fix: resize of Table.Drop() now decreases size

- Generalized Table.resize() to accept a capacity size for each bucket.

cuckoo_internal_test.go

@@ -25,6 +25,6 @@ func TestLoad(t *testing.T) {
 	for i := range 16 {
 		err := table.Put(i, true)
 		assert.NoError(err)
-		assert.Equal(float64(table.Size())/float64(table.Capacity()), table.load())
+		assert.Equal(float64(table.Size())/float64(table.TotalCapacity()), table.load())
 	}
 }

cuckoo_test.go

@@ -64,7 +64,7 @@ func TestStartingCapacity(t *testing.T) {
 	assert := assert.New(t)
 	table := cuckoo.NewTable[int, bool](cuckoo.Capacity(64))
 
-	assert.Equal(uint64(128), table.Capacity())
+	assert.Equal(uint64(128), table.TotalCapacity())
 }
 
 func TestResizeCapacity(t *testing.T) {
@@ -74,12 +74,12 @@ func TestResizeCapacity(t *testing.T) {
 		cuckoo.GrowthFactor(2),
 	)
 
-	for table.Capacity() == 16 {
+	for table.TotalCapacity() == 16 {
 		err := table.Put(rand.Int(), true)
 		assert.NoError(err)
 	}
 
-	assert.Equal(uint64(32), table.Capacity())
+	assert.Equal(uint64(32), table.TotalCapacity())
 }
 
 func TestPutMany(t *testing.T) {
@@ -128,3 +128,16 @@ func TestRemove(t *testing.T) {
 
 	assert.True(table.Has(0))
 }
+
+func TestDropItem(t *testing.T) {
+	assert := assert.New(t)
+	key, value := 0, true
+	table := cuckoo.NewTable[int, bool]()
+	(table.Put(key, value))
+
+	err := table.Drop(key)
+
+	assert.NoError(err)
+	assert.Equal(0, table.Size())
+	assert.False(table.Has(key))
+}

table.go

@@ -16,9 +16,9 @@ type Table[K, V any] struct {
 	minLoadFactor    float64
 }
 
-// Capacity returns the number of slots allocated for the [Table]. To get the
+// TotalCapacity returns the number of slots allocated for the [Table]. To get the
 // number of slots filled, look at [Table.Size].
-func (t Table[K, V]) Capacity() uint64 {
+func (t Table[K, V]) TotalCapacity() uint64 {
 	return t.bucketA.capacity + t.bucketB.capacity
 }
 
@@ -32,21 +32,21 @@ func log2(n uint64) (m int) {
 }
 
 func (t Table[K, V]) maxEvictions() int {
-	return 3 * log2(t.Capacity())
+	return 3 * log2(t.TotalCapacity())
 }
 
 func (t Table[K, V]) load() float64 {
-	return float64(t.Size()) / float64(t.Capacity())
+	return float64(t.Size()) / float64(t.TotalCapacity())
 }
 
-func (t *Table[K, V]) resize() error {
+func (t *Table[K, V]) resize(capacity uint64) error {
 	entries := make([]entry[K, V], 0, t.Size())
 	for k, v := range t.Entries() {
 		entries = append(entries, entry[K, V]{k, v})
 	}
 
-	t.bucketA.resize(t.growthFactor * t.bucketA.capacity)
-	t.bucketB.resize(t.growthFactor * t.bucketB.capacity)
+	t.bucketA.resize(capacity)
+	t.bucketB.resize(capacity)
 
 	for _, entry := range entries {
 		if err := t.Put(entry.key, entry.value); err != nil {
@@ -99,10 +99,10 @@ func (t *Table[K, V]) Put(key K, value V) (err error) {
 	}
 
 	if t.load() < t.minLoadFactor {
-		return fmt.Errorf("bad hash: resize on load %d/%d = %f", t.Size(), t.Capacity(), t.load())
+		return fmt.Errorf("bad hash: resize on load %d/%d = %f", t.Size(), t.TotalCapacity(), t.load())
 	}
 
-	if err := t.resize(); err != nil {
+	if err := t.resize(t.growthFactor * t.bucketA.capacity); err != nil {
 		return err
 	}
 
@@ -116,7 +116,7 @@ func (t Table[K, V]) Drop(key K) (err error) {
 	t.bucketB.drop(key)
 
 	if t.load() < t.minLoadFactor {
-		return t.resize()
+		return t.resize(t.bucketA.capacity / t.growthFactor)
 	}
 
 	return nil