/**
 * XXH64 checksum for zstd content validation.
 * Pure TypeScript implementation, seed=0 for frame checksum.
 */
/**
 * Compute XXH64 hash of data with given seed.
 * Returns full 64-bit hash as bigint.
 */
export declare function xxh64(data: Uint8Array, seed?: bigint): bigint;
/**
 * Validate content checksum: low 4 bytes of XXH64(data, 0) must match stored.
 */
export declare function validateContentChecksum(data: Uint8Array, storedChecksum: number): boolean;
/**
 * Compute the 32-bit frame content checksum (low 32 bits of XXH64).
 */
export declare function computeContentChecksum32(data: Uint8Array): number;