array_intersect: allow passing list of references for convenience

[pve-common.git] / src / PVE / Tools.pm

diff --git a/src/PVE/Tools.pm b/src/PVE/Tools.pm
index 4dd073f8cf6a07b02055fc0bb6a97b9145b2b1db..676647eefb375d8d1ad00e9d06ab404baab9c906 100644 (file)
--- a/src/PVE/Tools.pm
+++ b/src/PVE/Tools.pm
@@ -1649,4 +1649,43 @@ sub dev_t_minor($) {
     return (($dev_t >> 12) & 0xfff00) | ($dev_t & 0xff);
 }
 
+# Given an array of array refs [ \[a b c], \[a b b], \[e b a] ]
+# Returns the intersection of elements as a single array [a b]
+sub array_intersect {
+    my ($arrays) = @_;
+
+    if (!ref($arrays->[0])) {
+       $arrays = [ grep { ref($_) eq 'ARRAY' } @_ ];
+    }
+
+    return [] if scalar(@$arrays) == 0;
+    return $arrays->[0] if scalar(@$arrays) == 1;
+
+    my $array_unique = sub {
+       my %seen = ();
+       return grep { ! $seen{ $_ }++ } @_;
+    };
+
+    # base idea is to get all unique members from the first array, then
+    # check the common elements with the next (uniquely made) one, only keep
+    # those. Repeat for every array and at the end we only have those left
+    # which exist in all arrays
+    my $return_arr = [ $array_unique->(@{$arrays->[0]}) ];
+    for my $i (1 .. $#$arrays) {
+       my %count = ();
+       # $return_arr is already unique, explicit at before the loop, implicit below.
+       foreach my $element (@$return_arr, $array_unique->(@{$arrays->[$i]})) {
+           $count{$element}++;
+       }
+       $return_arr = [];
+       foreach my $element (keys %count) {
+           push @$return_arr, $element if $count{$element} > 1;
+       }
+       last if scalar(@$return_arr) == 0; # empty intersection, early exit
+    }
+
+    return $return_arr;
+}
+
+
 1;