Write into a file names of folders containing in C:\Program Files - c++

Question

I have this task:
1. In current directory create file subMape.dat
2. Write into it all names of folders, that stored in C:\Program Files folder
3. Display on the screen data, that was written in subMape.dat
#include <iostream>
#include <windows.h>
using namespace std;
int main() {
WIN32_FIND_DATA findFileData;
DWORD bytesWritten = 0;
HANDLE f;
HANDLE c = CreateFileW(L"subMape.txt", GENERIC_READ | GENERIC_WRITE, NULL, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
//TCHAR lpBuffer[32];
DWORD nNumberOfBytesToRead = 32;
//DWORD lpNumberOfBytesRead;
DWORD lengthSum = 0;
if (c) {
cout << "CreateFile() succeeded!\n";
if(f = FindFirstFile(L"C:\\Program Files\\*", &findFileData)){
if(f != INVALID_HANDLE_VALUE) {
while (FindNextFile(f, &findFileData)){
lengthSum += bytesWritten;
WriteFile(c, findFileData.cFileName, (DWORD)wcslen(findFileData.cFileName), &bytesWritten, NULL);
}
}
FindClose(f);
}
else {
cout << "FindFirstFile() failed :(\n";
}
}
else {
cout << "CreateFile() failed :(\n";
}
cout << lengthSum << endl;
//SetFilePointer(c, lengthSum, NULL, FILE_BEGIN);
//ReadFile(c, lpBuffer, lengthSum, &lpNumberOfBytesRead, NULL);
//wprintf(lpBuffer);
CloseHandle(c);
return 0;
}
I'm using UNICODE, when it writes findFileData.cFileName - it writes string, where characters splitted with spaces. For example: folder name "New Folder" (strlen = 10) will be written into the file as "N e w T o" (strlen = 10). What do?

Answer 1

Your text file viewer or editor just isn't smart enough to figure out that you've written a utf-16 encoded text file. Most text editors need help, write the BOM to the file:
cout << "CreateFile() succeeded!\n";
wchar_t bom = L'\xfeff';
WriteFile(c, &bom, sizeof(bom), &bytesWritten, NULL);

Answer 2

You need to use something like WideCharToMultiByte() to convert the UNICODE string to ANSI (or UTF8).

Answer 3

The reason you see "space" is that the program you are using to list the file treats it as one byte per character. When using Unicode in windows you will get two, and the second byte is a '\0'.
You need to choose how you want to encode the data in the file.
The easiest you can do is to use UTF-16LE, since this is the native encoding on Windows. Then you only need to prepend a byte order marker to the beginning of the file. This encoding has an advantage over UTF-8 since it is easy to destinguish from extended ASCII encodings due to the observed zero-bytes. Its drawback is that you need the BOM and it occupies more disk space uncompressed.
UTF-8 has the advantage of being more compact. It is also fully compatible with pure ASCII and favoured by the programming community.
If you have do not need to use extended ASCII in any context, you should encode your data in UTF-8. If you do, use UTF-16LE.
Those who argue that a text that passes an UTF-8 validation is encoded in UTF-8 is right if the whole text is available, but wrong if it is not:
Consider an alphabetical list of swedish names. If I only check the first part of the list and it is Latin-1 (ISO/IEC 8859-1), it will also pass the UTF-8 test.
Then in the end comes "Örjansson" which breaks down into mojibake In fact 'Ö' will be an invalid UTF-8 bit sequence. On the other hand, since all letters used actually fits in one byte when using UTF-16LE, I can be fully confident that it is not UTF-8, and not Latin-1 either.

Answer 4

You should know that in windows the "native" uncidode format is UTF-16 which is used by the W-style functions ( CreateFileW ). With that in mind writing the file should give you a valid UTF-16 text, but editor may not recognize that, to make sure your program works use a text editor where you can specify the encoding by hand ( you know what it needs to be ) in case it doesn't recognize it, for this Notepad++ is a good choice.
As others already mentioned, writing the BOM is very helpful for text editors and ensures that your file will be read correctly.
You can use WideCharToMultiByte to convert the UTF-16 into UTF-8 for even more compatibility.
And why did you use CreateFileW directly and not the FindFirstFileW do you have UNICODE defined in your project? If you do the compiler would resolve CreateFile into CreateFileW for you.
Also, here
WriteFile(c, findFileData.cFileName, (DWORD)wcslen(findFileData.cFileName), &bytesWritten, NULL);
wcslen gives the number of characters which is not the same as the data size for a non ANSI text, it should be something like
wcslen(findFileData.cFileName)*sizeof(wchar_t)

Answer 5

When dealing with UTF-16 files, it is important to write a byte-order mark and to write the data with lengths in bytes not characters. wcslen returns the string length in characters but a character is two bytes when using wide strings. Here's a fixed version. It explicitly calls the wide version of the Win32 APIs so will work whether UNICODE/_UNICODE are defined or not.
#include <iostream>
#include <windows.h>
using namespace std;
int main()
{
WIN32_FIND_DATAW findFileData; // Use the wide version explicitly
DWORD bytesWritten = 0;
HANDLE f;
HANDLE c = CreateFileW(L"subMape.txt", GENERIC_READ | GENERIC_WRITE, NULL, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
DWORD lengthSum = 0;
if(c != INVALID_HANDLE_VALUE) {
cout << "CreateFile() succeeded!\n";
// Write A byte-order mark...make sure length is bytes not characters.
WriteFile(c, L"\uFEFF", sizeof(wchar_t), &bytesWritten, NULL);
lengthSum += bytesWritten;
f = FindFirstFileW(L"C:\\Program Files\\*", &findFileData);
if(f != INVALID_HANDLE_VALUE) {
while(FindNextFileW(f, &findFileData)) {
// Write filename...length in bytes
WriteFile(c, findFileData.cFileName, (DWORD)wcslen(findFileData.cFileName) * sizeof(wchar_t), &bytesWritten, NULL);
// Add the length *after* writing...
lengthSum += bytesWritten;
// Add a carriage return/line feed to make Notepad happy.
WriteFile(c, L"\r\n", sizeof(wchar_t) * 2, &bytesWritten, NULL);
lengthSum += bytesWritten;
}
FindClose(f); // This should be inside findFirstFile succeeded block.
}
else {
cout << "FindFirstFile() failed :(\n";
}
// these should be inside CreateFile succeeded block.
CloseHandle(c);
cout << lengthSum << endl;
}
else {
cout << "CreateFile() failed :(\n";
}
return 0;
}