Add a generic ring buffer

Go's stdlib is very anemic

tools/utils/ring_test.go

@@ -0,0 +1,46 @@
+// License: GPLv3 Copyright: 2022, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package utils
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+)
+
+var _ = fmt.Print
+
+func TestRingBuffer(t *testing.T) {
+	r := NewRingBuffer[int](8)
+
+	test_contents := func(expected ...int) {
+		actual := make([]int, len(expected))
+		num_read := r.ReadTillEmpty(actual)
+		if num_read != uint64(len(actual)) {
+			t.Fatalf("Did not read expected num of items: %d != %d", num_read, len(expected))
+		}
+		if !reflect.DeepEqual(expected, actual) {
+			t.Fatalf("Did not read expected items:\n%#v != %#v", actual, expected)
+		}
+		if r.Len() != 0 {
+			t.Fatalf("Reading contents did not empty the buffer")
+		}
+	}
+	r.WriteTillFull([]int{1, 2, 3, 4})
+	test_contents(1, 2, 3, 4)
+	r.WriteTillFull([]int{1, 2, 3, 4})
+	test_contents(1, 2, 3, 4)
+
+	r.Clear()
+	r.WriteTillFull([]int{1, 2, 3, 4})
+	r.ReadTillEmpty([]int{0, 1})
+	test_contents(3, 4)
+	r.WriteTillFull([]int{1, 2, 3, 4, 5})
+	test_contents(1, 2, 3, 4, 5)
+
+	r.Clear()
+	r.WriteTillFull([]int{1, 2, 3, 4})
+	r.WriteAllAndDiscardOld([]int{5, 6, 7, 8, 9})
+	test_contents(2, 3, 4, 5, 6, 7, 8, 9)
+
+}