Store: Store objects out of memory in a stored object cache.

Description

These functions take objects in memory and store them on the disc in a directory we call a ``stored object cache''. The objects remain visible and are brought back into memory as required using the same mechanism as is used for lazy loading in packages. If the stored object cache does not already exist it is created. If it is not already attached to the search path it is silently attached.

Usage

Store(..., list = character(0), lib = Sys.getenv("R_LOCAL_CACHE", unset = ".R_Cache"), lib.loc = Sys.getenv("R_LOCAL_LIB_LOC", unset = "."), remove = TRUE)
StoreData(...)
StoreUtils(...)

Arguments

...

items to be removed. Names are taken as objects to be removed. Character strings, or calls resulting in character strings, are taken as providing names of items to be removed as character strings.

list

a character string vector providing the names of objects to be removed. An alternative to ... allowing the user to provide an explicit list of names.

lib

The name of the cache directory from which items are to be removed. May be given as a character string, or as a name, (i.e. without quotes) for convenience. The default is as follows:

For Store, the value of the R environment variable R_LOCAL_CACHE, or .R_Cache if unset,
For StoreData, the value of the R environment variable R_CENTRAL_DATA, or .R_Data if unset,
For StoreUtils, the value of the R environment variable R_CENTRAL_UTILS, or .R_Utils if unset.

lib.loc

The enclosing directory where the cache directory is to be found. The default is as follows:

For Store, the value of the R environment variable R_LOCAL_LIB_LOC, or the current working directory if unset,
For StoreDate and StoreUtils the value of the R environment variable R_CENTRAL_LIB_LOC, or he user's HOME directory if unset.

remove

Logical. Should the objects be removed from the current environment? Normally this would be the case.

Value

Nothing of interest. Used only for its side effect.

Details

These functions take objects currently in memory and store them as .RData files in a special directory on the disc, normally a sub-directory of the present working directory. We call the directory a ``stored object cache''. The objects are then made visible by attaching an environment to the search path which loads the file on demand using essentially the lazy loading technique. The path of the stored object cache is specified in two parts, the lib.loc giving the path of the parent directory and the lib, giving the name of the directory iteself. This is the same protocol as is used for loading packages using library or require, for example.

References

None.

Examples

Run this code

## change default cache, keeping any previous setting
oldLC <- Sys.getenv("R_LOCAL_CACHE", unset = ".R_Cache")
Sys.setenv(R_LOCAL_CACHE=".R_Test")

## generate some dummy data
dummy <- rnorm(100)
mn <- mean(dummy)
va <- var(dummy)

## store it in the stored object cache
Store(dummy, mn, va)
Search()
Objects()
Remove(mn, va)
Objects()
Remove(Objects())                   # empty the cache
detach(".R_Test")                   # remove from search path
Sys.setenv(R_LOCAL_CACHE=oldLC)     # restore normal default

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