maintain base capacity after IterPop iteration (#44)

* maintain base capacity after IterPop iteration

After iteration of the iterator returned from IterPopFront or IterPopBack, the internal buffer was resized using the default base capacity instead of the specified base capacity, if one was provided to the Deque. This issue does not cause any problems, but may lead to more allocations in cases where a larger than default base capacity was specified. This change uses the correct base capacity.

* use const for constant values in tests

Author: gammazero

deque.go

@@ -515,11 +515,11 @@ func (q *Deque[T]) shrinkToFit() {
 		if q.count == 0 {
 			q.head = 0
 			q.tail = 0
-			q.buf = make([]T, minCapacity)
+			q.buf = make([]T, q.minCap)
 			return
 		}
 
-		c := minCapacity
+		c := q.minCap
 		for c < q.count {
 			c <<= 1
 		}

deque_test.go

@@ -87,7 +87,7 @@ func TestFrontBack(t *testing.T) {
 
 func TestGrowShrinkBack(t *testing.T) {
 	var q Deque[int]
-	size := minCapacity * 2
+	const size = minCapacity * 2
 
 	for i := 0; i < size; i++ {
 		if q.Len() != i {
@@ -117,7 +117,7 @@ func TestGrowShrinkBack(t *testing.T) {
 
 func TestGrowShrinkFront(t *testing.T) {
 	var q Deque[int]
-	size := minCapacity * 2
+	const size = minCapacity * 2
 
 	for i := 0; i < size; i++ {
 		if q.Len() != i {
@@ -286,7 +286,7 @@ func TestGrow(t *testing.T) {
 }
 
 func TestNew(t *testing.T) {
-	minCap := 64
+	const minCap = 64
 	q := &Deque[string]{}
 	q.SetBaseCap(minCap)
 	if q.Cap() != 0 {
@@ -752,8 +752,16 @@ func TestRIter(t *testing.T) {
 }
 
 func TestIterPopBack(t *testing.T) {
+	const (
+		baseCap = 32
+		size    = baseCap * 5
+	)
 	var q Deque[int]
-	size := minCapacity * 5
+	q.SetBaseCap(baseCap)
+
+	for i := range q.IterPopBack() {
+		t.Fatalf("popped %d when nothig to pop", i)
+	}
 
 	q.Grow(size)
 	for i := 0; i < size; i++ {
@@ -779,6 +787,9 @@ func TestIterPopBack(t *testing.T) {
 	if q.Len() != 0 {
 		t.Error("q.Len() =", q.Len(), "expected 0")
 	}
+	if q.Cap() != baseCap {
+		t.Error("capacity should return to configured base capacity")
+	}
 
 	q.Grow(size)
 	for i := 0; i < size; i++ {
@@ -835,8 +846,12 @@ func TestIterPopBack(t *testing.T) {
 }
 
 func TestIterPopFront(t *testing.T) {
+	const (
+		baseCap = 32
+		size    = baseCap * 5
+	)
 	var q Deque[int]
-	size := minCapacity * 5
+	q.SetBaseCap(baseCap)
 
 	q.Grow(size)
 	for i := 0; i < size; i++ {
@@ -860,6 +875,10 @@ func TestIterPopFront(t *testing.T) {
 	if q.Len() != 0 {
 		t.Error("q.Len() =", q.Len(), "expected 0")
 	}
+	if q.Cap() != baseCap {
+		t.Error("capacity should return to configured base capacity")
+	}
+
 	for range q.IterPopFront() {
 		t.Fatal("iteration with 0 items")
 	}