Add methods for filling a buffer from an IO greedily/lazily about crystal HOT 5 OPEN

I second that. I'm not sure about the names, but having a couple methods to "try to read (nonblock)" and "try to fill (blocking, until EOF)" sounds good. Maybe:

• IO#fill(buffer : Bytes) : Int32 fills the buffer until EOF is reached; returns the number of bytes read (usually the buffer size, but may be less when EOF is reached). Raises after EOF has been reached.
• IO#fill?(buffer : Bytes) : Int32? same as #fill but returns nil instead of raising after EOF.

I'm also wondering about the following, but it's mixing two concepts (nonblock + eof) behind the ? suffix (not good):

• IO#read?(buffer : Bytes) : Int32? same as #read but doesn't block until data is ready, and immediately returns 0 when nothing was read; returns nil on EOF.

from crystal.

@ysbaddaden These methods are all related to IO#read and IMO their names should be similar. #read_greedy may not be a great name, but at least it establishes that it's a variant of #read. Maybe we can find something better with #read_ prefix though?

Also it would be very helpful for consistency to keep the same general semantics as #read: indicate EOF with a zero return value and only raise if closed.

The proposed behaviour of #read? can be implemented via #peek and #skip. That's even more efficient because it works without copy.

from crystal.

I've been thinking about this as well since I recommended using IO.copy for this use case yesterday in #14601 (comment).
So IO.copy can basically do this and even more because it reads into an IO. But of course this is not as convenient if you want to read directly into a slice.

So it might be a good idea to add a method for this.

from crystal.

I proposed read_greedy to be consistent with read_fully (which has nearly the same functionality and code).
Also, the term "greedy" should be familiar to most developers already since it's also used in regexes for the same behaviour.

I tried searching for better names for this method by looking at other programming languages, but the only language I could find with a similar method is Java with InputStream#readNBytes.

from crystal.

@straight-shoota I got confused, I thought we raised on eventual EOF.

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