On Wed, 16 Jan 2008, Richard Cotton wrote:
>
>
>
> Prof Brian Ripley wrote:
>>
>>> Yes. The problem is of course that we do want a sprintf() format there
>>> for "Rplot%03d.pdf" et al. One option would be to escape "%" except
>>> when in (regexp) "%[0-9]*d", which seems nontrivial, but not impossible.
>>
>> But there are other integer formats (%i, %u, %x, %X), and other flags (#
>> might be useful). So the list of valid inputs is also rather long. It
>> would be tedious to do at C level, but a check in the R-level wrapper
>> would be easier (if not 'simple').
>>
>
> Having just worked my way through the alphabet, I can say that it is only
> the letters 's' and 'n' that cause any problems. Thus, if you do decide to
> handle the error in the R wrapper functions, the regex for bad inputs is
> fairly straightforward "%[#[:blank:]\\+\\-]*[[:digit:]]*[sn]".
Thanks: but %% (escaped %) should be allowed (and only ASCII blank is
allowed as a flag, and only ASCII digits).
We decided to do the opposite and test for an allowed format
(you are only allowed to have one). So the current check is
### Check for a single valid integer format
checkIntFormat <- function(s)
{
## OK if no unescaped %, so first remove those
s <- gsub("%%", "", s)
if(length(grep("%", s)) == 0) return(TRUE)
## now remove at most one valid(ish) integer format
s <- sub("%[#0 +-]*[0-9.]*[diouxX]", "", s)
length(grep("%", s)) == 0
}
The set of flags is debatable, and not yet final. Not all strings that
pass that test are valid formats, but hopefully the exceptions are
- rare
- will not crash R.
Empirical testing of crashing is not comprehensive and machine-dependent
even if you use a tool like valgrind to detect violations (32- vs 64-bit
issues, for example).
Unfortunately there *is* a C-level call to the postscript driver, so some
C-level checking is needed.
--
Brian D. Ripley, [EMAIL PROTECTED]
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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