/**
 * A random-access, forward-readable byte source for the streaming parser.
 *
 * The streaming index builder (see streaming_index_builder.ts) reads the
 * source sequentially into a small moving window, so a `ByteSource` only has
 * to satisfy positioned reads — it never needs the whole file resident. The
 * in-memory `BufferByteSource` here is for tests and the resident case; a
 * file-descriptor source (node) or an HTTP-Range source (M4) implements the
 * same shape without holding the file in the JS heap.
 *
 * M0 keeps reads synchronous to reuse the existing synchronous parse loop
 * unchanged. The asynchronous variant (network pull-parser) is M4.
 */
export interface ByteSource {
    /** Total length of the source in bytes. */
    readonly byteLength: number;
    /**
     * Read up to `length` bytes starting at `offset` into `into` at
     * `intoOffset`, returning the number of bytes actually copied (fewer than
     * `length` only at end of source).
     *
     * @param offset Absolute source offset to read from.
     * @param length Maximum number of bytes to read.
     * @param into Destination buffer.
     * @param intoOffset Offset within `into` to write at.
     * @return {number} The number of bytes copied.
     */
    read(offset: number, length: number, into: Uint8Array, intoOffset: number): number;
}
/**
 * A `ByteSource` backed by an in-memory `Uint8Array`. Reads are `subarray`
 * copies into the destination window. Used by tests and the resident path;
 * note it does hold the whole buffer (that residency is the source's, not the
 * parser's — the parser still only touches a window).
 */
export declare class BufferByteSource implements ByteSource {
    private readonly buffer;
    /**
     * @param buffer The backing bytes.
     */
    constructor(buffer: Uint8Array);
    /**
     * @return {number} The buffer length.
     */
    get byteLength(): number;
    /**
     * @param offset Absolute source offset to read from.
     * @param length Maximum number of bytes to read.
     * @param into Destination buffer.
     * @param intoOffset Offset within `into` to write at.
     * @return {number} The number of bytes copied.
     */
    read(offset: number, length: number, into: Uint8Array, intoOffset: number): number;
}
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