golang ParseInt int8不是未签名的

Question

Try to turn 8-bit binary string into a byte (unsigned)

strconv.ParseInt("11111000", 2, 8)

return 127

strconv.ParseInt("11111000", 2, 16)

returns the correct number 248

According to ParseInt document, 8 stands for int8, which goes -128 to 127. If so, why not the return value be a negative number?

Answer 1

You parse positive signed integers, negative signed integers are prefixed with a minus sign. For unsigned integers, parse as unsigned. Also, always check for errors.

For example,

package main

import (
    "fmt"
    "strconv"
)

func main() {
    // +127
    i, err := strconv.ParseInt("01111111", 2, 8)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(i)
    // -128
    i, err = strconv.ParseInt("-10000000", 2, 8)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(i)
    // +248 out of range for int8
    i, err = strconv.ParseInt("11111000", 2, 8)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(i)
    // unsigned 248 in range for uint8 (byte)
    u, err := strconv.ParseUint("11111000", 2, 8)
    if err != nil {
        fmt.Println(err)
    }
    fmt.Println(u)
}

Output:

127
-128
strconv.ParseInt: parsing "11111000": value out of range
127
248