/**
 * Escape a string for safe storage in an OOXML cell. Already-escaped
 * sequences (`_xHHHH_`) are protected by escaping their leading
 * underscore; illegal codepoints are replaced with their `_xHHHH_`
 * representation.
 */
export declare function escapeCellString(s: string): string;
/**
 * Inverse of {@link escapeCellString}. Looking from left to right
 * we replace any `_xHHHH_` sequence with the corresponding code unit;
 * the protected `_x005F_` becomes a literal underscore which the
 * subsequent replacements skip safely (replace's regex is non-overlapping).
 */
export declare function unescapeCellString(s: string): string;
/**
 * Escape a string for safe placement in an XML text node. Replaces the three
 * codepoints that would otherwise terminate the text region or open a markup
 * sequence (`&`, `<`, `>`); `"` and `'` are not legal markup terminators
 * inside text and stay verbatim.
 */
export declare function escapeXmlText(s: string): string;
/**
 * Escape a string for safe placement inside a `"`-quoted XML attribute.
 * Handles `&`, `<`, `>` and the `"` that would otherwise close the value.
 *
 * Note: this deliberately does NOT escape `\r` / `\n` / `\t` to numeric
 * character references. XML 1.0 attribute-value normalisation would
 * collapse them to spaces in theory, but the parser used on the read side
 * (fast-xml-parser) does not decode numeric character references, so a
 * write-then-read round-trip would surface the literal `&#9;` instead of
 * recovering the original tab. Leaving the whitespace bytes literal keeps
 * the round-trip stable and matches what Excel itself emits.
 */
export declare function escapeXmlAttr(s: string): string;