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chg: [join] fix overflowing filters on join operation #18

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chg: [join] fix overflowing filters on join operation #18

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7 changes: 3 additions & 4 deletions bloom.go
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Original file line number Diff line number Diff line change
Expand Up @@ -262,14 +262,13 @@ func (s *BloomFilter) Join(s2 *BloomFilter) error {
return fmt.Errorf("filters have different dimensions (M = %d vs. %d))",
s.M, s2.M)
}
if (s.N + s2.N) > s.n {
return fmt.Errorf("addition of member counts would overflow")
}
for i = 0; i < s.M; i++ {
s.v[i] |= s2.v[i]
}
if s.N+s2.N < s.N {
return fmt.Errorf("addition of member counts would overflow")
}
s.N += s2.N

return nil
}

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22 changes: 16 additions & 6 deletions bloom_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -240,7 +240,7 @@ func GenerateDisjointExampleFilter(capacity uint64, p float64, samples uint64, o
return filter, testValues
}

//This tests the checking of values against a given filter
// This tests the checking of values against a given filter
func TestChecking(t *testing.T) {
capacity := uint64(100000)
p := float64(0.001)
Expand All @@ -255,7 +255,7 @@ func TestChecking(t *testing.T) {
}
}

//This tests the checking of values against a given filter after resetting it
// This tests the checking of values against a given filter after resetting it
func TestReset(t *testing.T) {
capacity := uint64(100000)
p := float64(0.001)
Expand All @@ -271,8 +271,8 @@ func TestReset(t *testing.T) {
}
}

//This tests the checking of values against a given filter
//see https://en.wikipedia.org/wiki/Bloom_filter#Probability_of_false_positives
// This tests the checking of values against a given filter
// see https://en.wikipedia.org/wiki/Bloom_filter#Probability_of_false_positives
func TestFalsePositives(t *testing.T) {
capacity := uint64(10000)
p := float64(0.001)
Expand Down Expand Up @@ -371,6 +371,7 @@ func TestAccessors(t *testing.T) {
func TestJoiningRegular(t *testing.T) {
a, aval := GenerateExampleFilter(100000, 0.0001, 10000)
b, bval := GenerateDisjointExampleFilter(100000, 0.0001, 20000, a)
c, _ := GenerateDisjointExampleFilter(100000, 0.0001, 85000, b)
for _, v := range bval {
if a.Check(v) {
t.Errorf("value not missing in joined filter: %s", string(v))
Expand Down Expand Up @@ -399,9 +400,18 @@ func TestJoiningRegular(t *testing.T) {
t.Errorf("value not found in joined filter: %s", string(v))
}
}
expected := "addition of member counts would overflow"
actual := b.Join(&c)
if actual == nil {
t.Errorf("Expected error %v not triggered", expected)
} else {
if actual.Error() != expected {
t.Errorf("Error actual = %v, and Expected = %v.", actual, expected)
}
}
}

//This benchmarks the checking of values against a given filter
// This benchmarks the checking of values against a given filter
func BenchmarkChecking(b *testing.B) {
capacity := uint64(1e9)
p := float64(0.001)
Expand All @@ -418,7 +428,7 @@ func BenchmarkChecking(b *testing.B) {
}
}

//This benchmarks the checking without using a fixed fingerprint variable (instead a temporary variable is created each time)
// This benchmarks the checking without using a fixed fingerprint variable (instead a temporary variable is created each time)
func BenchmarkSimpleChecking(b *testing.B) {
capacity := uint64(1e9)
p := float64(0.001)
Expand Down