简单问题，把盘符和文件名连到一起，为何出错了，高人指点一下吧？？

简单问题，把盘符和文件名连到一起，连接后的结果不正确，前面的盘符和冒号没有了，不知为何？
UNICODE_STRING FullName;
UNICODE_STRING UFullName;
WCHAR TEMP[512];

RtlInitEmptyUnicodeString(&FullName, TEMP, sizeof(TEMP));
FullName.Buffer[0] = DevExt->DriveLetter;
FullName.Buffer[1] = L':';
FullName.Buffer[2] = L'\0';
RtlAppendUnicodeStringToString(&FullName, &FileObject->FileName);
RtlUpcaseUnicodeString(&UFullName, &FullName, TRUE);

KdPrint(("*********************************************************"));
KdPrint(("The driver is \"%wc\"", DevExt->DriveLetter));
KdPrint(("The fileName is \"%ws\"", FileObject->FileName.Buffer));
KdPrint(("The fullpath is \"%ws\"", FullName.Buffer));
KdPrint(("The fullpath is \"%ws\"", UFullName.Buffer));
KdPrint(("*********************************************************"));
        
RtlFreeUnicodeString(&FullName);
RtlFreeUnicodeString(&UFullName);

在调用RtlAppendUnicodeStringToString之前先正确设置FullName.Length

tooflat版主，我按如下代码做法：
RtlInitEmptyUnicodeString(&FullName, TEMP, FileObject->FileName.Length + 2);
FullName.Length = 0;
FullName.Buffer[0] = DevExt->DriveLetter;
FullName.Buffer[1] = L':';
        
for ( u = 2; u < FileObject->FileName.Length + 2; u++)
{
    FullName.Buffer = FileObject->FileName.Buffer[u - 2];
}
FullName.Length = FileObject->FileName.Length + 2;
RtlUpcaseUnicodeString(&UFullName, &FullName, TRUE);

KdPrint(("****************************Read*****************************"));
KdPrint(("The driver is \"%wc\"", DevExt->DriveLetter));
KdPrint(("The fileName is \"%ws\"", FileObject->FileName.Buffer));
KdPrint(("The fullpath is \"%ws\"", FullName.Buffer));
KdPrint(("The fullpath is \"%ws\"", UFullName.Buffer));
KdPrint(("****************************Read*****************************"));

打印结果是：
00000008    1.08714151    ****************************Read*****************************    
00000009    1.08714855    The driver is "D"    
00000010    1.08715546    The fileName is "\OriginalKeyHNS.xml"    
00000011    1.08716166    The fullpath is "D:\OriginalKeyHNS.xml"    
00000012    1.08716810    The fullpath is "D:\ORIGINALKEYHNS.XM?"    
00000013    1.08717370    ****************************Read*****************************    
00000014    1.08778095    sfilter!SfIsObjectFile: fcb->NodeTypeCode = 705    
00000015    1.08779669    sfilter!SfCreate: FileName = D:\OriginalKeyHNS.xml    
00000016    1.08799303    sfilter!SfCreate: IsEncryptFlagExist = 0, IsNeedEncrypt = 0, NewElement = 0  
00000017    1.08808017    ****************************Read*****************************    
00000018    1.08808720    The driver is "D"    
00000019    1.08809388    The fileName is "\OriginalKeyHNS.xml"    
00000020    1.08810008    The fullpath is "D:\OriginalKeyHNS.xml"    
00000021    1.08810639    The fullpath is "D:\ORIGINALKEYHNS.XM?"    
00000022    1.08811200    ****************************Read*****************************    
00000023    35.05121613    sfilter!SfIsObjectFile: fcb->NodeTypeCode = 705    
00000024    35.05124283    sfilter!SfCreate: FileName = D:\qq.txt    
00000025    35.05144119    sfilter!SfCreate: IsEncryptFlagExist = 0, IsNeedEncrypt = 0, NewElement = 1    
00000026    35.05153275    ****************************Read*****************************    
00000027    35.05154037    The driver is "D"    
00000028    35.05154419    The fileName is "\qq.txt"    
00000029    35.05154800    The fullpath is "D:\qq.txt"    
00000030    35.05155563    The fullpath is "D:\QQ.TX["    
00000031    35.05155945    ****************************Read*****************************    


为何使用RtlUpcaseUnicodeString方法把路径转换为大写字母后，最后一个字母是乱码？？

楼主可以这样试一下：

RtlInitEmptyUnicodeString(&FullName, TEMP, FileObject->FileName.Length + 2);
FullName.Length = 0;
FullName.Buffer[0] = DevExt->DriveLetter;
FullName.Buffer[1] = L':';
      
for ( u = 2; u < FileObject->FileName.Length + 2; u++)
{
    FullName.Buffer = FileObject->FileName.Buffer[u - 2];
}
FullName.Length = FileObject->FileName.Length + 2;

//RtlUpcaseUnicodeString(&UFullName, &FullName, TRUE);
for (m = 0; m < FileObject->FileName.Length + 2; m++)
{
    FullName.Buffer[m] = towupper(FullName.Buffer[m]);
}

KdPrint(("****************************Read*****************************"));
KdPrint(("The driver is \"%wc\"", DevExt->DriveLetter));
KdPrint(("The fileName is \"%ws\"", FileObject->FileName.Buffer));
KdPrint(("The fullpath is \"%ws\"", FullName.Buffer));
KdPrint(("The fullpath is \"%ws\"", UFullName.Buffer));
KdPrint(("****************************Read*****************************"));

其实在看tooflat版主的程序中，不止一个地方要把小写字母转化成大写字母，用到的方法都是：
 *Name - L'a' + L'A';

其实用这个内置的方法towupper或许更简洁一些。

unicodestring的buffer没有空字符结尾,它是以长度确定字符串的.

你需要考虑这个问题

znsoft大哥讲的好啊，一语中的。

感谢版主、网管和linuxyf，问题解决了。

能告诉我你是怎样获取到盘符的么 ？ 特别是在irp_mj_read 里面 (2000系统)。
我的油箱是sunway_yin@sina.com 如能回答万分感激啊：）