Cannot write the full buffer with WriteFile function

I am trying to use WriteFile to write a simple text in a .TXT file. Here’s my declaration:

// For WriteFile fuction
    BOOL writeFile;
    LPCVOID textToWrite = L"SakyLabs: Hello, MDE.";
    DWORD numberOfBytes = (DWORD)wcslen(textToWrite);
    DWORD numberOfBytesWritten;

numberOfBytes was based on Microsoft’s example from here.

Next, the WriteFile function:

writeFile = WriteFile(createFile, textToWrite, numberOfBytes, &numberOfBytesWritten, NULL);

I am getting createFile from a previous CreateFileW call. Also, I am using Unicode functions.

WriteFile works, but I only get this part of the text written in the file:

S a k y L a b s :   H 

What am I doing wrong?

>Solution :

The problem is that you’re creating a wide-charecter string L"...". Each WCHAR is two bytes long — because Windows is using UTF-16 for wide strings. wcslen counts the number WCHARs in it rather than bytes.

Either multiply the string length by the size of a WCHAR:

DWORD numberOfBytes = (DWORD)wcslen(textToWrite)*sizeof(WCHAR);

or use narrow char strings (preferably UTF-8 encoded if you actually use non-ASCII):

LPCVOID textToWrite = "SakyLabs: Hello, MDE.";
DWORD numberOfBytes = (DWORD)strlen(textToWrite);