Go语言Reader

电玩女神 2023-10-03 10:06 7阅读 0赞

# `一、输入流` #

>  *  流(stream)是应用程序和外部资源进行数据交互的纽带
>  *  流分为输入流和输出流,输入和输出都是相对于程序,把外部数据传入到程序中叫做输入,反之叫做输出流
>  *  输入流(Input Stream),输出流(Output Stream) 平时所说的I/O流
>  *  在Go语言标准库中io包下是Reader接口表示输入流,只要实现这个接口就属于输入流

// Reader is the interface that wraps the basic Read method.
    //
    // Read reads up to len(p) bytes into p. It returns the number of bytes
    // read (0 <= n <= len(p)) and any error encountered. Even if Read
    // returns n < len(p), it may use all of p as scratch space during the call.
    // If some data is available but not len(p) bytes, Read conventionally
    // returns what is available instead of waiting for more.
    //
    // When Read encounters an error or end-of-file condition after
    // successfully reading n > 0 bytes, it returns the number of
    // bytes read. It may return the (non-nil) error from the same call
    // or return the error (and n == 0) from a subsequent call.
    // An instance of this general case is that a Reader returning
    // a non-zero number of bytes at the end of the input stream may
    // return either err == EOF or err == nil. The next Read should
    // return 0, EOF.
    //
    // Callers should always process the n > 0 bytes returned before
    // considering the error err. Doing so correctly handles I/O errors
    // that happen after reading some bytes and also both of the
    // allowed EOF behaviors.
    //
    // Implementations of Read are discouraged from returning a
    // zero byte count with a nil error, except when len(p) == 0.
    // Callers should treat a return of 0 and nil as indicating that
    // nothing happened; in particular it does not indicate EOF.
    //
    // Implementations must not retain p.
    type Reader interface {
        
    	Read(p []byte) (n int, err error)
    }

# `二、代码演示` #

> 可以使用strings包下的NewReader创建字符串流

r := strings.NewReader("hello 世界")
    b := make([]byte, r.Size())//创建字节切片,存放流中数据,根据流数据大小创建切片大小
    n, err := r.Read(b)//把流中数据读取到切片中
    if err != nil {
        
    	fmt.Println("读取失败,", err)
    	return
    }
    fmt.Println("读取数据长度,", n)
    
    fmt.Println("流中数据", string(b))//以字符串形式输入切片中数据

> 最常用的是文件流,把外部文件中数据读取到程序中

f, err := os.Open("D:/go.txt")//打开文件
    defer f.Close()
    if err != nil {
        
    	fmt.Println("文件读取失败,", err)
    	return
    }
    fileInfo, err := f.Stat()//获取文件信息
    if err != nil {
        
    	fmt.Println("文件信息获取失败,", err)
    	return
    }
    b := make([]byte, fileInfo.Size())//根据文件中数据大小创建切片
    _, err = f.Read(b)//读取数据到切片中
    if err != nil {
        
    	fmt.Println("文件流读取失败:", err)
    	return
    }
    fmt.Println("文件中内容为:", string(b))//以字符串形式输入切片中数据