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本文主要研究一下golang的zap的buffer

buffer

zap@v1.16.0/buffer/buffer.go

package buffer // import "go.uber.org/zap/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
}

// 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)
}

Buffer定义了[]byte及Pool属性，它提供了AppendByte、AppendString、AppendInt、AppendTime、AppendUint、AppendBool、AppendFloat、String、Reset、Write、TrimNewline、Free方法

pool

zap@v1.16.0/buffer/pool.go

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)
}

Pool定义了*sync.Pool属性，其NewPool方法创建sync.Pool，New方法为创建Buffer，_size默认为1024即1KB；其Get方法从pool获取buffer，其put方法用于将buffer归还到pool；由于归还时buffer可能没有reset，所以每次Get的时候都会先Reset一下再返回

bufferpool

zap@v1.16.0/internal/bufferpool/bufferpool.go

package bufferpool

import "go.uber.org/zap/buffer"

var (
    _pool = buffer.NewPool()
    // Get retrieves a buffer from the pool, creating one if necessary.
    Get = _pool.Get
)

bufferpool包创建了一个全局的_pool，并定义了Get func

FullPath

zap@v1.16.0/zapcore/entry.go

func (ec EntryCaller) FullPath() string {
    if !ec.Defined {
        return "undefined"
    }
    buf := bufferpool.Get()
    buf.AppendString(ec.File)
    buf.AppendByte(':')
    buf.AppendInt(int64(ec.Line))
    caller := buf.String()
    buf.Free()
    return caller
}

FullPath方法使用bufferpool来创建caller

newJSONEncoder

zap@v1.16.0/zapcore/json_encoder.go

func newJSONEncoder(cfg EncoderConfig, spaced bool) *jsonEncoder {
    return &jsonEncoder{
        EncoderConfig: &cfg,
        buf:           bufferpool.Get(),
        spaced:        spaced,
    }
}

newJSONEncoder使用bufferpool.Get()来获取buffer，然后创建jsonEncoder

实例

func bufferDemo() {
    buf := buffer.NewPool().Get()
    buf.AppendByte('v')
    fmt.Println(buf.String())
    buf.Reset()

    buf.AppendString("foo")
    fmt.Println(buf.String())
    buf.Reset()

    buf.AppendInt(42)
    fmt.Println(buf.String())
    buf.Reset()

    buf.AppendUint(42)
    fmt.Println(buf.String())
    buf.Reset()

    buf.AppendBool(true)
    fmt.Println(buf.String())
    buf.Reset()

    buf.AppendFloat(3.14, 32)
    fmt.Println(buf.String())
    buf.Reset()

    buf.Write([]byte("foo"))
    fmt.Println(buf.String())
    buf.Reset()

    buf.AppendTime(time.Date(2000, 1, 2, 3, 4, 5, 6, time.UTC), time.RFC3339)
    fmt.Println(buf.String())
    buf.Reset()

    buf.Free()
}

输出

v
foo
42
42
true
3.14
foo
2000-01-02T03:04:05Z

小结

Buffer定义了[]byte及Pool属性，它提供了AppendByte、AppendString、AppendInt、AppendTime、AppendUint、AppendBool、AppendFloat、String、Reset、Write、TrimNewline、Free方法；Pool定义了*sync.Pool属性，其NewPool方法创建sync.Pool，New方法为创建Buffer，_size默认为1024即1KB；其Get方法从pool获取buffer，其put方法用于将buffer归还到pool；由于归还时buffer可能没有reset，所以每次Get的时候都会先Reset一下再返回

doc

• zap