Base(1).pdf

(38 KB) Pobierz
Perl version 5.10.0 documentation - ExtUtils::Constant::Base
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
http://perldoc.perl.org
Page 1
Perl version 5.10.0 documentation - ExtUtils::Constant::Base
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
croaking
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.
http://perldoc.perl.org
Page 2
Perl version 5.10.0 documentation - ExtUtils::Constant::Base
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
ITEMs
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
http://perldoc.perl.org
Page 3

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika:

Zgłoś jeśli naruszono regulamin