Version 3.1.0 of R has imposed a very small data limit on writing to fifos on
Linux. Consider the following R code (Assumes that "ff" is a fifo in the R
process's current directory):
con <- fifo("ff", "a+b")
writeBin(raw(12501), con)
In R 3.0.3, this returns without error and the data is available on the fifo.
In R 3.1.0, however, this returns the following error:
Error in writeBin(raw(12501), con) : too large a block specified
In investigating R's source, the difference seems to be in
src/main/connections.c, in the function fifo_write() (around line 932). In R
3.0.3, fifo_write() has these lines:
if ((double) size * (double) nitems > SSIZE_MAX)
error(_("too large a block specified"));
R 3.1.0 has these lines changed to this:
if ((size * sizeof(wchar_t) * nitems) > 50000) {
error(_("too large a block specified"));
}
The change effectively places a limit of 12500 bytes on writes (since
sizeof(wchar_t) == 4). Does anyone know why this change was made? I understand
that fifos on Windows were implemented for R 3.1.0, but the code for fifos on
Windows is in a separate part of connections.c that doesn't get compiled on
Linux (i.e., the code given is Unix only). I also couldn't find any references
to fifo behavior changes under Linux in any of R's documentation.
My platform is Fedora 20 (64-bit) and I have built and installed R from source.
Thank you for your time and consideration.
James O Smith
Harmonia Holdings Group, LLC
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