Golangbufio文件读写优化技巧

file, err := os.Open("large.log")
if err != nil {
    log.Fatal(err)
}
defer file.Close()

reader := bufio.NewReader(file)
for {
    line, err := reader.ReadString('\n')
    if err != nil && err != io.EOF {
        log.Fatal(err)
    }
    if len(line) > 0 {
        fmt.Print(line)
    }
    if err == io.EOF {
        break
    }
}

file, err := os.Open("data.txt")
if err != nil {
    log.Fatal(err)
}
defer file.Close()

scanner := bufio.NewScanner(file)
for scanner.Scan() {
    fmt.Println(scanner.Text())
}
if err := scanner.Err(); err != nil {
    log.Fatal(err)
}

scanner.Split(bufio.ScanLines)

file, err := os.Create("output.txt")
if err != nil {
    log.Fatal(err)
}
defer file.Close()

writer := bufio.NewWriter(file)
data := []string{"line1", "line2", "line3"}

for _, line := range data {
    _, _ = writer.WriteString(line + "\n")
}

// 必须调用Flush，否则可能丢失数据
if err := writer.Flush(); err != nil {
    log.Fatal(err)
}

writer := bufio.NewWriterSize(file, 32*1024) // 32KB

func copyFile(src, dst string) error {
    s, err := os.Open(src)
    if err != nil {
        return err
    }
    defer s.Close()

    d, err := os.Create(dst)
    if err != nil {
        return err
    }
    defer d.Close()

    reader := bufio.NewReader(s)
    writer := bufio.NewWriter(d)
    buffer := make([]byte, 32*1024)

    for {
        n, err := reader.Read(buffer)
        if n > 0 {
            writer.Write(buffer[:n])
        }
        if err == io.EOF {
            break
        }
        if err != nil {
            return err
        }
    }

    return writer.Flush()
}