte("ab中,c", cpUTF8), cpUTF8)
End Sub