Go中各种newreader和newbuffer的使用总结

func main() {
    var byteArr []byte
    buf := bytes.NewBuffer(byteArr)
    buf.Write([]byte("今天不错"))
 
    fmt.Println(buf.String())
}

package main
 
import (
    "bytes"
    "fmt"
)
 
func main() {
    data := []byte("路多辛的所思所想")
    reader := bytes.NewReader(data)
 
    // 读取整个字节数组
    buf := make([]byte, len(data))
    _, err := reader.Read(buf)
    if err != nil {
        fmt.Println("Read failed:", err)
    }
    fmt.Println("Bytes read:", buf)
 
    // 读取字节切片的一部分
    part := make([]byte, 3)
    _, err = reader.Read(part)
    if err != nil {
        fmt.Println("Read failed:", err)
    }
    fmt.Println("Bytes read:", part)
 
    // 查找并读取字节切片中的某个字符
    offset, err := reader.Seek(6, 0)
    if err != nil {
        fmt.Println("Seek failed:", err)
    }
    ch, size, err := reader.ReadRune()
    if err != nil {
        fmt.Println("ReadRune failed:", err)
    }
    fmt.Printf("Read %c with size %d at offset %d\n", ch, size, offset)
}

    r := strings.NewReader("abcdefghijklmn")
    fmt.Println(r.Len())   // 输出14  初始时，未读长度等于字符串长度
    var buf []byte
    buf = make([]byte, 5)
    readLen, err := r.Read(buf)
    fmt.Println("读取到的长度:", readLen) //读取到的长度5
    if err != nil {
        fmt.Println("错误:", err)
    }
    fmt.Println(buf)            //adcde
    fmt.Println(r.Len())        //9   读取到了5个 剩余未读是14-5
    fmt.Println(r.Size())       //14   字符串的长度

package main
import (
    "fmt"
    "io"
    "os"
)
func main() {
    fmt.Println("嗨客网(www.haicoder.net)")
    fileName := "C:/haicoder.txt"
    file, err := os.Open(fileName)
    if err != nil{
        fmt.Println("Read file err, err =", err)
        return
    }
    defer file.Close()
    var chunk []byte
    buf := make([]byte, 1024)
    for{
        n, err := bufio.NewReader(buf)
        if err != nil && err != io.EOF{
            fmt.Println("read buf fail", err)
            return
        }
        //说明读取结束
        if n == 0 {
            break
        }
        //读取到最终的缓冲区中
        chunk = append(chunk, buf[:n]...)
    }
    fmt.Println("File Content =", string(chunk))
}

package main
import (
    "bufio"
    "fmt"
    "io/ioutil"
    "os"
)
func main() {
    fmt.Println("嗨客网(www.haicoder.net)")
    var(
        fileName = "C:/haicoder.txt"
        content = "Hello HaiCoder"
        file *os.File
        err error
    )
    //使用追加模式打开文件
    file, err = os.OpenFile(fileName, os.O_APPEND, 0666)
    if err != nil{
        fmt.Println("Open file err =", err)
        return
    }
    defer file.Close()
    writer := bufio.NewWriter(file)
    //写入文件
    n, err := writer.Write([]byte(content))
    if err != nil{
        fmt.Println("Write file err =", err)
        return
    }
    fmt.Println("Write file success, n =", n)
    writer.Flush()
    //读取文件
    fileContent, err := ioutil.ReadFile(fileName)
    if err != nil{
        fmt.Println("Read file err =", err)
        return
    }
    fmt.Println("Read file success =", string(fileContent))
}