base (version 3.3)

serialize: Simple Serialization Interface

Description

A simple low-level interface for serializing to connections.

Usage

serialize(object, connection, ascii, xdr = TRUE,
          version = NULL, refhook = NULL)
unserialize(connection, refhook = NULL)

Arguments

object

R object to serialize.

connection

an open connection or (for serialize) NULL or (for unserialize) a raw vector (see ‘Details’).

ascii

a logical. If TRUE or NA, an ASCII representation is written; otherwise (default) a binary one. See also the comments in the help for save.

xdr

a logical: if a binary representation is used, should a big-endian one (XDR) be used?

version

the workspace format version to use. NULL specifies the current default version (2). Versions prior to 2 are not supported, so this will only be relevant when there are later versions.

refhook

a hook function for handling reference objects.

Value

• For serialize, NULL unless connection = NULL, when the result is returned in a raw vector.

  For unserialize an Robject.

Warning

These functions have provided a stable interface since R 2.4.0 (when the storage of serialized objects was changed from character to raw vectors). However, the serialization format may change in future versions of R, so this interface should not be used for long-term storage of R objects. On 32-bit platforms a raw vector is limited to $2^31 - 1$ bytes, but R objects can exceed this and their serializations will normally be larger than the objects.

Details

The function serialize serializes object to the specified connection. If connection is NULL then object is serialized to a raw vector, which is returned as the result of serialize.

Sharing of reference objects is preserved within the object but not across separate calls to serialize.

unserialize reads an object (as written by serialize) from connection or a raw vector.

The refhook functions can be used to customize handling of non-system reference objects (all external pointers and weak references, and all environments other than namespace and package environments and .GlobalEnv). The hook function for serialize should return a character vector for references it wants to handle; otherwise it should return NULL. The hook for unserialize will be called with character vectors supplied to serialize and should return an appropriate object.

For a text-mode connection, the default value of ascii is set to TRUE: only ASCII representations can be written to text-mode connections and attempting to use ascii = FALSE will throw an error.

The format consists of a single line followed by the data: the first line contains a single character: X for binary serialization and A for ASCII serialization, followed by a new line. (The format used is identical to that used by readRDS.)

The option of xdr = FALSE was introduced in R2.15.0. As almost all systems in current use are little-endian, this can be used to avoid byte-shuffling at both ends when transferring data from one little-endian machine to another. Depending on the system, this can speed up serialization and unserialization by a factor of up to 3x.

See Also

saveRDS for a more convenient interface to serialize an object to a file or connection.

save and load to serialize and restore one or more named objects.

The R Internals manual for details of the format used.

Examples

x <- serialize(list(1,2,3), NULL)
unserialize(x)

## see also the examples for saveRDS