func (b *Buffer) AppendString(data string) {
	for len(data) > 0 {
		if cap(b.Buf) == len(b.Buf) {  
			b.EnsureSpace(1)
		}
		sz := cap(b.Buf) - len(b.Buf)
		if sz > len(data) {
			sz = len(data)
		}
		b.Buf = append(b.Buf, data[:sz]...)
		data = data[sz:]
	}
}
AppendBytes appends a string to buffer.
package buffer
import (
	"io"
	"sync"
)
type PoolConfig struct {
	StartSize  int  
	PooledSize int  
	MaxSize    int  
}
var config = PoolConfig{
	StartSize:  128,
	PooledSize: 512,
	MaxSize:    32768,
}
var buffers = map[int]*sync.Pool{}
func initBuffers() {
	for l := config.PooledSize; l <= config.MaxSize; l *= 2 {
		buffers[l] = new(sync.Pool)
	}
}
func init() {
	initBuffers()
}
func Init(cfg PoolConfig) {
	config = cfg
	initBuffers()
}
func putBuf(buf []byte) {
	size := cap(buf)
	if size < config.PooledSize {
		return
	}
	if c := buffers[size]; c != nil {
		c.Put(buf[:0])
	}
}
func getBuf(size int) []byte {
	if size < config.PooledSize {
		return make([]byte, 0, size)
	}
	if c := buffers[size]; c != nil {
		v := c.Get()
		if v != nil {
			return v.([]byte)
		}
	}
	return make([]byte, 0, size)
}
type Buffer struct {
	Buf []byte
	toPool []byte
	bufs   [][]byte
}
func (b *Buffer) EnsureSpace(s int) {
	if cap(b.Buf)-len(b.Buf) >= s {
		return
	}
	l := len(b.Buf)
	if l > 0 {
		if cap(b.toPool) != cap(b.Buf) {
			putBuf(b.toPool)
		}
		if cap(b.bufs) == 0 {
			b.bufs = make([][]byte, 0, 8)
		}
		b.bufs = append(b.bufs, b.Buf)
		l = cap(b.toPool) * 2
	} else {
		l = config.StartSize
	}
	if l > config.MaxSize {
		l = config.MaxSize
	}
	b.Buf = getBuf(l)
	b.toPool = b.Buf
}
func (b *Buffer) AppendByte(data byte) {
	if cap(b.Buf) == len(b.Buf) {  
		b.EnsureSpace(1)
	}
	b.Buf = append(b.Buf, data)
}
func (b *Buffer) AppendBytes(data []byte) {
	for len(data) > 0 {
		if cap(b.Buf) == len(b.Buf) {  
			b.EnsureSpace(1)
		}
		sz := cap(b.Buf) - len(b.Buf)
		if sz > len(data) {
			sz = len(data)
		}
		b.Buf = append(b.Buf, data[:sz]...)
		data = data[sz:]
	}
}