[R] End of File for binary files

[jim holtman]

If you are using readBin and want to read binary (and not 'character')
data, then use 'raw' which will return a value if it encounters a
binary zero and not think it is the end of a character string.  It is
easy enough to setup a test file and try out a couple of the options
to see what happen.  Not enough information was presented in the
original posting to conclude what was really wanted.  Does the binary
file consist of just bytes, it is integer (32 or 64 bit), is it
floating point, etc.  Once you understand the structure of the data,
is it not difficult to read in the data.  Binary and 'character' are
not necessarily the same information when trying to read from a file.

On Sun, Jan 24, 2010 at 12:15 PM, Henrik Bengtsson <hb at stat.berkeley.edu> wrote:
> On Sun, Jan 24, 2010 at 3:56 AM, Duncan Murdoch <murdoch at stats.uwo.ca> wrote:
>> On 23/01/2010 10:40 PM, rn00b wrote:
>>>
>>> I am using readBin to continuously read characters from the binary file.
>>> I'm
>>> trying to figure out how many characters are in the file. What I would
>>> like
>>> to do is something like
>>> (while! EOF)
>>> {
>>> charRead <-.Internal(readBin(con,"character",1L,NA,TRUE,swap))
>>> i++
>>> }
>>>
>>> I'm not clear on how to determine the EOF condition in this case.
>>
>> You should not be calling .Internal.  It's for internal use, subject to
>> change, etc.
>>
>> Using readBin(...)  you can detect EOF by reading fewer than n items when
>> you ask for n.
>
> Is this safe?  Is EOF the only case where readBin() returns fewer
> elements than you requested?  Does it depend on the type of connection
> you are reading from?  Does it depend on OS?
>
> The help("readBin") does not say much about this, but it says:
>
> "If readBin(what = character()) is used incorrectly on a file which
> does not contain C-style character strings, warnings (usually many)
> are given. From a file or connection, the input will be broken into
> pieces of length 10000 with any final part being discarded."
>
> which seems to suggest that you (at least in special cases) can get
> fewer items than requested without hitting EOF.  EOF behavior might be
> document elsewhere in R.
>
> /Henrik
>
>> So the loop would be something like
>>
>> while (length(charRead <- readBin(con, "character")) > 0) {
>>  i <- i + 1
>> }
>>
>> Duncan Murdoch
>>
>> ______________________________________________
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>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?