TheAlgorithms/Go · error

invalid hexadecimal string

Error message

invalid hexadecimal string

What it means

hexToDecimal validates the (prefix-stripped) string against ^[0-9A-Fa-f]+$; characters outside the hex alphabet — including signs, spaces, underscores, or a lone "0x" — cause rejection before parsing begins.

Source

Thrown at conversion/hexadecimaltodecimal.go:38

var isValidHexadecimal = regexp.MustCompile("^[0-9A-Fa-f]+$").MatchString

// hexToDecimal converts a hexadecimal string to a decimal integer.
func hexToDecimal(hexStr string) (int64, error) {

	hexStr = strings.TrimSpace(hexStr)

	if len(hexStr) == 0 {
		return 0, fmt.Errorf("input string is empty")
	}

	// Check if the string has a valid hexadecimal prefix
	if len(hexStr) > 2 && (hexStr[:2] == "0x" || hexStr[:2] == "0X") {
		hexStr = hexStr[2:]
	}

	// Validate the hexadecimal string
	if !isValidHexadecimal(hexStr) {
		return 0, fmt.Errorf("invalid hexadecimal string")
	}

	var decimalValue int64
	for _, char := range hexStr {
		var digit int64
		if char >= '0' && char <= '9' {
			digit = int64(char - '0')
		} else if char >= 'A' && char <= 'F' {
			digit = int64(char - 'A' + 10)
		} else if char >= 'a' && char <= 'f' {
			digit = int64(char - 'a' + 10)
		} else {
			return 0, fmt.Errorf("invalid character in hexadecimal string: %c", char)
		}
		decimalValue = decimalValue*16 + digit
	}

	return decimalValue, nil

View on GitHub (pinned to 5ba447ec5f)

Solutions

1. Sanitize/normalize input: trim, strip 0x/0X prefix, uppercase
2. Use strconv.ParseInt(s, 16, 64) for standard parsing and error reporting
3. Show the invalid string to the user for correction

When it happens

Trigger: Thrown at conversion/hexadecimaltodecimal.go:38 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of TheAlgorithms/Go@5ba447ec5f (2026-09-02). Data as JSON: /api/errors/dad4b5a108d310b2. Report an issue: GitHub.