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.
95 require 5.006; # I think, for [:cntrl:] in REGEXP
102 $Text::Wrap::huge = 'overflow';
103 $Text::Wrap::columns = 80;
107 %EXPORT_TAGS = ( 'all' => [ qw(
108 XS_constant constant_types return_clause memEQ_clause C_stringify
109 C_constant autoload WriteConstants
112 @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
116 UV => 'PUSHu((UV)iv)',
118 PV => 'PUSHp(pv, strlen(pv))',
119 PVN => 'PUSHp(pv, iv)',
121 YES => 'PUSHs(&PL_sv_yes)',
122 NO => 'PUSHs(&PL_sv_no)',
123 UNDEF => '', # implicit undef
127 IV => '*iv_return =',
128 UV => '*iv_return = (IV)',
129 NV => '*nv_return =',
130 PV => '*pv_return =',
131 PVN => ['*pv_return =', '*iv_return = (IV)'],
132 SV => '*sv_return = ',
139 =item C_stringify NAME
141 A function which returns a correctly \ escaped version of the string passed
142 suitable for C's "" or ''. It will also be valid as a perl "" string.
146 # Hopefully make a happy C identifier.
149 return unless defined $_;
151 s/([\"\'])/\\$1/g; # Grr. fix perl mode.
152 s/\n/\\n/g; # Ensure newlines don't end up in octal
157 s/([[:cntrl:]])/sprintf "\\%03o", ord $1/ge;
158 s/\177/\\177/g; # DEL doesn't seem to be a [:cntrl:]
164 A function returning a single scalar with C<#define> definitions for the
165 constants used internally between the generated C and XS functions.
169 sub constant_types () {
172 push @lines, "#define PERL_constant_NOTFOUND\t$start\n"; $start++;
173 push @lines, "#define PERL_constant_NOTDEF\t$start\n"; $start++;
174 foreach (sort keys %XS_Constant) {
175 push @lines, "#define PERL_constant_IS$_\t$start\n"; $start++;
177 push @lines, << 'EOT';
180 typedef double NV; /* 5.6 and later define NVTYPE, and typedef NV to it. */
184 return join '', @lines;
187 =item memEQ_clause NAME, CHECKED_AT, INDENT
189 A function to return a suitable C C<if> statement to check whether I<NAME>
190 is equal to the C variable C<name>. If I<CHECKED_AT> is defined, then it
191 is used to avoid C<memEQ> for short names, or to generate a comment to
192 highlight the position of the character in the C<switch> statement.
197 # if (memEQ(name, "thingy", 6)) {
198 # Which could actually be a character comparison or even ""
199 my ($name, $checked_at, $indent) = @_;
200 $indent = ' ' x ($indent || 4);
201 my $len = length $name;
204 return $indent . "{\n" if (defined $checked_at and $checked_at == 0);
205 # We didn't switch, drop through to the code for the 2 character string
208 if ($len < 3 and defined $checked_at) {
210 if ($checked_at == 1) {
212 } elsif ($checked_at == 0) {
215 if (defined $check) {
216 my $char = C_stringify (substr $name, $check, 1);
217 return $indent . "if (name[$check] == '$char') {\n";
220 # Could optimise a memEQ on 3 to 2 single character checks here
221 $name = C_stringify ($name);
222 my $body = $indent . "if (memEQ(name, \"$name\", $len)) {\n";
223 $body .= $indent . "/* ". (' ' x $checked_at) . '^'
224 . (' ' x ($len - $checked_at + length $len)) . " */\n"
225 if defined $checked_at;
229 =item assign INDENT, TYPE, PRE, POST, VALUE...
231 A function to return a suitable assignment clause. If I<TYPE> is aggregate
232 (eg I<PVN> expects both pointer and length) then there should be multiple
233 I<VALUE>s for the components. I<PRE> and I<POST> if defined give snippets
234 of C code to preceed and follow the assignment. I<PRE> will be at the start
235 of a block, so variables may be defined in it.
239 # Hmm. value undef to to NOTDEF? value () to do NOTFOUND?
245 my $post = shift || '';
250 $clause = $indent . "{\n$pre";
251 $clause .= ";" unless $pre =~ /;$/;
253 $close = "$indent}\n";
256 die "Can't generate code for type $type" unless exists $XS_TypeSet{$type};
257 my $typeset = $XS_TypeSet{$type};
259 die "Type $type is aggregate, but only single value given"
261 foreach (0 .. $#$typeset) {
262 $clause .= $indent . "$typeset->[$_] $_[$_];\n";
264 } elsif (defined $typeset) {
265 die "Aggregate value given for type $type"
267 $clause .= $indent . "$typeset $_[0];\n";
272 $clause .= ";" unless $post =~ /;$/;
275 $clause .= "${indent}return PERL_constant_IS$type;\n";
276 $clause .= $close if $close;
280 =item return_clause VALUE, TYPE, INDENT, MACRO, DEFAULT, PRE, POST, PRE, POST
282 A function to return a suitable C<#ifdef> clause. I<MACRO> defaults to
283 I<VALUE> when not defined. If I<TYPE> is aggregate (eg I<PVN> expects both
284 pointer and length) then I<VALUE> should be a reference to an array of
285 values in the order expected by the type. C<C_constant> will always call
286 this function with I<MACRO> defined, defaulting to the constant's name.
287 I<DEFAULT> if defined is an array reference giving default type and and
288 value(s) if the clause generated by I<MACRO> doesn't evaluate to true.
289 The two pairs I<PRE> and I<POST> if defined give C code snippets to proceed
290 and follow the value, and the default value.
294 sub return_clause ($$$$$$$$$) {
296 # *iv_return = thingy;
297 # return PERL_constant_ISIV;
299 # return PERL_constant_NOTDEF;
301 my ($value, $type, $indent, $macro, $default, $pre, $post,
302 $def_pre, $def_post) = @_;
303 $macro = $value unless defined $macro;
304 $indent = ' ' x ($indent || 6);
310 $clause = $macro->[0];
311 } elsif ($macro ne "1") {
312 $clause = "#ifdef $macro\n";
315 # *iv_return = thingy;
316 # return PERL_constant_ISIV;
317 $clause .= assign ($indent, $type, $pre, $post,
318 ref $value ? @$value : $value);
320 if (ref $macro or $macro ne "1") {
322 $clause .= "#else\n";
324 # return PERL_constant_NOTDEF;
325 if (!defined $default) {
326 $clause .= "${indent}return PERL_constant_NOTDEF;\n";
328 my @default = ref $default ? @$default : $default;
329 $type = shift @default;
330 $clause .= assign ($indent, $type, $def_pre, $def_post, @default);
335 $clause .= $macro->[1];
337 $clause .= "#endif\n";
343 =item switch_clause INDENT, NAMELEN, ITEMHASH, ITEM...
345 An internal function to generate a suitable C<switch> clause, called by
346 C<C_constant> I<ITEM>s are in the hash ref format as given in the description
347 of C<C_constant>, and must all have the names of the same length, given by
348 I<NAMELEN> (This is not checked). I<ITEMHASH> is a reference to a hash,
349 keyed by name, values being the hashrefs in the I<ITEM> list.
350 (No parameters are modified, and there can be keys in the I<ITEMHASH> that
351 are not in the list of I<ITEM>s without causing problems).
356 my ($indent, $comment, $namelen, $items, @items) = @_;
357 $indent = ' ' x ($indent || 2);
359 my @names = sort map {$_->{name}} @items;
360 my $leader = $indent . '/* ';
361 my $follower = ' ' x length $leader;
362 my $body = $indent . "/* Names all of length $namelen. */\n";
364 $body = wrap ($leader, $follower, $comment) . "\n";
367 $body .= wrap ($leader, $follower, join (" ", @names) . " */") . "\n";
368 # Figure out what to switch on.
369 # (RMS, Spread of jump table, Position, Hashref)
370 my @best = (1e38, ~0);
371 foreach my $i (0 .. ($namelen - 1)) {
372 my ($min, $max) = (~0, 0);
375 my $char = substr $_, $i, 1;
377 $max = $ord if $ord > $max;
378 $min = $ord if $ord < $min;
379 push @{$spread{$char}}, $_;
382 # I'm going to pick the character to split on that minimises the root
383 # mean square of the number of names in each case. Normally this should
384 # be the one with the most keys, but it may pick a 7 where the 8 has
385 # one long linear search. I'm not sure if RMS or just sum of squares is
387 # $max and $min are for the tie-breaker if the root mean squares match.
388 # Assuming that the compiler may be building a jump table for the
389 # switch() then try to minimise the size of that jump table.
390 # Finally use < not <= so that if it still ties the earliest part of
391 # the string wins. Because if that passes but the memEQ fails, it may
392 # only need the start of the string to bin the choice.
393 # I think. But I'm micro-optimising. :-)
395 $ss += @$_ * @$_ foreach values %spread;
396 my $rms = sqrt ($ss / keys %spread);
397 if ($rms < $best[0] || ($rms == $best[0] && ($max - $min) < $best[1])) {
398 @best = ($rms, $max - $min, $i, \%spread);
401 die "Internal error. Failed to pick a switch point for @names"
402 unless defined $best[2];
403 # use Data::Dumper; print Dumper (@best);
404 my ($offset, $best) = @best[2,3];
405 $body .= $indent . "/* Offset $offset gives the best switch position. */\n";
406 $body .= $indent . "switch (name[$offset]) {\n";
407 foreach my $char (sort keys %$best) {
408 $body .= $indent . "case '" . C_stringify ($char) . "':\n";
409 foreach my $name (sort @{$best->{$char}}) {
410 my $thisone = $items->{$name};
411 my ($value, $macro, $default, $pre, $post, $def_pre, $def_post)
412 = @$thisone{qw (value macro default pre post def_pre def_post)};
413 $value = $name unless defined $value;
414 $macro = $name unless defined $macro;
416 # We have checked this offset.
417 $body .= memEQ_clause ($name, $offset, 2 + length $indent);
418 $body .= return_clause ($value, $thisone->{type}, 4 + length $indent,
419 $macro, $default, $pre, $post,
420 $def_pre, $def_post);
421 $body .= $indent . " }\n";
423 $body .= $indent . " break;\n";
425 $body .= $indent . "}\n";
431 An internal function. I<WHAT> should be a hashref of types the constant
432 function will return. I<params> returns a hashref keyed IV NV PV SV to show
433 which combination of pointers will be needed in the C argument list.
439 foreach (sort keys %$what) {
440 warn "ExtUtils::Constant doesn't know how to handle values of type $_" unless defined $XS_Constant{$_};
443 $params->{IV} = 1 if $what->{IV} || $what->{UV} || $what->{PVN};
444 $params->{NV} = 1 if $what->{NV};
445 $params->{PV} = 1 if $what->{PV} || $what->{PVN};
446 $params->{SV} = 1 if $what->{SV};
452 dump_names PACKAGE, SUBNAME, DEFAULT_TYPE, TYPES, INDENT, BREAKOUT, ITEM...
454 An internal function to generate the embedded perl code that will regenerate
455 the constant subroutines. Parameters are the same as for C_constant.
460 my ($package, $subname, $default_type, $what, $indent, $breakout, @items)
462 my (@simple, @complex);
464 my $type = $_->{type} || $default_type;
465 if ($type eq $default_type and 0 == ($_->{name} =~ tr/A-Za-z0-9_//c)
466 and !defined ($_->{macro}) and !defined ($_->{value})
467 and !defined ($_->{default}) and !defined ($_->{pre})
468 and !defined ($_->{post}) and !defined ($_->{def_pre})
469 and !defined ($_->{def_post})) {
470 # It's the default type, and the name consists only of A-Za-z0-9_
471 push @simple, $_->{name};
476 my $result = <<"EOT";
477 /* When generated this function returned values for the list of names given
478 in this section of perl code. Rather than manually editing these functions
479 to add or remove constants, which would result in this comment and section
480 of code becoming inaccurate, we recommend that you edit this section of
481 code, and use it to regenerate a new set of constant functions which you
482 then use to replace the originals.
484 Regenerate these constant functions by feeding this entire source file to
488 use ExtUtils::Constant qw (constant_types C_constant XS_constant);
491 $result .= 'my $types = {map {($_, 1)} qw(' . join (" ", sort keys %$what)
493 $result .= wrap ("my \@names = (qw(",
494 " ", join (" ", sort @simple) . ")");
496 foreach my $item (sort {$a->{name} cmp $b->{name}} @complex) {
497 my $name = C_stringify $item->{name};
498 my $line = ",\n {name=>\"$name\"";
499 $line .= ", type=>\"$item->{type}\"" if defined $item->{type};
500 foreach my $thing (qw (macro value default pre post def_pre def_post)) {
501 my $value = $item->{$thing};
502 if (defined $value) {
504 $line .= ", $thing=>[\""
505 . join ('", "', map {C_stringify $_} @$value) . '"]';
507 $line .= ", $thing=>\"" . C_stringify($value) . "\"";
512 # Ensure that the enclosing C comment doesn't end
513 # by turning */ into *" . "/
514 $line =~ s!\*\/!\*" . "/!gs;
515 # gcc -Wall doesn't like finding /* inside a comment
516 $line =~ s!\/\*!/" . "\*!gs;
524 print constant_types(); # macro defs
526 $package = C_stringify($package);
528 "foreach (C_constant (\"$package\", '$subname', '$default_type', \$types, ";
529 # The form of the indent parameter isn't defined. (Yet)
530 if (defined $indent) {
531 require Data::Dumper;
532 $Data::Dumper::Terse=1;
533 $Data::Dumper::Terse=1; # Not used once. :-)
534 chomp ($indent = Data::Dumper::Dumper ($indent));
539 $result .= ", $breakout" . ', @names) ) {
540 print $_, "\n"; # C constant subs
542 print "#### XS Section:\n";
543 print XS_constant ("' . $package . '", $types);
554 C_constant PACKAGE, SUBNAME, DEFAULT_TYPE, TYPES, INDENT, BREAKOUT, ITEM...
556 A function that returns a B<list> of C subroutine definitions that return
557 the value and type of constants when passed the name by the XS wrapper.
558 I<ITEM...> gives a list of constant names. Each can either be a string,
559 which is taken as a C macro name, or a reference to a hash with the following
566 The name of the constant, as seen by the perl code.
570 The type of the constant (I<IV>, I<NV> etc)
574 A C expression for the value of the constant, or a list of C expressions if
575 the type is aggregate. This defaults to the I<name> if not given.
579 The C pre-processor macro to use in the C<#ifdef>. This defaults to the
580 I<name>, and is mainly used if I<value> is an C<enum>. If a reference an
581 array is passed then the first element is used in place of the C<#ifdef>
582 line, and the second element in place of the C<#endif>. This allows
583 pre-processor constructions such as
591 to be used to determine if a constant is to be defined.
593 A "macro" 1 signals that the constant is always defined, so the C<#if>/C<#endif>
598 Default value to use (instead of C<croak>ing with "your vendor has not
599 defined...") to return if the macro isn't defined. Specify a reference to
600 an array with type followed by value(s).
604 C code to use before the assignment of the value of the constant. This allows
605 you to use temporary variables to extract a value from part of a C<struct>
606 and return this as I<value>. This C code is places at the start of a block,
607 so you can declare variables in it.
611 C code to place between the assignment of value (to a temporary) and the
612 return from the function. This allows you to clear up anything in I<pre>.
618 Equivalents of I<pre> and I<post> for the default value.
622 I<PACKAGE> is the name of the package, and is only used in comments inside the
625 The next 5 arguments can safely be given as C<undef>, and are mainly used
626 for recursion. I<SUBNAME> defaults to C<constant> if undefined.
628 I<DEFAULT_TYPE> is the type returned by C<ITEM>s that don't specify their
629 type. In turn it defaults to I<IV>. I<TYPES> should be given either as a comma
630 separated list of types that the C subroutine C<constant> will generate or as
631 a reference to a hash. I<DEFAULT_TYPE> will be added to the list if not
632 present, as will any types given in the list of I<ITEM>s. The resultant list
633 should be the same list of types that C<XS_constant> is given. [Otherwise
634 C<XS_constant> and C<C_constant> may differ in the number of parameters to the
635 constant function. I<INDENT> is currently unused and ignored. In future it may
636 be used to pass in information used to change the C indentation style used.]
637 The best way to maintain consistency is to pass in a hash reference and let
638 this function update it.
640 I<BREAKOUT> governs when child functions of I<SUBNAME> are generated. If there
641 are I<BREAKOUT> or more I<ITEM>s with the same length of name, then the code
642 to switch between them is placed into a function named I<SUBNAME>_I<LEN>, for
643 example C<constant_5> for names 5 characters long. The default I<BREAKOUT> is
644 3. A single C<ITEM> is always inlined.
648 # The parameter now BREAKOUT was previously documented as:
650 # I<NAMELEN> if defined signals that all the I<name>s of the I<ITEM>s are of
651 # this length, and that the constant name passed in by perl is checked and
652 # also of this length. It is used during recursion, and should be C<undef>
653 # unless the caller has checked all the lengths during code generation, and
654 # the generated subroutine is only to be called with a name of this length.
656 # As you can see it now performs this function during recursion by being a
660 my ($package, $subname, $default_type, $what, $indent, $breakout, @items)
663 $subname ||= 'constant';
664 # I'm not using this. But a hashref could be used for full formatting without
668 my ($namelen, $items);
670 # We are called recursively. We trust @items to be normalised, $what to
671 # be a hashref, and pinch %$items from our parent to save recalculation.
672 ($namelen, $items) = @$breakout;
675 $default_type ||= 'IV';
677 # Convert line of the form IV,UV,NV to hash
678 $what = {map {$_ => 1} split /,\s*/, ($what || '')};
679 # Figure out what types we're dealing with, and assign all unknowns to the
686 # Make a copy which is a normalised version of the ref passed in.
688 my ($type, $macro, $value) = @$_{qw (type macro value)};
689 $type ||= $default_type;
691 $_ = {name=>$name, type=>$type};
693 undef $macro if defined $macro and $macro eq $name;
694 $_->{macro} = $macro if defined $macro;
695 undef $value if defined $value and $value eq $name;
696 $_->{value} = $value if defined $value;
697 foreach my $key (qw(default pre post def_pre def_post)) {
698 my $value = $orig->{$key};
699 $_->{$key} = $value if defined $value;
700 # warn "$key $value";
704 $_ = {name=>$_, type=>$default_type};
705 $what->{$default_type} = 1;
707 warn "ExtUtils::Constant doesn't know how to handle values of type $_ used in macro $name" unless defined $XS_Constant{$_->{type}};
708 if (exists $items->{$name}) {
709 die "Multiple definitions for macro $name";
711 $items->{$name} = $_;
714 my $params = params ($what);
716 my ($body, @subs) = "static int\n$subname (pTHX_ const char *name";
717 $body .= ", STRLEN len" unless defined $namelen;
718 $body .= ", IV *iv_return" if $params->{IV};
719 $body .= ", NV *nv_return" if $params->{NV};
720 $body .= ", const char **pv_return" if $params->{PV};
721 $body .= ", SV **sv_return" if $params->{SV};
724 if (defined $namelen) {
725 # We are a child subroutine. Print the simple description
726 my $comment = 'When generated this function returned values for the list'
727 . ' of names given here. However, subsequent manual editing may have'
728 . ' added or removed some.';
729 $body .= switch_clause (2, $comment, $namelen, $items, @items);
731 # We are the top level.
732 $body .= " /* Initially switch on the length of the name. */\n";
733 $body .= dump_names ($package, $subname, $default_type, $what, $indent,
735 $body .= " switch (len) {\n";
736 # Need to group names of the same length
739 push @{$by_length[length $_->{name}]}, $_;
741 foreach my $i (0 .. $#by_length) {
742 next unless $by_length[$i]; # None of this length
743 $body .= " case $i:\n";
744 if (@{$by_length[$i]} == 1) {
745 my $thisone = $by_length[$i]->[0];
746 my ($name, $value, $macro, $default, $pre, $post, $def_pre, $def_post)
747 = @$thisone{qw (name value macro default pre post def_pre def_post)};
748 $value = $name unless defined $value;
749 $macro = $name unless defined $macro;
751 $body .= memEQ_clause ($name);
752 $body .= return_clause ($value, $thisone->{type}, undef, $macro,
753 $default, $pre, $post, $def_pre, $def_post);
755 } elsif (@{$by_length[$i]} < $breakout) {
756 $body .= switch_clause (4, '', $i, $items, @{$by_length[$i]});
758 # Only use the minimal set of parameters actually needed by the types
759 # of the names of this length.
761 foreach (@{$by_length[$i]}) {
762 $what->{$_->{type}} = 1;
764 $params = params ($what);
765 push @subs, C_constant ($package, "${subname}_$i", $default_type, $what,
766 $indent, [$i, $items], @{$by_length[$i]});
767 $body .= " return ${subname}_$i (aTHX_ name";
768 $body .= ", iv_return" if $params->{IV};
769 $body .= ", nv_return" if $params->{NV};
770 $body .= ", pv_return" if $params->{PV};
771 $body .= ", sv_return" if $params->{SV};
774 $body .= " break;\n";
778 $body .= " return PERL_constant_NOTFOUND;\n}\n";
779 return (@subs, $body);
782 =item XS_constant PACKAGE, TYPES, SUBNAME, C_SUBNAME
784 A function to generate the XS code to implement the perl subroutine
785 I<PACKAGE>::constant used by I<PACKAGE>::AUTOLOAD to load constants.
786 This XS code is a wrapper around a C subroutine usually generated by
787 C<C_constant>, and usually named C<constant>.
789 I<TYPES> should be given either as a comma separated list of types that the
790 C subroutine C<constant> will generate or as a reference to a hash. It should
791 be the same list of types as C<C_constant> was given.
792 [Otherwise C<XS_constant> and C<C_constant> may have different ideas about
793 the number of parameters passed to the C function C<constant>]
795 You can call the perl visible subroutine something other than C<constant> if
796 you give the parameter I<SUBNAME>. The C subroutine it calls defaults to the
797 the name of the perl visible subroutine, unless you give the parameter
806 my $C_subname = shift;
807 $subname ||= 'constant';
808 $C_subname ||= $subname;
811 # Convert line of the form IV,UV,NV to hash
812 $what = {map {$_ => 1} split /,\s*/, ($what)};
814 my $params = params ($what);
822 dXSTARG; /* Faster if we have it. */
833 $xs .= " /* IV\t\tiv;\tUncomment this if you need to return IVs */\n";
838 $xs .= " /* NV\t\tnv;\tUncomment this if you need to return NVs */\n";
841 $xs .= " const char *pv;\n";
844 " /* const char\t*pv;\tUncomment this if you need to return PVs */\n";
850 const char * s = SvPV(sv, len);
854 if ($params->{IV} xor $params->{NV}) {
856 /* Change this to $C_subname(aTHX_ s, len, &iv, &nv);
857 if you need to return both NVs and IVs */
860 $xs .= " type = $C_subname(aTHX_ s, len";
861 $xs .= ', &iv' if $params->{IV};
862 $xs .= ', &nv' if $params->{NV};
863 $xs .= ', &pv' if $params->{PV};
864 $xs .= ', &sv' if $params->{SV};
868 /* Return 1 or 2 items. First is error message, or undef if no error.
869 Second, if present, is found value */
871 case PERL_constant_NOTFOUND:
872 sv = sv_2mortal(newSVpvf("%s is not a valid $package macro", s));
875 case PERL_constant_NOTDEF:
876 sv = sv_2mortal(newSVpvf(
877 "Your vendor has not defined $package macro %s, used", s));
882 foreach $type (sort keys %XS_Constant) {
883 $xs .= "\t/* Uncomment this if you need to return ${type}s\n"
884 unless $what->{$type};
885 $xs .= " case PERL_constant_IS$type:\n";
886 if (length $XS_Constant{$type}) {
893 # Do nothing. return (), which will be correctly interpreted as
897 unless ($what->{$type}) {
898 chop $xs; # Yes, another need for chop not chomp.
904 sv = sv_2mortal(newSVpvf(
905 "Unexpected return type %d while processing $package macro %s, used",
915 =item autoload PACKAGE, VERSION, AUTOLOADER
917 A function to generate the AUTOLOAD subroutine for the module I<PACKAGE>
918 I<VERSION> is the perl version the code should be backwards compatible with.
919 It defaults to the version of perl running the subroutine. If I<AUTOLOADER>
920 is true, the AUTOLOAD subroutine falls back on AutoLoader::AUTOLOAD for all
921 names that the constant() routine doesn't recognise.
925 # ' # Grr. syntax highlighters that don't grok pod.
928 my ($module, $compat_version, $autoloader) = @_;
929 $compat_version ||= $];
930 croak "Can't maintain compatibility back as far as version $compat_version"
931 if $compat_version < 5;
932 my $func = "sub AUTOLOAD {\n"
933 . " # This AUTOLOAD is used to 'autoload' constants from the constant()\n"
935 $func .= " If a constant is not found then control is passed\n"
936 . " # to the AUTOLOAD in AutoLoader." if $autoloader;
940 . " my \$constname;\n";
942 " our \$AUTOLOAD;\n" if ($compat_version >= 5.006);
945 (\$constname = \$AUTOLOAD) =~ s/.*:://;
946 croak "&${module}::constant not defined" if \$constname eq 'constant';
947 my (\$error, \$val) = constant(\$constname);
953 if ($error =~ /is not a valid/) {
954 $AutoLoader::AUTOLOAD = $AUTOLOAD;
955 goto &AutoLoader::AUTOLOAD;
963 " if (\$error) { croak \$error; }\n";
969 # Fixed between 5.005_53 and 5.005_61
970 #XXX if ($] >= 5.00561) {
971 #XXX *$AUTOLOAD = sub () { $val };
974 *$AUTOLOAD = sub { $val };
986 =item WriteConstants ATTRIBUTE =E<gt> VALUE [, ...]
988 Writes a file of C code and a file of XS code which you should C<#include>
989 and C<INCLUDE> in the C and XS sections respectively of your module's XS
990 code. You probaby want to do this in your C<Makefile.PL>, so that you can
991 easily edit the list of constants without touching the rest of your module.
992 The attributes supported are
998 Name of the module. This must be specified
1002 The default type for the constants. If not specified C<IV> is assumed.
1006 The names of the constants are grouped by length. Generate child subroutines
1007 for each group with this number or more names in.
1011 An array of constants' names, either scalars containing names, or hashrefs
1012 as detailed in L<"C_constant">.
1016 The name of the file to write containing the C code. The default is
1021 The name of the file to write containing the XS code. The default is
1026 The perl visible name of the XS subroutine generated which will return the
1027 constants. The default is C<constant>.
1031 The name of the C subroutine generated which will return the constants.
1032 The default is I<SUBNAME>. Child subroutines have C<_> and the name
1033 length appended, so constants with 10 character names would be in
1034 C<constant_10> with the default I<XS_SUBNAME>.
1040 sub WriteConstants {
1043 C_FILE => 'constants.c',
1044 XS_FILE => 'constants.xs',
1045 SUBNAME => 'constant',
1046 DEFAULT_TYPE => 'IV',
1049 $ARGS{C_SUBNAME} ||= $ARGS{SUBNAME}; # No-one sane will have C_SUBNAME eq '0'
1051 croak "Module name not specified" unless length $ARGS{NAME};
1053 open my $c_fh, ">$ARGS{C_FILE}" or die "Can't open $ARGS{C_FILE}: $!";
1054 open my $xs_fh, ">$ARGS{XS_FILE}" or die "Can't open $ARGS{XS_FILE}: $!";
1056 # As this subroutine is intended to make code that isn't edited, there's no
1057 # need for the user to specify any types that aren't found in the list of
1061 print $c_fh constant_types(); # macro defs
1064 # indent is still undef. Until anyone implents indent style rules with it.
1065 foreach (C_constant ($ARGS{NAME}, $ARGS{C_SUBNAME}, $ARGS{DEFAULT_TYPE},
1066 $types, undef, $ARGS{BREAKOUT_AT}, @{$ARGS{NAMES}})) {
1067 print $c_fh $_, "\n"; # C constant subs
1069 print $xs_fh XS_constant ($ARGS{NAME}, $types, $ARGS{XS_SUBNAME},
1072 close $c_fh or warn "Error closing $ARGS{C_FILE}: $!";
1073 close $xs_fh or warn "Error closing $ARGS{XS_FILE}: $!";
1083 Nicholas Clark <nick@ccl4.org> based on the code in C<h2xs> by Larry Wall and