p2p/rlpx: reduce allocation and syscalls

p2p/rlpx/buffer.go

@@ -0,0 +1,127 @@
+// Copyright 2021 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package rlpx
+
+import (
+	"io"
+)
+
+// readBuffer implements buffering for network reads. This type is similar to bufio.Reader,
+// with two crucial differences: the buffer slice is exposed, and the buffer keeps all
+// read data available until reset.
+//
+// How to use this type:
+//
+// Keep a readBuffer b alongside the underlying network connection. When reading a packet
+// from the connection, first call b.reset(). This empties b.data. Now perform reads
+// through b.read() until the end of the packet is reached. The complete packet data is
+// now available in b.data.
+type readBuffer struct {
+	data []byte
+	end  int
+}
+
+// reset removes all processed data which was read since the last call to reset.
+// After reset, len(b.data) is zero.
+func (b *readBuffer) reset() {
+	unprocessed := b.end - len(b.data)
+	copy(b.data[:unprocessed], b.data[len(b.data):b.end])
+	b.end = unprocessed
+	b.data = b.data[:0]
+}
+
+// read reads at least n bytes from r, returning the bytes.
+// The returned slice is valid until the next call to reset.
+func (b *readBuffer) read(r io.Reader, n int) ([]byte, error) {
+	offset := len(b.data)
+	have := b.end - len(b.data)
+
+	// If n bytes are available in the buffer, there is no need to read from r at all.
+	if have >= n {
+		b.data = b.data[:offset+n]
+		return b.data[offset : offset+n], nil
+	}
+
+	// Make buffer space available.
+	need := n - have
+	b.grow(need)
+
+	// Read.
+	rn, err := io.ReadAtLeast(r, b.data[b.end:cap(b.data)], need)
+	if err != nil {
+		return nil, err
+	}
+	b.end += rn
+	b.data = b.data[:offset+n]
+	return b.data[offset : offset+n], nil
+}
+
+// grow ensures the buffer has at least n bytes of unused space.
+func (b *readBuffer) grow(n int) {
+	if cap(b.data)-b.end >= n {
+		return
+	}
+	need := n - (cap(b.data) - b.end)
+	offset := len(b.data)
+	b.data = append(b.data[:cap(b.data)], make([]byte, need)...)
+	b.data = b.data[:offset]
+}
+
+// writeBuffer implements buffering for network writes. This is essentially
+// a convenience wrapper around a byte slice.
+type writeBuffer struct {
+	data []byte
+}
+
+func (b *writeBuffer) reset() {
+	b.data = b.data[:0]
+}
+
+func (b *writeBuffer) appendZero(n int) []byte {
+	offset := len(b.data)
+	b.data = append(b.data, make([]byte, n)...)
+	return b.data[offset : offset+n]
+}
+
+func (b *writeBuffer) Write(data []byte) (int, error) {
+	b.data = append(b.data, data...)
+	return len(data), nil
+}
+
+const maxUint24 = int(^uint32(0) >> 8)
+
+func readUint24(b []byte) uint32 {
+	return uint32(b[2]) | uint32(b[1])<<8 | uint32(b[0])<<16
+}
+
+func putUint24(v uint32, b []byte) {
+	b[0] = byte(v >> 16)
+	b[1] = byte(v >> 8)
+	b[2] = byte(v)
+}
+
+// growslice ensures b has the wanted length by either expanding it to its capacity
+// or allocating a new slice if b has insufficient capacity.
+func growslice(b []byte, wantLength int) []byte {
+	if len(b) >= wantLength {
+		return b
+	}
+	if cap(b) >= wantLength {
+		return b[:cap(b)]
+	}
+	return make([]byte, wantLength)
+}

p2p/rlpx/buffer_test.go

@@ -0,0 +1,51 @@
+// Copyright 2021 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package rlpx
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestReadBufferReset(t *testing.T) {
+	reader := bytes.NewReader(hexutil.MustDecode("0x010202030303040505"))
+	var b readBuffer
+
+	s1, _ := b.read(reader, 1)
+	s2, _ := b.read(reader, 2)
+	s3, _ := b.read(reader, 3)
+
+	assert.Equal(t, []byte{1}, s1)
+	assert.Equal(t, []byte{2, 2}, s2)
+	assert.Equal(t, []byte{3, 3, 3}, s3)
+
+	b.reset()
+
+	s4, _ := b.read(reader, 1)
+	s5, _ := b.read(reader, 2)
+
+	assert.Equal(t, []byte{4}, s4)
+	assert.Equal(t, []byte{5, 5}, s5)
+
+	s6, err := b.read(reader, 2)
+
+	assert.EqualError(t, err, "EOF")
+	assert.Nil(t, s6)
+}