Method IsValidHeaderValue

lib/remote/httputility.cpp:155–184

* Check if the given string is suitable to be used as an HTTP header value. * * @param value The value to check for validity * @return true if the argument is a valid header value, false otherwise */

 * @return true if the argument is a valid header value, false otherwise
 */
bool HttpUtility::IsValidHeaderValue(std::string_view value)
{
	/*
	 * Derived from the following syntax definition in RFC9110:
	 *
	 *     field-value = *field-content
	 *     field-content = field-vchar [ 1*( SP / HTAB / field-vchar ) field-vchar ]
	 *     field-vchar = VCHAR / obs-text
	 *     obs-text = %x80-FF
	 *     VCHAR = %x21-7E ; visible (printing) characters
	 *
	 * References:
	 * - https://datatracker.ietf.org/doc/html/rfc9110#section-5.5
	 * - https://datatracker.ietf.org/doc/html/rfc9110#appendix-A
	 * - https://www.rfc-editor.org/rfc/rfc5234#appendix-B.1
	 */

	if (!value.empty()) {
		// Must not start or end with space or tab.
		for (char c : {value.front(), value.back()}) {
			if (c == ' ' || c == '\t') {
				return false;
			}
		}
	}

	return std::all_of(value.begin(), value.end(), [](char c) {
		return c == ' ' || c == '\t' || ('\x21' <= c && c <= '\x7e') || ('\x80' <= c && c <= '\xff');
	});
}