[Rd] Possible changes to connections
Prof Brian Ripley
ripley at stats.ox.ac.uk
Wed May 30 19:06:43 CEST 2007
When I originally implemented connections in R 1.2.0, I followed the model
in the 'Green Book' closely. There were a number of features that forced
a particular implementation, and one was getConnection() that allows one
to recreate a connection object from a number.
I am wondering if anyone makes use of this, and if so for what?
It would seem closer to the R philosophy to have connection objects that
get garbage collected when no R object refers to them. This would allow
which currently leaks a connection slot as the connection cannot be closed
(except via closeAllConnections() or getConnection()) without an R object
The correct usage currently is
readLines(con <- gzfile("foo.gz")); close(con)
which is a little awkward but more importantly seems little understood.
Another issue is that the current connection objects can be saved and
restored but refer to a global table that is session-specific so they lose
their meaning (and perhaps gain an unintended one).
What I suspect is that very few users are aware of the Green Book
description and so we have freedom to make some substantial changes
to the implementation. Both issues suggest that connection objects should
be based on external pointers (which did not exist way back in 1.2.0).
[I know there is a call to getConnection in package gtools, but the return
value is unused!]
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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