=over 5
-=item B<perl_call_sv>
+=item perl_call_sv
I<perl_call_sv> takes two parameters, the first, C<sv>, is an SV*.
This allows you to specify the Perl subroutine to be called either as a
subroutine. The section, I<Using perl_call_sv>, shows how you can make
use of I<perl_call_sv>.
-=item B<perl_call_pv>
+=item perl_call_pv
The function, I<perl_call_pv>, is similar to I<perl_call_sv> except it
expects its first parameter to be a C char* which identifies the Perl
subroutine you want to call is in another package, just include the
package name in the string, e.g., C<"pkg::fred">.
-=item B<perl_call_method>
+=item perl_call_method
The function I<perl_call_method> is used to call a method from a Perl
class. The parameter C<methname> corresponds to the name of the method
static and virtual methods and L<Using perl_call_method> for an example
of using I<perl_call_method>.
-=item B<perl_call_argv>
+=item perl_call_argv
I<perl_call_argv> calls the Perl subroutine specified by the C string
stored in the C<subname> parameter. It also takes the usual C<flags>
As a general rule you should I<always> check the return value from
these functions. Even if you are expecting only a particular number of
values to be returned from the Perl subroutine, there is nothing to
-stop someone from doing something unexpected - don't say you haven't
+stop someone from doing something unexpected--don't say you haven't
been warned.
=head1 FLAG VALUES
It is possible for the Perl subroutine you are calling to terminate
abnormally, e.g., by calling I<die> explicitly or by not actually
-existing. By default, when either of these of events occurs, the
-process will terminate immediately. If though, you want to trap this
+existing. By default, when either of these events occurs, the
+process will terminate immediately. If you want to trap this
type of event, specify the G_EVAL flag. It will put an I<eval { }>
around the subroutine call.
=head2 Passing Parameters
Now let's make a slightly more complex example. This time we want to
-call a Perl subroutine, C<LeftString>, which will take 2 parameters - a
-string (C<$s>) and an integer (C<$n>). The subroutine will simply
-print the first C<$n> characters of the string.
+call a Perl subroutine, C<LeftString>, which will take 2 parameters--a
+string ($s) and an integer ($n). The subroutine will simply
+print the first $n characters of the string.
So the Perl subroutine would look like this
=item 2.
If you are going to put something onto the Perl stack, you need to know
-where to put it. This is the purpose of the macro C<dSP> - it declares
+where to put it. This is the purpose of the macro C<dSP>--it declares
and initializes a I<local> copy of the Perl stack pointer.
All the other macros which will be used in this example require you to
The exception to this rule is if you are calling a Perl subroutine
directly from an XSUB function. In this case it is not necessary to
-use the C<dSP> macro explicitly - it will be declared for you
+use the C<dSP> macro explicitly--it will be declared for you
automatically.
=item 3.
stack pointer. Even if you aren't passing any parameters (like the
example shown in the section I<No Parameters, Nothing returned>) you
must still call the C<PUSHMARK> macro before you can call any of the
-I<perl_call_*> functions - Perl still needs to know that there are no
+I<perl_call_*> functions--Perl still needs to know that there are no
parameters.
The C<PUTBACK> macro sets the global copy of the stack pointer to be
the same as our local copy. If we didn't do this I<perl_call_pv>
-wouldn't know where the two parameters we pushed were - remember that
+wouldn't know where the two parameters we pushed were--remember that
up to now all the stack pointer manipulation we have done is with our
local copy, I<not> the global copy.
To be able to access the two parameters that were pushed onto the stack
after they return from I<perl_call_pv> it is necessary to make a note
-of their addresses - thus the two variables C<sva> and C<svb>.
+of their addresses--thus the two variables C<sva> and C<svb>.
The reason this is necessary is that the area of the Perl stack which
held them will very likely have been overwritten by something else by
/* Check the eval first */
if (SvTRUE(ERRSV))
{
- printf ("Uh oh - %s\n", SvPV(ERRSV, PL_na)) ;
+ STRLEN n_a;
+ printf ("Uh oh - %s\n", SvPV(ERRSV, n_a)) ;
POPs ;
}
else
if (SvTRUE(ERRSV))
{
- printf ("Uh oh - %s\n", SvPV(ERRSV, PL_na)) ;
+ STRLEN n_a;
+ printf ("Uh oh - %s\n", SvPV(ERRSV, n_a)) ;
POPs ;
}
Not a CODE reference at ...
Undefined subroutine &main::47 called ...
-The variable C<$ref> may have referred to the subroutine C<fred>
+The variable $ref may have referred to the subroutine C<fred>
whenever the call to C<SaveSub1> was made but by the time
C<CallSavedSub1> gets called it now holds the number C<47>. Because we
saved only a pointer to the original SV in C<SaveSub1>, any changes to
-C<$ref> will be tracked by the pointer C<rememberSub>. This means that
+$ref will be tracked by the pointer C<rememberSub>. This means that
whenever C<CallSavedSub1> gets called, it will attempt to execute the
code which is referenced by the SV* C<rememberSub>. In this case
though, it now refers to the integer C<47>, so expect Perl to complain
call_PrintID('Mine', 'PrintID') ;
The only thing to note is that in both the static and virtual methods,
-the method name is not passed via the stack - it is used as the first
+the method name is not passed via the stack--it is used as the first
parameter to I<perl_call_method>.
=head2 Using GIMME_V
never happen. This means that as time goes on, your program will
create more and more temporaries, none of which will ever be freed. As
each of these temporaries consumes some memory your program will
-eventually consume all the available memory in your system - kapow!
+eventually consume all the available memory in your system--kapow!
-So here is the bottom line - if you are sure that control will revert
+So here is the bottom line--if you are sure that control will revert
back to the enclosing Perl scope fairly quickly after the end of your
callback, then it isn't absolutely necessary to dispose explicitly of
any temporaries you may have created. Mind you, if you are at all
the Perl subroutine we want to be called for that file.
Say the i/o library has a function C<asynch_read> which associates a C
-function C<ProcessRead> with a file handle C<fh> - this assumes that it
+function C<ProcessRead> with a file handle C<fh>--this assumes that it
has also provided some routine to open the file and so obtain the file
handle.
=head2 Creating and calling an anonymous subroutine in C
As we've already shown, C<perl_call_sv> can be used to invoke an
-anonymous subroutine. However, our example showed how Perl script
-invoking an XSUB to preform this operation. Let's see how it can be
+anonymous subroutine. However, our example showed a Perl script
+invoking an XSUB to perform this operation. Let's see how it can be
done inside our C code:
...
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