1 files changed, 41 insertions, 0 deletions
diff --git a/src/bytes/buffer_test.go b/src/bytes/buffer_test.go
index c0855007c1..81476fbae1 100644
--- a/src/bytes/buffer_test.go
+++ b/src/bytes/buffer_test.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io"
 	"math/rand"
+	"strconv"
 	"testing"
 	"unicode/utf8"
 )
@@ -326,6 +327,33 @@ func TestWriteTo(t *testing.T) {
 	}
 }
 
+func TestWriteAppend(t *testing.T) {
+	var got Buffer
+	var want []byte
+	for i := 0; i < 1000; i++ {
+		b := got.AvailableBuffer()
+		b = strconv.AppendInt(b, int64(i), 10)
+		want = strconv.AppendInt(want, int64(i), 10)
+		got.Write(b)
+	}
+	if !Equal(got.Bytes(), want) {
+		t.Fatalf("Bytes() = %q, want %q", got, want)
+	}
+
+	// With a sufficiently sized buffer, there should be no allocations.
+	n := testing.AllocsPerRun(100, func() {
+		got.Reset()
+		for i := 0; i < 1000; i++ {
+			b := got.AvailableBuffer()
+			b = strconv.AppendInt(b, int64(i), 10)
+			got.Write(b)
+		}
+	})
+	if n > 0 {
+		t.Errorf("allocations occurred while appending")
+	}
+}
+
 func TestRuneIO(t *testing.T) {
 	const NRune = 1000
 	// Built a test slice while we write the data
@@ -687,3 +715,16 @@ func BenchmarkBufferWriteBlock(b *testing.B) {
 		})
 	}
 }
+
+func BenchmarkBufferAppendNoCopy(b *testing.B) {
+	var bb Buffer
+	bb.Grow(16 << 20)
+	b.SetBytes(int64(bb.Available()))
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		bb.Reset()
+		b := bb.AvailableBuffer()
+		b = b[:cap(b)] // use max capacity to simulate a large append operation
+		bb.Write(b)    // should be nearly infinitely fast
+	}
+}