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1 \name{utils}
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2 \alias{is.nullptr}
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3 \alias{as.extptr}
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4 \alias{is.externalptr}
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5 \alias{floatraw}
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6 \alias{as.floatraw}
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7 \alias{floatraw2numeric}
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8 \alias{ptr2str}
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9 \alias{strarrayptr}
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10 \alias{strptr}
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11 \alias{offsetPtr}
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12 \title{Utility functions for working with foreign C data types}
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13 \description{Functions for low-level operations on C pointers as well as
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14 helper functions and objects to handle C \code{float} arrays and strings.}
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15 \usage{
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16 is.nullptr(x)
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17 as.extptr(x)
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18 is.externalptr(x)
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19 floatraw(n)
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20 as.floatraw(x)
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21 floatraw2numeric(x)
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22 ptr2str(x)
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23 strarrayptr(x)
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24 strptr(x)
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25 offsetPtr(x, offset)
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26 }
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27 \arguments{
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28 \item{x}{an R object.}
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29 \item{n}{number of elements to allocate.}
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30 \item{offset}{a offset given in bytes.}
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31 }
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32 \details{
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33
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34 \code{is.nullptr} tests if the external pointer given by \code{x} represents a C \code{NULL} pointer.
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35
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36 \code{as.extptr} returns an external pointer to the data area of atomic
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37 vector given by \code{x}. The external pointer holds an additional reference
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38 to the \code{x} R object to prevent it from garbage collection.
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39
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40 \code{is.externalptr} tests if the object given by \code{x} is an external pointer.
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41
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42 \code{floatraw} creates an array with a capacity to store \code{n} single-precision C \code{float} values.
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43 The array is implemented via a \code{\link[base]{raw}} vector.
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44
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45 \code{as.floatraw} coerces a numeric vector into a single-precision C \code{float} vector.
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46 Values given by \code{x} are converted to C \code{float} values and stored in the R raw vector via \code{.pack}.
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47 This function is useful when calling foreign functions that expeect a C \code{float} pointer via \code{\link{.dyncall}}.
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48
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49 \code{floatraw2numeric} coerces a C \code{float} (raw) vector to a numeric vector.
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50
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51 \code{ptr2str}, \code{strarrayptr}, \code{strptr} are currently experimental.
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52
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53 \code{offsetPtr} creates a new external pointer pointing to \code{x} plus the byte \code{offset}.
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54 If \code{x} is given as an external pointer, the address is increased by the \code{offset},
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55 or, if \code{x} is given as a atomic vector, the address of the data (pointing to offset zero) is taken as basis
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56 and increased by the \code{offset}.
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57 The returned external pointer is protected (as offered by the C function \code{R_MakeExternalPtr}) by the external pointer \code{x}.
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58 }
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59 \value{
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60 A logical value is returned by \code{is.nullptr} and \code{is.externalptr}.
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61 \code{as.extptr} returns an external pointer value.
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62 \code{floatraw} and \code{as.floatraw} return an atomic vector of type \code{raw}
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63 tagged with class \code{'floatraw'}.
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64 \code{floatraw2numeric} returns a \code{numeric} atomic vector.
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65 }
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66 \keyword{programming}
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67 \keyword{interface}
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