TheAlgorithms/Go · error

input string is empty

Error message

input string is empty

What it means

The unexported hexToBinary helper in conversion/hexadecimaltobinary.go trims whitespace and rejects an empty string with this error before parsing. It guarantees the parser loop never runs on zero-length input. It surfaces through the package's exported wrapper when the user passes a blank string.

Source

Thrown at conversion/hexadecimaltobinary.go:30

package conversion

import (
	"errors"
	"regexp"
	"strings"
)

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

// hexToBinary() function that will take Hexadecimal number as string,
// and return its Binary equivalent as a string.
func hexToBinary(hex string) (string, error) {
	// Trim any leading or trailing whitespace
	hex = strings.TrimSpace(hex)

	// Check if the hexadecimal string is empty
	if hex == "" {
		return "", errors.New("input string is empty")
	}

	// Check if the hexadecimal string is valid
	if !isValidHex(hex) {
		return "", errors.New("invalid hexadecimal string: " + hex)
	}

	// Parse the hexadecimal string to an integer
	var decimal int64
	for i := 0; i < len(hex); i++ {
		char := hex[i]
		var value int64
		if char >= '0' && char <= '9' {
			value = int64(char - '0')
		} else if char >= 'A' && char <= 'F' {
			value = int64(char - 'A' + 10)
		} else if char >= 'a' && char <= 'f' {
			value = int64(char - 'a' + 10)

View on GitHub (pinned to 5ba447ec5f)

Solutions

1. Check strings.TrimSpace(hex) != "" before calling.
2. Provide a default value when the input source is empty.
3. Handle the returned error and show a 'hex input required' validation message.

Example fix

// before
out, err := conversion.HexToBinary(hexInput) // empty input -> error
// after
if strings.TrimSpace(hexInput) == "" { return errors.New("hex input required") }
out, err = conversion.HexToBinary(hexInput)

func hasHexInput(hex string) bool { return strings.TrimSpace(hex) != "" }

out, err := conversion.HexToBinary(hex)
if err != nil {
    if err.Error() == "input string is empty" {
        return fmt.Errorf("hex input required")
    }
    return err
}

When it happens

Trigger: Calling the hex-to-binary conversion with "", a string of only spaces/tabs (TrimSpace reduces it to ""), or an unset variable.

Common situations: Empty environment variable or config field holding the hex value; reading a zero-byte file; splitting input where an empty tail element is produced.

Related errors

• invalid hexadecimal string:
• invalid character in hexadecimal string:
• no text to encrypt
• not a valid binary string
• binary number must be in range 0 to 2^(31-1)

AI-assisted analysis of TheAlgorithms/Go@5ba447ec5f (2026-09-02). Data as JSON: /api/errors/505e7edbb2974785. Report an issue: GitHub.