> ### Atoi * 為了方便, 我在調用的時候封裝一層 ~~~ func CommonAtoi(s string) (i int) { if i, err := strconv.Atoi(s); err == nil { return i } else { return 0 } } ~~~ * 源碼 ~~~ // Atoi returns the result of ParseInt(s, 10, 0) converted to type int. func Atoi(s string) (int, error) { const fnAtoi = "Atoi" sLen := len(s) if intSize == 32 && (0 < sLen && sLen < 10) || intSize == 64 && (0 < sLen && sLen < 19) { // Fast path for small integers that fit int type. s0 := s //截取第一個符號位后的字符 if s[0] == '-' || s[0] == '+' { s = s[1:] if len(s) < 1 { return 0, &NumError{fnAtoi, s0, ErrSyntax} } } n := 0 for _, ch := range []byte(s) { //減去字符0的編碼 ch -= '0' if ch > 9 { return 0, &NumError{fnAtoi, s0, ErrSyntax} } n = n*10 + int(ch) } if s0[0] == '-' { n = -n } return n, nil } // Slow path for invalid or big integers. i64, err := ParseInt(s, 10, 0) if nerr, ok := err.(*NumError); ok { nerr.Func = fnAtoi } return int(i64), err } ~~~ > ### Itoa ~~~ func Itoa(i int) string { return FormatInt(int64(i), 10) } ~~~ * 源碼 ~~~ func Itoa(i int) string { return FormatInt(int64(i), 10) } func FormatInt(i int64, base int) string { //0~99 采用字符串截取 if fastSmalls && 0 <= i && i < nSmalls && base == 10 { return small(int(i)) } _, s := formatBits(nil, uint64(i), base, i < 0, false) return s } us := uint(u) for us >= 100 { //取出最后兩位數, *2是因為smallsString用兩位數表示0~99 is := us % 100 * 2 us /= 100 i -= 2 a[i+1] = smallsString[is+1] a[i+0] = smallsString[is+0] } //處理前面剩余的一位或兩位數 // us < 100 is := us * 2 i-- a[i] = smallsString[is+1] if us >= 10 { i-- a[i] = smallsString[is] } ~~~