\HeaderA{readBin}{Transfer Binary Data To and From Connections}{readBin}
\aliasA{writeBin}{readBin}{writeBin}
\keyword{file}{readBin}
\keyword{connection}{readBin}
\begin{Description}\relax
Read binary data from a connection, or write binary data to a connection.
\end{Description}
\begin{Usage}
\begin{verbatim}
readBin(con, what, n = 1L, size = NA_integer_, signed = TRUE,
        endian = .Platform$endian)

writeBin(object, con, size = NA_integer_,
         endian = .Platform$endian)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{con}] A connection object or a character string naming a file or
a raw vector.
\item[\code{what}] Either an object whose mode will give the mode of the
vector to be read, or a character vector of length one describing
the mode: one of \code{"numeric", "double", "integer", "int",
      "logical", "complex", "character", "raw"}.
\item[\code{n}] integer.  The (maximal) number of records to be
read.  You can use an over-estimate here, but not too large as
storage is reserved for \code{n} items.
\item[\code{size}] integer.  The number of bytes per element in the byte
stream.  The default, \code{NA\_integer\_}, uses the natural size.
Size changing is not supported for raw and complex vectors.
\item[\code{signed}] logical. Only used for integers of sizes 1 and 2,
when it determines if the quantity on file
should be regarded as a signed or unsigned integer.
\item[\code{endian}] The endian-ness (\code{"big"} or \code{"little"} of the
target system for the file.  Using \code{"swap"} will force swapping
endian-ness.
\item[\code{object}] An \R{} object to be written to the connection.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
If \code{con} is a character string, the functions call
\code{\LinkA{file}{file}} to obtain an file connection which is opened for
the duration of the function call.

If the connection is open it is read/written from its current
position.  If it is not open, it is opened for the duration of the
call in an appropriate mode (binary read or write) and then closed
again.  An open connection must be in binary mode.

If \code{readBin} is called with \code{con} a raw vector, the data in
the vector is used as input.  If \code{writeBin} is called with
\code{con} a raw vector, it is just an indication that a raw vector
should be returned.

If \code{size} is specified and not the natural size of the object,
each element of the vector is coerced to an appropriate type before
being written or as it is read.  Possible sizes are 1, 2, 4 and
possibly 8 for integer or logical vectors, and 4, 8 and possibly 12/16
for numeric vectors.  (Note that coercion occurs as signed types
except if \code{signed = FALSE} when reading integers of sizes 1 and 2.)
Changing sizes is unlikely to preserve \code{NA}s, and the extended
precision sizes are unlikely to be portable across platforms.

\code{readBin} and \code{writeBin} read and write C-style
zero-terminated character strings.  Input strings are limited to 10000
characters.  \code{\LinkA{readChar}{readChar}} and \code{\LinkA{writeChar}{writeChar}} can
be used to read and write fixed-length strings.  No check is made that
the string is valid in the current locale.

Handling \R's missing and special (\code{Inf}, \code{-Inf} and
\code{NaN}) values is discussed in the \emph{R Data Import/Export} manual.
\end{Details}
\begin{Value}
For \code{readBin}, a vector of appropriate mode and length the number of
items read (which might be less than \code{n}).

For \code{writeBin}, a raw vector (if \code{con} is a raw vector) or
invisibly \code{NULL}.
\end{Value}
\begin{Note}\relax
Integer read/writes of size 8 will be available if either C type
\code{long} is of size 8 bytes or C type \code{long long} exists and
is of size 8 bytes.

Real read/writes of size \code{sizeof(long double)} (usually 12 or 16
bytes) will be available only if that type is available and different
from \code{double}.

If \code{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.
\end{Note}
\begin{SeeAlso}\relax
The \emph{R Data Import/Export} manual.

\code{readChar} to read/write fixed-length strings.

\code{\LinkA{connections}{connections}}, \code{\LinkA{readLines}{readLines}},
\code{\LinkA{writeLines}{writeLines}}.

\code{\LinkA{.Machine}{.Machine}} for the sizes of \code{long}, \code{long long}
and \code{long double}.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
zz <- file("testbin", "wb")
writeBin(1:10, zz)
writeBin(pi, zz, endian="swap")
writeBin(pi, zz, size=4)
writeBin(pi^2, zz, size=4, endian="swap")
writeBin(pi+3i, zz)
writeBin("A test of a connection", zz)
z <- paste("A very long string", 1:100, collapse=" + ")
writeBin(z, zz)
if(.Machine$sizeof.long == 8 || .Machine$sizeof.longlong == 8)
    writeBin(as.integer(5^(1:10)), zz, size = 8)
if((s <-.Machine$sizeof.longdouble) > 8)
    writeBin((pi/3)^(1:10), zz, size = s)
close(zz)

zz <- file("testbin", "rb")
readBin(zz, integer(), 4)
readBin(zz, integer(), 6)
readBin(zz, numeric(), 1, endian="swap")
readBin(zz, numeric(), size=4)
readBin(zz, numeric(), size=4, endian="swap")
readBin(zz, complex(), 1)
readBin(zz, character(), 1)
z2 <- readBin(zz, character(), 1)
if(.Machine$sizeof.long == 8 || .Machine$sizeof.longlong == 8)
    readBin(zz, integer(), 10,  size = 8)
if((s <-.Machine$sizeof.longdouble) > 8)
    readBin(zz, numeric(), 10, size = s)
close(zz)
unlink("testbin")
stopifnot(z2 == z)

## signed vs unsigned ints
zz <- file("testbin", "wb")
x <- as.integer(seq(0, 255, 32))
writeBin(x, zz, size=1)
writeBin(x, zz, size=1)
x <- as.integer(seq(0, 60000, 10000))
writeBin(x, zz, size=2)
writeBin(x, zz, size=2)
close(zz)
zz <- file("testbin", "rb")
readBin(zz, integer(), 8, size=1)
readBin(zz, integer(), 8, size=1, signed=FALSE)
readBin(zz, integer(), 7, size=2)
readBin(zz, integer(), 7, size=2, signed=FALSE)
close(zz)
unlink("testbin")

## use of raw
z <- writeBin(pi^{1:5}, raw(), size = 4)
readBin(z, numeric(), 5, size = 4)
z <- writeBin(c("a", "test", "of", "character"), raw())
rawToChar(z)
readBin(z, character(), 4)
\end{ExampleCode}
\end{Examples}

