R help - Oct 2005 - Questions about readBin function (Was: dec2bin?)

Hi,

The latest version of R had some changes to functions "readbin() and
writeBin() [which] now support raw vectors as well as filenames and
connections.". As a result I am working on retiring "raw2bin" and
"bin2raw"
functions from "caTools" package which do exactly the same. Thanks to
Prof.
Ripley for bringing this change to my attention.

Which brings me to my question: how to use readBin function to read the
whole file or vector "con" and not just requested number of elements
(n)
from it? In other words what to do if I do not know what to set argument
"n"
to ("The (maximal) number of records to be read"), and want to read
all
records?  

So far the simplest solution I found is to measure vector length (or file
size) of "con" and set n to length()%/%size. Which gets quite messy if
"size" is not provided and have to be deduced from "what"
(see code below).
Am I missing something? Is there an easier way to read the whole file or
vector? Shouldn't that be the default?

readBin(con, what, n = 1, size = NA, signed = TRUE, endian .Platform$endian)

bin2raw = function(x, ...) writeBin(x, raw(), ...) # old bin2raw can be
easily written using curent writeBin

raw2bin = function(r, what, size=NA, ...)
{
  TypeList = c("logical", "integer", "double",
"complex", "character",
"raw", 
               "numeric", "int")
  if (!is.character(what) || length(what) != 1 || !(what %in% TypeList)) 
    what <- typeof(what)
  if (!is.vector(r) || mode(r) == "list") 
    stop("raw2bin: 'r' has to be vector of type
'raw'")
  if (what=="raw") return(r)
  if (!is.na(size)) nBits=size 
  else nBits = switch(match(typeof(x), TypeList), 4, 4, 8, 16, 2, 1, 8, 4) 
  n = length(r)
  if (n%%nBits) 
    stop("raw2bin: number of elements in 'r' is not multiple of
'size'")
  x = readBin(r, what, n = n%/%nBits, size=size, ...)
  return (x)
}

 Jarek 
====================================================\==== 
 Jarek Tuszynski, PhD.                           o / \ 
 Science Applications International Corporation  <\__,|  
 (703) 676-4192                                   ">  \ 
 Jaroslaw.W.Tuszynski at saic.com                     `   \

I think you can use 'seek()' here, but it may not be completely reliable
on all
platforms.

-roger

Tuszynski, Jaroslaw W. wrote:
> Hi,
> 
> The latest version of R had some changes to functions "readbin() and
> writeBin() [which] now support raw vectors as well as filenames and
> connections.". As a result I am working on retiring
"raw2bin" and "bin2raw"
> functions from "caTools" package which do exactly the same.
Thanks to Prof.
> Ripley for bringing this change to my attention.
> 
> Which brings me to my question: how to use readBin function to read the
> whole file or vector "con" and not just requested number of
elements (n)
> from it? In other words what to do if I do not know what to set argument
"n"
> to ("The (maximal) number of records to be read"), and want to
read all
> records?  
> 
> So far the simplest solution I found is to measure vector length (or file
> size) of "con" and set n to length()%/%size. Which gets quite
messy if
> "size" is not provided and have to be deduced from
"what" (see code below).
> Am I missing something? Is there an easier way to read the whole file or
> vector? Shouldn't that be the default?
> 
> readBin(con, what, n = 1, size = NA, signed = TRUE, endian >
.Platform$endian)
> 
> bin2raw = function(x, ...) writeBin(x, raw(), ...) # old bin2raw can be
> easily written using curent writeBin
> 
> raw2bin = function(r, what, size=NA, ...)
> {
>   TypeList = c("logical", "integer",
"double", "complex", "character",
> "raw", 
>                "numeric", "int")
>   if (!is.character(what) || length(what) != 1 || !(what %in% TypeList)) 
>     what <- typeof(what)
>   if (!is.vector(r) || mode(r) == "list") 
>     stop("raw2bin: 'r' has to be vector of type
'raw'")
>   if (what=="raw") return(r)
>   if (!is.na(size)) nBits=size 
>   else nBits = switch(match(typeof(x), TypeList), 4, 4, 8, 16, 2, 1, 8, 4) 
>   n = length(r)
>   if (n%%nBits) 
>     stop("raw2bin: number of elements in 'r' is not multiple
of 'size'")
>   x = readBin(r, what, n = n%/%nBits, size=size, ...)
>   return (x)
> }
> 
>  Jarek 
> ====================================================\==== 
>  Jarek Tuszynski, PhD.                           o / \ 
>  Science Applications International Corporation  <\__,|  
>  (703) 676-4192                                   ">  \ 
>  Jaroslaw.W.Tuszynski at saic.com                     `   \
> 
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> 
-- 
Roger D. Peng
http://www.biostat.jhsph.edu/~rpeng/