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✏️ Editing: CheckLib.pm Read Only

package FFI::CheckLib;

use strict;
use warnings;
use File::Spec;
use List::Util 1.33 qw( any );
use Carp qw( croak carp );
use Env qw( @FFI_CHECKLIB_PATH );
use base qw( Exporter );

our @EXPORT = qw(
  find_lib
  assert_lib
  check_lib
  check_lib_or_exit
  find_lib_or_exit
  find_lib_or_die
);

our @EXPORT_OK = qw(
  which
  where
  has_symbols
);

# ABSTRACT: Check that a library is available for FFI
our $VERSION = '0.31'; # VERSION

our $system_path = [];
our $os ||= $^O;
my $try_ld_on_text = 0;

sub _homebrew_lib_path {
  require File::Which;
  return undef unless File::Which::which('brew');
  chomp(my $brew_path = (qx`brew --prefix`)[0]);
  return "$brew_path/lib";
}

sub _macports_lib_path {
  require File::Which;
  my $port_path = File::Which::which('port');
  return undef unless $port_path;
  $port_path =~ s|bin/port|lib|;
  return $port_path;
}

sub _darwin_extra_paths {
  my $pkg_managers = lc( $ENV{FFI_CHECKLIB_PACKAGE} || 'homebrew,macports' );
  return () if $pkg_managers eq 'none';
  my $supported_managers = {
      homebrew => \&_homebrew_lib_path,
      macports => \&_macports_lib_path
  };
  my @extra_paths = ();
  foreach my $pkg_manager (split( /,/, $pkg_managers )) {
    if (my $lib_path = $supported_managers->{$pkg_manager}()) {
      push @extra_paths, $lib_path;
    }
  }
  return @extra_paths;
}

my @extra_paths = ();
if($os eq 'MSWin32' || $os eq 'msys')
{
  $system_path = eval {
    require Env;
    Env->import('@PATH');
    \our @PATH;
  };
  die $@ if $@;
}
else
{
  $system_path = eval {
    require DynaLoader;
    no warnings 'once';
    \@DynaLoader::dl_library_path;
  };
  die $@ if $@;
  @extra_paths = _darwin_extra_paths() if $os eq 'darwin';
}

our $pattern = [ qr{^lib(.*?)\.so(?:\.([0-9]+(?:\.[0-9]+)*))?$} ];
our $version_split = qr/\./;

if($os eq 'cygwin')
{
  push @$pattern, qr{^cyg(.*?)(?:-([0-9])+)?\.dll$};
}
elsif($os eq 'msys')
{
  # doesn't seem as though msys uses psudo libfoo.so files
  # in the way that cygwin sometimes does.  we can revisit
  # this if we find otherwise.
  $pattern = [ qr{^msys-(.*?)(?:-([0-9])+)?\.dll$} ];
}
elsif($os eq 'MSWin32')
{
  #  handle cases like libgeos-3-7-0___.dll, libproj_9_1.dll and libgtk-2.0-0.dll
  $pattern = [ qr{^(?:lib)?(\w+?)(?:[_-]([0-9\-\._]+))?_*\.dll$}i ];
  $version_split = qr/[_\-]/;
}
elsif($os eq 'darwin')
{
  push @$pattern, qr{^lib(.*?)(?:\.([0-9]+(?:\.[0-9]+)*))?\.(?:dylib|bundle)$};
}
elsif($os eq 'linux')
{
  if(-e '/etc/redhat-release' && -x '/usr/bin/ld')
  {
    $try_ld_on_text = 1;
  }
}

sub _matches
{
  my($filename, $path) = @_;

foreach my $regex (@$pattern)
  {
    return [
      $1,                                            # 0    capture group 1 library name
      File::Spec->catfile($path, $filename),         # 1    full path to library
      defined $2 ? (split $version_split, $2) : (),  # 2... capture group 2 library version
    ] if $filename =~ $regex;
  }
  return ();
}

sub _cmp
{
  my($A,$B) = @_;

return $A->[0] cmp $B->[0] if $A->[0] ne $B->[0];

my $i=2;
  while(1)
  {
    return 0  if !defined($A->[$i]) && !defined($B->[$i]);
    return -1 if !defined $A->[$i];
    return 1  if !defined $B->[$i];
    return $B->[$i] <=> $A->[$i] if $A->[$i] != $B->[$i];
    $i++;
  }
}

my $diagnostic;

sub _is_binary
{
  -B $_[0]
}

sub find_lib
{
  my(%args) = @_;

undef $diagnostic;
  croak "find_lib requires lib argument" unless defined $args{lib};

my $recursive = $args{_r} || $args{recursive} || 0;

# make arguments be lists.
  foreach my $arg (qw( lib libpath symbol verify alien ))
  {
    next if ref $args{$arg} eq 'ARRAY';
    if(defined $args{$arg})
    {
      $args{$arg} = [ $args{$arg} ];
    }
    else
    {
      $args{$arg} = [];
    }
  }

if(defined $args{systempath} && !ref($args{systempath}))
  {
    $args{systempath} = [ $args{systempath} ];
  }

my @path = @{ $args{libpath} };
  @path = map { _recurse($_) } @path if $recursive;

if(defined $args{systempath})
  {
    push @path, grep { defined } @{ $args{systempath} }
  }
  else
  {
    # This is a little convaluted, but:
    # 1. These are modifications of what we consider the "system" path
    #    if systempath isn't explicitly passed in as systempath
    # 2. FFI_CHECKLIB_PATH is considered an authortative modification
    #    so it goes first and overrides FFI_CHECKLIB_PACKAGE
    # 3. otherwise FFI_CHECKLIB_PACKAGE does its thing and goes on
    #    the end because homebrew does a good job of not replacing
    #    anything in the system by default.
    # 4. We finally add what we consider the "system" path to the end of
    #    the search path so that libpath will be searched first.
    my @system_path = @$system_path;
    if($ENV{FFI_CHECKLIB_PATH})
    {
      @system_path = (@FFI_CHECKLIB_PATH, @system_path);
    }
    else
    {
      foreach my $extra_path (@extra_paths)
      {
        push @path, $extra_path unless any { $_ eq $extra_path } @path;
      }
    }
    push @path, @system_path;
  }

my $any = any { $_ eq '*' } @{ $args{lib} };
  my %missing = map { $_ => 1 } @{ $args{lib} };
  my %symbols = map { $_ => 1 } @{ $args{symbol} };
  my @found;

delete $missing{'*'};

alien: foreach my $alien (reverse @{ $args{alien} })
  {
    unless($alien =~ /^([A-Za-z_][A-Za-z_0-9]*)(::[A-Za-z_][A-Za-z_0-9]*)*$/)
    {
      croak "Doesn't appear to be a valid Alien name $alien";
    }
    unless(eval { $alien->can('dynamic_libs') })
    {
      {
        my $pm = "$alien.pm";
        $pm =~ s/::/\//g;
        local $@ = '';
        eval { require $pm };
        next alien if $@;
      }
      unless(eval { $alien->can('dynamic_libs') })
      {
        croak "Alien $alien doesn't provide a dynamic_libs method";
      }
    }
    unshift @path, [$alien->dynamic_libs];
  }

foreach my $path (@path)
  {
    next if ref $path ne 'ARRAY' && ! -d $path;

my @maybe =
      # make determinist based on names and versions
      sort { _cmp($a,$b) }
      # Filter out the items that do not match the name that we are looking for
      # Filter out any broken symbolic links
      grep { ($any || $missing{$_->[0]} ) && (-e $_->[1]) }
      ref $path eq 'ARRAY'
        ? do {
          map {
            my($v, $d, $f) = File::Spec->splitpath($_);
            _matches($f, File::Spec->catpath($v,$d,''));
          } @$path;
        }
        : do {
          my $dh;
          opendir $dh, $path;
          # get [ name, full_path ] mapping,
          # each entry is a 2 element list ref
          map { _matches($_,$path) } readdir $dh;
        };

if($try_ld_on_text && $args{try_linker_script})
    {
      # This is tested in t/ci.t only
      @maybe = map {
        -B $_->[1] ? $_ : do {
          my($name, $so) = @$_;
          my $output = `/usr/bin/ld -t $so -o /dev/null -shared`;
          $output =~ /$(.*?lib.*\.so.*?)$/
            ? [$name, $1]
            : die "unable to parse ld output";
        }
      } @maybe;
    }

midloop:
    foreach my $lib (@maybe)
    {
      next unless $any || $missing{$lib->[0]};

foreach my $verify (@{ $args{verify} })
      {
        next midloop unless $verify->(@$lib);
      }

delete $missing{$lib->[0]};

if(%symbols)
      {
        require DynaLoader;
        my $dll = DynaLoader::dl_load_file($lib->[1],0);
        foreach my $symbol (keys %symbols)
        {
          if(DynaLoader::dl_find_symbol($dll, $symbol) ? 1 : 0)
          {
            delete $symbols{$symbol}
          }
        }
        DynaLoader::dl_unload_file($dll);
      }

my $found = $lib->[1];

unless($any)
      {
        while(-l $found)
        {
          require File::Basename;
          my $dir = File::Basename::dirname($found);
          $found = File::Spec->rel2abs( readlink($found), $dir );
        }
      }

push @found, $found;
    }
  }

if(%missing)
  {
    my @missing = sort keys %missing;
    if(@missing > 1)
    { $diagnostic = "libraries not found: @missing" }
    else
    { $diagnostic = "library not found: @missing" }
  }
  elsif(%symbols)
  {
    my @missing = sort keys %symbols;
    if(@missing > 1)
    { $diagnostic = "symbols not found: @missing" }
    else
    { $diagnostic = "symbol not found: @missing" }
  }

return if %symbols;
  return $found[0] unless wantarray;
  return @found;
}

sub _recurse
{
  my($dir) = @_;
  return unless -d $dir;
  my $dh;
  opendir $dh, $dir;
  my @list = grep { -d $_ } map { File::Spec->catdir($dir, $_) } grep !/^\.\.?$/, readdir $dh;
  closedir $dh;
  ($dir, map { _recurse($_) } @list);
}

sub assert_lib
{
  croak $diagnostic || 'library not found' unless check_lib(@_);
}

sub check_lib_or_exit
{
  unless(check_lib(@_))
  {
    carp $diagnostic || 'library not found';
    exit;
  }
}

sub find_lib_or_exit
{
  my(@libs) = find_lib(@_);
  unless(@libs)
  {
    carp $diagnostic || 'library not found';
    exit;
  }
  return unless @libs;
  wantarray ? @libs : $libs[0];
}

sub find_lib_or_die
{
  my(@libs) = find_lib(@_);
  unless(@libs)
  {
    croak $diagnostic || 'library not found';
  }
  return unless @libs;
  wantarray ? @libs : $libs[0];
}

sub check_lib
{
  find_lib(@_) ? 1 : 0;
}

sub which
{
  my($name) = @_;
  croak("cannot which *") if $name eq '*';
  scalar find_lib( lib => $name );
}

sub where
{
  my($name) = @_;
  $name eq '*'
    ? find_lib(lib => '*')
    : find_lib(lib => '*', verify => sub { $_[0] eq $name });
}

sub has_symbols
{
  my($path, @symbols) = @_;
  require DynaLoader;
  my $dll = DynaLoader::dl_load_file($path, 0);

my $ok = 1;

foreach my $symbol (@symbols)
  {
    unless(DynaLoader::dl_find_symbol($dll, $symbol))
    {
      $ok = 0;
      last;
    }
  }

DynaLoader::dl_unload_file($dll);

$ok;
}

sub system_path
{
  $system_path;
}

__END__

=pod

=encoding UTF-8

=head1 NAME

FFI::CheckLib - Check that a library is available for FFI

=head1 VERSION

version 0.31

=head1 SYNOPSIS

use FFI::CheckLib;
 
 check_lib_or_exit( lib => 'jpeg', symbol => 'jinit_memory_mgr' );
 check_lib_or_exit( lib => [ 'iconv', 'jpeg' ] );
 
 # or prompt for path to library and then:
 print "where to find jpeg library: ";
 my $path = <STDIN>;
 check_lib_or_exit( lib => 'jpeg', libpath => $path );

=head1 DESCRIPTION

This module checks whether a particular dynamic library is available for
FFI to use. It is modeled heavily on L<Devel::CheckLib>, but will find
dynamic libraries even when development packages are not installed.  It
also provides a L<find_lib|FFI::CheckLib#find_lib> function that will
return the full path to the found dynamic library, which can be feed
directly into L<FFI::Platypus> or another FFI system.

Although intended mainly for FFI modules via L<FFI::Platypus> and
similar, this module does not actually use any FFI to do its detection
and probing.  This module does not have any non-core runtime dependencies.
The test suite does depend on L<Test2::Suite>.

=head1 FUNCTIONS

All of these take the same named parameters and are exported by default.

=head2 find_lib

my(@libs) = find_lib(%args);

This will return a list of dynamic libraries, or empty list if none were
found.

[version 0.05]

If called in scalar context it will return the first library found.

Arguments are key value pairs with these keys:

=over 4

=item lib

Must be either a string with the name of a single library or a reference
to an array of strings of library names.  Depending on your platform,
C<CheckLib> will prepend C<lib> or append C<.dll> or C<.so> when
searching.

[version 0.11]

As a special case, if C<*> is specified then any libs found will match.

=item libpath

A string or array of additional paths to search for libraries.

=item systempath

[version 0.11]

A string or array of system paths to search for instead of letting
L<FFI::CheckLib> determine the system path.  You can set this to C<[]>
in order to not search I<any> system paths.

=item symbol

A string or a list of symbol names that must be found.

=item verify

A code reference used to verify a library really is the one that you
want.  It should take two arguments, which is the name of the library
and the full path to the library pathname.  It should return true if it
is acceptable, and false otherwise.  You can use this in conjunction
with L<FFI::Platypus> to determine if it is going to meet your needs.
Example:

use FFI::CheckLib;
 use FFI::Platypus;
 
 my($lib) = find_lib(
   lib => 'foo',
   verify => sub {
     my($name, $libpath) = @_;
 
     my $ffi = FFI::Platypus->new;
     $ffi->lib($libpath);
 
     my $f = $ffi->function('foo_version', [] => 'int');
 
     return $f->call() >= 500; # we accept version 500 or better
   },
 );

=item recursive

[version 0.11]

Recursively search for libraries in any non-system paths (those provided
via C<libpath> above).

=item try_linker_script

[version 0.24]

Some vendors provide C<.so> files that are linker scripts that point to
the real binary shared library.  These linker scripts can be used by gcc
or clang, but are not directly usable by L<FFI::Platypus> and friends.
On select platforms, this options will use the linker command (C<ld>)
to attempt to resolve the real C<.so> for non-binary files.  Since there
is extra overhead this is off by default.

An example is libyaml on Red Hat based Linux distributions.  On Debian
these are handled with symlinks and no trickery is required.

=item alien

[version 0.25]

If no libraries can be found, try the given aliens instead.  The Alien
classes specified must provide the L<Alien::Base> interface for dynamic
libraries, which is to say they should provide a method called
C<dynamic_libs> that returns a list of dynamic libraries.

[version 0.28]

In 0.28 and later, if the L<Alien> is not installed then it will be
ignored and this module will search in system or specified directories
only.  This module I<will> still throw an exception, if the L<Alien>
doesn't look like a module name or if it does not provide a C<dynamic_libs>
method (which is implemented by all L<Alien::Base> subclasses).

[version 0.30]
[breaking change]

Starting with version 0.30, libraries provided by L<Alien>s is preferred
over the system libraries.  The original thinking was that you want to
prefer the system libraries because they are more likely to get patched
with regular system updates.  Unfortunately, the reason a module needs to
install an Alien is likely because the system library is not new enough,
so we now prefer the L<Alien>s instead.

=back

=head2 assert_lib

assert_lib(%args);

This behaves exactly the same as L<find_lib|FFI::CheckLib#find_lib>,
except that instead of returning empty list of failure it throws an
exception.

=head2 check_lib_or_exit

check_lib_or_exit(%args);

This behaves exactly the same as L<assert_lib|FFI::CheckLib#assert_lib>,
except that instead of dying, it warns (with exactly the same error
message) and exists.  This is intended for use in C<Makefile.PL> or
C<Build.PL>

=head2 find_lib_or_exit

[version 0.05]

my(@libs) = find_lib_or_exit(%args);

This behaves exactly the same as L<find_lib|FFI::CheckLib#find_lib>,
except that if the library is not found, it will call exit with an
appropriate diagnostic.

=head2 find_lib_or_die

[version 0.06]

my(@libs) = find_lib_or_die(%args);

This behaves exactly the same as L<find_lib|FFI::CheckLib#find_lib>,
except that if the library is not found, it will die with an appropriate
diagnostic.

=head2 check_lib

my $bool = check_lib(%args);

This behaves exactly the same as L<find_lib|FFI::CheckLib#find_lib>,
except that it returns true (1) on finding the appropriate libraries or
false (0) otherwise.

=head2 which

[version 0.17]

my $path = which($name);

Return the path to the first library that matches the given name.

Not exported by default.

=head2 where

[version 0.17]

my @paths = where($name);

Return the paths to all the libraries that match the given name.

Not exported by default.

=head2 has_symbols

[version 0.17]

my $bool = has_symbols($path, @symbol_names);

Returns true if I<all> of the symbols can be found in the dynamic library located
at the given path.  Can be useful in conjunction with C<verify> with C<find_lib>
above.

Not exported by default.

=head2 system_path

[version 0.20]

my $path = FFI::CheckLib::system_path;

Returns the system path as a list reference.  On some systems, this is C<PATH>
on others it might be C<LD_LIBRARY_PATH> on still others it could be something
completely different.  So although you I<may> add items to this list, you should
probably do some careful consideration before you do so.

This function is not exportable, even on request.

=head1 ENVIRONMENT

L<FFI::CheckLib> responds to these environment variables:

=over 4

=item FFI_CHECKLIB_PACKAGE

On macOS platforms with L<Homebrew|http://brew.sh> and/or L<MacPorts|https://www.macports.org>
installed, their corresponding lib paths will be automatically appended to C<$system_path>.
In case of having both managers installed, Homebrew will appear before.

This behaviour can be overridden using the environment variable C<FFI_CHECKLIB_PACKAGE>.

Allowed values are:

- C<none>: Won't use either Homebrew's path nor MacPorts
- C<homebrew>: Will append C<$(brew --prefix)/lib> to the system paths
- C<macports>: Will append C<port>'s default lib path

A comma separated list is also valid:

export FFI_CHECKLIB_PACKAGE=macports,homebrew

Order matters. So in this example, MacPorts' lib path appears before Homebrew's path.

=item FFI_CHECKLIB_PATH

List of directories that will be considered by L<FFI::CheckLib> as additional "system
directories".  They will be searched before other system directories but after C<libpath>.
The variable is colon separated on Unix and semicolon separated on Windows.  If you
use this variable, C<FFI_CHECKLIB_PACKAGE> will be ignored.

=item PATH

On Windows the C<PATH> environment variable will be used as a search path for
libraries.

=back

On some operating systems C<LD_LIBRARY_PATH>, C<DYLD_LIBRARY_PATH>,
C<DYLD_FALLBACK_LIBRARY_PATH> or others I<may> be used as part of the search
for dynamic libraries and I<may> be used (indirectly) by L<FFI::CheckLib>
as well.

=head1 FAQ

=over 4

=item Why not just use C<dlopen>?

Calling C<dlopen> on a library name and then C<dlclose> immediately can tell
you if you have the exact name of a library available on a system.  It does
have a number of drawbacks as well.

=over 4

=item No absolute or relative path

It only tells you that the library is I<somewhere> on the system, not having
the absolute or relative path makes it harder to generate useful diagnostics.

=item POSIX only

This doesn't work on non-POSIX systems like Microsoft Windows. If you are
using a POSIX emulation layer on Windows that provides C<dlopen>, like
Cygwin, there are a number of gotchas there as well.  Having a layer written
in Perl handles this means that developers on Unix can develop FFI that will
more likely work on these platforms without special casing them.

=item inconsistent implementations

Even on POSIX systems you have inconsistent implementations.  OpenBSD for
example don't usually include symlinks for C<.so> files meaning you need
to know the exact C<.so> version.

=item non-system directories

By default C<dlopen> only works for libraries in the system paths.  Most
platforms have a way of configuring the search for different non-system
paths, but none of them are portable, and are usually discouraged anyway.
L<Alien> and friends need to do searches for dynamic libraries in
non-system directories for C<share> installs.

=back

=item My 64-bit Perl is misconfigured and has 32-bit libraries in its search path.  Is that a bug in L<FFI::CheckLib>?

Nope.

=item The way L<FFI::CheckLib> is implemented it won't work on AIX, HP-UX, OpenVMS or Plan 9.

I know for a fact that it doesn't work on AIX I<as currently implemented>
because I used to develop on AIX in the early 2000s, and I am aware of some
of the technical challenges.  There are probably other systems that it won't
work on.  I would love to add support for these platforms.  Realistically
these platforms have a tiny market share, and absent patches from users or
the companies that own these operating systems (patches welcome), or hardware
/ CPU time donations, these platforms are unsupportable anyway.

=back

=head1 SEE ALSO

=over 4

=item L<FFI::Platypus>

Call library functions dynamically without a compiler.

=item L<Dist::Zilla::Plugin::FFI::CheckLib>

L<Dist::Zilla> plugin for this module.

=back

=head1 AUTHOR

Author: Graham Ollis E<lt>plicease@cpan.orgE<gt>

Contributors:

Bakkiaraj Murugesan (bakkiaraj)

Dan Book (grinnz, DBOOK)

Ilya Pavlov (Ilya, ILUX)

Shawn Laffan (SLAFFAN)

Petr Písař (ppisar)

Michael R. Davis (MRDVT)

Shawn Laffan (SLAFFAN)

Carlos D. Álvaro (cdalvaro)

=head1 COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut

✏️ Editing: CheckLib.pm Read Only

package FFI::CheckLib;

use strict;
use warnings;
use File::Spec;
use List::Util 1.33 qw( any );
use Carp qw( croak carp );
use Env qw( @FFI_CHECKLIB_PATH );
use base qw( Exporter );

our @EXPORT = qw(
  find_lib
  assert_lib
  check_lib
  check_lib_or_exit
  find_lib_or_exit
  find_lib_or_die
);

our @EXPORT_OK = qw(
  which
  where
  has_symbols
);

# ABSTRACT: Check that a library is available for FFI
our $VERSION = '0.31'; # VERSION

our $system_path = [];
our $os ||= $^O;
my $try_ld_on_text = 0;

sub _homebrew_lib_path {
  require File::Which;
  return undef unless File::Which::which('brew');
  chomp(my $brew_path = (qx`brew --prefix`)[0]);
  return "$brew_path/lib";
}

sub _macports_lib_path {
  require File::Which;
  my $port_path = File::Which::which('port');
  return undef unless $port_path;
  $port_path =~ s|bin/port|lib|;
  return $port_path;
}

our $pattern = [ qr{^lib(.*?)\.so(?:\.([0-9]+(?:\.[0-9]+)*))?$} ];
our $version_split = qr/\./;

sub _matches
{
  my($filename, $path) = @_;

sub _cmp
{
  my($A,$B) = @_;

return $A->[0] cmp $B->[0] if $A->[0] ne $B->[0];

my $diagnostic;

sub _is_binary
{
  -B $_[0]
}

sub find_lib
{
  my(%args) = @_;

undef $diagnostic;
  croak "find_lib requires lib argument" unless defined $args{lib};

my $recursive = $args{_r} || $args{recursive} || 0;

if(defined $args{systempath} && !ref($args{systempath}))
  {
    $args{systempath} = [ $args{systempath} ];
  }

my @path = @{ $args{libpath} };
  @path = map { _recurse($_) } @path if $recursive;

my $any = any { $_ eq '*' } @{ $args{lib} };
  my %missing = map { $_ => 1 } @{ $args{lib} };
  my %symbols = map { $_ => 1 } @{ $args{symbol} };
  my @found;

delete $missing{'*'};

foreach my $path (@path)
  {
    next if ref $path ne 'ARRAY' && ! -d $path;

midloop:
    foreach my $lib (@maybe)
    {
      next unless $any || $missing{$lib->[0]};

foreach my $verify (@{ $args{verify} })
      {
        next midloop unless $verify->(@$lib);
      }

delete $missing{$lib->[0]};

my $found = $lib->[1];

push @found, $found;
    }
  }

return if %symbols;
  return $found[0] unless wantarray;
  return @found;
}

sub assert_lib
{
  croak $diagnostic || 'library not found' unless check_lib(@_);
}

sub check_lib_or_exit
{
  unless(check_lib(@_))
  {
    carp $diagnostic || 'library not found';
    exit;
  }
}

sub find_lib_or_exit
{
  my(@libs) = find_lib(@_);
  unless(@libs)
  {
    carp $diagnostic || 'library not found';
    exit;
  }
  return unless @libs;
  wantarray ? @libs : $libs[0];
}

sub find_lib_or_die
{
  my(@libs) = find_lib(@_);
  unless(@libs)
  {
    croak $diagnostic || 'library not found';
  }
  return unless @libs;
  wantarray ? @libs : $libs[0];
}

sub check_lib
{
  find_lib(@_) ? 1 : 0;
}

sub which
{
  my($name) = @_;
  croak("cannot which *") if $name eq '*';
  scalar find_lib( lib => $name );
}

sub where
{
  my($name) = @_;
  $name eq '*'
    ? find_lib(lib => '*')
    : find_lib(lib => '*', verify => sub { $_[0] eq $name });
}

sub has_symbols
{
  my($path, @symbols) = @_;
  require DynaLoader;
  my $dll = DynaLoader::dl_load_file($path, 0);

my $ok = 1;

foreach my $symbol (@symbols)
  {
    unless(DynaLoader::dl_find_symbol($dll, $symbol))
    {
      $ok = 0;
      last;
    }
  }

DynaLoader::dl_unload_file($dll);

$ok;
}

sub system_path
{
  $system_path;
}

__END__

=pod

=encoding UTF-8

=head1 NAME

FFI::CheckLib - Check that a library is available for FFI

=head1 VERSION

version 0.31

=head1 SYNOPSIS

=head1 DESCRIPTION

=head1 FUNCTIONS

All of these take the same named parameters and are exported by default.

=head2 find_lib

my(@libs) = find_lib(%args);

This will return a list of dynamic libraries, or empty list if none were
found.

[version 0.05]

If called in scalar context it will return the first library found.

Arguments are key value pairs with these keys:

=over 4

=item lib

[version 0.11]

As a special case, if C<*> is specified then any libs found will match.

=item libpath

A string or array of additional paths to search for libraries.

=item systempath

[version 0.11]

A string or array of system paths to search for instead of letting
L<FFI::CheckLib> determine the system path.  You can set this to C<[]>
in order to not search I<any> system paths.

=item symbol

A string or a list of symbol names that must be found.

=item verify

=item recursive

[version 0.11]

Recursively search for libraries in any non-system paths (those provided
via C<libpath> above).

=item try_linker_script

[version 0.24]

An example is libyaml on Red Hat based Linux distributions.  On Debian
these are handled with symlinks and no trickery is required.

=item alien

[version 0.25]

[version 0.28]

[version 0.30]
[breaking change]

=back

=head2 assert_lib

assert_lib(%args);

This behaves exactly the same as L<find_lib|FFI::CheckLib#find_lib>,
except that instead of returning empty list of failure it throws an
exception.

=head2 check_lib_or_exit

check_lib_or_exit(%args);

=head2 find_lib_or_exit

[version 0.05]

my(@libs) = find_lib_or_exit(%args);

This behaves exactly the same as L<find_lib|FFI::CheckLib#find_lib>,
except that if the library is not found, it will call exit with an
appropriate diagnostic.

=head2 find_lib_or_die

[version 0.06]

my(@libs) = find_lib_or_die(%args);

This behaves exactly the same as L<find_lib|FFI::CheckLib#find_lib>,
except that if the library is not found, it will die with an appropriate
diagnostic.

=head2 check_lib

my $bool = check_lib(%args);

This behaves exactly the same as L<find_lib|FFI::CheckLib#find_lib>,
except that it returns true (1) on finding the appropriate libraries or
false (0) otherwise.

=head2 which

[version 0.17]

my $path = which($name);

Return the path to the first library that matches the given name.

Not exported by default.

=head2 where

[version 0.17]

my @paths = where($name);

Return the paths to all the libraries that match the given name.

Not exported by default.

=head2 has_symbols

[version 0.17]

my $bool = has_symbols($path, @symbol_names);

Returns true if I<all> of the symbols can be found in the dynamic library located
at the given path.  Can be useful in conjunction with C<verify> with C<find_lib>
above.

Not exported by default.

=head2 system_path

[version 0.20]

my $path = FFI::CheckLib::system_path;

This function is not exportable, even on request.

=head1 ENVIRONMENT

L<FFI::CheckLib> responds to these environment variables:

=over 4

=item FFI_CHECKLIB_PACKAGE

This behaviour can be overridden using the environment variable C<FFI_CHECKLIB_PACKAGE>.

Allowed values are:

- C<none>: Won't use either Homebrew's path nor MacPorts
- C<homebrew>: Will append C<$(brew --prefix)/lib> to the system paths
- C<macports>: Will append C<port>'s default lib path

A comma separated list is also valid:

export FFI_CHECKLIB_PACKAGE=macports,homebrew

Order matters. So in this example, MacPorts' lib path appears before Homebrew's path.

=item FFI_CHECKLIB_PATH

=item PATH

On Windows the C<PATH> environment variable will be used as a search path for
libraries.

=back

=head1 FAQ

=over 4

=item Why not just use C<dlopen>?

Calling C<dlopen> on a library name and then C<dlclose> immediately can tell
you if you have the exact name of a library available on a system.  It does
have a number of drawbacks as well.

=over 4

=item No absolute or relative path

It only tells you that the library is I<somewhere> on the system, not having
the absolute or relative path makes it harder to generate useful diagnostics.

=item POSIX only

=item inconsistent implementations

Even on POSIX systems you have inconsistent implementations.  OpenBSD for
example don't usually include symlinks for C<.so> files meaning you need
to know the exact C<.so> version.

=item non-system directories

=back

=item My 64-bit Perl is misconfigured and has 32-bit libraries in its search path.  Is that a bug in L<FFI::CheckLib>?

Nope.

=item The way L<FFI::CheckLib> is implemented it won't work on AIX, HP-UX, OpenVMS or Plan 9.

=back

=head1 SEE ALSO

=over 4

=item L<FFI::Platypus>

Call library functions dynamically without a compiler.

=item L<Dist::Zilla::Plugin::FFI::CheckLib>

L<Dist::Zilla> plugin for this module.

=back

=head1 AUTHOR

Author: Graham Ollis E<lt>plicease@cpan.orgE<gt>

Contributors:

Bakkiaraj Murugesan (bakkiaraj)

Dan Book (grinnz, DBOOK)

Ilya Pavlov (Ilya, ILUX)

Shawn Laffan (SLAFFAN)

Petr Písař (ppisar)

Michael R. Davis (MRDVT)

Shawn Laffan (SLAFFAN)

Carlos D. Álvaro (cdalvaro)

=head1 COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut

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