bytes: add Buffer.Available and Buffer.AvailableBuffer

[gostls13.git] / src / bytes / buffer_test.go

diff --git a/src/bytes/buffer_test.go b/src/bytes/buffer_test.go
index c0855007c188ea08c418a39c55c952037aa772bd..81476fbae15d4509da4465675b023327ac9cd9ef 100644 (file)
--- 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
+       }
+}