/**
 * The only cache of file BYTES in edfcore: opt-in, visible at the call site, and removed by
 * deleting one wrapper from the expression that built the source.
 *
 * "Of bytes" is the load-bearing half. `record-index.ts` memoises decoded record onsets in a Map
 * keyed by record index — that is what makes a second `index.locate()` near the first almost free
 * — and it is not opt-in, not visible at a call site, and lives as long as the index does. A
 * reader told this module is the only cache in the package concludes that dropping the wrapper
 * leaves edfcore retaining nothing, and then cannot account for an index that grows while a viewer
 * scrolls. `large-files.md` has always named both, calling them "the only two forms of memory in
 * the library"; this docblock, `cachedSource` below, `api-sources.md` and `data-sources.md` each
 * said "the only cache" flat (fixed in 0.6.48).
 *
 * Layer 5. A block-aligned LRU over an arbitrary `ByteSource`. Two properties matter more than
 * the hit rate:
 *
 * 1. A read returns a COPY, never a view into a retained block. `types.ts` gives the returned
 *    array to the caller, and a caller who writes into it must not be able to corrupt what the
 *    next reader sees.
 * 2. Concurrent reads wanting the same block issue ONE underlying read. Over HTTP the
 *    difference between one request and eight is the difference between usable and not.
 *
 * Block boundaries are byte-aligned, not record-aligned: this module is format-independent by
 * construction and has no access to a header, so there is no record size to align to.
 */
import type { ByteSource, CacheOptions } from '../types.js';
/**
 * Wraps a source in an LRU block cache — worth it over HTTP, where a scan re-reads neighbouring
 * bytes, and pointless over an in-memory one. It is the only cache of file bytes in edfcore and it
 * is a wrapper, so removing it is deleting this call rather than finding a flag. The record
 * index's onset memo is the other thing in the package that remembers, and no wrapper controls it.
 */
export declare function cachedSource(source: ByteSource, options?: CacheOptions): ByteSource;
//# sourceMappingURL=cached.d.ts.map