library.dynam              package:base              R Documentation

Loading DLLs from Packages

Description:

     Load the specified file of compiled code if it has not been loaded
     already, or unloads it.

Usage:

     library.dynam(chname, package = NULL, lib.loc = NULL,
                   verbose = getOption("verbose"),
                   file.ext = .Platform$dynlib.ext, ...)

     library.dynam.unload(chname, libpath,
                   verbose = getOption("verbose"),
                   file.ext = .Platform$dynlib.ext)

     .dynLibs(new)

Arguments:

  chname: a character string naming a DLL (also known as a dynamic
          shared object or library) to load.

 package: a character vector with the names of packages to search
          through, or 'NULL'.  By default, all packages in the search
          path are used.

 lib.loc: a character vector describing the location of R library trees
          to search through, or 'NULL'.  The default value of 'NULL'
          corresponds to all libraries currently known.

 libpath: the path to the loaded package whose DLL is to be unloaded.

 verbose: a logical value indicating whether an announcement is printed
          on the console before loading the DLL.  The default value is
          taken from the verbose entry in the system options.

file.ext: the extension to append to the file name to specify the
          library to be loaded. This defaults to the appropriate value
          for the operating system.

     ...: additional arguments needed by some libraries that are passed
          to the call to 'dyn.load' to control how the library is
          loaded.

     new: a list of '"DLLInfo"' objects corresponding to the DLLs
          loaded by packages.  Can be missing.

Details:

     See 'dyn.load' for what sort of objects these functions handle.

     'library.dynam' is designed to be used inside a package rather
     than at the command line, and should really only be used inside
     '.First.lib' or '.onLoad'.  The system-specific extension for DLLs
     (e.g., '.so' or '.sl' on Unix systems, '.so' on Mac OS X, '.dll'
     on Windows) should not be added.  Note that to allow for versioned
     installs, the 'chname' argument should not be set to the 'pkgname'
     argument of '.First.lib' or '.onLoad'.

     If '...' does not include a named argument 'Dllpath', 'dyn.load'
     is called with 'DLLpath' set to the package's 'libs' directory. 
     (Currently only used under Windows.)

     'library.dynam.unload' is designed for use in '.Last.lib' or
     '.onUnload': it unloads the DLL and updates the value of
     '.dynLibs()'

     '.dynLibs' is used for getting (with no argument) or setting the
     DLLs which are currently loaded by packages (using
     'library.dynam').

Value:

     If 'chname' is not specified, 'library.dynam' returns an object of
     class '"DLLInfoList"' corresponding to the DLLs loaded by
     packages.

     If 'chname' is specified, an object of class '"DLLInfo"' that
     identifies the DLL and can be used in future calls is returned
     invisibly.  For packages that have name spaces, a list of these
     objects is stored in the name space's environment for use at
     run-time.

     Note that the class 'DLLInfo' has an overloaded method for '$'
     which can be used to resolve native symbols within that DLL.

     'library.dynam.unload' invisibly returns an object of class
     '"DLLInfo"' identifying the DLL successfully unloaded.

     '.dynLibs' returns an object of class '"DLLInfoList"'
     corresponding corresponding to its current value.

Warning:

     Do not use 'dyn.unload' on a DLL loaded by 'library.dynam': use
     'library.dynam.unload' to ensure that '.dynLibs' gets updated. 
     Otherwise a subsequent call to 'library.dynam' will be told the
     object is already loaded.

References:

     Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) _The New S
     Language_. Wadsworth & Brooks/Cole.

See Also:

     'getLoadedDLLs' for information on '"DLLInfo"' and '"DLLInfoList"'
     objects.

     '.First.lib', 'library', 'dyn.load', '.packages', '.libPaths'

     'SHLIB' for how to create suitable DLLs.

Examples:

     ## Which DLLs were "dynamically loaded" by packages?
     library.dynam() 

