/**
 * Lightweight MIME type detection from magic bytes (file signatures).
 *
 * Designed for the blob store's auto-detection feature. Operates on the first 16 bytes of
 * plaintext — no filesystem access, no filename guessing.
 *
 * ## Detection strategies
 *
 * 1. **Prefix match** — magic bytes at offset 0 (most formats).
 * 2. **Offset match** — magic bytes at a fixed offset > 0 (ISOBMFF: offset 4).
 * 3. **Compound match** — two separate byte sequences at different offsets
 *    (RIFF-based: bytes 0-3 + bytes 8-11).
 *
 * ## Formats excluded (require offset > 16 bytes)
 *
 * - TAR (`ustar` at offset 257)
 * - ISO 9660 (`CD001` at offset 32769)
 *
 * @module
 */
/**
 * Detect MIME type from the first bytes of a file.
 *
 * @param header - The first 16 bytes (or more) of the plaintext. Passing
 *   fewer than 16 bytes may miss compound and offset-based matches.
 * @returns Detected MIME type, or `'application/octet-stream'` if unknown.
 */
export declare function detectMimeType(header: Uint8Array): string;
/**
 * Detect MIME type and whether the format is already compressed.
 *
 * Used by `BlobSet.put()` to decide whether to skip gzip compression.
 *
 * @param header - The first 16 bytes (or more) of the plaintext.
 * @returns `{ mime, preCompressed }` or `null` if no match.
 */
export declare function detectMagic(header: Uint8Array): {
    mime: string;
    format: string;
    preCompressed: boolean;
} | null;
/**
 * Check whether a format is already compressed (should skip gzip).
 *
 * @param mimeType - A MIME type string.
 * @returns `true` if the format is known to be pre-compressed.
 */
export declare function isPreCompressed(mimeType: string): boolean;