bufPoolItem to support more methods

[gonyyi]

Now all the buf pool item from GetBuffer() has to saved to buf.Buf again as below.
And this became common bug when writing a code with buf pool item.

buf := gosl.GetBuffer()
buf.Buf = buf.Buf.WriteString(s.time.Format("2006/01/02 15:04:05"))

Add methods to simplify as below.

buf := gosl.GetBuffer()
buf.WriteString(s.time.Format("2006/01/02 15:04:05"))

[gonyyi]

// Bytes returns []byte of current buffer
func (b *bufPoolItem) Bytes() []byte {
	return b.Buf.Bytes()
}

// Cap returns current capacity
func (b *bufPoolItem) Cap() int {
	return b.Buf.Cap()
}

// Len returns current length
func (b *bufPoolItem) Len() int {
	return b.Buf.Len()
}

// Println prints current buffer
func (b *bufPoolItem) Println() {
	b.Buf.Println()
}

// Reset resets current buffer 
func (b *bufPoolItem) Reset() {
	b.Buf = b.Buf.Reset()
}

// Set resets and set current buffer with a given string
func (b *bufPoolItem) Set(s string) {
	b.Buf = b.Buf.Set(s)
}

// String returns current buffer in string format 
func (b *bufPoolItem) String() string {
	return b.Buf.String()
}

// Write writes bytes into current buffer 
// This meets Writer interface.
func (b *bufPoolItem) Write(p []byte) (n int, err error) {
	return b.Buf.Write(p)
}

// WriteBytes will write byte or bytes to current buffer 
func (b *bufPoolItem) WriteBytes(bytes ...byte) {
	b.Buf = b.Buf.WriteBytes(bytes...)
}

// WriteBool will write boolean t to current buffer in string
// true => "true", false => "false"
func (b *bufPoolItem) WriteBool(t bool) {
	b.Buf = b.Buf.WriteBool(t)
}

// WriteFloat will write float f with decimal point dec to current buffer
func (b *bufPoolItem) WriteFloat(f float64, dec uint8) {
	b.Buf = b.Buf.WriteFloat(f, dec)
}

// WriteInt will write integer i to buffer as string format
func (b *bufPoolItem) WriteInt(i int) {
	b.Buf = b.Buf.WriteInt(i)
}

// WriteString will write a string s to current buffer
func (b *bufPoolItem) WriteString(s string) {
	b.Buf = b.Buf.WriteString(s)
}

// WriteStrings will write string slice to current buffer with a delimiter
func (b *bufPoolItem) WriteStrings(s []string, delim ...byte) {
	b.Buf = b.Buf.WriteStrings(s, delim...)
}

// WriteTo will write current buffer to writer w. 
func (b *bufPoolItem) WriteTo(w Writer) (n int, err error) {
	return b.Buf.WriteTo(w)
}

For test cases,

func TestBuffer(t *testing.T) {
	b1 := gosl.GetBuffer()
	t.Run("Bytes()", func(t *testing.T) {
		b1.Set("test1")
		tmp := b1.Bytes()
		gosl.Test(t, true,  gosl.BytesEqual(b1.Buf, tmp))
	})
	t.Run("Cap()", func(t *testing.T) {
		b1.Set("test2")
		gosl.Test(t, true, b1.Buf.Cap() == b1.Cap())
	})
	t.Run("Len()", func(t *testing.T) {
		b1.Set("test3")
		gosl.Test(t, 5, b1.Len())
	})
	t.Run("Println()", func(t *testing.T) {
		b1.Set("test4")
		// b1.Println()
	})
	t.Run("Reset()", func(t *testing.T) {
		b1.Set("test5")
		b1.Reset()
		gosl.Test(t, 0, b1.Len())
	})
	t.Run("Set()", func(t *testing.T) {
		b1.Reset()
		b1.Set("test5")
		b1.Set("test6")
		gosl.Test(t, "test6", b1.String())
	})
	t.Run("String()", func(t *testing.T) {
		b1.Reset()
		b1.Set("test7")
		gosl.Test(t, "test7", b1.String())
	})
	t.Run("Write()", func(t *testing.T) {
		b1.Set("te")
		n, err := b1.Write([]byte("st8"))
		gosl.Test(t, nil, err)
		gosl.Test(t, 3, n)
		gosl.Test(t, "test8", b1.String())
	})
	t.Run("WriteBytes()", func(t *testing.T) {
		b1.Set("test9")
		b1.WriteBytes('-')
		b1.WriteBytes('1','2','3')
		gosl.Test(t, "test9-123", b1.String())
	})
	t.Run("WriteBool()", func(t *testing.T) {
		b1.Set("test10")
		b1.WriteBool(true)
		b1.WriteBool(false)
		gosl.Test(t, "test10truefalse", b1.String())
	})
	t.Run("WriteFloat()", func(t *testing.T) {
		b1.Set("test11-")
		b1.WriteFloat(3.141592, 2)
		gosl.Test(t, "test11-3.14", b1.String())
	})
	t.Run("WriteInt()", func(t *testing.T) {
		b1.Set("test12-")
		b1.WriteInt(1212)
		gosl.Test(t, "test12-1212", b1.String())
	})
	t.Run("WriteString()", func(t *testing.T) {
		b1.Set("test13-")
		b1.WriteString("done")
		gosl.Test(t, "test13-done", b1.String())
	})
	t.Run("WriteStrings()", func(t *testing.T) {
		b1.Set("test14-")
		b1.WriteStrings([]string{"a", "b", "c"}, ',', ' ')
		gosl.Test(t, "test14-a, b, c", b1.String())
	})
	t.Run("WriteTo()", func(t *testing.T) {
		tmpBuf := make(gosl.Buf, 0, 1024)
		b1.Set("test15")
		b1.WriteTo(&tmpBuf)
		gosl.Test(t, "test15", string(tmpBuf))
	})
}

[gonyyi]

ef002fc

Done