/**
 * Windowed file access, ported from less's ch.c: the file is read in
 * fixed blocks kept in an LRU pool, so any position of an arbitrarily
 * large file is reachable without loading it. Positions are byte
 * offsets (less's POSITION), safe as JS numbers up to 2^53.
 */
/** Block size, like less's LBUFSIZE. */
export declare const BLOCK_SIZE = 8192;
export declare class BlockFile {
    private fd;
    /** Resident blocks by block index, in LRU order (oldest first). */
    private blocks;
    /** File length at open (or last refresh), like ch_length. */
    size: number;
    readonly path: string;
    constructor(path: string);
    /** Re-checks the file length, for F follow and growing files. */
    refreshSize(): number;
    /**
     * Whether a read at `pos` really has nothing left, like less's ch_get
     * reaching the cached length: "Apparently at end of file. Double-check
     * the file size in case it has changed" (ch.c:236), and only then
     * returning EOI.
     *
     * This is why less needs no command to follow a growing file - an
     * ordinary forward scroll past the old end picks up whatever has
     * been appended. The stat costs nothing until a read is already at
     * the end, which is exactly when less pays for it too.
     */
    atEnd(pos: number): boolean;
    /**
     * The maximum resident blocks: -b caps the pool like less's bufspace
     * (in KB); -B off pins the cap, on lets it grow to a sane ceiling.
     */
    private maxBlocks;
    /** Evicts blocks beyond the -b cap, like less's ch_setbufspace
     *  releasing excess buffers as soon as the option changes. */
    trim(): void;
    /** Returns one block's bytes, reading and pooling it on demand. */
    private blockAt;
    /**
     * Reads a byte range, assembled from pooled blocks; clipped at the
     * ends of the file.
     */
    readRange(pos: number, len: number): Buffer;
    /**
     * The next newline at or after `pos`, or -1 within the searched
     * span; scans block by block like ch_forw_get.
     */
    findNewline(pos: number, limit: number): number;
    /**
     * The last newline strictly before `pos`, or -1 within the span;
     * scans backward like ch_back_get.
     */
    findNewlineBack(pos: number, limit: number): number;
    close(): void;
}