/**
 * SHA-256 over a UTF-8 string, in plain TypeScript.
 *
 * **Why the package carries an implementation instead of taking a port**, when
 * `run/receipts.ts` deliberately does the opposite. Two differences decide it.
 *
 * The first is *when* the digest is needed. A receipt's hash is taken inside an
 * already-async tool dispatch, so `crypto.subtle.digest` — which is async
 * everywhere, and is the only digest workerd has — fits without changing any
 * signature. A skill's `contentSha` is computed at **registration**, which is
 * the synchronous act of a module declaring what it contributes. Taking an
 * async digest there forces either an async `register()` (so a plugin's
 * registration becomes something a host must await and order) or a lazily
 * resolved hash on every read path that wants one. Both cost more than this
 * file.
 *
 * The second is *what the value means*. A receipt hash is persisted by the host
 * forever and compared against rows written by earlier versions, so the host
 * must own the algorithm choice — and its input is tool arguments, routinely
 * user data, which is why that doc argues preimage resistance. A `contentSha`
 * identifies build content within one deployment: it is derived from source the
 * deployment already ships, and nothing reads it that did not just compute it.
 *
 * A host with a native digest can still supply one — {@link Sha256Hex} is a
 * parameter everywhere this is used — but it must be synchronous and it must be
 * SHA-256, or the hashes two hosts compute for the same skill diverge.
 *
 * The implementation is the FIPS 180-4 reference algorithm with no shortcuts.
 * `__tests__/sha256.test.ts` pins it against the published vectors, plus a
 * multi-block and a multi-byte-UTF-8 case, because a hash that is subtly wrong
 * fails silently: every value still looks like a hash.
 */
/** A synchronous SHA-256 that returns lowercase hex. */
export type Sha256Hex = (text: string) => string;
/** SHA-256 (lowercase hex) of a UTF-8 string. */
export declare const sha256Hex: Sha256Hex;
/** Byte length of a string in UTF-8 — what a resource listing reports. */
export declare function utf8ByteLength(text: string): number;