средствами API реализовать

#include <iostream>
#include <stdio.h>
#include <windows.h>
#include <string.h>
 
using namespace std;
 
string path;
_WIN32_FIND_DATAA opts;
 
const char* GetErrorMessage() {
  char *error_message;
  FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                FORMAT_MESSAGE_FROM_SYSTEM |
                FORMAT_MESSAGE_IGNORE_INSERTS,
                NULL, GetLastError(),
                MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                (LPTSTR) &error_message, 0, NULL);
  return error_message;
}
 
void waitForClose(FILE * f) {
    while (fclose(f)==-1) {
        cout<<"\nFile cannot be closed!\n";
        system("pause");
    }
}
 
bool dirExists(const string& dirName) {
    DWORD ftyp = GetFileAttributesA(dirName.c_str());
    if (ftyp == INVALID_FILE_ATTRIBUTES)
        return false;
    if (ftyp == FILE_ATTRIBUTE_DIRECTORY)
        return true;
    return false;
}
 
double FindAndWrite(FILE *file, string path, int depth) {
    double g_size=0;
    HANDLE hFoundFile;
    _WIN32_FIND_DATAA tmp;
    hFoundFile=FindFirstFile((path+"*").c_str(), &tmp); // skipping the "." dir
    FindNextFile(hFoundFile, &tmp);                     // skipping the ".." dir
    FindNextFile(hFoundFile, &opts);
    for (int i=1; i<depth; ++i, fprintf(file,"\t"));
    fprintf(file, "+ %s\n", path.c_str());
        do {
            if (dirExists(path+opts.cFileName)) {
                g_size+=FindAndWrite(file, path+opts.cFileName+"\\", depth+1);
                continue;
            }
            for (int i=0; i<depth; ++i, fprintf(file,"\t"));
            fprintf(file, "- %-30.20s%s%lu kByte\n", opts.cFileName, " | ", opts.nFileSizeLow/1024);
            g_size+=opts.nFileSizeLow/1024;
        }
        while (FindNextFile(hFoundFile, &opts));
        for (int i=1; i<depth; ++i, fprintf(file,"\t"));
        fprintf(file, "Total:\t%.2f kByte\n", g_size);
        FindClose(hFoundFile);
        return g_size;
}
 
void exec() {
    FILE * file;
    file=fopen((path+"sum.txt").c_str(), "w");
    FindAndWrite(file, path, 1);
    waitForClose(file);
}
 
int main() {
    cout<<"Enter path with ending \\: "; cin>>path;
    exec();
    system("pause");
    return 0;
}