#!/usr/bin/perl
use strict;
use File::Temp qw'tempdir';
use File::Spec;
use Getopt::Long;
my $dir = tempdir(CLEANUP => 1);

my ($cpu, $ar, $as, $nm, $objcopy, %replace);
GetOptions('cpu=s'=>\$cpu, 'ar=s'=>\$ar, 'as=s'=>\$as,'nm=s'=>\$nm, 'objcopy=s'=>\$objcopy, 'replace=s'=>\%replace);

# Args::
#   1) import lib to create
#   2) input dll
#   3...) extra objects to add

$_ = File::Spec->rel2abs($_) for @ARGV;

my $libdll = shift;
my $inpdll = shift;

open my $nm_fd, '-|', $nm, '-Apg', '--defined-only', $inpdll;
my %text = ();
my %import = ();
my %symfile = ();

my $is64bit = ($cpu eq 'x86_64' ? 1 : 0);
my $sym_prefix = ($is64bit ? '' : '_');

while (<$nm_fd>) {
    chomp;
    my ($fn, $type, $sym) = /^$inpdll:(.*?):\S+\s+(\S)\s+(\S+)$/o;
    next unless $fn;
    $text{$fn} = $sym if $type eq 'T';
    $import{$fn} = $sym if $type eq 'I';
    $symfile{$sym} = $fn;
}
close $nm_fd or exit 1;

for my $sym (keys %replace) {
    my $fn;
    my $_sym = $sym_prefix . $sym;
    if (!defined($fn = $symfile{$_sym})) {
	$fn = "$sym.o";
	$text{$fn} = $_sym;
    }
    my $imp_sym = '__imp_' . $sym_prefix . $replace{$sym};
    $import{$fn} = $imp_sym;
}

for my $f (keys %text) {
    my $imp_sym = delete $import{$f};
    my $glob_sym = $text{$f};
    if (!defined $imp_sym) {
	delete $text{$f};
    } elsif ($imp_sym eq '__imp_' . $sym_prefix) {
	$text{$f} = 0;
    } else {
	$text{$f} = 1;
	open my $as_fd, '|-', $as, '-o', "$dir/t-$f", "-";
	if ($is64bit) {
	    print $as_fd <<EOF;
	.text
	.extern	$imp_sym
	.global	$glob_sym
$glob_sym:
	jmp	*$imp_sym(%rip)
EOF
	} else {
	    print $as_fd <<EOF;
	.text
	.extern	$imp_sym
	.global	$glob_sym
$glob_sym:
	jmp	*$imp_sym
EOF
	}
	close $as_fd or exit 1;
    }
}

chdir $dir or die "$0: couldn't cd to $dir - $!\n";
system $ar, 'x', $inpdll;
exit 1 if $?;

for my $f (keys %text) {
    if (!$text{$f}) {
	unlink $f;
    } else {
	system $objcopy, '-R', '.text', $f and exit 1;
	system $objcopy, '-R', '.bss', '-R', '.data', "t-$f" and exit 1;
    }
}

unlink $libdll;
system $ar, 'crus', $libdll, glob('*.o'), @ARGV;
unlink glob('*.o');
exit 1 if $?;

END {
    chdir '/tmp';	# Allow $dir directory removal on Windows
}