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diff --git a/contrib/perl5/ext/Devel/Peek/Peek.pm b/contrib/perl5/ext/Devel/Peek/Peek.pm new file mode 100644 index 0000000..080251b --- /dev/null +++ b/contrib/perl5/ext/Devel/Peek/Peek.pm @@ -0,0 +1,432 @@ +# Devel::Peek - A data debugging tool for the XS programmer +# The documentation is after the __END__ + +package Devel::Peek; + +# Underscore to allow older Perls to access older version from CPAN +$VERSION = '1.00_01'; + +require Exporter; +use XSLoader (); + +@ISA = qw(Exporter); +@EXPORT = qw(Dump mstat DeadCode DumpArray DumpWithOP DumpProg); +@EXPORT_OK = qw(SvREFCNT SvREFCNT_inc SvREFCNT_dec CvGV); +%EXPORT_TAGS = ('ALL' => [@EXPORT, @EXPORT_OK]); + +XSLoader::load 'Devel::Peek'; + +sub DumpWithOP ($;$) { + local($Devel::Peek::dump_ops)=1; + my $depth = @_ > 1 ? $_[1] : 4 ; + Dump($_[0],$depth); +} + +1; +__END__ + +=head1 NAME + +Devel::Peek - A data debugging tool for the XS programmer + +=head1 SYNOPSIS + + use Devel::Peek; + Dump( $a ); + Dump( $a, 5 ); + DumpArray( 5, $a, $b, ... ); + mstat "Point 5"; + +=head1 DESCRIPTION + +Devel::Peek contains functions which allows raw Perl datatypes to be +manipulated from a Perl script. This is used by those who do XS programming +to check that the data they are sending from C to Perl looks as they think +it should look. The trick, then, is to know what the raw datatype is +supposed to look like when it gets to Perl. This document offers some tips +and hints to describe good and bad raw data. + +It is very possible that this document will fall far short of being useful +to the casual reader. The reader is expected to understand the material in +the first few sections of L<perlguts>. + +Devel::Peek supplies a C<Dump()> function which can dump a raw Perl +datatype, and C<mstat("marker")> function to report on memory usage +(if perl is compiled with corresponding option). The function +DeadCode() provides statistics on the data "frozen" into inactive +C<CV>. Devel::Peek also supplies C<SvREFCNT()>, C<SvREFCNT_inc()>, and +C<SvREFCNT_dec()> which can query, increment, and decrement reference +counts on SVs. This document will take a passive, and safe, approach +to data debugging and for that it will describe only the C<Dump()> +function. For format of output of mstats() see +L<perldebug/Using C<$ENV{PERL_DEBUG_MSTATS}>>. + +Function C<DumpArray()> allows dumping of multiple values (useful when you +need to analize returns of functions). + +The global variable $Devel::Peek::pv_limit can be set to limit the +number of character printed in various string values. Setting it to 0 +means no limit. + +=head1 EXAMPLES + +The following examples don't attempt to show everything as that would be a +monumental task, and, frankly, we don't want this manpage to be an internals +document for Perl. The examples do demonstrate some basics of the raw Perl +datatypes, and should suffice to get most determined people on their way. +There are no guidewires or safety nets, nor blazed trails, so be prepared to +travel alone from this point and on and, if at all possible, don't fall into +the quicksand (it's bad for business). + +Oh, one final bit of advice: take L<perlguts> with you. When you return we +expect to see it well-thumbed. + +=head2 A simple scalar string + +Let's begin by looking a simple scalar which is holding a string. + + use Devel::Peek; + $a = "hello"; + Dump $a; + +The output: + + SV = PVIV(0xbc288) + REFCNT = 1 + FLAGS = (POK,pPOK) + IV = 0 + PV = 0xb2048 "hello"\0 + CUR = 5 + LEN = 6 + +This says C<$a> is an SV, a scalar. The scalar is a PVIV, a string. +Its reference count is 1. It has the C<POK> flag set, meaning its +current PV field is valid. Because POK is set we look at the PV item +to see what is in the scalar. The \0 at the end indicate that this +PV is properly NUL-terminated. +If the FLAGS had been IOK we would look +at the IV item. CUR indicates the number of characters in the PV. +LEN indicates the number of bytes requested for the PV (one more than +CUR, in this case, because LEN includes an extra byte for the +end-of-string marker). + +=head2 A simple scalar number + +If the scalar contains a number the raw SV will be leaner. + + use Devel::Peek; + $a = 42; + Dump $a; + +The output: + + SV = IV(0xbc818) + REFCNT = 1 + FLAGS = (IOK,pIOK) + IV = 42 + +This says C<$a> is an SV, a scalar. The scalar is an IV, a number. Its +reference count is 1. It has the C<IOK> flag set, meaning it is currently +being evaluated as a number. Because IOK is set we look at the IV item to +see what is in the scalar. + +=head2 A simple scalar with an extra reference + +If the scalar from the previous example had an extra reference: + + use Devel::Peek; + $a = 42; + $b = \$a; + Dump $a; + +The output: + + SV = IV(0xbe860) + REFCNT = 2 + FLAGS = (IOK,pIOK) + IV = 42 + +Notice that this example differs from the previous example only in its +reference count. Compare this to the next example, where we dump C<$b> +instead of C<$a>. + +=head2 A reference to a simple scalar + +This shows what a reference looks like when it references a simple scalar. + + use Devel::Peek; + $a = 42; + $b = \$a; + Dump $b; + +The output: + + SV = RV(0xf041c) + REFCNT = 1 + FLAGS = (ROK) + RV = 0xbab08 + SV = IV(0xbe860) + REFCNT = 2 + FLAGS = (IOK,pIOK) + IV = 42 + +Starting from the top, this says C<$b> is an SV. The scalar is an RV, a +reference. It has the C<ROK> flag set, meaning it is a reference. Because +ROK is set we have an RV item rather than an IV or PV. Notice that Dump +follows the reference and shows us what C<$b> was referencing. We see the +same C<$a> that we found in the previous example. + +Note that the value of C<RV> coincides with the numbers we see when we +stringify $b. The addresses inside RV() and IV() are addresses of +C<X***> structure which holds the current state of an C<SV>. This +address may change during lifetime of an SV. + +=head2 A reference to an array + +This shows what a reference to an array looks like. + + use Devel::Peek; + $a = [42]; + Dump $a; + +The output: + + SV = RV(0xf041c) + REFCNT = 1 + FLAGS = (ROK) + RV = 0xb2850 + SV = PVAV(0xbd448) + REFCNT = 1 + FLAGS = () + IV = 0 + NV = 0 + ARRAY = 0xb2048 + ALLOC = 0xb2048 + FILL = 0 + MAX = 0 + ARYLEN = 0x0 + FLAGS = (REAL) + Elt No. 0 0xb5658 + SV = IV(0xbe860) + REFCNT = 1 + FLAGS = (IOK,pIOK) + IV = 42 + +This says C<$a> is an SV and that it is an RV. That RV points to +another SV which is a PVAV, an array. The array has one element, +element zero, which is another SV. The field C<FILL> above indicates +the last element in the array, similar to C<$#$a>. + +If C<$a> pointed to an array of two elements then we would see the +following. + + use Devel::Peek 'Dump'; + $a = [42,24]; + Dump $a; + +The output: + + SV = RV(0xf041c) + REFCNT = 1 + FLAGS = (ROK) + RV = 0xb2850 + SV = PVAV(0xbd448) + REFCNT = 1 + FLAGS = () + IV = 0 + NV = 0 + ARRAY = 0xb2048 + ALLOC = 0xb2048 + FILL = 0 + MAX = 0 + ARYLEN = 0x0 + FLAGS = (REAL) + Elt No. 0 0xb5658 + SV = IV(0xbe860) + REFCNT = 1 + FLAGS = (IOK,pIOK) + IV = 42 + Elt No. 1 0xb5680 + SV = IV(0xbe818) + REFCNT = 1 + FLAGS = (IOK,pIOK) + IV = 24 + +Note that C<Dump> will not report I<all> the elements in the array, +only several first (depending on how deep it already went into the +report tree). + +=head2 A reference to a hash + +The following shows the raw form of a reference to a hash. + + use Devel::Peek; + $a = {hello=>42}; + Dump $a; + +The output: + + SV = RV(0xf041c) + REFCNT = 1 + FLAGS = (ROK) + RV = 0xb2850 + SV = PVHV(0xbd448) + REFCNT = 1 + FLAGS = () + NV = 0 + ARRAY = 0xbd748 + KEYS = 1 + FILL = 1 + MAX = 7 + RITER = -1 + EITER = 0x0 + Elt "hello" => 0xbaaf0 + SV = IV(0xbe860) + REFCNT = 1 + FLAGS = (IOK,pIOK) + IV = 42 + +This shows C<$a> is a reference pointing to an SV. That SV is a PVHV, a +hash. Fields RITER and EITER are used by C<L<each>>. + +=head2 Dumping a large array or hash + +The C<Dump()> function, by default, dumps up to 4 elements from a +toplevel array or hash. This number can be increased by supplying a +second argument to the function. + + use Devel::Peek; + $a = [10,11,12,13,14]; + Dump $a; + +Notice that C<Dump()> prints only elements 10 through 13 in the above code. +The following code will print all of the elements. + + use Devel::Peek 'Dump'; + $a = [10,11,12,13,14]; + Dump $a, 5; + +=head2 A reference to an SV which holds a C pointer + +This is what you really need to know as an XS programmer, of course. When +an XSUB returns a pointer to a C structure that pointer is stored in an SV +and a reference to that SV is placed on the XSUB stack. So the output from +an XSUB which uses something like the T_PTROBJ map might look something like +this: + + SV = RV(0xf381c) + REFCNT = 1 + FLAGS = (ROK) + RV = 0xb8ad8 + SV = PVMG(0xbb3c8) + REFCNT = 1 + FLAGS = (OBJECT,IOK,pIOK) + IV = 729160 + NV = 0 + PV = 0 + STASH = 0xc1d10 "CookBookB::Opaque" + +This shows that we have an SV which is an RV. That RV points at another +SV. In this case that second SV is a PVMG, a blessed scalar. Because it is +blessed it has the C<OBJECT> flag set. Note that an SV which holds a C +pointer also has the C<IOK> flag set. The C<STASH> is set to the package +name which this SV was blessed into. + +The output from an XSUB which uses something like the T_PTRREF map, which +doesn't bless the object, might look something like this: + + SV = RV(0xf381c) + REFCNT = 1 + FLAGS = (ROK) + RV = 0xb8ad8 + SV = PVMG(0xbb3c8) + REFCNT = 1 + FLAGS = (IOK,pIOK) + IV = 729160 + NV = 0 + PV = 0 + +=head2 A reference to a subroutine + +Looks like this: + + SV = RV(0x798ec) + REFCNT = 1 + FLAGS = (TEMP,ROK) + RV = 0x1d453c + SV = PVCV(0x1c768c) + REFCNT = 2 + FLAGS = () + IV = 0 + NV = 0 + COMP_STASH = 0x31068 "main" + START = 0xb20e0 + ROOT = 0xbece0 + XSUB = 0x0 + XSUBANY = 0 + GVGV::GV = 0x1d44e8 "MY" :: "top_targets" + FILE = "(eval 5)" + DEPTH = 0 + PADLIST = 0x1c9338 + +This shows that + +=over + +=item * + +the subroutine is not an XSUB (since C<START> and C<ROOT> are +non-zero, and C<XSUB> is zero); + +=item * + +that it was compiled in the package C<main>; + +=item * + +under the name C<MY::top_targets>; + +=item * + +inside a 5th eval in the program; + +=item * + +it is not currently executed (see C<DEPTH>); + +=item * + +it has no prototype (C<PROTOTYPE> field is missing). + +=back + +=head1 EXPORTS + +C<Dump>, C<mstat>, C<DeadCode>, C<DumpArray>, C<DumpWithOP> and +C<DumpProg> by default. Additionally available C<SvREFCNT>, +C<SvREFCNT_inc> and C<SvREFCNT_dec>. + +=head1 BUGS + +Readers have been known to skip important parts of L<perlguts>, causing much +frustration for all. + +=head1 AUTHOR + +Ilya Zakharevich ilya@math.ohio-state.edu + +Copyright (c) 1995-98 Ilya Zakharevich. All rights reserved. +This program is free software; you can redistribute it and/or +modify it under the same terms as Perl itself. + +Author of this software makes no claim whatsoever about suitability, +reliability, edability, editability or usability of this product, and +should not be kept liable for any damage resulting from the use of +it. If you can use it, you are in luck, if not, I should not be kept +responsible. Keep a handy copy of your backup tape at hand. + +=head1 SEE ALSO + +L<perlguts>, and L<perlguts>, again. + +=cut |
