1 package ExtUtils::Constant;
2 use vars qw (@ISA $VERSION %XS_Constant %XS_TypeSet @EXPORT_OK %EXPORT_TAGS);
7 ExtUtils::Constant - generate XS code to import C header constants
11 use ExtUtils::Constant qw (WriteConstants);
14 NAMES => [qw(FOO BAR BAZ)],
15 C_FILE => 'constants.c',
16 XS_FILE => 'constants.xs',
18 # Generates wrapper code to make the values of the constants FOO BAR BAZ
23 ExtUtils::Constant facilitates generating C and XS wrapper code to allow
24 perl modules to AUTOLOAD constants defined in C library header files.
25 It is principally used by the C<h2xs> utility, on which this code is based.
26 It doesn't contain the routines to scan header files to extract these
31 Generally one only needs to call the C<WriteConstants> function, and then
33 #include "constants.c"
35 in the C section of C<Foo.xs>
39 in the XS section of C<Foo.xs>.
41 For greater flexibility use C<constant_types()>, C<C_constant> and
42 C<XS_constant>, with which C<WriteConstants> is implemented.
44 Currently this module understands the following types. h2xs may only know
45 a subset. The sizes of the numeric types are chosen by the C<Configure>
46 script at compile time.
52 signed integer, at least 32 bits.
56 unsigned integer, the same size as I<IV>
60 floating point type, probably C<double>, possibly C<long double>
64 NUL terminated string, length will be determined with C<strlen>
68 A fixed length thing, given as a [pointer, length] pair. If you know the
69 length of a string at compile time you may use this instead of I<PV>
77 Truth. (C<PL_sv_yes>) The value is not needed (and ignored).
81 Defined Falsehood. (C<PL_sv_no>) The value is not needed (and ignored).
85 C<undef>. The value of the macro is not needed.
96 eval "use warnings; 1" or die $@;
103 $Text::Wrap::huge = 'overflow';
104 $Text::Wrap::columns = 80;
108 %EXPORT_TAGS = ( 'all' => [ qw(
109 XS_constant constant_types return_clause memEQ_clause C_stringify
110 C_constant autoload WriteConstants WriteMakefileSnippet
113 @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
117 UV => 'PUSHu((UV)iv)',
119 PV => 'PUSHp(pv, strlen(pv))',
120 PVN => 'PUSHp(pv, iv)',
122 YES => 'PUSHs(&PL_sv_yes)',
123 NO => 'PUSHs(&PL_sv_no)',
124 UNDEF => '', # implicit undef
128 IV => '*iv_return =',
129 UV => '*iv_return = (IV)',
130 NV => '*nv_return =',
131 PV => '*pv_return =',
132 PVN => ['*pv_return =', '*iv_return = (IV)'],
133 SV => '*sv_return = ',
140 =item C_stringify NAME
142 A function which returns a correctly \ escaped version of the string passed
143 suitable for C's "" or ''. It will also be valid as a perl "" string.
147 # Hopefully make a happy C identifier.
150 return unless defined $_;
152 s/([\"\'])/\\$1/g; # Grr. fix perl mode.
153 s/\n/\\n/g; # Ensure newlines don't end up in octal
158 unless ($] < 5.006) {
159 # This will elict a warning on 5.005_03 about [: :] being reserved unless
161 my $cheat = '([[:^print:]])';
162 s/$cheat/sprintf "\\%03o", ord $1/ge;
165 s/([^A-Za-z0-9_])/POSIX::isprint($1) ? $1 : sprintf "\\%03o", ord $1/ge;
172 A function returning a single scalar with C<#define> definitions for the
173 constants used internally between the generated C and XS functions.
177 sub constant_types () {
180 push @lines, "#define PERL_constant_NOTFOUND\t$start\n"; $start++;
181 push @lines, "#define PERL_constant_NOTDEF\t$start\n"; $start++;
182 foreach (sort keys %XS_Constant) {
183 push @lines, "#define PERL_constant_IS$_\t$start\n"; $start++;
185 push @lines, << 'EOT';
188 typedef double NV; /* 5.6 and later define NVTYPE, and typedef NV to it. */
191 #define aTHX_ /* 5.6 or later define this for threading support. */
194 #define pTHX_ /* 5.6 or later define this for threading support. */
198 return join '', @lines;
201 =item memEQ_clause NAME, CHECKED_AT, INDENT
203 A function to return a suitable C C<if> statement to check whether I<NAME>
204 is equal to the C variable C<name>. If I<CHECKED_AT> is defined, then it
205 is used to avoid C<memEQ> for short names, or to generate a comment to
206 highlight the position of the character in the C<switch> statement.
211 # if (memEQ(name, "thingy", 6)) {
212 # Which could actually be a character comparison or even ""
213 my ($name, $checked_at, $indent) = @_;
214 $indent = ' ' x ($indent || 4);
215 my $len = length $name;
218 return $indent . "{\n" if (defined $checked_at and $checked_at == 0);
219 # We didn't switch, drop through to the code for the 2 character string
222 if ($len < 3 and defined $checked_at) {
224 if ($checked_at == 1) {
226 } elsif ($checked_at == 0) {
229 if (defined $check) {
230 my $char = C_stringify (substr $name, $check, 1);
231 return $indent . "if (name[$check] == '$char') {\n";
234 # Could optimise a memEQ on 3 to 2 single character checks here
235 $name = C_stringify ($name);
236 my $body = $indent . "if (memEQ(name, \"$name\", $len)) {\n";
237 $body .= $indent . "/* ". (' ' x $checked_at) . '^'
238 . (' ' x ($len - $checked_at + length $len)) . " */\n"
239 if defined $checked_at;
243 =item assign INDENT, TYPE, PRE, POST, VALUE...
245 A function to return a suitable assignment clause. If I<TYPE> is aggregate
246 (eg I<PVN> expects both pointer and length) then there should be multiple
247 I<VALUE>s for the components. I<PRE> and I<POST> if defined give snippets
248 of C code to preceed and follow the assignment. I<PRE> will be at the start
249 of a block, so variables may be defined in it.
253 # Hmm. value undef to to NOTDEF? value () to do NOTFOUND?
259 my $post = shift || '';
264 $clause = $indent . "{\n$pre";
265 $clause .= ";" unless $pre =~ /;$/;
267 $close = "$indent}\n";
270 die "Can't generate code for type $type" unless exists $XS_TypeSet{$type};
271 my $typeset = $XS_TypeSet{$type};
273 die "Type $type is aggregate, but only single value given"
275 foreach (0 .. $#$typeset) {
276 $clause .= $indent . "$typeset->[$_] $_[$_];\n";
278 } elsif (defined $typeset) {
279 die "Aggregate value given for type $type"
281 $clause .= $indent . "$typeset $_[0];\n";
286 $clause .= ";" unless $post =~ /;$/;
289 $clause .= "${indent}return PERL_constant_IS$type;\n";
290 $clause .= $close if $close;
296 return_clause VALUE, TYPE, INDENT, MACRO, DEFAULT, PRE, POST, PRE, POST
298 A function to return a suitable C<#ifdef> clause. I<MACRO> defaults to
299 I<VALUE> when not defined. If I<TYPE> is aggregate (eg I<PVN> expects both
300 pointer and length) then I<VALUE> should be a reference to an array of
301 values in the order expected by the type. C<C_constant> will always call
302 this function with I<MACRO> defined, defaulting to the constant's name.
303 I<DEFAULT> if defined is an array reference giving default type and
304 value(s) if the clause generated by I<MACRO> doesn't evaluate to true.
305 The two pairs I<PRE> and I<POST> if defined give C code snippets to proceed
306 and follow the value, and the default value.
310 sub return_clause ($$$$$$$$$) {
312 # *iv_return = thingy;
313 # return PERL_constant_ISIV;
315 # return PERL_constant_NOTDEF;
317 my ($value, $type, $indent, $macro, $default, $pre, $post,
318 $def_pre, $def_post) = @_;
319 $macro = $value unless defined $macro;
320 $indent = ' ' x ($indent || 6);
326 $clause = $macro->[0];
327 } elsif ($macro ne "1") {
328 $clause = "#ifdef $macro\n";
331 # *iv_return = thingy;
332 # return PERL_constant_ISIV;
333 $clause .= assign ($indent, $type, $pre, $post,
334 ref $value ? @$value : $value);
336 if (ref $macro or $macro ne "1") {
338 $clause .= "#else\n";
340 # return PERL_constant_NOTDEF;
341 if (!defined $default) {
342 $clause .= "${indent}return PERL_constant_NOTDEF;\n";
344 my @default = ref $default ? @$default : $default;
345 $type = shift @default;
346 $clause .= assign ($indent, $type, $def_pre, $def_post, @default);
351 $clause .= $macro->[1];
353 $clause .= "#endif\n";
359 =item switch_clause INDENT, NAMELEN, ITEMHASH, ITEM...
361 An internal function to generate a suitable C<switch> clause, called by
362 C<C_constant> I<ITEM>s are in the hash ref format as given in the description
363 of C<C_constant>, and must all have the names of the same length, given by
364 I<NAMELEN> (This is not checked). I<ITEMHASH> is a reference to a hash,
365 keyed by name, values being the hashrefs in the I<ITEM> list.
366 (No parameters are modified, and there can be keys in the I<ITEMHASH> that
367 are not in the list of I<ITEM>s without causing problems).
372 my ($indent, $comment, $namelen, $items, @items) = @_;
373 $indent = ' ' x ($indent || 2);
375 my @names = sort map {$_->{name}} @items;
376 my $leader = $indent . '/* ';
377 my $follower = ' ' x length $leader;
378 my $body = $indent . "/* Names all of length $namelen. */\n";
380 $body = wrap ($leader, $follower, $comment) . "\n";
383 $body .= wrap ($leader, $follower, join (" ", @names) . " */") . "\n";
384 # Figure out what to switch on.
385 # (RMS, Spread of jump table, Position, Hashref)
386 my @best = (1e38, ~0);
387 foreach my $i (0 .. ($namelen - 1)) {
388 my ($min, $max) = (~0, 0);
391 my $char = substr $_, $i, 1;
393 $max = $ord if $ord > $max;
394 $min = $ord if $ord < $min;
395 push @{$spread{$char}}, $_;
398 # I'm going to pick the character to split on that minimises the root
399 # mean square of the number of names in each case. Normally this should
400 # be the one with the most keys, but it may pick a 7 where the 8 has
401 # one long linear search. I'm not sure if RMS or just sum of squares is
403 # $max and $min are for the tie-breaker if the root mean squares match.
404 # Assuming that the compiler may be building a jump table for the
405 # switch() then try to minimise the size of that jump table.
406 # Finally use < not <= so that if it still ties the earliest part of
407 # the string wins. Because if that passes but the memEQ fails, it may
408 # only need the start of the string to bin the choice.
409 # I think. But I'm micro-optimising. :-)
411 $ss += @$_ * @$_ foreach values %spread;
412 my $rms = sqrt ($ss / keys %spread);
413 if ($rms < $best[0] || ($rms == $best[0] && ($max - $min) < $best[1])) {
414 @best = ($rms, $max - $min, $i, \%spread);
417 die "Internal error. Failed to pick a switch point for @names"
418 unless defined $best[2];
419 # use Data::Dumper; print Dumper (@best);
420 my ($offset, $best) = @best[2,3];
421 $body .= $indent . "/* Offset $offset gives the best switch position. */\n";
422 $body .= $indent . "switch (name[$offset]) {\n";
423 foreach my $char (sort keys %$best) {
424 $body .= $indent . "case '" . C_stringify ($char) . "':\n";
425 foreach my $name (sort @{$best->{$char}}) {
426 my $thisone = $items->{$name};
427 my ($value, $macro, $default, $pre, $post, $def_pre, $def_post)
428 = @$thisone{qw (value macro default pre post def_pre def_post)};
429 $value = $name unless defined $value;
430 $macro = $name unless defined $macro;
432 # We have checked this offset.
433 $body .= memEQ_clause ($name, $offset, 2 + length $indent);
434 $body .= return_clause ($value, $thisone->{type}, 4 + length $indent,
435 $macro, $default, $pre, $post,
436 $def_pre, $def_post);
437 $body .= $indent . " }\n";
439 $body .= $indent . " break;\n";
441 $body .= $indent . "}\n";
447 An internal function. I<WHAT> should be a hashref of types the constant
448 function will return. I<params> returns a hashref keyed IV NV PV SV to show
449 which combination of pointers will be needed in the C argument list.
455 foreach (sort keys %$what) {
456 warn "ExtUtils::Constant doesn't know how to handle values of type $_" unless defined $XS_Constant{$_};
459 $params->{IV} = 1 if $what->{IV} || $what->{UV} || $what->{PVN};
460 $params->{NV} = 1 if $what->{NV};
461 $params->{PV} = 1 if $what->{PV} || $what->{PVN};
462 $params->{SV} = 1 if $what->{SV};
468 dump_names DEFAULT_TYPE, TYPES, INDENT, OPTIONS, ITEM...
470 An internal function to generate the embedded perl code that will regenerate
471 the constant subroutines. I<DEFAULT_TYPE>, I<TYPES> and I<ITEM>s are the
472 same as for C_constant. I<INDENT> is treated as number of spaces to indent
473 by. I<OPTIONS> is a hashref of options. Currently only C<declare_types> is
474 recognised. If the value is true a C<$types> is always declared in the perl
475 code generated, if defined and false never declared, and if undefined C<$types>
476 is only declared if the values in I<TYPES> as passed in cannot be inferred from
477 I<DEFAULT_TYPES> and the I<ITEM>s.
482 my ($default_type, $what, $indent, $options, @items) = @_;
483 my $declare_types = $options->{declare_types};
484 $indent = ' ' x ($indent || 0);
487 my (@simple, @complex, %used_types);
491 $type = $_->{type} || $default_type;
494 $type = $default_type;
496 $used_types{$type}++;
497 if ($type eq $default_type and 0 == ($_->{name} =~ tr/A-Za-z0-9_//c)
498 and !defined ($_->{macro}) and !defined ($_->{value})
499 and !defined ($_->{default}) and !defined ($_->{pre})
500 and !defined ($_->{post}) and !defined ($_->{def_pre})
501 and !defined ($_->{def_post})) {
502 # It's the default type, and the name consists only of A-Za-z0-9_
503 push @simple, $_->{name};
509 if (!defined $declare_types) {
510 # Do they pass in any types we weren't already using?
511 foreach (keys %$what) {
512 next if $used_types{$_};
513 $declare_types++; # Found one in $what that wasn't used.
514 last; # And one is enough to terminate this loop
517 if ($declare_types) {
518 $result = $indent . 'my $types = {map {($_, 1)} qw('
519 . join (" ", sort keys %$what) . ")};\n";
521 $result .= wrap ($indent . "my \@names = (qw(",
522 $indent . " ", join (" ", sort @simple) . ")");
524 foreach my $item (sort {$a->{name} cmp $b->{name}} @complex) {
525 my $name = C_stringify $item->{name};
526 my $line = ",\n$indent {name=>\"$name\"";
527 $line .= ", type=>\"$item->{type}\"" if defined $item->{type};
528 foreach my $thing (qw (macro value default pre post def_pre def_post)) {
529 my $value = $item->{$thing};
530 if (defined $value) {
532 $line .= ", $thing=>[\""
533 . join ('", "', map {C_stringify $_} @$value) . '"]';
535 $line .= ", $thing=>\"" . C_stringify($value) . "\"";
540 # Ensure that the enclosing C comment doesn't end
541 # by turning */ into *" . "/
542 $line =~ s!\*\/!\*" . "/!gs;
543 # gcc -Wall doesn't like finding /* inside a comment
544 $line =~ s!\/\*!/" . "\*!gs;
556 dogfood PACKAGE, SUBNAME, DEFAULT_TYPE, TYPES, INDENT, BREAKOUT, ITEM...
558 An internal function to generate the embedded perl code that will regenerate
559 the constant subroutines. Parameters are the same as for C_constant.
564 my ($package, $subname, $default_type, $what, $indent, $breakout, @items)
566 my $result = <<"EOT";
567 /* When generated this function returned values for the list of names given
568 in this section of perl code. Rather than manually editing these functions
569 to add or remove constants, which would result in this comment and section
570 of code becoming inaccurate, we recommend that you edit this section of
571 code, and use it to regenerate a new set of constant functions which you
572 then use to replace the originals.
574 Regenerate these constant functions by feeding this entire source file to
578 use ExtUtils::Constant qw (constant_types C_constant XS_constant);
581 $result .= dump_names ($default_type, $what, 0, {declare_types=>1}, @items);
584 print constant_types(); # macro defs
586 $package = C_stringify($package);
588 "foreach (C_constant (\"$package\", '$subname', '$default_type', \$types, ";
589 # The form of the indent parameter isn't defined. (Yet)
590 if (defined $indent) {
591 require Data::Dumper;
592 $Data::Dumper::Terse=1;
593 $Data::Dumper::Terse=1; # Not used once. :-)
594 chomp ($indent = Data::Dumper::Dumper ($indent));
599 $result .= ", $breakout" . ', @names) ) {
600 print $_, "\n"; # C constant subs
602 print "#### XS Section:\n";
603 print XS_constant ("' . $package . '", $types);
614 C_constant PACKAGE, SUBNAME, DEFAULT_TYPE, TYPES, INDENT, BREAKOUT, ITEM...
616 A function that returns a B<list> of C subroutine definitions that return
617 the value and type of constants when passed the name by the XS wrapper.
618 I<ITEM...> gives a list of constant names. Each can either be a string,
619 which is taken as a C macro name, or a reference to a hash with the following
626 The name of the constant, as seen by the perl code.
630 The type of the constant (I<IV>, I<NV> etc)
634 A C expression for the value of the constant, or a list of C expressions if
635 the type is aggregate. This defaults to the I<name> if not given.
639 The C pre-processor macro to use in the C<#ifdef>. This defaults to the
640 I<name>, and is mainly used if I<value> is an C<enum>. If a reference an
641 array is passed then the first element is used in place of the C<#ifdef>
642 line, and the second element in place of the C<#endif>. This allows
643 pre-processor constructions such as
651 to be used to determine if a constant is to be defined.
653 A "macro" 1 signals that the constant is always defined, so the C<#if>/C<#endif>
658 Default value to use (instead of C<croak>ing with "your vendor has not
659 defined...") to return if the macro isn't defined. Specify a reference to
660 an array with type followed by value(s).
664 C code to use before the assignment of the value of the constant. This allows
665 you to use temporary variables to extract a value from part of a C<struct>
666 and return this as I<value>. This C code is places at the start of a block,
667 so you can declare variables in it.
671 C code to place between the assignment of value (to a temporary) and the
672 return from the function. This allows you to clear up anything in I<pre>.
678 Equivalents of I<pre> and I<post> for the default value.
682 I<PACKAGE> is the name of the package, and is only used in comments inside the
685 The next 5 arguments can safely be given as C<undef>, and are mainly used
686 for recursion. I<SUBNAME> defaults to C<constant> if undefined.
688 I<DEFAULT_TYPE> is the type returned by C<ITEM>s that don't specify their
689 type. In turn it defaults to I<IV>. I<TYPES> should be given either as a comma
690 separated list of types that the C subroutine C<constant> will generate or as
691 a reference to a hash. I<DEFAULT_TYPE> will be added to the list if not
692 present, as will any types given in the list of I<ITEM>s. The resultant list
693 should be the same list of types that C<XS_constant> is given. [Otherwise
694 C<XS_constant> and C<C_constant> may differ in the number of parameters to the
695 constant function. I<INDENT> is currently unused and ignored. In future it may
696 be used to pass in information used to change the C indentation style used.]
697 The best way to maintain consistency is to pass in a hash reference and let
698 this function update it.
700 I<BREAKOUT> governs when child functions of I<SUBNAME> are generated. If there
701 are I<BREAKOUT> or more I<ITEM>s with the same length of name, then the code
702 to switch between them is placed into a function named I<SUBNAME>_I<LEN>, for
703 example C<constant_5> for names 5 characters long. The default I<BREAKOUT> is
704 3. A single C<ITEM> is always inlined.
708 # The parameter now BREAKOUT was previously documented as:
710 # I<NAMELEN> if defined signals that all the I<name>s of the I<ITEM>s are of
711 # this length, and that the constant name passed in by perl is checked and
712 # also of this length. It is used during recursion, and should be C<undef>
713 # unless the caller has checked all the lengths during code generation, and
714 # the generated subroutine is only to be called with a name of this length.
716 # As you can see it now performs this function during recursion by being a
720 my ($package, $subname, $default_type, $what, $indent, $breakout, @items)
723 $subname ||= 'constant';
724 # I'm not using this. But a hashref could be used for full formatting without
728 my ($namelen, $items);
730 # We are called recursively. We trust @items to be normalised, $what to
731 # be a hashref, and pinch %$items from our parent to save recalculation.
732 ($namelen, $items) = @$breakout;
735 $default_type ||= 'IV';
737 # Convert line of the form IV,UV,NV to hash
738 $what = {map {$_ => 1} split /,\s*/, ($what || '')};
739 # Figure out what types we're dealing with, and assign all unknowns to the
746 # Make a copy which is a normalised version of the ref passed in.
748 my ($type, $macro, $value) = @$_{qw (type macro value)};
749 $type ||= $default_type;
751 $_ = {name=>$name, type=>$type};
753 undef $macro if defined $macro and $macro eq $name;
754 $_->{macro} = $macro if defined $macro;
755 undef $value if defined $value and $value eq $name;
756 $_->{value} = $value if defined $value;
757 foreach my $key (qw(default pre post def_pre def_post)) {
758 my $value = $orig->{$key};
759 $_->{$key} = $value if defined $value;
760 # warn "$key $value";
764 $_ = {name=>$_, type=>$default_type};
765 $what->{$default_type} = 1;
767 warn "ExtUtils::Constant doesn't know how to handle values of type $_ used in macro $name" unless defined $XS_Constant{$_->{type}};
768 if (exists $items->{$name}) {
769 die "Multiple definitions for macro $name";
771 $items->{$name} = $_;
774 my $params = params ($what);
776 my ($body, @subs) = "static int\n$subname (pTHX_ const char *name";
777 $body .= ", STRLEN len" unless defined $namelen;
778 $body .= ", IV *iv_return" if $params->{IV};
779 $body .= ", NV *nv_return" if $params->{NV};
780 $body .= ", const char **pv_return" if $params->{PV};
781 $body .= ", SV **sv_return" if $params->{SV};
784 if (defined $namelen) {
785 # We are a child subroutine. Print the simple description
786 my $comment = 'When generated this function returned values for the list'
787 . ' of names given here. However, subsequent manual editing may have'
788 . ' added or removed some.';
789 $body .= switch_clause (2, $comment, $namelen, $items, @items);
791 # We are the top level.
792 $body .= " /* Initially switch on the length of the name. */\n";
793 $body .= dogfood ($package, $subname, $default_type, $what, $indent,
795 $body .= " switch (len) {\n";
796 # Need to group names of the same length
799 push @{$by_length[length $_->{name}]}, $_;
801 foreach my $i (0 .. $#by_length) {
802 next unless $by_length[$i]; # None of this length
803 $body .= " case $i:\n";
804 if (@{$by_length[$i]} == 1) {
805 my $thisone = $by_length[$i]->[0];
806 my ($name, $value, $macro, $default, $pre, $post, $def_pre, $def_post)
807 = @$thisone{qw (name value macro default pre post def_pre def_post)};
808 $value = $name unless defined $value;
809 $macro = $name unless defined $macro;
811 $body .= memEQ_clause ($name);
812 $body .= return_clause ($value, $thisone->{type}, undef, $macro,
813 $default, $pre, $post, $def_pre, $def_post);
815 } elsif (@{$by_length[$i]} < $breakout) {
816 $body .= switch_clause (4, '', $i, $items, @{$by_length[$i]});
818 # Only use the minimal set of parameters actually needed by the types
819 # of the names of this length.
821 foreach (@{$by_length[$i]}) {
822 $what->{$_->{type}} = 1;
824 $params = params ($what);
825 push @subs, C_constant ($package, "${subname}_$i", $default_type, $what,
826 $indent, [$i, $items], @{$by_length[$i]});
827 $body .= " return ${subname}_$i (aTHX_ name";
828 $body .= ", iv_return" if $params->{IV};
829 $body .= ", nv_return" if $params->{NV};
830 $body .= ", pv_return" if $params->{PV};
831 $body .= ", sv_return" if $params->{SV};
834 $body .= " break;\n";
838 $body .= " return PERL_constant_NOTFOUND;\n}\n";
839 return (@subs, $body);
842 =item XS_constant PACKAGE, TYPES, SUBNAME, C_SUBNAME
844 A function to generate the XS code to implement the perl subroutine
845 I<PACKAGE>::constant used by I<PACKAGE>::AUTOLOAD to load constants.
846 This XS code is a wrapper around a C subroutine usually generated by
847 C<C_constant>, and usually named C<constant>.
849 I<TYPES> should be given either as a comma separated list of types that the
850 C subroutine C<constant> will generate or as a reference to a hash. It should
851 be the same list of types as C<C_constant> was given.
852 [Otherwise C<XS_constant> and C<C_constant> may have different ideas about
853 the number of parameters passed to the C function C<constant>]
855 You can call the perl visible subroutine something other than C<constant> if
856 you give the parameter I<SUBNAME>. The C subroutine it calls defaults to
857 the name of the perl visible subroutine, unless you give the parameter
866 my $C_subname = shift;
867 $subname ||= 'constant';
868 $C_subname ||= $subname;
871 # Convert line of the form IV,UV,NV to hash
872 $what = {map {$_ => 1} split /,\s*/, ($what)};
874 my $params = params ($what);
882 dXSTARG; /* Faster if we have it. */
893 $xs .= " /* IV\t\tiv;\tUncomment this if you need to return IVs */\n";
898 $xs .= " /* NV\t\tnv;\tUncomment this if you need to return NVs */\n";
901 $xs .= " const char *pv;\n";
904 " /* const char\t*pv;\tUncomment this if you need to return PVs */\n";
910 const char * s = SvPV(sv, len);
914 if ($params->{IV} xor $params->{NV}) {
916 /* Change this to $C_subname(aTHX_ s, len, &iv, &nv);
917 if you need to return both NVs and IVs */
920 $xs .= " type = $C_subname(aTHX_ s, len";
921 $xs .= ', &iv' if $params->{IV};
922 $xs .= ', &nv' if $params->{NV};
923 $xs .= ', &pv' if $params->{PV};
924 $xs .= ', &sv' if $params->{SV};
928 /* Return 1 or 2 items. First is error message, or undef if no error.
929 Second, if present, is found value */
931 case PERL_constant_NOTFOUND:
932 sv = sv_2mortal(newSVpvf("%s is not a valid $package macro", s));
935 case PERL_constant_NOTDEF:
936 sv = sv_2mortal(newSVpvf(
937 "Your vendor has not defined $package macro %s, used", s));
942 foreach $type (sort keys %XS_Constant) {
943 $xs .= "\t/* Uncomment this if you need to return ${type}s\n"
944 unless $what->{$type};
945 $xs .= " case PERL_constant_IS$type:\n";
946 if (length $XS_Constant{$type}) {
953 # Do nothing. return (), which will be correctly interpreted as
957 unless ($what->{$type}) {
958 chop $xs; # Yes, another need for chop not chomp.
964 sv = sv_2mortal(newSVpvf(
965 "Unexpected return type %d while processing $package macro %s, used",
975 =item autoload PACKAGE, VERSION, AUTOLOADER
977 A function to generate the AUTOLOAD subroutine for the module I<PACKAGE>
978 I<VERSION> is the perl version the code should be backwards compatible with.
979 It defaults to the version of perl running the subroutine. If I<AUTOLOADER>
980 is true, the AUTOLOAD subroutine falls back on AutoLoader::AUTOLOAD for all
981 names that the constant() routine doesn't recognise.
985 # ' # Grr. syntax highlighters that don't grok pod.
988 my ($module, $compat_version, $autoloader) = @_;
989 $compat_version ||= $];
990 croak "Can't maintain compatibility back as far as version $compat_version"
991 if $compat_version < 5;
992 my $func = "sub AUTOLOAD {\n"
993 . " # This AUTOLOAD is used to 'autoload' constants from the constant()\n"
995 $func .= " If a constant is not found then control is passed\n"
996 . " # to the AUTOLOAD in AutoLoader." if $autoloader;
1000 . " my \$constname;\n";
1002 " our \$AUTOLOAD;\n" if ($compat_version >= 5.006);
1005 (\$constname = \$AUTOLOAD) =~ s/.*:://;
1006 croak "&${module}::constant not defined" if \$constname eq 'constant';
1007 my (\$error, \$val) = constant(\$constname);
1013 if ($error =~ /is not a valid/) {
1014 $AutoLoader::AUTOLOAD = $AUTOLOAD;
1015 goto &AutoLoader::AUTOLOAD;
1023 " if (\$error) { croak \$error; }\n";
1029 # Fixed between 5.005_53 and 5.005_61
1030 #XXX if ($] >= 5.00561) {
1031 #XXX *$AUTOLOAD = sub () { $val };
1034 *$AUTOLOAD = sub { $val };
1046 =item WriteMakefileSnippet
1048 WriteMakefileSnippet ATTRIBUTE =E<gt> VALUE [, ...]
1050 A function to generate perl code for Makefile.PL that will regenerate
1051 the constant subroutines. Parameters are named as passed to C<WriteConstants>,
1052 with the addition of C<INDENT> to specify the number of leading spaces
1055 Currently only C<INDENT>, C<NAME>, C<DEFAULT_TYPE>, C<NAMES>, C<C_FILE> and
1056 C<XS_FILE> are recognised.
1060 sub WriteMakefileSnippet {
1062 my $indent = $args{INDENT} || 2;
1064 my $result = <<"EOT";
1065 ExtUtils::Constant::WriteConstants(
1066 NAME => '$args{NAME}',
1068 DEFAULT_TYPE => '$args{DEFAULT_TYPE}',
1070 foreach (qw (C_FILE XS_FILE)) {
1071 next unless exists $args{$_};
1072 $result .= sprintf " %-12s => '%s',\n",
1079 $result =~ s/^/' 'x$indent/gem;
1080 return dump_names ($args{DEFAULT_TYPE}, undef, $indent, undef,
1085 =item WriteConstants ATTRIBUTE =E<gt> VALUE [, ...]
1087 Writes a file of C code and a file of XS code which you should C<#include>
1088 and C<INCLUDE> in the C and XS sections respectively of your module's XS
1089 code. You probaby want to do this in your C<Makefile.PL>, so that you can
1090 easily edit the list of constants without touching the rest of your module.
1091 The attributes supported are
1097 Name of the module. This must be specified
1101 The default type for the constants. If not specified C<IV> is assumed.
1105 The names of the constants are grouped by length. Generate child subroutines
1106 for each group with this number or more names in.
1110 An array of constants' names, either scalars containing names, or hashrefs
1111 as detailed in L<"C_constant">.
1115 The name of the file to write containing the C code. The default is
1120 The name of the file to write containing the XS code. The default is
1125 The perl visible name of the XS subroutine generated which will return the
1126 constants. The default is C<constant>.
1130 The name of the C subroutine generated which will return the constants.
1131 The default is I<SUBNAME>. Child subroutines have C<_> and the name
1132 length appended, so constants with 10 character names would be in
1133 C<constant_10> with the default I<XS_SUBNAME>.
1139 sub WriteConstants {
1142 C_FILE => 'constants.c',
1143 XS_FILE => 'constants.xs',
1144 SUBNAME => 'constant',
1145 DEFAULT_TYPE => 'IV',
1148 $ARGS{C_SUBNAME} ||= $ARGS{SUBNAME}; # No-one sane will have C_SUBNAME eq '0'
1150 croak "Module name not specified" unless length $ARGS{NAME};
1152 open my $c_fh, ">$ARGS{C_FILE}" or die "Can't open $ARGS{C_FILE}: $!";
1153 open my $xs_fh, ">$ARGS{XS_FILE}" or die "Can't open $ARGS{XS_FILE}: $!";
1155 # As this subroutine is intended to make code that isn't edited, there's no
1156 # need for the user to specify any types that aren't found in the list of
1160 print $c_fh constant_types(); # macro defs
1163 # indent is still undef. Until anyone implents indent style rules with it.
1164 foreach (C_constant ($ARGS{NAME}, $ARGS{C_SUBNAME}, $ARGS{DEFAULT_TYPE},
1165 $types, undef, $ARGS{BREAKOUT_AT}, @{$ARGS{NAMES}})) {
1166 print $c_fh $_, "\n"; # C constant subs
1168 print $xs_fh XS_constant ($ARGS{NAME}, $types, $ARGS{XS_SUBNAME},
1171 close $c_fh or warn "Error closing $ARGS{C_FILE}: $!";
1172 close $xs_fh or warn "Error closing $ARGS{XS_FILE}: $!";
1182 Nicholas Clark <nick@ccl4.org> based on the code in C<h2xs> by Larry Wall and