Feature #15560: Add support for read/write offsets.

• Status: Closed
• Priority: Normal
• Assignee: ioquatix (Samuel Williams)
• Target version: -

[ioquatix (Samuel Williams)]

It would be nice if read/write/send/recv/etc methods could accept an offset argument.

e.g.

socket = Socket.new(...)
buffer = String.b

socket.read(1024, buffer)
socket.read(1024, buffer, offset: buffer.bytesize)

The same for write, e.g.

socket = Socket.new(...)
buffer = String.b

amount = socket.write(buffer)
socket.write(buffer, offset: amount)

Could also include "size:" so that we can selectively write parts of the buffer.

[shyouhei (Shyouhei Urabe)]

I can imagine it is useful for TCPSocket#write to accept only a part of a buffer crafted by somebody else. But I cannot think of any actual use case when #read is useful with that extension. Do you have one?

[ioquatix (Samuel Williams)]

It is useful for read when user wants to read some data, and it wasn't enough (e.g. implementing gets) so you need to read some more at the end of what you already have.

[ioquatix (Samuel Williams)]

Also, rather than using a keyword argument, it could be a 3rd argument after buffer, since buffer must be supplied in order for this to work.

[ioquatix (Samuel Williams)]

• Target version deleted (2.7)

[ioquatix (Samuel Williams)]

I've added this to the IO::Buffer interface which is good enough for my requirements.

buffer = IO::Buffer.new
buffer.read(io, length, offset)
buffer.write(io, length, offset)

If we want to introduce the same model to IO.read(length, [buffer, [offset]]) and IO.write(length, [buffer, [offset]]) that would be reasonable.

[ioquatix (Samuel Williams)]

• Status changed from Open to Closed
• Assignee set to ioquatix (Samuel Williams)

I tried making a PR, but I think we should give up.

IO#read(length, buffer, offset) can work okay.

But doing the same for write is very hard because the interface is more general - it tries to write all arguments. It would need to be a keyword argument, and I'm not sure how you'd make it work since you can specify multiple arguments.

I think the solution here, for more complex use cases, is just to use IO::Buffer which supports this very naturally.