# 08.12 关于bytes包

\#**关于bytes包**

`byte`包包含处理字节切片的函数，方法与帮助处理字符串的`strings`包方法相同。`Go`源代码文件的名称是`bytes.go`。它分为三部分。

> *这部分内容不包含在`Go`系统编程中，Packet出版，2017*

`byte.go`第一部分代码如下：

```go
package main

import (
	"bytes"
	"fmt"
	"io"
	"os"
)
```

`byte.go`第二部分代码如下：

```go
func main() {
	var buffer bytes.Buffer
	buffer.Write([]byte("This is"))
	fmt.Fprintf(&buffer, " a string!\n")
	buffer.WriteTo(os.Stdout)
	buffer.WriteTo(os.Stdout)
```

首先，创建一个新的`bytes.Buffer`变量，通过`buffer.Write()`和`fmt.Fprintf()`写入数据。然后调用`buffer.WriteTo()`两次。

第一次调用`buffer.WriteTo()`将打印`buffer`的内容。然而，第二次调用`buffer.WriteTo()`将不会有任何输出，因为在第一次调用后，`buffer`内容为空。

`bytes.go`最后一部分代码如下：

```go
	buffer.Reset()
	buffer.Write([]byte("Mastering Go!"))
	r := bytes.NewReader([]byte(buffer.String()))
	fmt.Println(buffer.String())
	for {
		b := make([]byte, 3)
		n, err := r.Read(b)
		if err == io.EOF {
			break
		}

		if err != nil {
			fmt.Println(err)
			continue
		}

		fmt.Printf("Read %s Bytes: %d\n", b, n)
	}
}
```

`Reset()`方法重置`buffer`变量，通过`Write()`方法再次写入一些数据。然后你可以通过`bytes.NewReader()`创建新的读对象，再使用`io.Reader`接口方法`Read()`从`buffer`变量读取数据。

执行`bytes.go`会产生如下的输出：

```shell
$ go run byte.go 
This is a string!
Mastering Go!
Read Mas Bytes: 3
Read ter Bytes: 3
Read ing Bytes: 3
Read  Go Bytes: 3
Read ! Bytes: 1
```


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