从符文/ int8数组转换为字符串，反之亦然

Question

I'm porting a library from Java to Go. This library passes all parameters and returns as strings, and I must maintain this way due subsequent steps. I noticed when I cast a rune/int8 array to string and I convert back to rune/int8 array I get different values. I believe that is caused by Unicode characters. Is there a way to get the same values?

package main

import "fmt"

func main() {  

    runes := make([]rune,3)
    runes[0] = 97
    runes[1] = -22
    runes[2] = 99

    s := string(runes)

    fmt.Println(runes)  
    for _,r := range(s) {
        fmt.Println(r)
    }
}

Output:

[97 -22 99]
97
65533
99

Answer 1

The Go Programming Language Specification

Conversions

Conversions to and from a string type

Converting a signed or unsigned integer value to a string type yields a string containing the UTF-8 representation of the integer. Values outside the range of valid Unicode code points are converted to "\uFFFD".

Converting a slice of runes to a string type yields a string that is the concatenation of the individual rune values converted to strings.

---

Type byte in Go is an alias for type uint8.

Type rune, a Unicode code point (24-bit unsigned integer), is an alias for int32.

Go encodes Unicode code points (runes) as UTF-8 encoded strings.

For your example,

package main

import (
    "fmt"
    "unicode"
)

func main() {

    // Unicode code points are 24-bit unsigned integers
    runes := make([]rune, 3)
    runes[0] = 97
    runes[1] = -22 // invalid Unicode code point
    runes[2] = 99
    fmt.Println(runes)

    // Encode Unicode code points as UTF-8
    // Invalid code points converted to Unicode replacement character (U+FFFD)
    s := string(runes)
    fmt.Println(s)

    // Decode UTF-8 as Unicode code points
    for _, r := range s {
        fmt.Println(r, string(r), r == unicode.ReplacementChar)
    }
}

Playground: https://play.golang.org/p/AZUBd2iZp1F

Output:

[97 -22 99]
a�c
97 a false
65533 � true
99 c false

---

References:

The Go Programming Language Specification

The Go Blog: Strings, bytes, runes and characters in Go

The Unicode Consortium