\name{externalStorage-class}
\docType{class}
\alias{externalStorage-class}
\alias{allocator,externalStorage-method}
\alias{getNativeStorageMethods,externalStorage-method}
\alias{getPointer,externalStorage-method}
\alias{initialize,externalStorage-method}
\alias{initializeResource,externalStorage-method}
\alias{internalType,externalStorage-method}

\title{Class "externalStorage", base class for external storage for
  objects of class "externalVectorWithStorage" }
\description{ The \code{"externalStorage"} class represents the base
  class of the storage backend implementation used by the class
  \code{"externalVectorWithSToraghe"}. A pointer to the external storage
  allocated or accessed by an object of class \code{"externalStorage"}
  is kept in an external pointer. }
\section{Objects from the Class}{A virtual Class: No objects may be created from it.}
\section{Slots}{
  \describe{
    \item{\code{ptr}:}{Object of class \code{"externalptr"}, keeps the
      pointer to the external storage. }
    \item{\code{type}:}{Object of class \code{"vector"}, a vector object
      of length one representing the type of object stored in the
      external storage. Usually one of the basic R vector types. }
    \item{\code{length}:}{Object of class \code{"integer"}, Cached value
      for the length of the vector stored in the external storage. }
  }
}
\section{Extends}{
Class \code{"externalResource"}, directly.
}
\section{Methods}{
  Signature components for the methods:

  \tabular{ll}{
    resource \tab The class "externalStorage"\cr
    x \tab The class "externalStorage"\cr
    ptr \tab The class "externalptr"\cr
    size \tab The class "ANY"\cr
    type \tab The class "ANY"\cr
  }

  \describe{
      \item{allocator(resource):}{ The allocator to be used by default with
	this \code{resource}. Returns an object of class
	\code{"gcAllocator"}. }
      \item{getPointer(reource):}{ Return the \code{ptr} slot. }
      \item{initializeResource(resource, ptr, size, type, \dots):}{
	Set the \code{ptr} slot of resource to \code{ptr}. }
      \item{initialize(.Object, type = logical(1), length =
	as.integer(0)):}{ This checks the validity of \code{type} and
	\code{length} arguments and coerce the \code{length} argument to
	class \code{"integer"} before using them to set the
	corresponding slots. Finally a call to \code{callNextMethod} is
	made to use the initializer for class \code{"externalResource"}
	which, via a call to the \code{initializeResource} method above
	sets \code{ptr} slot. }
      \item{internalType(x):}{ The type of object to be stored
	within the resource. It is an \R basic vector type
	(\code{"logical"}, \code{"integer"}, \code{"numeric"},
	\code{"complex"}, \code{"character"} or \code{"list"}). }
      \item{getNativeStorageMethods(x):}{ Get the \code{"externalptr"}
	stored in the \code{"nativeStorageMethods"} object associated
	with a particular subclass of \code{"externalStorage"} and a
	basic R vector type. }
  }
}
\seealso{
  \code{\link{setExternalStorageClass}} for how to set a subclass of
  \code{"externalStorage"}.
  
  \code{\link{nativeStorageMethods-class}} for the C structure
  containing C function pointers for a particular storage methods class.
  
  \code{\link{externalVectorWithStorage-class}} for how the
  \code{"externalStorage"} class is used.
  
  \code{\link{simpleStorage-class}} for a simple implementation of
  \code{"externalStorage"}.
}
\keyword{classes}