xml-sec 0.1.5

Pure Rust XML Security: XMLDSig, XMLEnc, C14N. Drop-in replacement for libxmlsec1.
Documentation 
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//! Internal XML whitespace helpers shared across XMLDSig parsing and verification.

/// Return `true` when the text contains only XML 1.0 whitespace chars.
#[inline]
pub(crate) fn is_xml_whitespace_only(text: &str) -> bool {
    text.chars()
        .all(|ch| matches!(ch, ' ' | '\t' | '\r' | '\n'))
}

/// Error returned when non-XML ASCII whitespace appears in base64 text.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) struct XmlBase64NormalizeError {
    /// Offending ASCII byte.
    pub invalid_byte: u8,
    /// Offset in the normalized output where the byte was encountered.
    pub normalized_offset: usize,
}

/// Normalize base64 text by stripping XML whitespace and rejecting other ASCII whitespace.
pub(crate) fn normalize_xml_base64_text(
    text: &str,
    normalized: &mut String,
) -> Result<(), XmlBase64NormalizeError> {
    for ch in text.chars() {
        if matches!(ch, ' ' | '\t' | '\r' | '\n') {
            continue;
        }
        if ch.is_ascii_whitespace() {
            let mut utf8 = [0_u8; 4];
            let encoded = ch.encode_utf8(&mut utf8);
            let invalid_byte = encoded.as_bytes()[0];
            return Err(XmlBase64NormalizeError {
                invalid_byte,
                normalized_offset: normalized.len(),
            });
        }
        normalized.push(ch);
    }
    Ok(())
}