net: add Buffers type, do writev on unix

No fast path currently for solaris, windows, nacl, plan9.

Fixes #13451

Change-Id: I24b3233a2e3a57fc6445e276a5c0d7b097884007
Reviewed-on: https://go-review.googlesource.com/29951
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 171 insertions, 0 deletions

diff --git a/src/net/writev_test.go b/src/net/writev_test.go
new file mode 100644
index 0000000000..cc53adcdd1
--- /dev/null
+++ b/src/net/writev_test.go
@@ -0,0 +1,171 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"reflect"
+	"runtime"
+	"sync"
+	"testing"
+)
+
+func TestBuffers_read(t *testing.T) {
+	const story = "once upon a time in Gopherland ... "
+	buffers := Buffers{
+		[]byte("once "),
+		[]byte("upon "),
+		[]byte("a "),
+		[]byte("time "),
+		[]byte("in "),
+		[]byte("Gopherland ... "),
+	}
+	got, err := ioutil.ReadAll(&buffers)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != story {
+		t.Errorf("read %q; want %q", got, story)
+	}
+	if len(buffers) != 0 {
+		t.Errorf("len(buffers) = %d; want 0", len(buffers))
+	}
+}
+
+func TestBuffers_consume(t *testing.T) {
+	tests := []struct {
+		in      Buffers
+		consume int64
+		want    Buffers
+	}{
+		{
+			in:      Buffers{[]byte("foo"), []byte("bar")},
+			consume: 0,
+			want:    Buffers{[]byte("foo"), []byte("bar")},
+		},
+		{
+			in:      Buffers{[]byte("foo"), []byte("bar")},
+			consume: 2,
+			want:    Buffers{[]byte("o"), []byte("bar")},
+		},
+		{
+			in:      Buffers{[]byte("foo"), []byte("bar")},
+			consume: 3,
+			want:    Buffers{[]byte("bar")},
+		},
+		{
+			in:      Buffers{[]byte("foo"), []byte("bar")},
+			consume: 4,
+			want:    Buffers{[]byte("ar")},
+		},
+		{
+			in:      Buffers{nil, nil, nil, []byte("bar")},
+			consume: 1,
+			want:    Buffers{[]byte("ar")},
+		},
+		{
+			in:      Buffers{nil, nil, nil, []byte("foo")},
+			consume: 0,
+			want:    Buffers{[]byte("foo")},
+		},
+		{
+			in:      Buffers{nil, nil, nil},
+			consume: 0,
+			want:    Buffers{},
+		},
+	}
+	for i, tt := range tests {
+		in := tt.in
+		in.consume(tt.consume)
+		if !reflect.DeepEqual(in, tt.want) {
+			t.Errorf("%d. after consume(%d) = %+v, want %+v", i, tt.consume, in, tt.want)
+		}
+	}
+}
+
+func TestBuffers_WriteTo(t *testing.T) {
+	for _, name := range []string{"WriteTo", "Copy"} {
+		for _, size := range []int{0, 10, 1023, 1024, 1025} {
+			t.Run(fmt.Sprintf("%s/%d", name, size), func(t *testing.T) {
+				testBuffer_writeTo(t, size, name == "Copy")
+			})
+		}
+	}
+}
+
+func testBuffer_writeTo(t *testing.T, chunks int, useCopy bool) {
+	oldHook := testHookDidWritev
+	defer func() { testHookDidWritev = oldHook }()
+	var writeLog struct {
+		sync.Mutex
+		log []int
+	}
+	testHookDidWritev = func(size int) {
+		writeLog.Lock()
+		writeLog.log = append(writeLog.log, size)
+		writeLog.Unlock()
+	}
+	var want bytes.Buffer
+	for i := 0; i < chunks; i++ {
+		want.WriteByte(byte(i))
+	}
+
+	withTCPConnPair(t, func(c *TCPConn) error {
+		buffers := make(Buffers, chunks)
+		for i := range buffers {
+			buffers[i] = want.Bytes()[i : i+1]
+		}
+		var n int64
+		var err error
+		if useCopy {
+			n, err = io.Copy(c, &buffers)
+		} else {
+			n, err = buffers.WriteTo(c)
+		}
+		if err != nil {
+			return err
+		}
+		if len(buffers) != 0 {
+			return fmt.Errorf("len(buffers) = %d; want 0", len(buffers))
+		}
+		if n != int64(want.Len()) {
+			return fmt.Errorf("Buffers.WriteTo returned %d; want %d", n, want.Len())
+		}
+		return nil
+	}, func(c *TCPConn) error {
+		all, err := ioutil.ReadAll(c)
+		if !bytes.Equal(all, want.Bytes()) || err != nil {
+			return fmt.Errorf("client read %q, %v; want %q, nil", all, err, want.Bytes())
+		}
+
+		writeLog.Lock() // no need to unlock
+		var gotSum int
+		for _, v := range writeLog.log {
+			gotSum += v
+		}
+
+		var wantSum int
+		var wantMinCalls int
+		switch runtime.GOOS {
+		case "darwin", "dragonfly", "freebsd", "linux", "netbsd", "openbsd":
+			wantSum = want.Len()
+			v := chunks
+			for v > 0 {
+				wantMinCalls++
+				v -= 1024
+			}
+		}
+		if len(writeLog.log) < wantMinCalls {
+			t.Errorf("write calls = %v < wanted min %v", len(writeLog.log), wantMinCalls)
+		}
+		if gotSum != wantSum {
+			t.Errorf("writev call sum  = %v; want %v", gotSum, wantSum)
+		}
+		return nil
+	})
+}