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.\" ========================================================================
.\"
.IX Title "FFI::C::Util 3pm"
.TH FFI::C::Util 3pm "2023-02-06" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
FFI::C::Util \- Utility functions for dealing with structured C data
.SH "VERSION"
.IX Header "VERSION"
version 0.15
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 3
\& use FFI::C::Util qw( perl_to_c take );
\& use FFI::C::StructDef;
\& use FFI::Platypus::Memory qw( free );
\& 
\& my $def = FFI::C::StructDef\->new(
\&   members => [
\&     x => \*(Aquint8\*(Aq,
\&     y => \*(Aqsint64\*(Aq,
\&   ],
\& );
\& my $inst = $def\->create;
\& 
\& # initialize members
\& perl_to_c($inst, { x => 1, y => 2 });
\& 
\& # take ownership
\& my $ptr = take $inst;
\& 
\& # since we took ownership, we are responsible for freeing the memory:
\& free $ptr;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module provides some useful utility functions for dealing with
the various def instances provided by \s-1FFI::C\s0
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.SS "perl_to_c"
.IX Subsection "perl_to_c"
.Vb 2
\& perl_to_c $instance, \e%values;  # for Struct/Union
\& perl_to_c $instance, \e@values;  # for Array
.Ve
.PP
This function initializes the members of an instance.
.SS "c_to_perl"
.IX Subsection "c_to_perl"
.Vb 1
\& my $perl = c_to_perl $instance;
.Ve
.PP
This function takes an instance and returns the nested members as Perl data structures.
.SS "owned"
.IX Subsection "owned"
.Vb 1
\& my $bool = owned $instance;
.Ve
.PP
Returns true of the \f(CW$instance\fR owns its allocated memory.  That is,
it will free up the allocated memory when it falls out of scope.
Reasons an instance might not be owned are:
.IP "the instance is nested inside another object that owns the memory" 4
.IX Item "the instance is nested inside another object that owns the memory"
.PD 0
.IP "the instance was returned from a C function that owns the memory" 4
.IX Item "the instance was returned from a C function that owns the memory"
.ie n .IP "ownership was taken away by the ""take"" function below." 4
.el .IP "ownership was taken away by the \f(CWtake\fR function below." 4
.IX Item "ownership was taken away by the take function below."
.PD
.SS "take"
.IX Subsection "take"
.Vb 1
\& my $ptr = take $instance;
.Ve
.PP
This function takes ownership of the instance pointer, and returns
the opaque pointer.  This means a couple of things:
.ie n .IP "$instance will not free its data automatically" 4
.el .IP "\f(CW$instance\fR will not free its data automatically" 4
.IX Item "$instance will not free its data automatically"
You should call \f(CW\*(C`free\*(C'\fR on it manually to free the memory it is using.
.ie n .IP "$instance cannot be used anymore" 4
.el .IP "\f(CW$instance\fR cannot be used anymore" 4
.IX Item "$instance cannot be used anymore"
So don't try to get/set any of its members, or pass it into a function.
.PP
The returned pointer can be cast into something else or passed into
a function that takes an \f(CW\*(C`opaque\*(C'\fR argument.
.SS "addressof"
.IX Subsection "addressof"
[version 0.11]
.PP
.Vb 1
\& my $ptr = addressof $instance;
.Ve
.PP
This function returns the address (as an \f(CW\*(C`opaque\*(C'\fR type) of the
instance object.  This is similar to \f(CW\*(C`take\*(C'\fR above in that it gets
you the address of the object, but doesn't take ownership of it,
so care needs to be taken when using \f(CW$ptr\fR that the object
is still allocated.
.SS "set_array_count"
.IX Subsection "set_array_count"
.Vb 1
\& set_array_count $inst, $count;
.Ve
.PP
This function sets the element count on a variable array returned from
C (where normally there is no way to know from just the return value).
If you try to set a count on a non-array or a fixed sized array an
exception will be thrown.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.IP "\s-1FFI::C\s0" 4
.IX Item "FFI::C"
.PD 0
.IP "FFI::C::Array" 4
.IX Item "FFI::C::Array"
.IP "FFI::C::ArrayDef" 4
.IX Item "FFI::C::ArrayDef"
.IP "FFI::C::Def" 4
.IX Item "FFI::C::Def"
.IP "FFI::C::File" 4
.IX Item "FFI::C::File"
.IP "FFI::C::PosixFile" 4
.IX Item "FFI::C::PosixFile"
.IP "FFI::C::Struct" 4
.IX Item "FFI::C::Struct"
.IP "FFI::C::StructDef" 4
.IX Item "FFI::C::StructDef"
.IP "FFI::C::Union" 4
.IX Item "FFI::C::Union"
.IP "FFI::C::UnionDef" 4
.IX Item "FFI::C::UnionDef"
.IP "FFI::C::Util" 4
.IX Item "FFI::C::Util"
.IP "FFI::Platypus::Record" 4
.IX Item "FFI::Platypus::Record"
.PD
.SH "AUTHOR"
.IX Header "AUTHOR"
Graham Ollis <plicease@cpan.org>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
This software is copyright (c) 2020\-2022 by Graham Ollis.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.