I see following code example on this Vala documentation page:

public static int main (string[] args) {
    // Opens "foo.txt" for reading ("r")
    FileStream stream = FileStream.open ("foo.txt", "r");
    assert (stream != null);

    // buffered:
    char buf[100];
    while (stream.gets (buf) != null) {
        print ((string) buf);
    }

    return 0;
}

However, I cannot find a close() function. I want to open file once for reading and later again for writing. Is it safe to do so without a close in between?

(I do not want to use a etc mode which permit both reading and writing as both may not be needed while running the application.)

CodePudding user response：

There are two key items at play:

1. The FileStream class is a binding to standard C library functions (e.g. open for fopen, read for fread, etc.). (See: this Stack Overflow answer for a good overview of various file APIs)
2. Vala does automatic reference counting and will free objects for you (See: Vala's Memory Management Explained).

Now if we look at the definition for the FileStream Vala binding, we see:

[ CCode ( cname = "FILE" , free_function = "fclose" ) ]
public class FileStream

Notice the free_function = "fclose" part. This means that when it comes time for Vala to free a FileStream object, it will implicitly call fclose. So no need to attempt this manually. (Also see: Writing VAPI files under the Defining Classes section for details on free_function)

What this means for you is that once your stream object goes out of scope, reference count hits 0, etc. it will get cleaned up for you as you would expect with any other object. You can safely open the file for reading again later by using FileStream.open and getting a new FileStream object.