/ 
XS-Parse-Keyword-FromPerl-0.08
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/ XS::Parse::Keyword::FromPerl

NAME

XS::Parse::Keyword::FromPerl - drive XS::Parse::Keyword directly from Perl

DESCRIPTION

This module provides a Perl-visible API wrapping (some of) the functionality provided by XS::Parse::Keyword, allowing extension keywords to be added to the Perl language by writing code in Perl itself.

It provides a thin wrapping layer over the XS functions provided by XPK itself. No real attempt is made here to provide further abstractions on top of the API already provided by Perl and XPK, so users will have to be familiar with the overall concepts there as well.

This module is currently experimental, on top of the already-experimental nature of XS::Parse::Keyword itself.

OPTREE FUNCTIONS

The Optree::Generate module contains a selection of helper functions to allow Perl code to get access to various parts of the C-level API that would be useful when building optrees for keywords. They used to be part of this module, and so are currently re-exported for convenience, but a later version of this module may start emitting warnings when they are used this way, and eventually that may stop being provided at all.

Code needing these should import them directly:

use Optree::Generate qw( opcode newUNOP ... );

XPK FUNCTIONS

register_xs_parse_keyword

register_xs_parse_keyword "name" => %args;

Registers a new extension keyword into the XS::Parse::Keyword registry, defined using the given name and arguments.

Takes the following named arguments:

flags => INT

Optional. If present, a bitmask of the following flag constants:

XPK_FLAG_EXPR

The build phase is expected to return KEYWORD_PLUGIN_EXPR.

XPK_FLAG_STMT

The build phase is expected to return KEYWORD_PLUGIN_STMT.

XPK_FLAG_AUTOSEMI

The syntax forms a complete statement, which should be followed by ;.

pieces => ARRAY

Optional. If present, contains definitions for the syntax pieces to be parsed for the syntax of this keyword. This must be composed of a list of calls to the various XPK_... piece-generating functions; documented below.

permit_hintkey => STRING

Optional. A string value to use for the "permit_hintkey".

permit => CODE

Optional. Callback function for the "permit" phase of keyword parsing.

$ok = $permit->( $hookdata );

When invoked, it is passed a single arugment containing the (optional) hookdata value, and its result should be a boolean scalar.

At least one of permit_hintkey or permit must be provided.

check => CODE

Optional. Callback function for the "check" phase of keyword parsing.

$check->( $hookdata );

When invoked, it is passsed a single argument containing the (optional) bookdata value.

build => CODE

Callback function for the "build" phase of keyword parsing.

$ret = $build->( \$out, \@args, $hookdata );

When invoked, it is passed a SCALAR ref to store the output optree into, an ARRAY reference containing the parsed arguments, and the (optional) hookdata value.

The @args array will contain object references referring to the individual arguments parsed by the parser pieces. See "Parser Arguments".

The callback function should be build an optree as a B::OP fragment, possibly by calling the various new*OP() functions defined above, and store the eventual result into the scalar referred to by the first argument.

The callback should return one of KEYWORD_PLUGIN_EXPR or KEYWORD_PLUGIN_STMT to indicate how its syntax should be interpreted by the perl parser.

hookdata => SCALAR

Optional. If present, this scalar value is stored by the keyword definition and passed into each of the phase callbacks when invoked. If not present then undef will be passed to the callbacks instead.

Piece Type Functions

The following functions can be used to generate parsing pieces.

XPK_BLOCK

A block of code, returned in the op field.

XPK_ANONSUB

An anonymous subroutine, returned in the cv field.

XPK_ARITHEXPR

An arithemetic expression, returned in the op field.

XPK_TERMEXPR

A term expression, returned in the op field.

XPK_LISTEXPR

A list expression, returned in the op field.

XPK_IDENT, XPK_IDENT_OPT

An identifier, returned as a string in the sv field.

The _OPT variant is optional.

XPK_PACKAGENAME, XPK_PACKAGENAME_OPT

A package name, returned as a string in the sv field.

The _OPT variant is optional.

XPK_LEXVARNAME

XPK_LEXVARNAME($kind)

A lexical variable name, returned as a string in the sv field.

The $kind must be a bitmask of XPK_LEXVAR_SCALAR, XPK_LEXVAR_ARRAY, XPK_LEXVAR_HASH; or XPK_LEXVAR_ANY for convenience to set all three.

XPK_VSTRING, XPK_VSTRING_OPT

A version string, returned as a version object instance in the sv field.

The _OPT variant is optional.

XPK_LEXVAR

XPK_LEXVAR($kind)

A lexical variable that already exists in the pad, returned as a pad offset in the padix field.

$kind is specified as in XPK_LEXVARNAME.

XPK_LEXVAR_MY

XPK_LEXVAR_MY($kind)

A lexical variable, parsed as if it appeared in a my expression. It will be added to the pad and returned as a pad offset in the padix field.

XPK_COMMA

XPK_COLON

XPK_EQUALS

A literal comma, colon or equals sign. These do not appear in the arguments list.

XPK_LITERAL

XPK_LISTEXPR($string)

A literal string match. No value is returned.

This should be avoided if at all possible, in favour of the character matches above, or XPK_KEYWORD.

XPK_KEYWORD

XPK_KEYWORD($string)

A literal string match, which requires that the following text does not begin with an identifier character (thus avoiding prefix-match problems). No value is returned.

XPK_INTRO_MY

Calls the perl intro_my() function immediately. No input is consumed and no output value is generated.

XPK_SEQUENCE

XPK_SEQUENCE(@pieces)

A sub-sequence. Normally this is not necessary, as most of the structure-forming functions already take a sequence of pieces. It is mostly useful as as an option to the XPK_CHOICE function.

Nothing extra is returned, beyond the values from the individual pieces.

XPK_OPTIONAL

XPK_OPTIONAL(@pieces)

An optional sequence of pieces that may or may not be present. Returns an integer value in the i field of 0 if the sequence was not found, or 1 followed by its values if the sequence was found.

XPK_REPEATED

XPK_REPEATED(@pieces)

A repeating sequence of pieces. Returns an integer value in the i field indicating how many times the sequence repeated, followed by all the values returned by each.

XPK_CHOICE

XPK_CHOICE(@pieces)

The pieces of this function are not interpreted as a sequence, but instead as a list of possible choices. Returns an integer value in the i field indicating which choice was found, followed by all the values returned by that sequence.

The first possible choice is numbered 0. If no choice matched, it returns -1. To cause an error instead, use XPK_FAILURE.

XPK_FAILURE

XPK_FAILURE($message)

Attempting to parse this piece type will immediately cause a compile-time failure with the given message. This can be used as the final option in XPK_CHOICE to ensure a valid match.

XPK_PARENS

XPK_PARENS(@pieces)

Expects to find a sequence of pieces, all surrounded by parentheses (round brackets, ( ... )).

Nothing extra is returned, beyond the values from the individual contained pieces.

XPK_ARGS

XPK_ARGS(@pieces)

A container similar to XPK_PARENS except that the parentheses themselves are optional, similar to perl's parsing of calls to known functions.

XPK_BRACKETS

XPK_BRACKETS(@pieces)

Expects to find a sequence of pieces, all surrounded by square brackets ([ ... ]).

Nothing extra is returned, beyond the values from the individual contained pieces.

XPK_BRACES

XPK_BRACES(@pieces)

Expects to find a sequence of pieces, all surrounded by braces ({ ... }).

Nothing extra is returned, beyond the values from the individual contained pieces.

XPK_CHEVRONS

XPK_CHEVRONS(@pieces)

Expects to find a sequence of pieces, all surrounded by chevrons (angle brackets, < ... >).

Nothing extra is returned, beyond the values from the individual contained pieces.

Parser Arguments

Each of the values given in the @args array for the "build" phase callback are given as object references having the following methods

op

$op = $arg->op;

Returns an optree.

cv

$cv = $arg->cv;

Returns a CV wrapped in a CODE reference.

sv

$sv = $arg->sv;

Returns the SV itself, or undef if the optional SV was absent.

has_sv

$ok = $arg->has_sv;

Returns true if the optional SV was present (even if it was undef), or false if it was absent.

i

$i = $arg->i;

Returns an integer.

padix

$padix = $arg->padix;

Returns a pad offset index as an integer.

line

$line = $arg->line;

Returns the line number of the source text on which the piece was started.

AUTHOR

Paul Evans <leonerd@leonerd.org.uk>