NAME

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

VERSION

version 0.10

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.

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

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 <cubranic@stat.ubc.ca>

COPYRIGHT AND LICENSE

This software is Copyright (c) 2014 by University of British Columbia.

This is free software, licensed under:

  The GNU General Public License, Version 3, June 2007