Treat memory as a file with a name.

[Steve Teale]

This is probably not exactly a D question.

The library librsvg expects to get an SVG file filename. I have 
the data of such a file in memory.

How do I dress up that memory as a file with a name so that I can 
pass the name to the librsvg open function.

I've looked at std.mmfile, and played with it, giving a name to 
the constructor, along with the address and size of my memory 
block.

import std.mmfile;
import std.stdio;
import std.stream;

void main()
{
    char[] ca;
    ca.length = 100000;
    ca[] = 'X';
    MmFile mmf = new MmFile("glob", 0, 100000UL, ca.ptr);
    std.stream.File sf = new std.stream.File("glob", FileMode.In);
    char[] b;
    b.length = 20;
    sf.readExact(b.ptr, 20);
    writefln("%s", b);
}

But then I just get 'No such file or directory', which is what 
I'd expect after I'd taken the trouble to read mmfile.d.

I had expected it to create a stub entry in the file system or 
something, and the somehow use fmemopen(), but it just looks for 
an existing file.

At the moment I'm having to write the data to a temporary file, 
and then pass the name of the temp to rsvg.

There must be some elegant way to do this!