Diff: perlcall(1) - Waikato Linux Users Group

Differences between current version and predecessor to the previous major change of perlcall(1).

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Newer page:	version 2	Last edited on Monday, June 3, 2002 6:50:42 pm	by perry
Older page:	version 1	Last edited on Monday, June 3, 2002 6:50:42 pm	by perry	Revert

@@ -618,26 +618,26 @@

__Passing Parameters__

Now let's make a slightly more complex example. This time we

-want to call a Perl subroutine, LeftString, which

+want to call a Perl subroutine, ! 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

- sub LeftString

+ sub ! LeftString

{

my($s, $n) = @_ ;

print substr($s, 0, $n),

-The C function required to call ''LeftString'' would look like this.

+The C function required to call ''! LeftString'' would look like this.

static void

-call_LeftString(a, b)

+call_! LeftString(a, b)

char * a ;

int b ;

{

dSP ;

@@ -650,9 +650,9 @@

call_pv(

FREETMPS ;

LEAVE ;

}

-Here are a few notes on the C function ''call_LeftString''.

+Here are a few notes on the C function ''call_! LeftString''.

@@ -767,9 +767,9 @@

-Finally, ''LeftString'' can now be called via the

+Finally, ''! LeftString'' can now be called via the

''call_pv'' function. The only flag specified this time

is G_DISCARD. Because we are passing 2 parameters to the

Perl subroutine this time, we have not specified

G_NOARGS.

@@ -902,18 +902,18 @@

Here is the Perl subroutine

- sub AddSubtract

+ sub ! AddSubtract

{

my($a, $b) = @_ ;

($a+$b, $a-$b) ;

}

and this is the C function

static void

-call_AddSubtract(a, b)

+call_! AddSubtract(a, b)

int a ;

int b ;

{

dSP ;

@@ -932,12 +932,12 @@

PUTBACK ;

FREETMPS ;

LEAVE ;

}

-If ''call_AddSubtract'' is called like this

+If ''call_! AddSubtract'' is called like this

- call_AddSubtract(7, 4) ;

+ call_! AddSubtract(7, 4) ;

then here is the output

7 - 4 = 3

@@ -968,9 +968,9 @@

in a scalar context, like this

static void

-call_AddSubScalar(a, b)

+call_! AddSubScalar(a, b)

int a ;

int b ;

{

dSP ;

@@ -989,18 +989,18 @@

PUTBACK ;

FREETMPS ;

LEAVE ;

}

-The other modification made is that ''call_AddSubScalar'' will print the number of items returned from the Perl subroutine and their value (for simplicity it assumes that they are integer). So if ''call_AddSubScalar'' is called

+The other modification made is that ''call_! AddSubScalar'' will print the number of items returned from the Perl subroutine and their value (for simplicity it assumes that they are integer). So if ''call_! AddSubScalar'' is called

- call_AddSubScalar(7, 4) ;

+ call_! AddSubScalar(7, 4) ;

then the output will be

Items Returned = 1

Value 1 = 3

-In this case the main point to note is that only the last item in the list is returned from the subroutine, ''AddSubtract'' actually made it back to ''call_AddSubScalar''.

+In this case the main point to note is that only the last item in the list is returned from the subroutine, ''! AddSubtract'' actually made it back to ''call_! AddSubScalar''.

__Returning Data from Perl via the parameter

list__

@@ -1305,18 +1305,18 @@

Here is a Perl subroutine which prints whatever parameters

are passed to it.

- sub PrintList

+ sub ! PrintList

{

my(@list) = @_ ;

foreach (@list) { print

-and here is an example of ''call_argv'' which will call ''PrintList''.

+and here is an example of ''call_argv'' which will call ''! PrintList''.

static char * words[[] = {

static void

-call_PrintList()

+call_! PrintList()

{

dSP ;

call_argv(

Note that it is not necessary to call PUSHMARK in this instance. This is because ''call_argv'' will do it for you.

@@ -1407,19 +1407,19 @@

context in which it is currently executing.

void

-PrintContext()

+! PrintContext()

CODE:

I32 gimme = GIMME_V;

if (gimme == G_VOID)

printf (

and here is some Perl to test it

- PrintContext ;

-$a = PrintContext ;

-@a = PrintContext ;

+ ! PrintContext ;

+$a = ! PrintContext ;

+@a = ! PrintContext ;

The output from that will be

Context is Void

@@ -1609,20 +1609,20 @@

want to be called for that file.

Say the i/o library has a function asynch_read

-which associates a C function ProcessRead with a

+which associates a C function ! ProcessRead with a

file handle fh--this assumes that it has also

provided some routine to open the file and so obtain the

file handle.

- asynch_read(fh, ProcessRead)

-This may expect the C ''ProcessRead'' function of this form

+ asynch_read(fh, ! ProcessRead)

+This may expect the C ''! ProcessRead'' function of this form

void

-ProcessRead(fh, buffer)

+! ProcessRead(fh, buffer)

int fh ;

char * buffer ;

{

...

@@ -1692,9 +1692,9 @@

parameter like this

void

-ProcessRead(buffer)

+! ProcessRead(buffer)

char * buffer ;

{

...

}

@@ -1707,18 +1707,18 @@

#define MAX_CB 3

#define NULL_HANDLE -1

-typedef void (*FnMap)() ;

- struct MapStruct {

-FnMap Function ;

-SV * PerlSub ;

+typedef void (*! FnMap)() ;

+ struct ! MapStruct {

+! FnMap Function ;

+SV * ! PerlSub ;

int Handle ;

} ;

static void fn1() ;

static void fn2() ;

static void fn3() ;

- static struct MapStruct Map [[MAX_CB] =

+ static struct ! MapStruct Map [[MAX_CB] =

{

{ fn1, NULL, NULL_HANDLE },

{ fn2, NULL, NULL_HANDLE },

{ fn3, NULL, NULL_HANDLE }

@@ -1732,9 +1732,9 @@

PUSHMARK(SP) ;

XPUSHs(sv_2mortal(newSVpv(buffer, 0))) ;

PUTBACK ;

/* Call the Perl sub */

-call_sv(Map[[index].PerlSub, G_DISCARD) ;

+call_sv(Map[[index].! PerlSub, G_DISCARD) ;

}

static void

fn1(buffer)

char * buffer ;

@@ -1770,12 +1770,12 @@

index = null_index ;

/* Save the file handle */

Map[[index].Handle = fh ;

/* Remember the Perl sub */

-if (Map[[index].PerlSub == (SV*)NULL)

-Map[[index].PerlSub = newSVsv(callback) ;

+if (Map[[index].! PerlSub == (SV*)NULL)

+Map[[index].! PerlSub = newSVsv(callback) ;

else

-SvSetSV(Map[[index].PerlSub, callback) ;

+SvSetSV(Map[[index].! PerlSub, callback) ;

asynch_read(fh, Map[[index].Function) ;

void

array_asynch_close(fh)

int fh

@@ -1785,10 +1785,10 @@

for (index = 0; index

if (index == MAX_CB)

croak (

Map[[index].Handle = NULL_HANDLE ;

-SvREFCNT_dec(Map[[index].PerlSub) ;

-Map[[index].PerlSub = (SV*)NULL ;

+SvREFCNT_dec(Map[[index].! PerlSub) ;

+Map[[index].! PerlSub = (SV*)NULL ;

asynch_close(fh) ;

In this case the functions fn1, fn2, and fn3 are used to remember the Perl subroutine to be called. Each of the functions holds a separate hard-wired index which is used in the function Pcb to access the Map array and actually call the Perl subroutine.