--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/R/rdyncall/man/packing.Rd	Thu Mar 19 22:26:28 2015 +0100
@@ -0,0 +1,49 @@
+\name{packing}
+\alias{.pack}
+\alias{packing}
+\alias{.unpack}
+\title{Handling of foreign C fundamental data types}
+\description{Functions to unpack/pack (read/write) foreign C data types from/to R atomic vectors and C data objects such as arrays and pointers to structures.}
+\usage{
+.pack(x, offset, sigchar, value)
+.unpack(x, offset, sigchar)
+}
+\arguments{
+\item{x}{atomic vector (logical, raw, integer or double) or external pointer.}
+\item{offset}{integer specifying \emph{byte offset} starting at 0.} 
+\item{sigchar}{character string specifying the C data type by a \link{type signature}.}
+\item{value}{R object value to be coerced and packed to a foreign C data type.} 
+}
+\details{
+The function \code{.pack} converts an R \code{value} into a C data type specified by the \link{signature} \code{sigchar} 
+and it writes the raw C foreign data value at byte position \code{offset} into the object \code{x}.
+The function \code{.unpack} extracts a C data type according to the \link{signature} \code{sigchar} 
+at byte position \code{offset} from the object \code{x} and converts the C value to an R value and returns it.
+
+Byte \code{offset} calculations start at 0 relative to the first byte in an atomic vectors data area.
+
+If \code{x} is an atomic vector, a bound check is carried out before read/write access.
+Otherwise, if \code{x} is an external pointer, there is only a C NULL pointer check.
+}
+\value{
+\code{.unpack} returns a read C data type coerced to an R value.
+}
+\seealso{
+\code{\link{.dyncall}} for details on type signatures.
+}
+\examples{
+# transfer double to array of floats and back, compare precision:
+n <- 6
+input <- rnorm(n)
+buf <- raw(n*4)
+for (i in 1:n) {
+  .pack(buf, 4*(i-1), "f", input[i])
+}
+output <- numeric(n)
+for (i in 1:n) {
+  output[i] <- .unpack(buf, 4*(i-1), "f")
+}
+# difference between double and float
+difference <- output-input
+print( cbind(input,output,difference) )
+}