michael@0: /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "nsISupports.idl"
michael@0: 
michael@0: interface nsIInputStream;
michael@0: interface nsIOutputStream;
michael@0: 
michael@0: /**
michael@0:  * The nsIStorageStream interface maintains an internal data buffer that can be
michael@0:  * filled using a single output stream.  One or more independent input streams
michael@0:  * can be created to read the data from the buffer non-destructively.
michael@0:  */
michael@0: 
michael@0: [scriptable, uuid(44a200fe-6c2b-4b41-b4e3-63e8c14e7c0d)]
michael@0: interface nsIStorageStream : nsISupports
michael@0: {
michael@0:     /**
michael@0:      *
michael@0:      * Initialize the stream, setting up the amount of space that will be
michael@0:      * allocated for the stream's backing-store.
michael@0:      *
michael@0:      * @param segmentSize
michael@0:      *        Size of each segment. Must be a power of two.
michael@0:      * @param maxSize
michael@0:      *        Maximum total size of this stream. length will always be less
michael@0:      *        than or equal to this value. Passing UINT32_MAX is safe.
michael@0:      */
michael@0:     void init(in uint32_t segmentSize, in uint32_t maxSize);
michael@0: 
michael@0:     /**
michael@0:      * Get a reference to the one and only output stream for this instance.
michael@0:      * The zero-based startPosition argument is used is used to set the initial
michael@0:      * write cursor position.  The startPosition cannot be set larger than the
michael@0:      * current buffer length.  Calling this method has the side-effect of
michael@0:      * truncating the internal buffer to startPosition bytes.
michael@0:      */
michael@0:     nsIOutputStream getOutputStream(in int32_t startPosition);
michael@0: 
michael@0:     /**
michael@0:      * Create a new input stream to read data (written by the singleton output
michael@0:      * stream) from the internal buffer.  Multiple, independent input streams
michael@0:      * can be created.
michael@0:      */
michael@0:     nsIInputStream newInputStream(in int32_t startPosition);
michael@0: 
michael@0:     /** 
michael@0:      * The length attribute indicates the total number of bytes stored in the
michael@0:      * nsIStorageStream internal buffer, regardless of any consumption by input
michael@0:      * streams.  Assigning to the length field can be used to truncate the
michael@0:      * buffer data, but can not be used when either the instance's output
michael@0:      * stream is in use.
michael@0:      *
michael@0:      * @See #writeInProgress */
michael@0:     attribute uint32_t length;
michael@0: 
michael@0:     /**
michael@0:      * True, when output stream has not yet been Close'ed
michael@0:      */
michael@0:     readonly attribute boolean writeInProgress;
michael@0: };
michael@0: 
michael@0: %{C++
michael@0: // Factory method
michael@0: nsresult
michael@0: NS_NewStorageStream(uint32_t segmentSize, uint32_t maxSize, nsIStorageStream **result);
michael@0: %}