readBin should check that its endian argument is a legal value

Thank you for reporting this problem, R-devel now has a check in readBin
and writeBin.

I've identified two CRAN packages with an incorrect value for "endian"
and reported to maintainers, unfortunately in their case the intention
was to specify "little".

Best
Tomas

On 11/18/19 11:22 PM, Jennifer Lyon wrote:

I think it would be helpful if readBin checked that its endian argument

is

a legal value.

Why? I was reviewing some of our code and noticed that the author had
readBin(..., endian="network") and never having heard of "network", I
looked at the man page for readBin, and it hadn't heard of "network"
either. Not good.

I then looked at the R code for readBin, which has this line:
  swap <- endian != .Platform$endian

and swap is passed into the .Internal(readBin). Further use of Google
revealed that "network" is a known endian in the universe, and our code

was

working by essentially a lucky chance that the data was "big" and our
current machines are "little". Really not good. I don't know enough about
endian stuff to know if it makes sense that "network" should be one of

the

choices for endian for readBin (which from the documentation currently

are:

"big", "little" or "swap"), but in my opinion R should have failed with

the

choice of "network" in our code in the current version of R. I did
eventually find an aside in the R Data Import/Export document that
"network" is "big" so I will patch our code to be legal. Of course some
code may depend on this undocumented behavior, but I would guess that in
the vast majority of cases an illegal value really is a mistake.

Jen

sessionInfo()

R version 3.6.1 (2019-07-05)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 18.04.3 LTS

Matrix products: default
BLAS:   /home/mbr/r-project/R-3.6.1/lib/libRblas.so
LAPACK: /home/mbr/r-project/R-3.6.1/lib/libRlapack.so

locale:
  [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
  [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
  [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
  [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
  [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] compiler_3.6.1

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