Help needed calling GetVolumeInformationW, kernel32.dll

Question

Hello,
I'm trying to get the file system of disks using the GetVolumeInformation function. I got it to work using the ANSI version, but now need to use the unicode version. I can't get a sensible response from the unicode version ( I get what look like chinese characters or it crashes). I'm new to c++ and JNI. I've tried variations of (*env).NewString(szFileSystemNameBuffer, strlen(szFileSystemNameBuffer)) and (*env).NewStringUTF(szFileSystemNameBuffer) but no joy. The closest I've come is when I got back "N" from the call, thought this may have been the start of "NTFS" and I didn't have enough space for the rest.
JNIEXPORT jstring JNICALL Java_com_nortel_cc_dsf_utils_systeminfo_JniConfigDetail_getFileSystem(JNIEnv *env, jclass obj, jchar path) {
      CHAR szDrive[4];
      szDrive[0] = path;
      szDrive[1] = ':';
      szDrive[2] = '\\';
      szDrive[3] = '\0';
      CHAR szVolumeNameBuffer[12]; //this will have the name of your drive
      DWORD dwVolumeSerialNumber; //this will have the serial number of your drive
      DWORD dwMaximumComponentLength; //this is the max length in between each \ in a path
      DWORD dwFileSystemFlags; //this will return flags about the drive's file system
      CHAR szFileSystemNameBuffer[10]; //this will contain the type of file system (ex: NTFS)
      //make call to kernell32.dll
      BOOL result = GetVolumeInformationW((LPCWSTR)szDrive, (LPWSTR)szVolumeNameBuffer, 12, &dwVolumeSerialNumber, &dwMaximumComponentLength, &dwFileSystemFlags, (LPWSTR)szFileSystemNameBuffer, 10);
return env->NewString((jchar *)szFileSystemNameBuffer, strlen(szFileSystemNameBuffer));Can anyone shed any light on what I need to do to get back the file system?
Thanks
Tom

Answer 1

Here's what I have in the function.
JNIEXPORT jstring JNICALL Java_JniConfigDetail_getFileSystem(JNIEnv *env, jclass obj, jchar path) {
      WCHAR szDrive[4];
      szDrive[0] = path;
      szDrive[1] = ':';
      szDrive[2] = '\\';
      szDrive[3] = '\0';
      CHAR szVolumeNameBuffer[10]; //this will have the name of your drive
      DWORD dwVolumeSerialNumber; //this will have the serial number of your drive
      DWORD dwMaximumComponentLength; //this is the max length in between each \ in a path
      DWORD dwFileSystemFlags; //this will return flags about the drive's file system
      WCHAR szFileSystemNameBuffer[12]; //this will contain the type of file system (ex: NTFS)
      //make call to kernell32.dll
      BOOL result = GetVolumeInformationW((LPCWSTR)szDrive, (LPWSTR)szVolumeNameBuffer, 12, &dwVolumeSerialNumber, &dwMaximumComponentLength, &dwFileSystemFlags, (LPWSTR)szFileSystemNameBuffer, 10);
      if (result) {
           if (szFileSystemNameBuffer[0] == 'N' &&
               szFileSystemNameBuffer[1] == 'T' &&
               szFileSystemNameBuffer[2] == 'F' &&
               szFileSystemNameBuffer[3] == 'S') {
               return (*env).NewString(szFileSystemNameBuffer, strlen(szFileSystemNameBuffer));
      return (*env).NewStringUTF("null");
}And here are the errors the above function causes.
Errors:
1>ConfigDetail.cpp
1>..\..\ConfigDetail\ConfigDetail\ConfigDetail.cpp(61) : error C2664: 'strlen' : cannot convert parameter 1 from 'WCHAR [12]' to 'const char *'
1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
1>..\..\ConfigDetail\ConfigDetail\ConfigDetail.cpp(61) : error C2664: 'JNIEnv_::NewString' : cannot convert parameter 1 from 'WCHAR [12]' to 'const jchar *'
1> Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
After looking more closely at the errors, I tried the reinterpret cast like so.
return (*env).NewString(reinterpret_cast <const jchar*>(szFileSystemNameBuffer), strlen(reinterpret_cast <const char*>(szFileSystemNameBuffer)));This returns me "N" only. So the question remains how do I get the full "NTFS" which we now know is being returned.