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1403920367
Replace byte-at-a-time ReadByte loops with Peek+Discard in the DERP
read path. Peek returns a slice into bufio's internal buffer without
allocating, and Discard advances the read pointer without copying.
Introduce util/bufiox with a BufferedReader interface and ReadFull
helper that uses Peek+copy+Discard as an allocation-free alternative
to io.ReadFull.
- derp.ReadFrameHeader: replace 5× ReadByte with Peek(5)+Discard(5),
reading the frame type and length directly from the peeked slice.
Remove now-unused readUint32 helper.
name old ns/op new ns/op speedup
ReadFrameHeader-8 24.2 12.4 ~2x
(0 allocs/op in both)
- key.NodePublic.ReadRawWithoutAllocating: replace 32× ReadByte with
bufiox.ReadFull. Addresses the "Dear future" comment about switching
away from byte-at-a-time reads once a non-escaping alternative exists.
name old ns/op new ns/op speedup
NodeReadRawWithoutAllocating-8 140 43.6 ~3.2x
(0 allocs/op in both)
- derpserver.handleFramePing: replace io.ReadFull with bufiox.ReadFull.
Updates tailscale/corp#38509
Signed-off-by: Mike O'Driscoll <mikeo@tailscale.com>
99 lines
2.0 KiB
Go
99 lines
2.0 KiB
Go
// Copyright (c) Tailscale Inc & contributors
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// SPDX-License-Identifier: BSD-3-Clause
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package bufiox
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import (
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"bufio"
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"bytes"
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"io"
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"testing"
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)
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func TestReadFull(t *testing.T) {
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data := []byte{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08}
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br := bufio.NewReader(bytes.NewReader(data))
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var buf [5]byte
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n, err := ReadFull(br, buf[:])
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if err != nil {
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t.Fatalf("ReadFull: %v", err)
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}
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if n != len(buf) {
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t.Fatalf("n = %d, want %d", n, len(buf))
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}
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if want := [5]byte{0x01, 0x02, 0x03, 0x04, 0x05}; buf != want {
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t.Fatalf("buf = %v, want %v", buf, want)
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}
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// Remaining bytes should still be readable.
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var rest [3]byte
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n, err = ReadFull(br, rest[:])
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if err != nil {
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t.Fatalf("ReadFull rest: %v", err)
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}
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if n != len(rest) {
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t.Fatalf("rest n = %d, want %d", n, len(rest))
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}
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if want := [3]byte{0x06, 0x07, 0x08}; rest != want {
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t.Fatalf("rest = %v, want %v", rest, want)
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}
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}
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func TestReadFullShort(t *testing.T) {
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data := []byte{0x01, 0x02}
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br := bufio.NewReader(bytes.NewReader(data))
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var buf [5]byte
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_, err := ReadFull(br, buf[:])
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if err != io.ErrUnexpectedEOF {
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t.Fatalf("err = %v, want %v", err, io.ErrUnexpectedEOF)
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}
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}
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func TestReadFullEmpty(t *testing.T) {
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br := bufio.NewReader(bytes.NewReader(nil))
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var buf [1]byte
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_, err := ReadFull(br, buf[:])
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if err != io.EOF {
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t.Fatalf("err = %v, want %v", err, io.EOF)
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}
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}
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func TestReadFullZeroAllocs(t *testing.T) {
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data := make([]byte, 64)
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rd := bytes.NewReader(data)
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br := bufio.NewReader(rd)
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var buf [32]byte
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got := testing.AllocsPerRun(1000, func() {
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rd.Reset(data)
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br.Reset(rd)
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_, err := ReadFull(br, buf[:])
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if err != nil {
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t.Fatalf("ReadFull: %v", err)
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}
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})
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if got != 0 {
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t.Fatalf("ReadFull allocs = %f, want 0", got)
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}
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}
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type nopReader struct{}
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func (nopReader) Read(p []byte) (int, error) { return len(p), nil }
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func BenchmarkReadFull(b *testing.B) {
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br := bufio.NewReader(nopReader{})
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var buf [32]byte
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b.ReportAllocs()
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b.ResetTimer()
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for range b.N {
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_, err := ReadFull(br, buf[:])
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if err != nil {
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b.Fatal(err)
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}
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}
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}
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