| |
man : ExtUtils::Constant::Base(3p)
ExtUtils::ConstanPerlaProgrammers RefExtUtils::Constant::Base(3p)
NAME
ExtUtils::Constant::Base - base class for
ExtUtils::Constant objects
SYNOPSIS
require ExtUtils::Constant::Base;
@ISA = 'ExtUtils::Constant::Base';
DESCRIPTION
ExtUtils::Constant::Base provides a base implementation of
methods to generate C code to give fast constant value
lookup by named string. Currently it's mostly used
ExtUtils::Constant::XS, which generates the lookup code
for the constant() subroutine found in many XS modules.
USAGE
ExtUtils::Constant::Base exports no subroutines. The
following methods are available
header
A method returning a scalar containing definitions
needed, typically for a C header file.
memEQ_clause args_hashref
A method to return a suitable C "if" statement to
check whether name is equal to the C variable "name".
If checked_at is defined, then it is used to avoid
"memEQ" for short names, or to generate a comment to
highlight the position of the character in the
"switch" statement.
If i<checked_at> is a reference to a scalar, then
instead it gives the characters pre-checked at the
beginning, (and the number of chars by which the C
variable name has been advanced. These need to be
chopped from the front of name).
dump_names arg_hashref, ITEM...
An internal function to generate the embedded perl
code that will regenerate the constant subroutines.
default_type, types and ITEMs are the same as for
C_constant. indent is treated as number of spaces to
indent by. If "declare_types" is true a $types is
always declared in the perl code generated, if defined
and false never declared, and if undefined $types is
only declared if the values in types as passed in
cannot be inferred from default_types and the ITEMs.
assign arg_hashref, VALUE...
A method to return a suitable assignment clause. If
type is aggregate (eg PVN expects both pointer and
length) then there should be multiple VALUEs for the
components. pre and post if defined give snippets of C
code to proceed and follow the assignment. pre will be
perl v5.10.0 2008-09-30 1
ExtUtils::ConstanPerlaProgrammers RefExtUtils::Constant::Base(3p)
at the start of a block, so variables may be defined
in it.
return_clause arg_hashref, ITEM
A method to return a suitable "#ifdef" clause. ITEM is
a hashref (as passed to "C_constant" and
"match_clause". indent is the number of spaces to
indent, defaulting to 6.
switch_clause arg_hashref, NAMELEN, ITEMHASH, ITEM...
An internal method to generate a suitable "switch"
clause, called by "C_constant" ITEMs are in the hash
ref format as given in the description of
"C_constant", and must all have the names of the same
length, given by NAMELEN. ITEMHASH is a reference to
a hash, keyed by name, values being the hashrefs in
the ITEM list. (No parameters are modified, and there
can be keys in the ITEMHASH that are not in the list
of ITEMs without causing problems - the hash is passed
in to save generating it afresh for each call).
params WHAT
An "internal" method, subject to change, currently
called to allow an overriding class to cache
information that will then be passed into all the
"*param*" calls. (Yes, having to read the source to
make sense of this is considered a known bug). WHAT is
be a hashref of types the constant function will
return. In ExtUtils::Constant::XS this method is used
to returns a hashref keyed IV NV PV SV to show which
combination of pointers will be needed in the C
argument list generated by
C_constant_other_params_definition and
C_constant_other_params
dogfood arg_hashref, ITEM...
An internal function to generate the embedded perl
code that will regenerate the constant subroutines.
Parameters are the same as for C_constant.
Currently the base class does nothing and returns an
empty string.
normalise_items args, default_type, seen_types,
seen_items, ITEM...
Convert the items to a normalised form. For 8 bit and
Unicode values converts the item to an array of 1 or 2
items, both 8 bit and UTF-8 encoded.
C_constant arg_hashref, ITEM...
A function that returns a list of C subroutine
definitions that return the value and type of
constants when passed the name by the XS wrapper.
ITEM... gives a list of constant names. Each can
perl v5.10.0 2008-09-30 2
ExtUtils::ConstanPerlaProgrammers RefExtUtils::Constant::Base(3p)
either be a string, which is taken as a C macro name,
or a reference to a hash with the following keys
name The name of the constant, as seen by the perl
code.
type The type of the constant (IV, NV etc)
value A C expression for the value of the constant,
or a list of C expressions if the type is
aggregate. This defaults to the name if not
given.
macro The C pre-processor macro to use in the
"#ifdef". This defaults to the name, and is
mainly used if value is an "enum". If a
reference an array is passed then the first
element is used in place of the "#ifdef" line,
and the second element in place of the
"#endif". This allows pre-processor
constructions such as
#if defined (foo)
#if !defined (bar)
...
#endif
#endif
to be used to determine if a constant is to be
defined.
A "macro" 1 signals that the constant is
always defined, so the "#if"/"#endif" test is
omitted.
default Default value to use (instead of "croak"ing
with "your vendor has not defined...") to
return if the macro isn't defined. Specify a
reference to an array with type followed by
value(s).
pre C code to use before the assignment of the
value of the constant. This allows you to use
temporary variables to extract a value from
part of a "struct" and return this as value.
This C code is places at the start of a block,
so you can declare variables in it.
post C code to place between the assignment of
value (to a temporary) and the return from the
function. This allows you to clear up anything
in pre. Rarely needed.
def_pre
perl v5.10.0 2008-09-30 3
ExtUtils::ConstanPerlaProgrammers RefExtUtils::Constant::Base(3p)
def_post
Equivalents of pre and post for the default
value.
utf8 Generated internally. Is zero or undefined if
name is 7 bit ASCII, "no" if the name is 8 bit
(and so should only match if SvUTF8() is
false), "yes" if the name is utf8 encoded.
The internals automatically clone any name
with characters 128-255 but none 256+ (ie one
that could be either in bytes or utf8) into a
second entry which is utf8 encoded.
weight Optional sorting weight for names, to
determine the order of linear testing when
multiple names fall in the same case of a
switch clause. Higher comes earlier,
undefined defaults to zero.
In the argument hashref, package is the name of the
package, and is only used in comments inside the
generated C code. subname defaults to "constant" if
undefined.
default_type is the type returned by "ITEM"s that
don't specify their type. It defaults to the value of
"default_type()". types should be given either as a
comma separated list of types that the C subroutine
subname will generate or as a reference to a hash.
default_type will be added to the list if not present,
as will any types given in the list of ITEMs. The
resultant list should be the same list of types that
"XS_constant" is given. [Otherwise "XS_constant" and
"C_constant" may differ in the number of parameters to
the constant function. indent is currently unused and
ignored. In future it may be used to pass in
information used to change the C indentation style
used.] The best way to maintain consistency is to
pass in a hash reference and let this function update
it.
breakout governs when child functions of subname are
generated. If there are breakout or more ITEMs with
the same length of name, then the code to switch
between them is placed into a function named
subname_len, for example "constant_5" for names 5
characters long. The default breakout is 3. A single
"ITEM" is always inlined.
BUGS
Not everything is documented yet.
Probably others.
perl v5.10.0 2008-09-30 4
ExtUtils::ConstanPerlaProgrammers RefExtUtils::Constant::Base(3p)
AUTHOR
Nicholas Clark <nickATccl4.org> based on the code in "h2xs"
by Larry Wall and others
perl v5.10.0 2008-09-30 5
|
