Statistics::R::IO::QapEncoding(3pm)

NAME

Statistics::R::IO::QapEncoding - Functions for parsing Rserve packets

VERSION

version 1.0002

SYNOPSIS

    use Statistics::R::IO::QapEncoding qw( decode );
    # Assume $data comes from an Rserve response body
    my ($rexp, $state) = @{ decode($data) }
        or die "couldn't parse";
    
    # If we're reading a QAP response, there should be no data left
    # unparsed
    die 'Unread data remaining' unless $state->eof;
    # the result of the unserialization is a REXP
    say $rexp;
    # REXPs can be converted to the closest native Perl data type
    print $rexp->to_pl;

DESCRIPTION

This module implements the actual reading of serialized R objects encoded with Rserve's QAP protocol and their conversion to a Statistics::R::REXP. You are not expected to use it directly, as it's normally wrapped by "evalRserve" in Statistics::R::IO and "eval" in Statistics::R::IO::Rserve.

SUBROUTINES

decode $data: Constructs a Statistics::R::REXP object from its serialization in $data. Returns a pair of the object and the Statistics::R::IO::ParserState at the end of serialization.

decode_sexp, decode_int: Parsers for Rserve's "DT_SEXP" and "DT_INT" data types, respectively.

dt_sexp_data: Parses the body of an RServe "DT_SEXP" object by parsing its header ("XT_" type and length) and content (done by sequencing "unpack_sexp_info" and "sexp_data".

unpack_sexp_info: Parser for the header (consisting of the "XT_*" type, flags, and object length) of a serialized SEXP. Returns a hash with keys "object_type", "has_attributes", and "length", each corresponding to the field in R serialization described in QAP1 protocol description <http://www.rforge.net/Rserve/dev.html>.

sexp_data $obj_info: Parser for a QAP-serialized R object, using the object type stored in $obj_info hash's "object_type" key to use the correct parser for the particular type.

intsxp, langsxp, lglsxp, listsxp, rawsxp, dblsxp, cplxsxp, strsxp, symsxp, vecsxp, expsxp, closxp, s4sxp: Parsers for the corresponding R SEXP-types.

nosxp: Parser for the Rserve's "XT_UNKNOWN" type, encoding an R SEXP-type that does not have a corresponding representation in QAP.

maybe_attributes $object_info: Convenience parser for SEXP attributes, which are serialized as a tagged pairlist "XT_LIST_TAG" followed by a SEXP for the object value. Attributes are stored only if $object_info indicates their presence. Returns a pair of $object_info and a hash reference to the attributes, as returned by "tagged_pairlist_to_attribute_hash".

tagged_pairlist: Parses a pairlist (optionally tagged) and returns an array where each element is a hash containing keys "value" (the REXP of the pairlist element) and, optionally, "tag".

tagged_pairlist_to_rexp_hash: Converts a pairlist to a REXP hash whose keys are the pairlist's element tags and values the pairlist elements themselves.

tagged_pairlist_to_attribute_hash

Converts object attributes, which are serialized as a pairlist with attribute name in the element's tag, to a hash that can be used as the "attributes" argument to Statistics::R::REXP constructors.

Some attributes are serialized using a compact encoding (for instance, when a table's row names are just integers 1:nrows), and this function will decode them to a complete REXP.

BUGS AND LIMITATIONS

There are no known bugs in this module. Please see Statistics::R::IO for bug reporting.

SUPPORT

See Statistics::R::IO for support and contact information.

AUTHOR

Davor Cubranic <[email protected]>

COPYRIGHT AND LICENSE

This is free software, licensed under:

  The GNU General Public License, Version 3, June 2007