Provided by: libdevel-callparser-perl_0.002-2_amd64 
NAME
Devel::CallParser - custom parsing attached to subroutines
SYNOPSIS
# to generate header prior to XS compilation
perl -MDevel::CallParser=callparser0_h \
-e 'print callparser0_h' > callparser0.h
perl -MDevel::CallParser=callparser1_h \
-e 'print callparser1_h' > callparser1.h
# in Perl part of module
use Devel::CallParser;
/* in XS */
#include "callparser0.h"
cv_get_call_parser(cv, &psfun, &psobj);
static OP *my_psfun(pTHX_ GV *namegv, SV *psobj, U32 *flagsp);
cv_set_call_parser(cv, my_psfun, psobj);
#include "callparser1.h"
cv_get_call_parser(cv, &psfun, &psobj);
static OP *my_psfun(pTHX_ GV *namegv, SV *psobj, U32 *flagsp);
cv_set_call_parser(cv, my_psfun, psobj);
args = parse_args_parenthesised(&flags);
args = parse_args_nullary(&flags);
args = parse_args_unary(&flags);
args = parse_args_list(&flags);
args = parse_args_block_list(&flags);
args = parse_args_proto(namegv, protosv, &flags);
args = parse_args_proto_or_list(namegv, protosv, &flags);
DESCRIPTION
This module provides a C API, for XS modules, concerned with custom parsing. It is
centred around the function "cv_set_call_parser", which allows XS code to attach a magical
annotation to a Perl subroutine, resulting in resolvable calls to that subroutine having
their arguments parsed by arbitrary C code. (This is a more conveniently structured
facility than the core's "PL_keyword_plugin" API.) This module makes "cv_set_call_parser"
and several supporting functions available.
This module provides the implementation of the functions at runtime. It also, at compile
time, supplies the C header file and link library which provide access to the functions.
In normal use, "callparser0_h"/"callparser1_h" and "callparser_linkable" should be called
at build time (not authoring time) for the module that wishes to use the C functions.
CONSTANTS
callparser0_h
Content of a C header file, intended to be named ""callparser0.h"". It is to be
included in XS code, and "perl.h" must be included first. When the XS module is
loaded at runtime, the "Devel::CallParser" module must be loaded first. This will
result in a limited form of the C functions "cv_get_call_parser" and
"cv_set_call_parser" being available to the XS code.
The "cv_get_call_parser" and "cv_set_call_parser" functions supplied by this header
are mostly as described below. However, for subroutines that have default argument
parsing behaviour, "cv_get_call_parser" will return null pointers for the parsing
function and its SV argument, rather than pointing to a real function that implements
default parsing. Correspondingly, "cv_set_call_parser" will accept such a pair of
null pointers to restore default argument parsing for a subroutine. The advantage of
these modified semantics is that this much of the functionality is available on Perl
versions where it is not possible to implement standard argument parsing as a distinct
function. This is the case on all Perl versions prior to 5.13.8.
This header is only available on Perl versions 5.11.2 and higher.
callparser1_h
Content of a C header file, intended to be named ""callparser1.h"". It is to be
included in XS code, and "perl.h" must be included first. When the XS module is
loaded at runtime, the "Devel::CallParser" module must be loaded first. This will
result in the C functions "cv_get_call_parser", "cv_set_call_parser",
"parse_args_parenthesised", "parse_args_nullary", "parse_args_unary",
"parse_args_list", "parse_args_block_list", "parse_args_proto", and
"parse_args_proto_or_list", as defined below, being available to the XS code.
This header is only available on Perl versions 5.13.8 and higher.
callparser_linkable
List of names of files that must be used as additional objects when linking an XS
module that uses the C functions supplied by this module. This list will be empty on
many platforms.
C FUNCTIONS
cv_get_call_parser
Retrieves the function that will be used to parse the arguments for a call to cv.
Specifically, the function is used for a subroutine call, not marked with "&", where
the callee can be identified at compile time as cv.
The C-level function pointer is returned in *psfun_p, and an SV argument for it is
returned in *psobj_p. The function is intended to be called in this manner:
argsop = (*psfun_p)(aTHX_ namegv, (*psobj_p), &flags);
This call is to be made when the parser has just scanned and accepted a bareword and
determined that it begins the syntax of a call to cv. namegv is a GV supplying the
name that should be used by the parsing function to refer to the callee if it needs to
emit any diagnostics, and flags is a "U32" that the parsing function can write to as
an additional output. It is permitted to apply the parsing function in non-standard
situations, such as to a call to a different subroutine.
The parsing function's main output is an op tree describing a list of argument
expressions. This may be null for an empty list. The argument expressions will be
combined with the expression that identified cv and used to build an "entersub" op
describing a complete subroutine call. The parsing function may also set flag bits in
flags for special effects. The bit "CALLPARSER_PARENS" indicates that the argument
list was fully parenthesised, which makes a difference only in obscure situations.
The bit "CALLPARSER_STATEMENT" indicates that what was parsed was syntactically not an
expression but a statement.
By default, the parsing function is Perl_parse_args_proto_or_list, and the SV
parameter is cv itself. This implements standard subroutine argument parsing. It can
be changed, for a particular subroutine, by "cv_set_call_parser".
void cv_get_call_parser(CV *cv, Perl_call_parser *psfun_p,
SV **psobj_p)
cv_set_call_parser
Sets the function that will be used to parse the arguments for a call to cv.
Specifically, the function is used for a subroutine call, not marked with "&", where
the callee can be identified at compile time as cv.
The C-level function pointer is supplied in psfun, and an SV argument for it is
supplied in psobj. The function is intended to be called in this manner:
argsop = (*psfun_p)(aTHX_ namegv, (*psobj_p), &flags);
This call is to be made when the parser has just scanned and accepted a bareword and
determined that it begins the syntax of a call to cv. namegv is a GV supplying the
name that should be used by the parsing function to refer to the callee if it needs to
emit any diagnostics, and flags is a "U32" that the parsing function can write to as
an additional output. It is permitted to apply the parsing function in non-standard
situations, such as to a call to a different subroutine.
The parsing function's main output is an op tree describing a list of argument
expressions. This may be null for an empty list. The argument expressions will be
combined with the expression that identified cv and used to build an "entersub" op
describing a complete subroutine call. The parsing function may also set flag bits in
flags for special effects. The bit "CALLPARSER_PARENS" indicates that the argument
list was fully parenthesised, which makes a difference only in obscure situations.
The bit "CALLPARSER_STATEMENT" indicates that what was parsed was syntactically not an
expression but a statement.
The current setting for a particular CV can be retrieved by "cv_get_call_parser".
void cv_set_call_parser(CV *cv, Perl_call_parser psfun,
SV *psobj)
parse_args_parenthesised
Parse a parenthesised argument list for a subroutine call. The argument list consists
of an optional expression enclosed in parentheses. This is the syntax that is used
for any subroutine call where the first thing following the subroutine name is an open
parenthesis. It is used regardless of the subroutine's prototype.
The op tree representing the argument list is returned. The bit "CALLPARSER_PARENS"
is set in *flags_p, to indicate that the argument list was fully parenthesised.
OP *parse_args_parenthesised(U32 *flags_p)
parse_args_nullary
Parse an argument list for a call to a subroutine that is syntactically a nullary
function. The argument list is either parenthesised or completely absent. This is
the syntax that is used for a call to a subroutine with a "()" prototype.
The op tree representing the argument list is returned. The bit "CALLPARSER_PARENS"
is set in *flags_p if the argument list was parenthesised.
OP *parse_args_nullary(U32 *flags_p)
parse_args_unary
Parse an argument list for a call to a subroutine that is syntactically a unary
function. The argument list is either parenthesised, absent, or consists of an
unparenthesised arithmetic expression. This is the syntax that is used for a call to
a subroutine with prototype "($)", "(;$)", or certain similar prototypes.
The op tree representing the argument list is returned. The bit "CALLPARSER_PARENS"
is set in *flags_p if the argument list was parenthesised.
OP *parse_args_unary(U32 *flags_p)
parse_args_list
Parse an argument list for a call to a subroutine that is syntactically a list
function. The argument list is either parenthesised, absent, or consists of an
unparenthesised list expression. This is the syntax that is used for a call to a
subroutine with any prototype that does not have special handling (such as "(@)" or
"($$)") or with no prototype at all.
The op tree representing the argument list is returned. The bit "CALLPARSER_PARENS"
is set in *flags_p if the argument list was parenthesised.
OP *parse_args_list(U32 *flags_p)
parse_args_block_list
Parse an argument list for a call to a subroutine that is syntactically a block-and-
list function. The argument list is either parenthesised, absent, an unparenthesised
list expression, or consists of a code block followed by an optionl list expression.
Where the first thing seen is an open brace, it is always interpreted as a code block.
This is the syntax that is used for a call to a subroutine with any prototype
beginning with "&", such as "(&@)" or "(&$)".
The op tree representing the argument list is returned. The bit "CALLPARSER_PARENS"
is set in *flags_p if the argument list was parenthesised.
OP *parse_args_block_list(U32 *flags_p)
parse_args_proto
Parse a subroutine argument list based on a subroutine prototype. The syntax used for
the argument list will be that implemented by "parse_args_nullary",
"parse_args_unary", "parse_args_list", or "parse_args_block_list", depending on the
prototype. This is the standard treatment used on a subroutine call, not marked with
"&", where the callee can be identified at compile time and has a prototype.
protosv supplies the subroutine prototype to be applied to the call. It may be a
normal defined scalar, of which the string value will be used. Alternatively, for
convenience, it may be a subroutine object (a "CV*" that has been cast to "SV*") which
has a prototype.
The namegv parameter would be used to refer to the callee if required in any error
message, but currently no message does so.
The op tree representing the argument list is returned. The bit "CALLPARSER_PARENS"
is set in *flags_p if the argument list was parenthesised.
OP *parse_args_proto(GV *namegv, SV *protosv, U32 *flags_p)
parse_args_proto_or_list
Parse a subroutine argument list either based on a subroutine prototype or using
default list-function syntax. The syntax used for the argument list will be that
implemented by "parse_args_nullary", "parse_args_unary", "parse_args_list", or
"parse_args_block_list", depending on the prototype. This is the standard treatment
used on a subroutine call, not marked with "&", where the callee can be identified at
compile time.
protosv supplies the subroutine prototype to be applied to the call, or indicates that
there is no prototype. It may be a normal scalar, in which case if it is defined then
the string value will be used as a prototype, and if it is undefined then there is no
prototype. Alternatively, for convenience, it may be a subroutine object (a "CV*"
that has been cast to "SV*"), of which the prototype will be used if it has one.
The namegv parameter would be used to refer to the callee if required in any error
message, but currently no message does so.
The op tree representing the argument list is returned. The bit "CALLPARSER_PARENS"
is set in *flags_p if the argument list was parenthesised.
OP *parse_args_proto_or_list(GV *namegv, SV *protosv,
U32 *flags_p)
BUGS
Due to reliance on Perl core features to do anything interesting, only a very limited form
of custom parsing is possible prior to Perl 5.13.8, and none at all prior to Perl 5.11.2.
The way this module determines which parsing code to use for a subroutine conflicts with
the expectations of some particularly tricky modules that use nasty hacks to perform
custom parsing without proper support from the Perl core. In particular, this module is
incompatible with versions of Devel::Declare prior to 0.006004 and versions of Data::Alias
prior to 1.13. An arrangement has been reached that allows later versions of those
modules to coexist with this module.
Custom parsing code is only invoked if the subroutine to which it is attached is invoked
using an unqualified name. For example, the name "foo" works, but the name "main::foo"
will not, despite referring to the same subroutine. This is an unavoidable limitation
imposed by the core's interim facility for custom parser plugins. This should be resolved
if the API provided by this module, or something similar, migrates into the core in a
future version of Perl.
SEE ALSO
Devel::CallChecker
AUTHOR
Andrew Main (Zefram) <zefram@fysh.org>
COPYRIGHT
Copyright (C) 2011, 2013 Andrew Main (Zefram) <zefram@fysh.org>
LICENSE
This module is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.