Provided by: perl-doc_5.38.2-3.2ubuntu0.1_all 
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 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
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
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.
AUTHOR
Nicholas Clark <nick@ccl4.org> based on the code in "h2xs" by Larry Wall and others
perl v5.38.2 2025-04-08 ExtUtils::Constant::Base(3perl)