/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"

interface nsITransport;
interface nsIInputStream;
interface nsIOutputStream;

/**
 * This service read/writes a stream on a background thread.
 *
 * Use this service to transform any blocking stream (e.g., file stream)
 * into a fully asynchronous stream that can be read/written without 
 * blocking the main thread.
 */
[scriptable, uuid(51CAC889-ABC6-4948-97A3-4F135A6E7630)]
interface nsIStreamTransportService : nsISupports
{
    /**
     * CreateInputTransport
     *
     * @param aStream
     *        The input stream that will be read on a background thread.
     *        This stream must implement "blocking" stream semantics.
     * @param aStartOffset
     *        The input stream will be read starting from this offset.  Pass
     *        -1 to read from the current stream offset.  NOTE: this parameter
     *        is ignored if the stream does not support nsISeekableStream.
     * @param aReadLimit
     *        This parameter limits the number of bytes that will be read from
     *        the input stream.  Pass -1 to read everything.
     * @param aCloseWhenDone
     *        Specify this flag to have the input stream closed once its
     *        contents have been completely read.
     *
     * @return nsITransport instance.
     */
    nsITransport createInputTransport(in nsIInputStream aStream,
                                      in long long aStartOffset,
                                      in long long aReadLimit,
                                      in boolean aCloseWhenDone);

    /**
     * CreateOutputTransport
     *
     * @param aStream
     *        The output stream that will be written to on a background thread.
     *        This stream must implement "blocking" stream semantics.
     * @param aStartOffset
     *        The output stream will be written starting at this offset.  Pass
     *        -1 to write to the current stream offset.  NOTE: this parameter
     *        is ignored if the stream does not support nsISeekableStream.
     * @param aWriteLimit
     *        This parameter limits the number of bytes that will be written to
     *        the output stream.  Pass -1 for unlimited writing.
     * @param aCloseWhenDone
     *        Specify this flag to have the output stream closed once its
     *        contents have been completely written.
     *
     * @return nsITransport instance.
     */
    nsITransport createOutputTransport(in nsIOutputStream aStream,
                                       in long long aStartOffset,
                                       in long long aWriteLimit,
                                       in boolean aCloseWhenDone);

    /**
     * Raise the maximum number of active threads by one.
     *
     * Calling this method won't create any additional thread synchronously.
     * It will be only created when it's needed (lazily).
     *
     * Used by mozilla::dom::file::FileService to increase the maximum number
     * of active threads in the thread pool for asynchronous file IO.
     */
    void raiseThreadLimit();

    /**
     * Lower the maximum number of active threads by one.
     * lowerThreadLimit() should be always paired with raiseThreadLimit().
     *
     * Calling this method won't destroy any already running thread
     * synchronously. It will be only destroyed when it's done with
     * currently running event.
     *
     * This will never lower the maximum number of active threads beyond
     * the internal limit.
     *
     * @throws NS_ERROR_UNEXPECTED
     *         When trying to lower the maximum number of active threads
     *         beyond the internal limit (for example in the case of badly
     *         nested calls)
     */
    void lowerThreadLimit();
};