GetLogicalDriveStrings() and char - Where am I doing wrongly - c++

Question

I want to search a file which may be present in any drives such as C:\, D:\ etc. Using GetLogicalDriveStrings I can able to get the list of drives but when I add anything extra for the output, I am getting a null in the output prompt. Here is my code:
#include "StdAfx.h"
#include <windows.h>
#include <stdio.h>
#include <conio.h>
// Buffer length
DWORD mydrives = 100;
// Buffer for drive string storage
char lpBuffer[100];
const char *extFile = "text.ext";
// You may want to try the wmain() version
int main(void)
{
DWORD test;
int i;
test = GetLogicalDriveStrings(mydrives, (LPWSTR)lpBuffer);
if(test != 0)
{
printf("GetLogicalDriveStrings() return value: %d, Error (if any): %d \n", test, GetLastError());
printf("The logical drives of this machine are:\n");
// Check up to 100 drives...
for(i = 0; i<100; i++)
printf("%c%s", lpBuffer[i],extFile);
printf("\n");
}
else
printf("GetLogicalDriveStrings() is failed lor!!! Error code: %d\n", GetLastError());
_getch();
return 0;
}
I want above output as C:\text.ext D:\text.ext ... rather I am getting text.ext only. I am using Microsoft Visual C++ 2010 Express

Answer 1

GetLogicalDriveStrings() returns a double-null terminated list of null-terminated strings. E.g., say you had drives A, B and C in your machine. The returned string would look like this:
A:\<nul>B:\<nul>C:\<nul><nul>
You can use the following code to iterate through the strings in the returned buffer and print each one in turn:
DWORD dwSize = MAX_PATH;
char szLogicalDrives[MAX_PATH] = {0};
DWORD dwResult = GetLogicalDriveStrings(dwSize,szLogicalDrives);
if (dwResult > 0 && dwResult <= MAX_PATH)
{
char* szSingleDrive = szLogicalDrives;
while(*szSingleDrive)
{
printf("Drive: %s\n", szSingleDrive);
// get the next drive
szSingleDrive += strlen(szSingleDrive) + 1;
}
}
Note that the details of how the function works, including the example code that I shamelessly copied and pasted, can be found by reading the docs.

Answer 2

Did you mean to put the printf in the loop?
Currently, you set extFile 100 times (just to be sure?!)
for(i = 0; i<100; i++)
extFile = "text.ext";
You meant to show all the drive letters in a loop:
for(i = 0; i<100; i++)
{
extFile = "text.ext";
printf("%c%s", lpBuffer[i], extFile); //I guess you mean extFile here?
}

Answer 3

DWORD dwSize = MAX_PATH;
WCHAR szLogicalDrives[MAX_PATH] = { 0 };
DWORD dwResult = GetLogicalDriveStrings(dwSize, szLogicalDrives);
CStringArray m_Drives;
m_Drives.RemoveAll();
if (dwResult > 0 && dwResult <= MAX_PATH)
{
WCHAR* szSingleDrive = szLogicalDrives;
while (*szSingleDrive)
{
UINT nDriveType = GetDriveType(szSingleDrive);
m_Drives.Add(CString(szSingleDrive, 2));
// get the next drive
szSingleDrive += wcslen(szSingleDrive) + 1;
}
}
return m_Drives;

Answer 4

class DriveList {
protected:
LPTSTR m_driveList;
DWORD m_driveCount;
DWORD m_bufSize = 32 * sizeof(TCHAR);
public:
virtual ~DriveList() {
free(m_driveList);
}
DriveList() {
m_driveList = (LPTSTR)malloc(m_bufSize);
}
int getDriveCount() const {
return m_driveCount;
}
TCHAR operator[] (const int index) const {
return m_driveList[index];
}
void loadDriveList() {
DWORD mask;
if((mask = GetLogicalDrives()) == 0) {
throw;
}
m_driveCount = 0;
for(int x = 0; x <= 25; x++ ) {
if(mask & 1) {
m_driveList[m_driveCount] = TCHAR(65 + x);
m_driveCount += 1;
}
mask >>= 1;
}
}
};