go – reading binary file with struct

huangapple
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英文:

go - reading binary file with struct

问题

我正在尝试使用Go语言读取二进制文件，但有一个问题。

如果我按照以下方式读取，一切都正常：

  1. package main
  3. import (
  4.     "encoding/binary"
  5.     "fmt"
  6.     "os"
  7. )
  9. type Header struct {
  10.     str1 int32
  11.     str2 [255]byte
  12.     str3 float64
  13. }
  15. func main() {
  17.     path := "test.BIN"
  19.     file, _ := os.Open(path)
  21.     defer file.Close()
  23.     thing := Header{}
  24.     binary.Read(file, binary.LittleEndian, &thing.str1)
  25.     binary.Read(file, binary.LittleEndian, &thing.str2)
  26.     binary.Read(file, binary.LittleEndian, &thing.str3)
  28.     fmt.Println(thing)
  29. }

但如果我将.Read部分优化为：

  1. binary.Read(file, binary.LittleEndian, &thing)
  2. //binary.Read(file, binary.LittleEndian, &thing.str1)
  3. //binary.Read(file, binary.LittleEndian, &thing.str2)
  4. //binary.Read(file, binary.LittleEndian, &thing.str3)

我会得到以下错误：

panic: reflect: reflect.Value.SetInt using value obtained using unexported field

有人能告诉我为什么吗？

所有的示例都使用了"优化方式"。

谢谢 go – reading binary file with struct

英文:

I'm trying to reading binary files with golang, but have a question.

If I read it this way, all will be fine

  1. package main
  3. import (
  4.     "encoding/binary"
  5.     "fmt"
  6.     "os"
  7. )
  9. type Header struct {
  10.     str1 int32
  11.     str2 [255]byte
  12.     str3 float64
  13. }
  15. func main() {
  17.     path := "test.BIN"
  19.     file, _ := os.Open(path)
  21.     defer file.Close()
  23.     thing := Header{}
  24.     binary.Read(file, binary.LittleEndian, &thing.str1)
  25.     binary.Read(file, binary.LittleEndian, &thing.str2)
  26.     binary.Read(file, binary.LittleEndian, &thing.str3)
  28.     fmt.Println(thing)
  29. }

But if I optimize the .Read-Section to

  1. binary.Read(file, binary.LittleEndian, &thing)
  2. //binary.Read(file, binary.LittleEndian, &thing.str1)
  3. //binary.Read(file, binary.LittleEndian, &thing.str2)
  4. //binary.Read(file, binary.LittleEndian, &thing.str3)

I get the following error:

  1. panic: reflect: reflect.Value.SetInt using value obtained using unexported field

Could anybody say me why?

All examples are useing the "optimized-way"

Thanks go – reading binary file with struct

答案1

得分: 6

str1、str2和str3是未导出的。这意味着其他包无法访问它们。要导出它们，将首字母大写。

  1. type Header struct {
  2.     Str1 int32
  3.     Str2 [255]byte
  4.     Str3 float64
  5. }
英文:

str1, str2, and str3 are unexported. That means other packages can't see them. To export them, capitalize the first letter.

  1. type Header struct {
  2.     Str1 int32
  3.     Str2 [255]byte
  4.     Str3 float64
  5. }

huangapple
  • 本文由 发表于 2017年2月26日 07:27:28
  • 转载请务必保留本文链接：https://go.coder-hub.com/42462869.html
  • binary
  • file
  • go
  • struct
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