streams 0.3.0

Streams

A collection of useful stream primitives and implementations. Designed to be a candidate for inclusion in Phobos. The concept of a stream is of a component that implements a int read(T[] buffer) or int write(T[] buffer) method for some element type T.

Similar to Phobos' ranges, streams are defined and type-checked using a primitives package that contains various compile-time functions like isInputRange and isOutputRange. Let's look at an example where we write some data to a socket using streams:

import streams;

void sayHello(Socket socket) {
    auto outputStream = SocketOutputStream(socket);
    auto dataOutput = dataOutputStreamFor(outputStream);
    dataOutput.write!(char[5])("Hello");
}

Stream primitives are generally compatible with BetterC, although there may be incompatibilities in various implementations where dynamic arrays or exceptions are used. You may certainly write streams that are safe, no-gc compatible, pure, and so on.

Features

• Compile-time functions for identifying streams of various kinds, useful for when you want to accept streams as parameters or use them in templates.
• Convenience functions for dealing with streams, like reading all elements to a buffer, or transfering the contents of one stream to another.
• Pre-defined stream implementations for common use cases:
  • ArrayInputStream and ArrayOutputStream for performing IO on in-memory arrays.
  • DataInputStream and DataOutputStream are wrappers over any ubyte stream, adding the ability to read and write scalar values (int, float, bool, char, etc.) and static arrays, by automatically serializing them.
  • FileInputStream and FileOutputStream are ubyte streams for reading and writing files using std.stdio : File.
  • SocketInputStream and SocketOutputStream are ubyte streams for reading and writing to sockets using std.socket : Socket.
• Functions to convert between streams and Phobos ranges.

Difference with Ranges

Phobos' concept of an Input Range relies on implicit buffering of results, because of the contract it defines with front() needing to return the same result in consecutive calls without calling popFront(). This doesn't map as easily to many low-level resources, and also introduces additional cognitive complexity to programmers who don't need that functionality.

This isn't to say that ranges aren't useful! They certainly are in many cases, but the argument is that a simpler stream interface is more useful in IO-heavy tasks or other cases where you simply want to read or write data to/from a buffer.

Furthermore, streams of this nature are a common feature in many other programming languages, and thus provides a bit of a "comfort zone" to help welcome programmers.

For compatibility, this library provides the functions asInputRange and asOutputRange to wrap an input stream as a Phobos input range and an output stream as a Phobos output range, respectively. Note that due to the inherently un-buffered nature of streams, these range implementations may not be as performant as existing range implementations for certain resources.

Development

Simply clone this repository, and ensure you have a recent version of D with any compiler, and run dub test to test the library.

Documentation can be generated with ./gen_docs.d, which internally uses Adrdox to generate documentation at generated-docs/.

This codebase is expected to maintain a high code-quality, and while no automated checks are in-place, it is expected that pull requests that add significant new code adhere to the conventions already in use, and document any new symbols you added.