[phobos] Improvement of stream

[Andrei Alexandrescu]

On 9/26/10 23:34 PDT, Shin Fujishiro wrote:
> Thus I think we need a buffering layer that exposes a randomly
> accessible array to upper layers.  ByLine() can be easily and
> efficiently implemented with the following primitives defined:
>
> Buffer
> {
>      // The entire buffer.
>      ubyte[] buffer();
>
>      // Slice of buffer() where data is available.
>      ubyte[] available();
>
>      // Moves the beginning of available() by n in buffer().
>      void bump(sizediff_t n);
>
>      // Reads next blob from a source.
>      bool fetch();
> }
>
> Yes, cstdio-esque rawRead() is no good for high-level ByLine.  What
> high-level I/O entities want is:  A randomly accessible buffer. Device
> handles may expose block-oriented streaming primitives, but they
> must be made "partially random accessible" by the buffering layer.

But that's too big an interface. When would one ever need buffer[], when 
the beginning and the end of the buffer may be used for different 
portions of the input?

A better stream interface, which actually extends the standard input 
range interface:

struct Stream(T)
{
     @property T[] front();
     void munchFront(size_t bytes) in { assert(bytes <= front.length; }
     bool empty();
     void popFront();
}

This still doesn't allow filling the buffer with a new line, but it does 
offer the ability to a client to copy lines into its own buffer.

Andrei