Question

I’m having a problem with vectors which I tried to solve for quite some time now. I will just post the code right away and explain it then.

#include "filesystem.h"
#include <vector>
using namespace Filesystem;

wchar_t** Path::ListDir()
{
    /*struct dirEntry
    {
        wchar_t entry[MAX_PATH];
    };*/
    vector<wchar_t*> pathList = vector<wchar_t*>();
    WIN32_FIND_DATA findData;
    HANDLE dirHandle = new HANDLE;
    wchar_t* path = L"C:\\*";

    dirHandle = FindFirstFile(path, &findData);
    if (dirHandle == INVALID_HANDLE_VALUE)
        return NULL;

    while (FindNextFile(dirHandle, &findData) != 0)
    {
        pathList.push_back(findData.cFileName);
    }

    FindClose(dirHandle);

    return NULL;
}

This is part of a filesystem class I am coding right now. It’s supposed to list all the files in a directory and return them as a 2 dimensional array of strings. If I do it like this, it fills up the list with the last file times the count of files in the folder. Which is not what I want it to do. I thought that it could be since I deliver a pointer to the push_back, but I haven’t found a way to fix it. I’m coding on windows, btw.

It would be nice if someone on here has any idea on how to do that.

Answer 1

You are storing the address of findData.cFileName in the vector N times.

You need to copy this. Possibly using:

vector<std::wstring> pathList;

EDIT: Other minor points:

vector<wchar_t*> pathList = vector<wchar_t*>();
HANDLE dirHandle = new HANDLE;

can be replaced with:

vector<wchar_t*> pathList;
HANDLE dirHandle;

If you must return a wchar_t** then (for example):

// '+1' for NULL terminating string as the callers needs
// know where the array ends.
wchar_t** result = new wchar_t*[pathList.size() + 1];
*(result + pathList.size()) = 0;

for (size_t i = 0; i < pathList.size(); i++)
{
    wchar_t* name = new wchar_t[pathList[i].length() + 1];
    std::copy(pathList[i].begin(), pathList[i].end(), name);
    *(name + pathList[i].length()) = L'\0';
    *(result + i) = name;
}

return result;

The caller must remember to delete[] returned array:

Path p;
wchar_t** list = p.ListDir();
...
for (size_t i = 0; 0 != *(list + i); i++)
{
    delete[] *(list + i);
}
delete[] list;

Though as this is C++ you should use std::vector<std::wstring>.