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;
282 return_clause VALUE, TYPE, INDENT, MACRO, DEFAULT, PRE, POST, PRE, POST
284 A function to return a suitable C<#ifdef> clause. I<MACRO> defaults to
285 I<VALUE> when not defined. If I<TYPE> is aggregate (eg I<PVN> expects both
286 pointer and length) then I<VALUE> should be a reference to an array of
287 values in the order expected by the type. C<C_constant> will always call
288 this function with I<MACRO> defined, defaulting to the constant's name.
289 I<DEFAULT> if defined is an array reference giving default type and and
290 value(s) if the clause generated by I<MACRO> doesn't evaluate to true.
291 The two pairs I<PRE> and I<POST> if defined give C code snippets to proceed
292 and follow the value, and the default value.
296 sub return_clause ($$$$$$$$$) {
298 # *iv_return = thingy;
299 # return PERL_constant_ISIV;
301 # return PERL_constant_NOTDEF;
303 my ($value, $type, $indent, $macro, $default, $pre, $post,
304 $def_pre, $def_post) = @_;
305 $macro = $value unless defined $macro;
306 $indent = ' ' x ($indent || 6);
312 $clause = $macro->[0];
313 } elsif ($macro ne "1") {
314 $clause = "#ifdef $macro\n";
317 # *iv_return = thingy;
318 # return PERL_constant_ISIV;
319 $clause .= assign ($indent, $type, $pre, $post,
320 ref $value ? @$value : $value);
322 if (ref $macro or $macro ne "1") {
324 $clause .= "#else\n";
326 # return PERL_constant_NOTDEF;
327 if (!defined $default) {
328 $clause .= "${indent}return PERL_constant_NOTDEF;\n";
330 my @default = ref $default ? @$default : $default;
331 $type = shift @default;
332 $clause .= assign ($indent, $type, $def_pre, $def_post, @default);
337 $clause .= $macro->[1];
339 $clause .= "#endif\n";
345 =item switch_clause INDENT, NAMELEN, ITEMHASH, ITEM...
347 An internal function to generate a suitable C<switch> clause, called by
348 C<C_constant> I<ITEM>s are in the hash ref format as given in the description
349 of C<C_constant>, and must all have the names of the same length, given by
350 I<NAMELEN> (This is not checked). I<ITEMHASH> is a reference to a hash,
351 keyed by name, values being the hashrefs in the I<ITEM> list.
352 (No parameters are modified, and there can be keys in the I<ITEMHASH> that
353 are not in the list of I<ITEM>s without causing problems).
358 my ($indent, $comment, $namelen, $items, @items) = @_;
359 $indent = ' ' x ($indent || 2);
361 my @names = sort map {$_->{name}} @items;
362 my $leader = $indent . '/* ';
363 my $follower = ' ' x length $leader;
364 my $body = $indent . "/* Names all of length $namelen. */\n";
366 $body = wrap ($leader, $follower, $comment) . "\n";
369 $body .= wrap ($leader, $follower, join (" ", @names) . " */") . "\n";
370 # Figure out what to switch on.
371 # (RMS, Spread of jump table, Position, Hashref)
372 my @best = (1e38, ~0);
373 foreach my $i (0 .. ($namelen - 1)) {
374 my ($min, $max) = (~0, 0);
377 my $char = substr $_, $i, 1;
379 $max = $ord if $ord > $max;
380 $min = $ord if $ord < $min;
381 push @{$spread{$char}}, $_;
384 # I'm going to pick the character to split on that minimises the root
385 # mean square of the number of names in each case. Normally this should
386 # be the one with the most keys, but it may pick a 7 where the 8 has
387 # one long linear search. I'm not sure if RMS or just sum of squares is
389 # $max and $min are for the tie-breaker if the root mean squares match.
390 # Assuming that the compiler may be building a jump table for the
391 # switch() then try to minimise the size of that jump table.
392 # Finally use < not <= so that if it still ties the earliest part of
393 # the string wins. Because if that passes but the memEQ fails, it may
394 # only need the start of the string to bin the choice.
395 # I think. But I'm micro-optimising. :-)
397 $ss += @$_ * @$_ foreach values %spread;
398 my $rms = sqrt ($ss / keys %spread);
399 if ($rms < $best[0] || ($rms == $best[0] && ($max - $min) < $best[1])) {
400 @best = ($rms, $max - $min, $i, \%spread);
403 die "Internal error. Failed to pick a switch point for @names"
404 unless defined $best[2];
405 # use Data::Dumper; print Dumper (@best);
406 my ($offset, $best) = @best[2,3];
407 $body .= $indent . "/* Offset $offset gives the best switch position. */\n";
408 $body .= $indent . "switch (name[$offset]) {\n";
409 foreach my $char (sort keys %$best) {
410 $body .= $indent . "case '" . C_stringify ($char) . "':\n";
411 foreach my $name (sort @{$best->{$char}}) {
412 my $thisone = $items->{$name};
413 my ($value, $macro, $default, $pre, $post, $def_pre, $def_post)
414 = @$thisone{qw (value macro default pre post def_pre def_post)};
415 $value = $name unless defined $value;
416 $macro = $name unless defined $macro;
418 # We have checked this offset.
419 $body .= memEQ_clause ($name, $offset, 2 + length $indent);
420 $body .= return_clause ($value, $thisone->{type}, 4 + length $indent,
421 $macro, $default, $pre, $post,
422 $def_pre, $def_post);
423 $body .= $indent . " }\n";
425 $body .= $indent . " break;\n";
427 $body .= $indent . "}\n";
433 An internal function. I<WHAT> should be a hashref of types the constant
434 function will return. I<params> returns a hashref keyed IV NV PV SV to show
435 which combination of pointers will be needed in the C argument list.
441 foreach (sort keys %$what) {
442 warn "ExtUtils::Constant doesn't know how to handle values of type $_" unless defined $XS_Constant{$_};
445 $params->{IV} = 1 if $what->{IV} || $what->{UV} || $what->{PVN};
446 $params->{NV} = 1 if $what->{NV};
447 $params->{PV} = 1 if $what->{PV} || $what->{PVN};
448 $params->{SV} = 1 if $what->{SV};
454 dump_names PACKAGE, SUBNAME, DEFAULT_TYPE, TYPES, INDENT, BREAKOUT, ITEM...
456 An internal function to generate the embedded perl code that will regenerate
457 the constant subroutines. Parameters are the same as for C_constant.
462 my ($package, $subname, $default_type, $what, $indent, $breakout, @items)
464 my (@simple, @complex);
466 my $type = $_->{type} || $default_type;
467 if ($type eq $default_type and 0 == ($_->{name} =~ tr/A-Za-z0-9_//c)
468 and !defined ($_->{macro}) and !defined ($_->{value})
469 and !defined ($_->{default}) and !defined ($_->{pre})
470 and !defined ($_->{post}) and !defined ($_->{def_pre})
471 and !defined ($_->{def_post})) {
472 # It's the default type, and the name consists only of A-Za-z0-9_
473 push @simple, $_->{name};
478 my $result = <<"EOT";
479 /* When generated this function returned values for the list of names given
480 in this section of perl code. Rather than manually editing these functions
481 to add or remove constants, which would result in this comment and section
482 of code becoming inaccurate, we recommend that you edit this section of
483 code, and use it to regenerate a new set of constant functions which you
484 then use to replace the originals.
486 Regenerate these constant functions by feeding this entire source file to
490 use ExtUtils::Constant qw (constant_types C_constant XS_constant);
493 $result .= 'my $types = {map {($_, 1)} qw(' . join (" ", sort keys %$what)
495 $result .= wrap ("my \@names = (qw(",
496 " ", join (" ", sort @simple) . ")");
498 foreach my $item (sort {$a->{name} cmp $b->{name}} @complex) {
499 my $name = C_stringify $item->{name};
500 my $line = ",\n {name=>\"$name\"";
501 $line .= ", type=>\"$item->{type}\"" if defined $item->{type};
502 foreach my $thing (qw (macro value default pre post def_pre def_post)) {
503 my $value = $item->{$thing};
504 if (defined $value) {
506 $line .= ", $thing=>[\""
507 . join ('", "', map {C_stringify $_} @$value) . '"]';
509 $line .= ", $thing=>\"" . C_stringify($value) . "\"";
514 # Ensure that the enclosing C comment doesn't end
515 # by turning */ into *" . "/
516 $line =~ s!\*\/!\*" . "/!gs;
517 # gcc -Wall doesn't like finding /* inside a comment
518 $line =~ s!\/\*!/" . "\*!gs;
526 print constant_types(); # macro defs
528 $package = C_stringify($package);
530 "foreach (C_constant (\"$package\", '$subname', '$default_type', \$types, ";
531 # The form of the indent parameter isn't defined. (Yet)
532 if (defined $indent) {
533 require Data::Dumper;
534 $Data::Dumper::Terse=1;
535 $Data::Dumper::Terse=1; # Not used once. :-)
536 chomp ($indent = Data::Dumper::Dumper ($indent));
541 $result .= ", $breakout" . ', @names) ) {
542 print $_, "\n"; # C constant subs
544 print "#### XS Section:\n";
545 print XS_constant ("' . $package . '", $types);
556 C_constant PACKAGE, SUBNAME, DEFAULT_TYPE, TYPES, INDENT, BREAKOUT, ITEM...
558 A function that returns a B<list> of C subroutine definitions that return
559 the value and type of constants when passed the name by the XS wrapper.
560 I<ITEM...> gives a list of constant names. Each can either be a string,
561 which is taken as a C macro name, or a reference to a hash with the following
568 The name of the constant, as seen by the perl code.
572 The type of the constant (I<IV>, I<NV> etc)
576 A C expression for the value of the constant, or a list of C expressions if
577 the type is aggregate. This defaults to the I<name> if not given.
581 The C pre-processor macro to use in the C<#ifdef>. This defaults to the
582 I<name>, and is mainly used if I<value> is an C<enum>. If a reference an
583 array is passed then the first element is used in place of the C<#ifdef>
584 line, and the second element in place of the C<#endif>. This allows
585 pre-processor constructions such as
593 to be used to determine if a constant is to be defined.
595 A "macro" 1 signals that the constant is always defined, so the C<#if>/C<#endif>
600 Default value to use (instead of C<croak>ing with "your vendor has not
601 defined...") to return if the macro isn't defined. Specify a reference to
602 an array with type followed by value(s).
606 C code to use before the assignment of the value of the constant. This allows
607 you to use temporary variables to extract a value from part of a C<struct>
608 and return this as I<value>. This C code is places at the start of a block,
609 so you can declare variables in it.
613 C code to place between the assignment of value (to a temporary) and the
614 return from the function. This allows you to clear up anything in I<pre>.
620 Equivalents of I<pre> and I<post> for the default value.
624 I<PACKAGE> is the name of the package, and is only used in comments inside the
627 The next 5 arguments can safely be given as C<undef>, and are mainly used
628 for recursion. I<SUBNAME> defaults to C<constant> if undefined.
630 I<DEFAULT_TYPE> is the type returned by C<ITEM>s that don't specify their
631 type. In turn it defaults to I<IV>. I<TYPES> should be given either as a comma
632 separated list of types that the C subroutine C<constant> will generate or as
633 a reference to a hash. I<DEFAULT_TYPE> will be added to the list if not
634 present, as will any types given in the list of I<ITEM>s. The resultant list
635 should be the same list of types that C<XS_constant> is given. [Otherwise
636 C<XS_constant> and C<C_constant> may differ in the number of parameters to the
637 constant function. I<INDENT> is currently unused and ignored. In future it may
638 be used to pass in information used to change the C indentation style used.]
639 The best way to maintain consistency is to pass in a hash reference and let
640 this function update it.
642 I<BREAKOUT> governs when child functions of I<SUBNAME> are generated. If there
643 are I<BREAKOUT> or more I<ITEM>s with the same length of name, then the code
644 to switch between them is placed into a function named I<SUBNAME>_I<LEN>, for
645 example C<constant_5> for names 5 characters long. The default I<BREAKOUT> is
646 3. A single C<ITEM> is always inlined.
650 # The parameter now BREAKOUT was previously documented as:
652 # I<NAMELEN> if defined signals that all the I<name>s of the I<ITEM>s are of
653 # this length, and that the constant name passed in by perl is checked and
654 # also of this length. It is used during recursion, and should be C<undef>
655 # unless the caller has checked all the lengths during code generation, and
656 # the generated subroutine is only to be called with a name of this length.
658 # As you can see it now performs this function during recursion by being a
662 my ($package, $subname, $default_type, $what, $indent, $breakout, @items)
665 $subname ||= 'constant';
666 # I'm not using this. But a hashref could be used for full formatting without
670 my ($namelen, $items);
672 # We are called recursively. We trust @items to be normalised, $what to
673 # be a hashref, and pinch %$items from our parent to save recalculation.
674 ($namelen, $items) = @$breakout;
677 $default_type ||= 'IV';
679 # Convert line of the form IV,UV,NV to hash
680 $what = {map {$_ => 1} split /,\s*/, ($what || '')};
681 # Figure out what types we're dealing with, and assign all unknowns to the
688 # Make a copy which is a normalised version of the ref passed in.
690 my ($type, $macro, $value) = @$_{qw (type macro value)};
691 $type ||= $default_type;
693 $_ = {name=>$name, type=>$type};
695 undef $macro if defined $macro and $macro eq $name;
696 $_->{macro} = $macro if defined $macro;
697 undef $value if defined $value and $value eq $name;
698 $_->{value} = $value if defined $value;
699 foreach my $key (qw(default pre post def_pre def_post)) {
700 my $value = $orig->{$key};
701 $_->{$key} = $value if defined $value;
702 # warn "$key $value";
706 $_ = {name=>$_, type=>$default_type};
707 $what->{$default_type} = 1;
709 warn "ExtUtils::Constant doesn't know how to handle values of type $_ used in macro $name" unless defined $XS_Constant{$_->{type}};
710 if (exists $items->{$name}) {
711 die "Multiple definitions for macro $name";
713 $items->{$name} = $_;
716 my $params = params ($what);
718 my ($body, @subs) = "static int\n$subname (pTHX_ const char *name";
719 $body .= ", STRLEN len" unless defined $namelen;
720 $body .= ", IV *iv_return" if $params->{IV};
721 $body .= ", NV *nv_return" if $params->{NV};
722 $body .= ", const char **pv_return" if $params->{PV};
723 $body .= ", SV **sv_return" if $params->{SV};
726 if (defined $namelen) {
727 # We are a child subroutine. Print the simple description
728 my $comment = 'When generated this function returned values for the list'
729 . ' of names given here. However, subsequent manual editing may have'
730 . ' added or removed some.';
731 $body .= switch_clause (2, $comment, $namelen, $items, @items);
733 # We are the top level.
734 $body .= " /* Initially switch on the length of the name. */\n";
735 $body .= dump_names ($package, $subname, $default_type, $what, $indent,
737 $body .= " switch (len) {\n";
738 # Need to group names of the same length
741 push @{$by_length[length $_->{name}]}, $_;
743 foreach my $i (0 .. $#by_length) {
744 next unless $by_length[$i]; # None of this length
745 $body .= " case $i:\n";
746 if (@{$by_length[$i]} == 1) {
747 my $thisone = $by_length[$i]->[0];
748 my ($name, $value, $macro, $default, $pre, $post, $def_pre, $def_post)
749 = @$thisone{qw (name value macro default pre post def_pre def_post)};
750 $value = $name unless defined $value;
751 $macro = $name unless defined $macro;
753 $body .= memEQ_clause ($name);
754 $body .= return_clause ($value, $thisone->{type}, undef, $macro,
755 $default, $pre, $post, $def_pre, $def_post);
757 } elsif (@{$by_length[$i]} < $breakout) {
758 $body .= switch_clause (4, '', $i, $items, @{$by_length[$i]});
760 # Only use the minimal set of parameters actually needed by the types
761 # of the names of this length.
763 foreach (@{$by_length[$i]}) {
764 $what->{$_->{type}} = 1;
766 $params = params ($what);
767 push @subs, C_constant ($package, "${subname}_$i", $default_type, $what,
768 $indent, [$i, $items], @{$by_length[$i]});
769 $body .= " return ${subname}_$i (aTHX_ name";
770 $body .= ", iv_return" if $params->{IV};
771 $body .= ", nv_return" if $params->{NV};
772 $body .= ", pv_return" if $params->{PV};
773 $body .= ", sv_return" if $params->{SV};
776 $body .= " break;\n";
780 $body .= " return PERL_constant_NOTFOUND;\n}\n";
781 return (@subs, $body);
784 =item XS_constant PACKAGE, TYPES, SUBNAME, C_SUBNAME
786 A function to generate the XS code to implement the perl subroutine
787 I<PACKAGE>::constant used by I<PACKAGE>::AUTOLOAD to load constants.
788 This XS code is a wrapper around a C subroutine usually generated by
789 C<C_constant>, and usually named C<constant>.
791 I<TYPES> should be given either as a comma separated list of types that the
792 C subroutine C<constant> will generate or as a reference to a hash. It should
793 be the same list of types as C<C_constant> was given.
794 [Otherwise C<XS_constant> and C<C_constant> may have different ideas about
795 the number of parameters passed to the C function C<constant>]
797 You can call the perl visible subroutine something other than C<constant> if
798 you give the parameter I<SUBNAME>. The C subroutine it calls defaults to the
799 the name of the perl visible subroutine, unless you give the parameter
808 my $C_subname = shift;
809 $subname ||= 'constant';
810 $C_subname ||= $subname;
813 # Convert line of the form IV,UV,NV to hash
814 $what = {map {$_ => 1} split /,\s*/, ($what)};
816 my $params = params ($what);
824 dXSTARG; /* Faster if we have it. */
835 $xs .= " /* IV\t\tiv;\tUncomment this if you need to return IVs */\n";
840 $xs .= " /* NV\t\tnv;\tUncomment this if you need to return NVs */\n";
843 $xs .= " const char *pv;\n";
846 " /* const char\t*pv;\tUncomment this if you need to return PVs */\n";
852 const char * s = SvPV(sv, len);
856 if ($params->{IV} xor $params->{NV}) {
858 /* Change this to $C_subname(aTHX_ s, len, &iv, &nv);
859 if you need to return both NVs and IVs */
862 $xs .= " type = $C_subname(aTHX_ s, len";
863 $xs .= ', &iv' if $params->{IV};
864 $xs .= ', &nv' if $params->{NV};
865 $xs .= ', &pv' if $params->{PV};
866 $xs .= ', &sv' if $params->{SV};
870 /* Return 1 or 2 items. First is error message, or undef if no error.
871 Second, if present, is found value */
873 case PERL_constant_NOTFOUND:
874 sv = sv_2mortal(newSVpvf("%s is not a valid $package macro", s));
877 case PERL_constant_NOTDEF:
878 sv = sv_2mortal(newSVpvf(
879 "Your vendor has not defined $package macro %s, used", s));
884 foreach $type (sort keys %XS_Constant) {
885 $xs .= "\t/* Uncomment this if you need to return ${type}s\n"
886 unless $what->{$type};
887 $xs .= " case PERL_constant_IS$type:\n";
888 if (length $XS_Constant{$type}) {
895 # Do nothing. return (), which will be correctly interpreted as
899 unless ($what->{$type}) {
900 chop $xs; # Yes, another need for chop not chomp.
906 sv = sv_2mortal(newSVpvf(
907 "Unexpected return type %d while processing $package macro %s, used",
917 =item autoload PACKAGE, VERSION, AUTOLOADER
919 A function to generate the AUTOLOAD subroutine for the module I<PACKAGE>
920 I<VERSION> is the perl version the code should be backwards compatible with.
921 It defaults to the version of perl running the subroutine. If I<AUTOLOADER>
922 is true, the AUTOLOAD subroutine falls back on AutoLoader::AUTOLOAD for all
923 names that the constant() routine doesn't recognise.
927 # ' # Grr. syntax highlighters that don't grok pod.
930 my ($module, $compat_version, $autoloader) = @_;
931 $compat_version ||= $];
932 croak "Can't maintain compatibility back as far as version $compat_version"
933 if $compat_version < 5;
934 my $func = "sub AUTOLOAD {\n"
935 . " # This AUTOLOAD is used to 'autoload' constants from the constant()\n"
937 $func .= " If a constant is not found then control is passed\n"
938 . " # to the AUTOLOAD in AutoLoader." if $autoloader;
942 . " my \$constname;\n";
944 " our \$AUTOLOAD;\n" if ($compat_version >= 5.006);
947 (\$constname = \$AUTOLOAD) =~ s/.*:://;
948 croak "&${module}::constant not defined" if \$constname eq 'constant';
949 my (\$error, \$val) = constant(\$constname);
955 if ($error =~ /is not a valid/) {
956 $AutoLoader::AUTOLOAD = $AUTOLOAD;
957 goto &AutoLoader::AUTOLOAD;
965 " if (\$error) { croak \$error; }\n";
971 # Fixed between 5.005_53 and 5.005_61
972 #XXX if ($] >= 5.00561) {
973 #XXX *$AUTOLOAD = sub () { $val };
976 *$AUTOLOAD = sub { $val };
988 =item WriteConstants ATTRIBUTE =E<gt> VALUE [, ...]
990 Writes a file of C code and a file of XS code which you should C<#include>
991 and C<INCLUDE> in the C and XS sections respectively of your module's XS
992 code. You probaby want to do this in your C<Makefile.PL>, so that you can
993 easily edit the list of constants without touching the rest of your module.
994 The attributes supported are
1000 Name of the module. This must be specified
1004 The default type for the constants. If not specified C<IV> is assumed.
1008 The names of the constants are grouped by length. Generate child subroutines
1009 for each group with this number or more names in.
1013 An array of constants' names, either scalars containing names, or hashrefs
1014 as detailed in L<"C_constant">.
1018 The name of the file to write containing the C code. The default is
1023 The name of the file to write containing the XS code. The default is
1028 The perl visible name of the XS subroutine generated which will return the
1029 constants. The default is C<constant>.
1033 The name of the C subroutine generated which will return the constants.
1034 The default is I<SUBNAME>. Child subroutines have C<_> and the name
1035 length appended, so constants with 10 character names would be in
1036 C<constant_10> with the default I<XS_SUBNAME>.
1042 sub WriteConstants {
1045 C_FILE => 'constants.c',
1046 XS_FILE => 'constants.xs',
1047 SUBNAME => 'constant',
1048 DEFAULT_TYPE => 'IV',
1051 $ARGS{C_SUBNAME} ||= $ARGS{SUBNAME}; # No-one sane will have C_SUBNAME eq '0'
1053 croak "Module name not specified" unless length $ARGS{NAME};
1055 open my $c_fh, ">$ARGS{C_FILE}" or die "Can't open $ARGS{C_FILE}: $!";
1056 open my $xs_fh, ">$ARGS{XS_FILE}" or die "Can't open $ARGS{XS_FILE}: $!";
1058 # As this subroutine is intended to make code that isn't edited, there's no
1059 # need for the user to specify any types that aren't found in the list of
1063 print $c_fh constant_types(); # macro defs
1066 # indent is still undef. Until anyone implents indent style rules with it.
1067 foreach (C_constant ($ARGS{NAME}, $ARGS{C_SUBNAME}, $ARGS{DEFAULT_TYPE},
1068 $types, undef, $ARGS{BREAKOUT_AT}, @{$ARGS{NAMES}})) {
1069 print $c_fh $_, "\n"; # C constant subs
1071 print $xs_fh XS_constant ($ARGS{NAME}, $types, $ARGS{XS_SUBNAME},
1074 close $c_fh or warn "Error closing $ARGS{C_FILE}: $!";
1075 close $xs_fh or warn "Error closing $ARGS{XS_FILE}: $!";
1085 Nicholas Clark <nick@ccl4.org> based on the code in C<h2xs> by Larry Wall and