---
name: "Statistics::R::IO::QapEncoding"
section: "3pm"
platform: "linux"
package: "libstatistics-r-io-perl"
version: "1.0002-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Statistics::R::IO::QapEncoding"
---

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

Functions for parsing Rserve packets

## 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 \<cubranic@stat.ubc.ca\>

## COPYRIGHT AND LICENSE

This software is Copyright (c) 2017 by University of British Columbia.

This is free software, licensed under:

```
  The GNU General Public License, Version 3, June 2007
```