Converting LPCWSTR with WideCharToMultiByte. Need help.

Question

i have a function like this:

BOOL WINAPI MyFunction(HDC hdc, LPCWSTR text, UINT cbCount){

char AnsiBuffer[255];
int written = WideCharToMultiByte(CP_ACP, 0, text, cbCount, AnsiBuffer , 0, NULL, NULL);
if(written > -1) AnsiBuffer[written] = '\0';

if(written>0){

 ofstream myfile;
 myfile.open ("C:\\example.txt", ios::app);
 myfile.write(AnsiBuffer, sizeof(AnsiBuffer));
 myfile.write("\n", 1);
 myfile.close();

}


....

When i display the input LPCWSTR text with MessageBoxW(), the text shows up fine. When i try to convert it to multibyte, the return value looks normal (ex: 22, 45, etc), but the result is strings of gibberish (ex ÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌÌ). Suggestions?

Answer 1

I see two problems;

1) You are passing '0' to WideCharToMultiByte for the size of the multibyte buffer. If you read the documents this results in the function returning the NUMBER of bytes needed but performing no actual conversion. (This is to allow you to subsequently allocate a buffer of the correct size and recall the function).

2) in file.write sizeof(AnsiBuffer) will result in 255 bytes being written regardless of what is in the buffer. sizeof is a compile-time calculation that returns the size of a variable. You should replace this with the 'written' variable that represents the length of the string.

Answer 2

You need to pass the length of the buffer to the API, instead of passing 0. When you pass 0, the function returns the required length of the buffer, but doesn't write to it. You're seeing the results of the uninitialized array.

Here's the right call, with the 255 in the right place:

int written = WideCharToMultiByte(CP_ACP, 0, text, cbCount, AnsiBuffer , 255, NULL, NULL);