Go: deep copy slices

huangapple
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英文:

Go: deep copy slices

问题

我想读取一个表示十六进制数的字符串切片，并将它们解码为字节切片的切片（[]string --> [][]byte）。这是我目前的代码：

  1. func (self *algo_t) decode_args(args []string) ([][]byte, error) {
  2.     var data [][]byte
  3.     for i := uint32(0); i < self.num_args; i++ {
  4.         data = make([][]byte, self.num_args)
  5.         tmp, err := hex.DecodeString(args[i])
  6.         fmt.Printf("i = %d\ttmp = %x\n", i, tmp)
  7.         data[i] = make([]byte, len(tmp))
  8.         copy(data[i], tmp)
  9.         if err != nil {
  10.             fmt.Fprintf(os.Stderr, "Error decoding hex string %s: %s\n", args[i], err.Error())
  11.             return nil, err
  12.         }
  13.     }
  14.     fmt.Printf("line 69\tdata[0] = %x\tdata[1] = %x\tdata[2] = %x\n",data[0], data[1], data[2])
  15.     return data, nil
  16. }

调用这段代码并传入 args = []string{"010203","040506","070809"} 会产生以下输出：

  1. i = 0    tmp = 010203
  2. i = 1    tmp = 040506
  3. i = 3    tmp = 070809
  4. line 69 data[0] =     data[1] =     data[2] = 070809

推测该函数返回 [][]byte{[]byte{}, []byte{}, []byte{0x07, 0x08, 0x09}}。

我理解这是由于Go语言的指针行为导致的；在这种情况下，如何进行深拷贝是最佳实践呢？

英文:

I would like to read a slice of strings representing hexadecimal numbers, and decode them to a slice of byte slices ([]string --&gt; [][]byte). This is my code so far:

  1. func (self *algo_t) decode_args(args []string) ([][]byte, error) {
  2. 	var data [][]byte
  3. 	for i := uint32(0); i &lt; self.num_args; i++ {
  4. 		data = make([][]byte, self.num_args)
  5. 		tmp, err := hex.DecodeString(args[i])
  6. 		fmt.Printf(&quot;i = %d\ttmp = %x\n&quot;, i, tmp)
  7. 		data[i] = make([]byte, len(tmp))
  8. 		copy(data[i], tmp)
  9. 		if err != nil {
  10. 			fmt.Fprintf(os.Stderr, &quot;Error decoding hex string %s: %s\n&quot;, args[i], err.Error())
  11. 			return nil, err
  12. 		}
  13. 	}
  14. 	fmt.Printf(&quot;line 69\tdata[0] = %x\tdata[1] = %x\tdata[2] = %x\n&quot;,data[0], data[1], data[2])
  15. 	return data, nil
  16. }

calling this code and passing args = []string{&quot;010203&quot;,&quot;040506&quot;,&quot;070809&quot;} yields the following output:

  1. i = 0    tmp = 010203
  2. i = 1    tmp = 040506
  3. i = 3    tmp = 070809
  4. line 69 data[0] =     data[1] =     data[2] = 070809

Presumably the function returns [][]byte{[]byte{}, []byte{}, []byte{0x07, 0x08, 0x09}}.

I understand that this is because of the pointer behavior of Go; what is the best practice for doing a deep copy of this kind?

答案1

得分: 2

例如，

  1. package main
  3. import (
  4.     "encoding/hex"
  5.     "fmt"
  6. )
  8. // 将十六进制字符串解码为字节数组
  9. func decode(s []string) ([][]byte, error) {
  10.     b := make([][]byte, len(s))
  11.     for i, ss := range s {
  12.         h, err := hex.DecodeString(ss)
  13.         if err != nil {
  14.             err = fmt.Errorf(
  15.                 "解码十六进制字符串 %s 出错：%s\n",
  16.                 ss, err.Error(),
  17.             )
  18.             return nil, err
  19.         }
  20.         b[i] = h
  21.     }
  22.     return b, nil
  23. }
  25. func main() {
  26.     s := []string{"010203", "040506", "070809"}
  27.     fmt.Println(s)
  28.     b, err := decode(s)
  29.     if err != nil {
  30.         fmt.Println(err)
  31.     } else {
  32.         fmt.Println(b)
  33.     }
  34.     s = []string{"ABCDEF", "012345", "09AF"}
  35.     fmt.Println(s)
  36.     b, err = decode(s)
  37.     if err != nil {
  38.         fmt.Println(err)
  39.     } else {
  40.         fmt.Println(b)
  41.     }
  42.     s = []string{"01", "123XYZ"}
  43.     fmt.Println(s)
  44.     b, err = decode(s)
  45.     if err != nil {
  46.         fmt.Println(err)
  47.     } else {
  48.         fmt.Println(b)
  49.     }
  50. }

输出结果：

  1. [010203 040506 070809]
  2. [[1 2 3] [4 5 6] [7 8 9]]
  3. [ABCDEF 012345 09AF]
  4. [[171 205 239] [1 35 69] [9 175]]
  5. [01 123XYZ]
  6. 解码十六进制字符串 123XYZ 出错：encoding/hex: invalid byte: U+0058 'X'
英文:

For example,

  1. package main
  3. import (
  4. 	&quot;encoding/hex&quot;
  5. 	&quot;fmt&quot;
  6. )
  8. // Decode hex []string to [][]byte
  9. func decode(s []string) ([][]byte, error) {
  10. 	b := make([][]byte, len(s))
  11. 	for i, ss := range s {
  12. 		h, err := hex.DecodeString(ss)
  13. 		if err != nil {
  14. 			err = fmt.Errorf(
  15. 				&quot;Error decoding hex string %s: %s\n&quot;,
  16. 				ss, err.Error(),
  17. 			)
  18. 			return nil, err
  19. 		}
  20. 		b[i] = h
  21. 	}
  22. 	return b, nil
  23. }
  25. func main() {
  26. 	s := []string{&quot;010203&quot;, &quot;040506&quot;, &quot;070809&quot;}
  27. 	fmt.Println(s)
  28. 	b, err := decode(s)
  29. 	if err != nil {
  30. 		fmt.Println(err)
  31. 	} else {
  32. 		fmt.Println(b)
  33. 	}
  34. 	s = []string{&quot;ABCDEF&quot;, &quot;012345&quot;, &quot;09AF&quot;}
  35. 	fmt.Println(s)
  36. 	b, err = decode(s)
  37. 	if err != nil {
  38. 		fmt.Println(err)
  39. 	} else {
  40. 		fmt.Println(b)
  41. 	}
  42. 	s = []string{&quot;01&quot;, &quot;123XYZ&quot;}
  43. 	fmt.Println(s)
  44. 	b, err = decode(s)
  45. 	if err != nil {
  46. 		fmt.Println(err)
  47. 	} else {
  48. 		fmt.Println(b)
  49. 	}
  50. }

Output:

  1. [010203 040506 070809]
  2. [[1 2 3] [4 5 6] [7 8 9]]
  3. [ABCDEF 012345 09AF]
  4. [[171 205 239] [1 35 69] [9 175]]
  5. [01 123XYZ]
  6. Error decoding hex string 123XYZ: encoding/hex: invalid byte: U+0058 &#39;X&#39;

答案2

得分: 0

有一个专门用于处理深拷贝的包：http://godoc.org/code.google.com/p/rog-go/exp/deepcopy

你可以在这里查看源代码：https://code.google.com/p/rog-go/source/browse/exp/deepcopy/deepcopy.go。它涵盖了对切片和指针的拷贝，所以应该适用于你的情况。

英文:

There is a package built specifically to handle deep copy: http://godoc.org/code.google.com/p/rog-go/exp/deepcopy

You can look at the source here: https://code.google.com/p/rog-go/source/browse/exp/deepcopy/deepcopy.go. It covers copying slices and pointers, so it should cover your case.

huangapple
  • 本文由 发表于 2014年4月24日 05:34:18
  • 转载请务必保留本文链接：https://go.coder-hub.com/23255629.html
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