如何设计一个go的buffer?

以下设计来自go.uber.org/zap/buffer

Buffer是一个字节序列的包裹，这里的Buffer只能通过Pool来创建。

package buffer
import (
	"strconv"
	"time"
)

const _size = 1024 // by default, create 1 KiB buffers

// Buffer is a thin wrapper around a byte slice. It's intended to be pooled, so
// the only way to construct one is via a Pool.
type Buffer struct {
	bs   []byte
	pool Pool
}

// AppendByte writes a single byte to the Buffer.
func (b *Buffer) AppendByte(v byte) {
	b.bs = append(b.bs, v)
}

// AppendString writes a string to the Buffer.
func (b *Buffer) AppendString(s string) {
	b.bs = append(b.bs, s...)
}

// AppendInt appends an integer to the underlying buffer (assuming base 10).
func (b *Buffer) AppendInt(i int64) {
	b.bs = strconv.AppendInt(b.bs, i, 10)
}

// AppendTime appends the time formatted using the specified layout.
func (b *Buffer) AppendTime(t time.Time, layout string) {
	b.bs = t.AppendFormat(b.bs, layout)
}

// AppendUint appends an unsigned integer to the underlying buffer (assuming
// base 10).
func (b *Buffer) AppendUint(i uint64) {
	b.bs = strconv.AppendUint(b.bs, i, 10)
}

// AppendBool appends a bool to the underlying buffer.
func (b *Buffer) AppendBool(v bool) {
	b.bs = strconv.AppendBool(b.bs, v)
}

// AppendFloat appends a float to the underlying buffer. It doesn't quote NaN
// or +/- Inf.
func (b *Buffer) AppendFloat(f float64, bitSize int) {
	b.bs = strconv.AppendFloat(b.bs, f, 'f', -1, bitSize)
}

// Len returns the length of the underlying byte slice.
func (b *Buffer) Len() int {
	return len(b.bs)
}

// Cap returns the capacity of the underlying byte slice.
func (b *Buffer) Cap() int {
	return cap(b.bs)
}

// Bytes returns a mutable reference to the underlying byte slice.
func (b *Buffer) Bytes() []byte {
	return b.bs
}

// String returns a string copy of the underlying byte slice.
func (b *Buffer) String() string {
	return string(b.bs)
}

// Reset resets the underlying byte slice. Subsequent writes re-use the slice's
// backing array.
func (b *Buffer) Reset() {
	b.bs = b.bs[:0]
}

// Write implements io.Writer.
func (b *Buffer) Write(bs []byte) (int, error) {
	b.bs = append(b.bs, bs...)
	return len(bs), nil
}

// WriteByte writes a single byte to the Buffer.
//
// Error returned is always nil, function signature is compatible
// with bytes.Buffer and bufio.Writer
func (b *Buffer) WriteByte(v byte) error {
	b.AppendByte(v)
	return nil
}

// WriteString writes a string to the Buffer.
//
// Error returned is always nil, function signature is compatible
// with bytes.Buffer and bufio.Writer
func (b *Buffer) WriteString(s string) (int, error) {
	b.AppendString(s)
	return len(s), nil
}

// TrimNewline trims any final "\n" byte from the end of the buffer.
func (b *Buffer) TrimNewline() {
	if i := len(b.bs) - 1; i >= 0 {
		if b.bs[i] == '\n' {
			b.bs = b.bs[:i]
		}
	}
}

// Free returns the Buffer to its Pool.
//
// Callers must not retain references to the Buffer after calling Free.
func (b *Buffer) Free() {
	b.pool.put(b)
}

下面看一下Pool的实现：

package buffer

import "sync"

// A Pool is a type-safe wrapper around a sync.Pool.
type Pool struct {
	p *sync.Pool
}

// NewPool constructs a new Pool.
func NewPool() Pool {
	return Pool{p: &sync.Pool{
		New: func() interface{} {
			return &Buffer{bs: make([]byte, 0, _size)}
		},
	}}
}

// Get retrieves a Buffer from the pool, creating one if necessary.
func (p Pool) Get() *Buffer {
	buf := p.p.Get().(*Buffer)
	buf.Reset()
	buf.pool = p
	return buf
}

func (p Pool) put(buf *Buffer) {
	p.p.Put(buf)
}