如何使函数检测go中的字符串是否是二进制安全的（golang）？

Question

I have received a few close requests says its unclear what I am asking. For me its extremely clear what I am asking and I might have added a few extra thoughts on the issue, but my question is extremely direct. Here is the goal/thesis of my question:

How does one detects if a string is binary safe or not in go.

A function like:

IsBinarySafe(str) //returns true if its safe and false if its not.

Please ask clarifying comments if there is something unclear. I always take a lot of care and time to make good question, so put as much effort as I do to my question and help me make it better so everyone can get as much benefit as I do.

Any comment after this are just things I have thought or attempted to solve this:

---

I assumed that there must exist a library that already does this but had a tough time finding it. If there isn't one, how do you implement this?

I was thinking of some solution but wasn't really convinced they were good solutions. One of them was to iterate over the bytes, and have a hash map of all the illegal byte sequences. I also thought of maybe writing a regex with all the illegal strings but wasn't sure if that was a good solution. I also was not sure if a sequence of bytes from other languages counted as binary safe. Say the typical golang example:

世界

Would:

IsBinarySafe(世界) //true or false?

Would it return true or false? I was assuming that all binary safe string should only use 1 byte. So iterating over it in the following way:

const nihongo = "日本語abc日本語"
    for i, w := 0, 0; i < len(nihongo); i += w {
        runeValue, width := utf8.DecodeRuneInString(nihongo[i:])
        fmt.Printf("%#U starts at byte position %d
", runeValue, i)
        w = width
    }

and returning false whenever the width was great than 1. These are just some ideas I had just in case there wasn't a library for something like this already but I wasn't sure.

Answer 1

Binary safety has nothing to do with how wide a character is, it's mainly to check for non-printable characters more or less, like null bytes and such.

From Wikipedia:

Binary-safe is a computer programming term mainly used in connection with string manipulating functions. A binary-safe function is essentially one that treats its input as a raw stream of data without any specific format. It should thus work with all 256 possible values that a character can take (assuming 8-bit characters).

I'm not sure what your goal is, almost all languages handle utf8/16 just fine now, however for your specific question there's a rather simple solution:

// checks if s is ascii and printable, aka doesn't include tab, backspace, etc.
func IsAsciiPrintable(s string) bool {
    for _, r := range s {
        if r > unicode.MaxASCII || !unicode.IsPrint(r) {
            return false
        }
    }
    return true
}

func main() {
    fmt.Printf("len([]rune(s)) = %d, len([]byte(s)) = %d
", len([]rune(s)), len([]byte(s)))

    fmt.Println(IsAsciiPrintable(s), IsAsciiPrintable("test"))
}

<kbd>playground</kbd>

From unicode.IsPrint:

IsPrint reports whether the rune is defined as printable by Go. Such characters include letters, marks, numbers, punctuation, symbols, and the ASCII space character, from categories L, M, N, P, S and the ASCII space character. This categorization is the same as IsGraphic except that the only spacing character is ASCII space, U+0020.