Adding filenames from a directory to a char* array. c++ - c++

Question

I ame trying to get filenames from a directory and put it in a char* array for latter use. But this dont seem to work the way i want to. When printing it only showes the last filename on all spots.
So my question howe can i add the file names in every spot inside the char*[]?
/*Placed outside*/
int i = 0;
char* Files[20] = {};
/*Placed outside*/
while (handle != INVALID_HANDLE_VALUE)
{
char buffer[4100];
sprintf_s(buffer, "%ls", search_data.cFileName);
Files[i] = buffer;
i++;
if (FindNextFile(handle, &search_data) == FALSE)
/*Printing I use ImGui*/
#define IM_ARRAYSIZE(_ARR) ((int)(sizeof(_ARR)/sizeof(*_ARR)))
static int listbox_item_current = 1;
ImGui::ListBox("", &listbox_item_current, Files, i, 4);

Answer 1

You could use C++ standard filesystem, but for that I guess you would need C++17 (or atleast VS15), not really sure.
You would have to include:
#include <experimental/filesystem>
#include <filesystem>
using namespace std::experimental::filesystem::v1;
Using it should be simple:
int i = 0;
const char * directoryToSearch = "C:\etc\etc";
for (const auto & file : directory_iterator(directoryToSearch)) {
files[i] = new char[file.path().stem().string().length() + 1];
strcpy(files[i], file.path().stem().string().c_str());
++i;
}
Indeed, you should clean up the array after you're done using it. Don't forget, not many compilers support this at the moment.

Answer 2

When printing it only shows the last filename on all spots. That is just normal: you store the filename on each iteration in the same buffer and just copy the address of the buffer into your array. Unrelated to the question, as buffer is an automatic variable declared inside a loop (block scoped), using it outside of the loop is Undefined Behaviour, so you end with an array of dangling pointers.
The correct way would be to either use a 2D-array char Files[MAX_PATH][20]; and store a file name in each slot, or use dynamic memory allocate by new (or malloc at a lower level). For the second option, you can do it by hand, allocating memory for each file name - and remember to free anything at the end, or you can let the standard library manage it for you by using:
std::vector<std::string> Files;
...
while(...) {
...
File.push_back(search_data.cFileName);
Dear ImGui provides a ListBoxctor that allows to pass an opaque data storage along with an extractor, and it can be used here:
bool string_vector_items_getter(void* data, int idx, const char** out_text) {
std::vector<std::string> *v = reinterpret_cast<std::vector<std::string> >(data);
if (idx < 0 || idx >= v.size()) return false;
*out_text = v[idx].c_str();
return true;
}
and then:
ImGui::ListBox("", &listbox_item_current, &string_vector_items_getter, &Files, i, 4);
(beware: untested code!)