doukang1962
2018-10-08 06:57 阅读 151
已采纳

以固定的跨度读取golang缓冲区中的字节

I'd like to read and process 1024 bytes at a time in my file given by filename. I don't understand how to construct the outer loop correctly, especially to accommodate the final stride in which the buffer will contain fewer than 1024 bytes

What I have tried:

fs, _ := os.Open(filename)
defer fs.Close()
n := 1024 // 1kb
buff := make([]byte, n)
for {
    buff = make([]byte, n) // is this initialized correctly?
    n1, err := fs.Read(buff)
    if err != nil {
        if err == io.EOF {
            break
        }
        fmt.Println(err)
        break
    }
    fmt.Println("read n1 bytes...", n1)
    fmt.Println("%v", buff)
  }

It has produced the following errors:

  • 'buff declared and not used', which doesn't make sense to me as it is clearly right there
  • 'n1 declared and not used'
  • "invalid argument"

I have seen the following resources:

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1条回答 默认 最新

  • 已采纳
    dou4381 dou4381 2018-10-08 07:31

    I'd like to read and process 1024 bytes at a time in my file given by filename.

    I would expect to see something like this:

    package main
    
    import (
        "bufio"
        "fmt"
        "io"
        "os"
    )
    
    func main() {
        filename := `test.file`
        f, err := os.Open(filename)
        if err != nil {
            fmt.Println(err)
            return
        }
        defer f.Close()
        r := bufio.NewReader(f)
        buf := make([]byte, 0, 1024)
        for {
            n, err := io.ReadFull(r, buf[:cap(buf)])
            buf = buf[:n]
            if err != nil {
                if err == io.EOF {
                    break
                }
                if err != io.ErrUnexpectedEOF {
                    fmt.Println(err)
                    break
                }
            }
            fmt.Println("read n bytes...", n)
            // process buf
        }
    }
    

    Output:

    read n bytes... 1024
    read n bytes... 1024
    read n bytes... 1024
    read n bytes... 80
    
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