MD5 hash on a file and rawRead

[Andrej Mitrovic]

I'm trying to use the std.md5.sum method. It takes as an argument a digest to 
output the hash to, and the second argument is plain data.

So I'm trying to read an entire file at once. I thought about using rawRead, 
but I get a runtime exception:
        auto filename = r"C:\file.dat";
        File file;
        try
        {
            file = File(filename, "r");
        }
        catch (ErrnoException exc)
        {
            return;
        }
        ubyte[] buffer;
        file.rawRead(buffer);
 
error: stdio.d:rawRead must take a non-empty buffer

There are no size methods for the File structure (why?). There's a getSize 
function but it's in std.file, and I can't use it because:

        auto filename = r"C:\file.dat";
        File file;
        try
        {
            file = File(filename, "r");
        }
        catch (ErrnoException exc)
        {
            return;
        }
        
        ubyte[] buffer = new ubyte[](getSize(filename));
        ubyte[16] digest;
        file.rawRead(buffer);
        std.md5.sum(digest, buffer);

Error: cannot implicitly convert expression 
(getSize(cast(const(char[]))this._libFileName)) of type ulong to uint

I can use the buffered version fine:
        auto filename = r"C:\file.dat";
        File file;
        try
        {
            file = File(filename, "r");
        }
        catch (ErrnoException exc)
        {
            return;
        }
        
        ubyte[16] digest;
        MD5_CTX context;
        context.start();
        
        foreach (ubyte[] buffer; file.byChunk(4096 * 1024))
        {
            context.update(buffer);
        }
        
        context.finish(digest);
        writefln("MD5 (%s) = %s", filename, digestToString(digest));

But I'd prefer to write simpler code and use rawRead to read the entire file at 
once. I'm reading really small files, so rawRead should be fine.

Also, why do we have file handling in two different modules? I'd expect to find 
all file handling ops in std.file, not scattered around Phobos.

Let me know if I'm doing something obviously stupid. :)