fix: allow 0 capacity for table

- Added guards at the bucket level, to ensure that getting an item in an empty bucket doesn't cause an error.
- Added grow() and shrink() functions to Table, to prevent a capacity of 0 from not being able to grow.
- Updated the fuzz test to use `go_fuzz-utils`.

table.go

@@ -28,7 +28,7 @@ func (t Table[K, V]) Size() int {
 }
 
 func log2(n uint64) (m int) {
-	return bits.Len64(n) - 1
+	return max(0, bits.Len64(n)-1)
 }
 
 func (t Table[K, V]) maxEvictions() int {
@@ -36,6 +36,12 @@ func (t Table[K, V]) maxEvictions() int {
 }
 
 func (t Table[K, V]) load() float64 {
+	// When there are no slots in the table, we still treat the load as 100%.
+	// Every slot in the table is full.
+	if t.TotalCapacity() == 0 {
+		return 1.0
+	}
+
 	return float64(t.Size()) / float64(t.TotalCapacity())
 }
 
@@ -57,6 +63,22 @@ func (t *Table[K, V]) resize(capacity uint64) error {
 	return nil
 }
 
+func (t *Table[K, V]) grow() error {
+	var newCapacity uint64
+
+	if t.TotalCapacity() == 0 {
+		newCapacity = 1
+	} else {
+		newCapacity = t.bucketA.capacity * t.growthFactor
+	}
+
+	return t.resize(newCapacity)
+}
+
+func (t *Table[K, V]) shrink() error {
+	return t.resize(t.bucketA.capacity / t.growthFactor)
+}
+
 // Get fetches the value for a key in the [Table]. Returns an error if no value
 // is found.
 func (t Table[K, V]) Get(key K) (value V, err error) {
@@ -102,7 +124,7 @@ func (t *Table[K, V]) Put(key K, value V) (err error) {
 		return fmt.Errorf("bad hash: resize on load %d/%d = %f", t.Size(), t.TotalCapacity(), t.load())
 	}
 
-	if err := t.resize(t.growthFactor * t.bucketA.capacity); err != nil {
+	if err := t.grow(); err != nil {
 		return err
 	}
 
@@ -116,7 +138,7 @@ func (t *Table[K, V]) Drop(key K) (err error) {
 	t.bucketB.drop(key)
 
 	if t.load() < t.minLoadFactor {
-		return t.resize(t.bucketA.capacity / t.growthFactor)
+		return t.shrink()
 	}
 
 	return nil