Merge pull request #990 from micro/buffer

Add debug/buffer package as a simple ring buffer

debug/buffer/buffer.go

@@ -0,0 +1,58 @@
+// Package buffer provides a simple ring buffer for storing local data
+package buffer
+
+import (
+	"sync"
+)
+
+type Buffer struct {
+	size int
+	sync.RWMutex
+	vals []interface{}
+}
+
+func (b *Buffer) Put(v interface{}) {
+	b.Lock()
+	defer b.Unlock()
+
+	// append to values
+	b.vals = append(b.vals, v)
+
+	// trim if bigger than size required
+	if len(b.vals) > b.size {
+		b.vals = b.vals[1:]
+	}
+}
+
+// Get returns the last n entries
+func (b *Buffer) Get(n int) []interface{} {
+	// reset any invalid values
+	if n > b.size || n < 0 {
+		n = b.size
+	}
+
+	b.RLock()
+	defer b.RUnlock()
+
+	// create a delta
+	delta := b.size - n
+
+	// if all the values are less than delta
+	if len(b.vals) < delta {
+		return b.vals
+	}
+
+	// return the delta set
+	return b.vals[delta:]
+}
+
+func (b *Buffer) Size() int {
+	return b.size
+}
+
+// New returns a new buffer of the given size
+func New(i int) *Buffer {
+	return &Buffer{
+		size: i,
+	}
+}

debug/buffer/buffer_test.go

@@ -0,0 +1,52 @@
+package buffer
+
+import (
+	"testing"
+)
+
+func TestBuffer(t *testing.T) {
+	b := New(10)
+
+	// test one value
+	b.Put("foo")
+	v := b.Get(1)
+
+	if val := v[0].(string); val != "foo" {
+		t.Fatalf("expected foo got %v", val)
+	}
+
+	b = New(10)
+
+	// test 10 values
+	for i := 0; i < 10; i++ {
+		b.Put(i)
+	}
+
+	v = b.Get(10)
+
+	for i := 0; i < 10; i++ {
+		val := v[i].(int)
+
+		if val != i {
+			t.Fatalf("expected %d got %d", i, val)
+		}
+	}
+
+	// test more values
+
+	for i := 0; i < 10; i++ {
+		v := i * 2
+		b.Put(v)
+	}
+
+	v = b.Get(10)
+
+	for i := 0; i < 10; i++ {
+		val := v[i].(int)
+		expect := i * 2
+		if val != expect {
+			t.Fatalf("expected %d got %d", expect, val)
+		}
+	}
+
+}