PL_rsfp_filters - what does it contain ?

sawoy has asked for the wisdom of the Perl Monks concerning the following question:

Hello,
i have the following problem during creation my own source filter written as XS:

1. for checking that filter is only one applied for source code i do:

if ( av_len(PL_rsfp_filters) > 1 )
{
 warn("too many filters\n");
}
[download]

but this check doesn't work if i use perl script like:

#!/usr/bin/perl
use myfilter; use otherfilter;
...
[download]

av_len(PL_rsfp_filters) is equal to 1 in this case!

2. i look at sources of perl and found that new filter is added to PL_rsfp_filters after call of filter_add() function.
so i moved my check code after call filter_add() in my module.
but this didn't help.

in result i have a question: what does PL_rsfp_filters contain ? all enabled filters? or something else ?
Thank in advance.

Comment on PL_rsfp_filters - what does it contain ? Select or Download Code

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Re: PL_rsfp_filters - what does it contain ? by Anno (Deacon) on Mar 16, 2007 at 12:31 UTC
`#!/usr/bin/perl use myfilter; use otherfilter;` [download] av_len(PL_rsfp_filters) is equal to 1 in this case! Yes, meaning there are two active filters. `av_len()`, despite its name, returns the highest index in the array, not the number of elements. Anno	[reply] [d/l] [select]
Re^2: PL_rsfp_filters - what does it contain ? by sawoy (Initiate) on Mar 16, 2007 at 16:42 UTC
thanks, Anno! i search aroung PL_rsfp_filters but forget about av_len() as i see in sources number of array's elements is always (av_len() + 1). so i can use statement like: if ( (av_len(PL_rsfp_filters) + 1) > 1 ) that is equal to already founded checking: if ( av_len(PL_rsfp_filters) > 0 )	[reply]
Re^3: PL_rsfp_filters - what does it contain ? by Anno (Deacon) on Mar 17, 2007 at 15:08 UTC
i search aroung PL_rsfp_filters but forget about av_len() Ah yes, that's known as an XY problem: You asked (first yourself, then the Perl Monks) about the content of `PL_rsfp_filters` (that's X), but your problem was understanding `av_len()` (Y). Good thing you mentioned `av_len()` in the body of your query. It might have been unanswerable otherwise. `if ( av_len(PL_rsfp_filters) > 0 )` Right, that checks for two or more filters. In view of the problem you had with the statement, it probably deserves a comment: `if ( av_len(PL_rsfp_filters) > 0 ) { /* We only deal with a single filter /` [download] Anno Update:* Identified X and Y in the XY problem	[reply] [d/l] [select]