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package ExtUtils::Constant::Base;
use strict;
use vars qw($VERSION);
use Carp;
use Text::Wrap;
use ExtUtils::Constant::Utils qw(C_stringify perl_stringify);
$VERSION = '0.07';
use constant is_perl56 => ($] < 5.007 && $] > 5.005_50);
=head1 NAME
ExtUtils::Constant::Base - base class for ExtUtils::Constant objects
=head1 SYNOPSIS
require ExtUtils::Constant::Base;
@ISA = 'ExtUtils::Constant::Base';
=head1 DESCRIPTION
ExtUtils::Constant::Base provides a base implementation of methods to
generate C code to give fast constant value lookup by named string. Currently
it's mostly used ExtUtils::Constant::XS, which generates the lookup code
for the constant() subroutine found in many XS modules.
=head1 USAGE
ExtUtils::Constant::Base exports no subroutines. The following methods are
available
=over 4
=cut
sub valid_type {
# Default to assuming that you don't need different types of return data.
1;
}
sub default_type {
'';
}
=item header
A method returning a scalar containing definitions needed, typically for a
C header file.
=cut
sub header {
''
}
# This might actually be a return statement. Note that you are responsible
# for any space you might need before your value, as it lets to perform
# "tricks" such as "return KEY_" and have strings appended.
sub assignment_clause_for_type;
# In which case this might be an empty string
sub return_statement_for_type {undef};
sub return_statement_for_notdef;
sub return_statement_for_notfound;
# "#if 1" is true to a C pre-processor
sub macro_from_name {
1;
}
sub macro_from_item {
1;
}
sub macro_to_ifdef {
my ($self, $macro) = @_;
if (ref $macro) {
return $macro->[0];
}
if (defined $macro && $macro ne "" && $macro ne "1") {
return $macro ? "#ifdef $macro\n" : "#if 0\n";
}
return "";
}
sub macro_to_ifndef {
my ($self, $macro) = @_;
if (ref $macro) {
# Can't invert these stylishly, so "bodge it"
return "$macro->[0]#else\n";
}
if (defined $macro && $macro ne "" && $macro ne "1") {
return $macro ? "#ifndef $macro\n" : "#if 1\n";
}
croak "Can't generate an ifndef for unconditional code";
}
sub macro_to_endif {
my ($self, $macro) = @_;
if (ref $macro) {
return $macro->[1];
}
if (defined $macro && $macro ne "" && $macro ne "1") {
return "#endif\n";
}
return "";
}
sub name_param {
'name';
}
# This is possibly buggy, in that it's not mandatory (below, in the main
# C_constant parameters, but is expected to exist here, if it's needed)
# Buggy because if you're definitely pure 8 bit only, and will never be
# presented with your constants in utf8, the default form of C_constant can't
# be told not to do the utf8 version.
sub is_utf8_param {
'utf8';
}
sub memEQ {
"!memcmp";
}
=item memEQ_clause args_hashref
A method to return a suitable C C<if> statement to check whether I<name>
is equal to the C variable C<name>. If I<checked_at> is defined, then it
is used to avoid C<memEQ> for short names, or to generate a comment to
highlight the position of the character in the C<switch> statement.
If i<checked_at> is a reference to a scalar, then instead it gives
the characters pre-checked at the beginning, (and the number of chars by
which the C variable name has been advanced. These need to be chopped from
the front of I<name>).
=cut
sub memEQ_clause {
# if (memEQ(name, "thingy", 6)) {
# Which could actually be a character comparison or even ""
my ($self, $args) = @_;
my ($name, $checked_at, $indent) = @{$args}{qw(name checked_at indent)};
$indent = ' ' x ($indent || 4);
my $front_chop;
if (ref $checked_at) {
# regexp won't work on 5.6.1 without use utf8; in turn that won't work
# on 5.005_03.
substr ($name, 0, length $$checked_at,) = '';
$front_chop = C_stringify ($$checked_at);
undef $checked_at;
}
my $len = length $name;
if ($len < 2) {
return $indent . "{\n"
if (defined $checked_at and $checked_at == 0) or $len == 0;
# We didn't switch, drop through to the code for the 2 character string
$checked_at = 1;
}
my $name_param = $self->name_param;
if ($len < 3 and defined $checked_at) {
my $check;
if ($checked_at == 1) {
$check = 0;
} elsif ($checked_at == 0) {
$check = 1;
}
if (defined $check) {
my $char = C_stringify (substr $name, $check, 1);
# Placate 5.005 with a break in the string. I can't see a good way of
# getting it to not take [ as introducing an array lookup, even with
# ${name_param}[$check]
return $indent . "if ($name_param" . "[$check] == '$char') {\n";
}
}
if (($len == 2 and !defined $checked_at)
or ($len == 3 and defined ($checked_at) and $checked_at == 2)) {
my $char1 = C_stringify (substr $name, 0, 1);
my $char2 = C_stringify (substr $name, 1, 1);
return $indent .
"if ($name_param" . "[0] == '$char1' && $name_param" . "[1] == '$char2') {\n";
}
if (($len == 3 and defined ($checked_at) and $checked_at == 1)) {
my $char1 = C_stringify (substr $name, 0, 1);
my $char2 = C_stringify (substr $name, 2, 1);
return $indent .
"if ($name_param" . "[0] == '$char1' && $name_param" . "[2] == '$char2') {\n";
}
my $pointer = '^';
my $have_checked_last = defined ($checked_at) && $len == $checked_at + 1;
if ($have_checked_last) {
# Checked at the last character, so no need to memEQ it.
$pointer = C_stringify (chop $name);
$len--;
}
$name = C_stringify ($name);
my $memEQ = $self->memEQ();
my $body = $indent . "if ($memEQ($name_param, \"$name\", $len)) {\n";
# Put a little ^ under the letter we checked at
# Screws up for non printable and non-7 bit stuff, but that's too hard to
# get right.
if (defined $checked_at) {
$body .= $indent . "/* " . (' ' x length $memEQ)
. (' ' x length $name_param)
. (' ' x $checked_at) . $pointer
. (' ' x ($len - $checked_at + length $len)) . " */\n";
} elsif (defined $front_chop) {
$body .= $indent . "/* $front_chop"
. (' ' x ($len + 1 + length $len)) . " */\n";
}
return $body;
}
=item dump_names arg_hashref, ITEM...
An internal function to generate the embedded perl code that will regenerate
the constant subroutines. I<default_type>, I<types> and I<ITEM>s are the
same as for C_constant. I<indent> is treated as number of spaces to indent
by. If C<declare_types> is true a C<$types> is always declared in the perl
code generated, if defined and false never declared, and if undefined C<$types>
is only declared if the values in I<types> as passed in cannot be inferred from
I<default_types> and the I<ITEM>s.
=cut
sub dump_names {
my ($self, $args, @items) = @_;
my ($default_type, $what, $indent, $declare_types)
= @{$args}{qw(default_type what indent declare_types)};
$indent = ' ' x ($indent || 0);
my $result;
my (@simple, @complex, %used_types);
foreach (@items) {
my $type;
if (ref $_) {
$type = $_->{type} || $default_type;
if ($_->{utf8}) {
# For simplicity always skip the bytes case, and reconstitute this entry
# from its utf8 twin.
next if $_->{utf8} eq 'no';
# Copy the hashref, as we don't want to mess with the caller's hashref.
$_ = {%$_};
unless (is_perl56) {
utf8::decode ($_->{name});
} else {
$_->{name} = pack 'U*', unpack 'U0U*', $_->{name};
}
delete $_->{utf8};
}
} else {
$_ = {name=>$_};
$type = $default_type;
}
$used_types{$type}++;
if ($type eq $default_type
# grr 5.6.1
and length $_->{name}
and length $_->{name} == ($_->{name} =~ tr/A-Za-z0-9_//)
and !defined ($_->{macro}) and !defined ($_->{value})
and !defined ($_->{default}) and !defined ($_->{pre})
and !defined ($_->{post}) and !defined ($_->{def_pre})
and !defined ($_->{def_post}) and !defined ($_->{weight})) {
# It's the default type, and the name consists only of A-Za-z0-9_
push @simple, $_->{name};
} else {
push @complex, $_;
}
}
if (!defined $declare_types) {
# Do they pass in any types we weren't already using?
foreach (keys %$what) {
next if $used_types{$_};
$declare_types++; # Found one in $what that wasn't used.
last; # And one is enough to terminate this loop
}
}
if ($declare_types) {
$result = $indent . 'my $types = {map {($_, 1)} qw('
. join (" ", sort keys %$what) . ")};\n";
}
local $Text::Wrap::huge = 'overflow';
local $Text::Wrap::columns = 80;
$result .= wrap ($indent . "my \@names = (qw(",
$indent . " ", join (" ", sort @simple) . ")");
if (@complex) {
foreach my $item (sort {$a->{name} cmp $b->{name}} @complex) {
my $name = perl_stringify $item->{name};
my $line = ",\n$indent {name=>\"$name\"";
$line .= ", type=>\"$item->{type}\"" if defined $item->{type};
foreach my $thing (qw (macro value default pre post def_pre def_post)) {
my $value = $item->{$thing};
if (defined $value) {
if (ref $value) {
$line .= ", $thing=>[\""
. join ('", "', map {perl_stringify $_} @$value) . '"]';
} else {
$line .= ", $thing=>\"" . perl_stringify($value) . "\"";
}
}
}
$line .= "}";
# Ensure that the enclosing C comment doesn't end
# by turning */ into *" . "/
$line =~ s!\*\/!\*" . "/!gs;
# gcc -Wall doesn't like finding /* inside a comment
$line =~ s!\/\*!/" . "\*!gs;
$result .= $line;
}
}
$result .= ");\n";
$result;
}
=item assign arg_hashref, VALUE...
A method to return a suitable assignment clause. If I<type> is aggregate
(eg I<PVN> expects both pointer and length) then there should be multiple
I<VALUE>s for the components. I<pre> and I<post> if defined give snippets
of C code to proceed and follow the assignment. I<pre> will be at the start
of a block, so variables may be defined in it.
=cut
# Hmm. value undef to do NOTDEF? value () to do NOTFOUND?
sub assign {
my $self = shift;
my $args = shift;
my ($indent, $type, $pre, $post, $item)
= @{$args}{qw(indent type pre post item)};
$post ||= '';
my $clause;
my $close;
if ($pre) {
chomp $pre;
$close = "$indent}\n";
$clause = $indent . "{\n";
$indent .= " ";
$clause .= "$indent$pre";
$clause .= ";" unless $pre =~ /;$/;
$clause .= "\n";
}
confess "undef \$type" unless defined $type;
confess "Can't generate code for type $type"
unless $self->valid_type($type);
$clause .= join '', map {"$indent$_\n"}
$self->assignment_clause_for_type({type=>$type,item=>$item}, @_);
chomp $post;
if (length $post) {
$clause .= "$post";
$clause .= ";" unless $post =~ /;$/;
$clause .= "\n";
}
my $return = $self->return_statement_for_type($type);
$clause .= "$indent$return\n" if defined $return;
$clause .= $close if $close;
return $clause;
}
=item return_clause arg_hashref, ITEM
A method to return a suitable C<#ifdef> clause. I<ITEM> is a hashref
(as passed to C<C_constant> and C<match_clause>. I<indent> is the number
of spaces to indent, defaulting to 6.
=cut
sub return_clause {
##ifdef thingy
# *iv_return = thingy;
# return PERL_constant_ISIV;
##else
# return PERL_constant_NOTDEF;
##endif
my ($self, $args, $item) = @_;
my $indent = $args->{indent};
my ($name, $value, $default, $pre, $post, $def_pre, $def_post, $type)
= @$item{qw (name value default pre post def_pre def_post type)};
$value = $name unless defined $value;
my $macro = $self->macro_from_item($item);
$indent = ' ' x ($indent || 6);
unless (defined $type) {
# use Data::Dumper; print STDERR Dumper ($item);
confess "undef \$type";
}
##ifdef thingy
my $clause = $self->macro_to_ifdef($macro);
# *iv_return = thingy;
# return PERL_constant_ISIV;
$clause
.= $self->assign ({indent=>$indent, type=>$type, pre=>$pre, post=>$post,
item=>$item}, ref $value ? @$value : $value);
if (defined $macro && $macro ne "" && $macro ne "1") {
##else
$clause .= "#else\n";
# return PERL_constant_NOTDEF;
if (!defined $default) {
my $notdef = $self->return_statement_for_notdef();
$clause .= "$indent$notdef\n" if defined $notdef;
} else {
my @default = ref $default ? @$default : $default;
$type = shift @default;
$clause .= $self->assign ({indent=>$indent, type=>$type, pre=>$pre,
post=>$post, item=>$item}, @default);
}
}
##endif
$clause .= $self->macro_to_endif($macro);
return $clause;
}
sub match_clause {
# $offset defined if we have checked an offset.
my ($self, $args, $item) = @_;
my ($offset, $indent) = @{$args}{qw(checked_at indent)};
$indent = ' ' x ($indent || 4);
my $body = '';
my ($no, $yes, $either, $name, $inner_indent);
if (ref $item eq 'ARRAY') {
($yes, $no) = @$item;
$either = $yes || $no;
confess "$item is $either expecting hashref in [0] || [1]"
unless ref $either eq 'HASH';
$name = $either->{name};
} else {
confess "$item->{name} has utf8 flag '$item->{utf8}', should be false"
if $item->{utf8};
$name = $item->{name};
$inner_indent = $indent;
}
$body .= $self->memEQ_clause ({name => $name, checked_at => $offset,
indent => length $indent});
# If we've been presented with an arrayref for $item, then the user string
# contains in the range 128-255, and we need to check whether it was utf8
# (or not).
# In the worst case we have two named constants, where one's name happens
# encoded in UTF8 happens to be the same byte sequence as the second's
# encoded in (say) ISO-8859-1.
# In this case, $yes and $no both have item hashrefs.
if ($yes) {
$body .= $indent . " if (" . $self->is_utf8_param . ") {\n";
} elsif ($no) {
$body .= $indent . " if (!" . $self->is_utf8_param . ") {\n";
}
if ($either) {
$body .= $self->return_clause ({indent=>4 + length $indent}, $either);
if ($yes and $no) {
$body .= $indent . " } else {\n";
$body .= $self->return_clause ({indent=>4 + length $indent}, $no);
}
$body .= $indent . " }\n";
} else {
$body .= $self->return_clause ({indent=>2 + length $indent}, $item);
}
$body .= $indent . "}\n";
}
=item switch_clause arg_hashref, NAMELEN, ITEMHASH, ITEM...
An internal method to generate a suitable C<switch> clause, called by
C<C_constant> I<ITEM>s are in the hash ref format as given in the description
of C<C_constant>, and must all have the names of the same length, given by
I<NAMELEN>. I<ITEMHASH> is a reference to a hash, keyed by name, values being
the hashrefs in the I<ITEM> list. (No parameters are modified, and there can
be keys in the I<ITEMHASH> that are not in the list of I<ITEM>s without
causing problems - the hash is passed in to save generating it afresh for
each call).
=cut
sub switch_clause {
my ($self, $args, $namelen, $items, @items) = @_;
my ($indent, $comment) = @{$args}{qw(indent comment)};
$indent = ' ' x ($indent || 2);
local $Text::Wrap::huge = 'overflow';
local $Text::Wrap::columns = 80;
my @names = sort map {$_->{name}} @items;
my $leader = $indent . '/* ';
my $follower = ' ' x length $leader;
my $body = $indent . "/* Names all of length $namelen. */\n";
if (defined $comment) {
$body = wrap ($leader, $follower, $comment) . "\n";
$leader = $follower;
}
my @safe_names = @names;
foreach (@safe_names) {
confess sprintf "Name '$_' is length %d, not $namelen", length
unless length == $namelen;
# Argh. 5.6.1
# next unless tr/A-Za-z0-9_//c;
next if tr/A-Za-z0-9_// == length;
$_ = '"' . perl_stringify ($_) . '"';
# Ensure that the enclosing C comment doesn't end
# by turning */ into *" . "/
s!\*\/!\*"."/!gs;
# gcc -Wall doesn't like finding /* inside a comment
s!\/\*!/"."\*!gs;
}
$body .= wrap ($leader, $follower, join (" ", @safe_names) . " */") . "\n";
# Figure out what to switch on.
# (RMS, Spread of jump table, Position, Hashref)
my @best = (1e38, ~0);
# Prefer the last character over the others. (As it lets us shorten the
# memEQ clause at no cost).
foreach my $i ($namelen - 1, 0 .. ($namelen - 2)) {
my ($min, $max) = (~0, 0);
my %spread;
if (is_perl56) {
# Need proper Unicode preserving hash keys for bytes in range 128-255
# here too, for some reason. grr 5.6.1 yet again.
tie %spread, 'ExtUtils::Constant::Aaargh56Hash';
}
foreach (@names) {
my $char = substr $_, $i, 1;
my $ord = ord $char;
confess "char $ord is out of range" if $ord > 255;
$max = $ord if $ord > $max;
$min = $ord if $ord < $min;
push @{$spread{$char}}, $_;
# warn "$_ $char";
}
# I'm going to pick the character to split on that minimises the root
# mean square of the number of names in each case. Normally this should
# be the one with the most keys, but it may pick a 7 where the 8 has
# one long linear search. I'm not sure if RMS or just sum of squares is
# actually better.
# $max and $min are for the tie-breaker if the root mean squares match.
# Assuming that the compiler may be building a jump table for the
# switch() then try to minimise the size of that jump table.
# Finally use < not <= so that if it still ties the earliest part of
# the string wins. Because if that passes but the memEQ fails, it may
# only need the start of the string to bin the choice.
# I think. But I'm micro-optimising. :-)
# OK. Trump that. Now favour the last character of the string, before the
# rest.
my $ss;
$ss += @$_ * @$_ foreach values %spread;
my $rms = sqrt ($ss / keys %spread);
if ($rms < $best[0] || ($rms == $best[0] && ($max - $min) < $best[1])) {
@best = ($rms, $max - $min, $i, \%spread);
}
}
confess "Internal error. Failed to pick a switch point for @names"
unless defined $best[2];
# use Data::Dumper; print Dumper (@best);
my ($offset, $best) = @best[2,3];
$body .= $indent . "/* Offset $offset gives the best switch position. */\n";
my $do_front_chop = $offset == 0 && $namelen > 2;
if ($do_front_chop) {
$body .= $indent . "switch (*" . $self->name_param() . "++) {\n";
} else {
$body .= $indent . "switch (" . $self->name_param() . "[$offset]) {\n";
}
foreach my $char (sort keys %$best) {
confess sprintf "'$char' is %d bytes long, not 1", length $char
if length ($char) != 1;
confess sprintf "char %#X is out of range", ord $char if ord ($char) > 255;
$body .= $indent . "case '" . C_stringify ($char) . "':\n";
foreach my $thisone (sort {
# Deal with the case of an item actually being an array ref to 1 or 2
# hashrefs. Don't assign to $a or $b, as they're aliases to the
# original
my $l = ref $a eq 'ARRAY' ? ($a->[0] || $->[1]) : $a;
my $r = ref $b eq 'ARRAY' ? ($b->[0] || $->[1]) : $b;
# Sort by weight first
($r->{weight} || 0) <=> ($l->{weight} || 0)
# Sort equal weights by name
or $l->{name} cmp $r->{name}}
# If this looks evil, maybe it is. $items is a
# hashref, and we're doing a hash slice on it
@{$items}{@{$best->{$char}}}) {
# warn "You are here";
if ($do_front_chop) {
$body .= $self->match_clause ({indent => 2 + length $indent,
checked_at => \$char}, $thisone);
} else {
$body .= $self->match_clause ({indent => 2 + length $indent,
checked_at => $offset}, $thisone);
}
}
$body .= $indent . " break;\n";
}
$body .= $indent . "}\n";
return $body;
}
sub C_constant_return_type {
"static int";
}
sub C_constant_prefix_param {
'';
}
sub C_constant_prefix_param_defintion {
'';
}
sub name_param_definition {
"const char *" . $_[0]->name_param;
}
sub namelen_param {
'len';
}
sub namelen_param_definition {
'size_t ' . $_[0]->namelen_param;
}
sub C_constant_other_params {
'';
}
sub C_constant_other_params_defintion {
'';
}
=item 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 C<*param*> calls. (Yes, having to read the source to make sense of this is
considered a known bug). I<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
=cut
sub params {
'';
}
=item 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.
=cut
sub dogfood {
''
}
=item 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.
=cut
sub normalise_items
{
my $self = shift;
my $args = shift;
my $default_type = shift;
my $what = shift;
my $items = shift;
my @new_items;
foreach my $orig (@_) {
my ($name, $item);
if (ref $orig) {
# Make a copy which is a normalised version of the ref passed in.
$name = $orig->{name};
my ($type, $macro, $value) = @$orig{qw (type macro value)};
$type ||= $default_type;
$what->{$type} = 1;
$item = {name=>$name, type=>$type};
undef $macro if defined $macro and $macro eq $name;
$item->{macro} = $macro if defined $macro;
undef $value if defined $value and $value eq $name;
$item->{value} = $value if defined $value;
foreach my $key (qw(default pre post def_pre def_post weight
not_constant)) {
my $value = $orig->{$key};
$item->{$key} = $value if defined $value;
# warn "$key $value";
}
} else {
$name = $orig;
$item = {name=>$name, type=>$default_type};
$what->{$default_type} = 1;
}
warn +(ref ($self) || $self)
. "doesn't know how to handle values of type $_ used in macro $name"
unless $self->valid_type ($item->{type});
# tr///c is broken on 5.6.1 for utf8, so my original tr/\0-\177//c
# doesn't work. Upgrade to 5.8
# if ($name !~ tr/\0-\177//c || $] < 5.005_50) {
if ($name !~ /[[:^ascii:]]/ || $] < 5.005_50
|| $args->{disable_utf8_duplication}) {
# No characters outside 7 bit ASCII.
if (exists $items->{$name}) {
die "Multiple definitions for macro $name";
}
$items->{$name} = $item;
} else {
# No characters outside 8 bit. This is hardest.
if (exists $items->{$name} and ref $items->{$name} ne 'ARRAY') {
confess "Unexpected ASCII definition for macro $name";
}
# Again, 5.6.1 tr broken, so s/5\.6.*/5\.8\.0/;
# if ($name !~ tr/\0-\377//c) {
if ($name =~ tr/\0-\377// == length $name) {
# if ($] < 5.007) {
# $name = pack "C*", unpack "U*", $name;
# }
$item->{utf8} = 'no';
$items->{$name}[1] = $item;
push @new_items, $item;
# Copy item, to create the utf8 variant.
$item = {%$item};
}
# Encode the name as utf8 bytes.
unless (is_perl56) {
utf8::encode($name);
} else {
# warn "Was >$name< " . length ${name};
$name = pack 'C*', unpack 'C*', $name . pack 'U*';
# warn "Now '${name}' " . length ${name};
}
if ($items->{$name}[0]) {
die "Multiple definitions for macro $name";
}
$item->{utf8} = 'yes';
$item->{name} = $name;
$items->{$name}[0] = $item;
# We have need for the utf8 flag.
$what->{''} = 1;
}
push @new_items, $item;
}
@new_items;
}
=item C_constant arg_hashref, ITEM...
A function that returns a B<list> of C subroutine definitions that return
the value and type of constants when passed the name by the XS wrapper.
I<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
=over 8
=item name
The name of the constant, as seen by the perl code.
=item type
The type of the constant (I<IV>, I<NV> etc)
=item 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 I<name> if not given.
=item macro
The C pre-processor macro to use in the C<#ifdef>. This defaults to the
I<name>, and is mainly used if I<value> is an C<enum>. If a reference an
array is passed then the first element is used in place of the C<#ifdef>
line, and the second element in place of the C<#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 C<#if>/C<#endif>
test is omitted.
=item default
Default value to use (instead of C<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).
=item 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 C<struct>
and return this as I<value>. This C code is places at the start of a block,
so you can declare variables in it.
=item 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 I<pre>.
Rarely needed.
=item def_pre
=item def_post
Equivalents of I<pre> and I<post> for the default value.
=item 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.
=item 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.
=back
In the argument hashref, I<package> is the name of the package, and is only
used in comments inside the generated C code. I<subname> defaults to
C<constant> if undefined.
I<default_type> is the type returned by C<ITEM>s that don't specify their
type. It defaults to the value of C<default_type()>. I<types> should be given
either as a comma separated list of types that the C subroutine I<subname>
will generate or as a reference to a hash. I<default_type> will be added to
the list if not present, as will any types given in the list of I<ITEM>s. The
resultant list should be the same list of types that C<XS_constant> is
given. [Otherwise C<XS_constant> and C<C_constant> may differ in the number of
parameters to the constant function. I<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.
I<breakout> governs when child functions of I<subname> are generated. If there
are I<breakout> or more I<ITEM>s with the same length of name, then the code
to switch between them is placed into a function named I<subname>_I<len>, for
example C<constant_5> for names 5 characters long. The default I<breakout> is
3. A single C<ITEM> is always inlined.
=cut
# The parameter now BREAKOUT was previously documented as:
#
# I<NAMELEN> if defined signals that all the I<name>s of the I<ITEM>s are of
# this length, and that the constant name passed in by perl is checked and
# also of this length. It is used during recursion, and should be C<undef>
# unless the caller has checked all the lengths during code generation, and
# the generated subroutine is only to be called with a name of this length.
#
# As you can see it now performs this function during recursion by being a
# scalar reference.
sub C_constant {
my ($self, $args, @items) = @_;
my ($package, $subname, $default_type, $what, $indent, $breakout) =
@{$args}{qw(package subname default_type types indent breakout)};
$package ||= 'Foo';
$subname ||= 'constant';
# I'm not using this. But a hashref could be used for full formatting without
# breaking this API
# $indent ||= 0;
my ($namelen, $items);
if (ref $breakout) {
# We are called recursively. We trust @items to be normalised, $what to
# be a hashref, and pinch %$items from our parent to save recalculation.
($namelen, $items) = @$breakout;
} else {
$items = {};
if (is_perl56) {
# Need proper Unicode preserving hash keys.
require ExtUtils::Constant::Aaargh56Hash;
tie %$items, 'ExtUtils::Constant::Aaargh56Hash';
}
$breakout ||= 3;
$default_type ||= $self->default_type();
if (!ref $what) {
# Convert line of the form IV,UV,NV to hash
$what = {map {$_ => 1} split /,\s*/, ($what || '')};
# Figure out what types we're dealing with, and assign all unknowns to the
# default type
}
@items = $self->normalise_items ({}, $default_type, $what, $items, @items);
# use Data::Dumper; print Dumper @items;
}
my $params = $self->params ($what);
# Probably "static int"
my ($body, @subs);
$body = $self->C_constant_return_type($params) . "\n$subname ("
# Eg "pTHX_ "
. $self->C_constant_prefix_param_defintion($params)
# Probably "const char *name"
. $self->name_param_definition($params);
# Something like ", STRLEN len"
$body .= ", " . $self->namelen_param_definition($params)
unless defined $namelen;
$body .= $self->C_constant_other_params_defintion($params);
$body .= ") {\n";
if (defined $namelen) {
# We are a child subroutine. Print the simple description
my $comment = 'When generated this function returned values for the list'
. ' of names given here. However, subsequent manual editing may have'
. ' added or removed some.';
$body .= $self->switch_clause ({indent=>2, comment=>$comment},
$namelen, $items, @items);
} else {
# We are the top level.
$body .= " /* Initially switch on the length of the name. */\n";
$body .= $self->dogfood ({package => $package, subname => $subname,
default_type => $default_type, what => $what,
indent => $indent, breakout => $breakout},
@items);
$body .= ' switch ('.$self->namelen_param().") {\n";
# Need to group names of the same length
my @by_length;
foreach (@items) {
push @{$by_length[length $_->{name}]}, $_;
}
foreach my $i (0 .. $#by_length) {
next unless $by_length[$i]; # None of this length
$body .= " case $i:\n";
if (@{$by_length[$i]} == 1) {
my $only_thing = $by_length[$i]->[0];
if ($only_thing->{utf8}) {
if ($only_thing->{utf8} eq 'yes') {
# With utf8 on flag item is passed in element 0
$body .= $self->match_clause (undef, [$only_thing]);
} else {
# With utf8 off flag item is passed in element 1
$body .= $self->match_clause (undef, [undef, $only_thing]);
}
} else {
$body .= $self->match_clause (undef, $only_thing);
}
} elsif (@{$by_length[$i]} < $breakout) {
$body .= $self->switch_clause ({indent=>4},
$i, $items, @{$by_length[$i]});
} else {
# Only use the minimal set of parameters actually needed by the types
# of the names of this length.
my $what = {};
foreach (@{$by_length[$i]}) {
$what->{$_->{type}} = 1;
$what->{''} = 1 if $_->{utf8};
}
$params = $self->params ($what);
push @subs, $self->C_constant ({package=>$package,
subname=>"${subname}_$i",
default_type => $default_type,
types => $what, indent => $indent,
breakout => [$i, $items]},
@{$by_length[$i]});
$body .= " return ${subname}_$i ("
# Eg "aTHX_ "
. $self->C_constant_prefix_param($params)
# Probably "name"
. $self->name_param($params);
$body .= $self->C_constant_other_params($params);
$body .= ");\n";
}
$body .= " break;\n";
}
$body .= " }\n";
}
my $notfound = $self->return_statement_for_notfound();
$body .= " $notfound\n" if $notfound;
$body .= "}\n";
return (@subs, $body);
}
1;
__END__
=back
=head1 BUGS
Not everything is documented yet.
Probably others.
=head1 AUTHOR
Nicholas Clark <nick@ccl4.org> based on the code in C<h2xs> by Larry Wall and
others