# Copyright © 2009-2010 Modestas Vainius <modax@debian.org>
# Copyright © 2010, 2012-2015 Guillem Jover <guillem@debian.org>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

=encoding utf8

=head1 NAME

Dpkg::Shlibs::Cppfilt - C++ symbol mangling support via c++filt

=head1 DESCRIPTION

This module provides functions that wrap over c++filt for its easy and
fast usage.

B<Note>: This is a private module, its API can change at any time.

=cut

package Dpkg::Shlibs::Cppfilt 0.01;

use v5.36;

our @EXPORT = qw(
    cppfilt_demangle_cpp
);
our @EXPORT_OK = qw(
    cppfilt_demangle
);

use Exporter qw(import);

use Dpkg::ErrorHandling;
use Dpkg::IPC;

# A hash of 'objects' referring to preforked c++filt processes for the distinct
# demangling types.
my %cppfilts;

sub get_cppfilt {
    my $type = shift || 'auto';

    # Fork c++filt process for demangling $type unless it is forked already.
    # Keeping c++filt running improves performance a lot.
    my $filt;
    if (exists $cppfilts{$type}) {
        $filt = $cppfilts{$type};
    } else {
        $filt = {
            from => undef,
            to => undef,
            last_symbol => '',
            last_result => '',
        };
        $filt->{pid} = spawn(
            exec => [ 'c++filt', "--format=$type" ],
            from_pipe => \$filt->{from},
            to_pipe => \$filt->{to},
        );
        syserr(g_('cannot execute %s'), 'c++filt')
            unless defined $filt->{from};
        $filt->{from}->autoflush(1);

        $cppfilts{$type} = $filt;
    }
    return $filt;
}

# Demangle the given $symbol using demangler for the specified $type (defaults
# to 'auto') . Extraneous characters trailing after a mangled name are kept
# intact. If neither whole $symbol nor portion of it could be demangled, undef
# is returned.
sub cppfilt_demangle {
    my ($symbol, $type) = @_;

    # Start or get c++filt 'object' for the requested type.
    my $filt = get_cppfilt($type);

    # Remember the last result. Such a local optimization is cheap and useful
    # when sequential pattern matching is performed.
    if ($filt->{last_symbol} ne $symbol) {
        # This write/read operation should not deadlock because c++filt flushes
        # output buffer on LF or each invalid character.
        print { $filt->{from} } $symbol, "\n";
        my $demangled = readline($filt->{to});
        chop $demangled;

        # If the symbol was not demangled, return undef. Otherwise normalize
        # it as llvm packs ending angle brackets with no intermediate spaces
        # as allowed by C++11, contrary to GNU binutils.
        if ($symbol eq $demangled) {
            $demangled = undef;
        } elsif ($demangled =~ m{operator>>}) {
            # Special case operator>> and operator>>=.
        } else {
            $demangled =~ s{(?<=>)(?=>)}{ }g;
        }

        # Remember the last result.
        $filt->{last_symbol} = $symbol;
        $filt->{last_result} = $demangled;
    }
    return $filt->{last_result};
}

sub cppfilt_demangle_cpp {
    my $symbol = shift;
    return cppfilt_demangle($symbol, 'auto');
}

sub terminate_cppfilts {
    foreach my $type (keys %cppfilts) {
        next if not defined $cppfilts{$type}{pid};
        close $cppfilts{$type}{from};
        close $cppfilts{$type}{to};
        wait_child($cppfilts{$type}{pid},
            cmdline => 'c++filt',
            no_check => 1,
            timeout => 5,
        );
        delete $cppfilts{$type};
    }
}

# Close/terminate running c++filt process(es).
END {
    # Make sure exitcode is not changed (by wait_child).
    my $exitcode = $?;
    terminate_cppfilts();
    $? = $exitcode;
}

=head1 CHANGES

=head2 Version 0.xx

This is a private module.

=cut

1;
