Fill string with multiple lines from standard_input

["Vincent Smeets" <No@Spam.org>]

Hallo,

How can I fill a string with multiple lines from the standard_input? I want
to have all the characters read from the input till a end of file in a
string.

In C I can do it like this:
    char buffer[1024];
    ssize_t length;

    length = read (1, buffer, sizeof (buffer));
    if (length < 0) {
        perror ("read");
        exit (1);
    }

I can do it with Get_Immediate:
    Buffer : String (1 .. 1024);
    Length : Natural;

    Length := 0;
    while not Ent_Of_File and Length < Buffer'Last loop
        Length := Length + 1;
        Get_Immediate (Buffer (Length));
    end loop;
This works but is very slow with GNAT 3.13p on Windows 2000.

I haven't tried sequential IO, but that is also character by character. I
want something to read a buffer at once. I have been thinking about using
streams. Something like:
    Buffer : String (1 .. 1024);

    String'Read (
        Text_IO.Text_Streams.Stream (Text_IO.Standard_Input),
        Buffer);
But here I don't know how much of the Buffer has been filled.

The last non portable design is to use a pragma import for the C "read"
function. It will work but I don't like it because it isn't portable.

Is the a nice Ada95 way to do this?