xpcom/io/nsIStorageStream.idl

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   2  * This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "nsISupports.idl"
   7
   8 interface nsIInputStream;
   9 interface nsIOutputStream;
  10
  11 /**
  12  * The nsIStorageStream interface maintains an internal data buffer that can be
  13  * filled using a single output stream.  One or more independent input streams
  14  * can be created to read the data from the buffer non-destructively.
  15  */
  16
  17 [scriptable, uuid(44a200fe-6c2b-4b41-b4e3-63e8c14e7c0d)]
  18 interface nsIStorageStream : nsISupports
  19 {
  20     /**
  21      *
  22      * Initialize the stream, setting up the amount of space that will be
  23      * allocated for the stream's backing-store.
  24      *
  25      * @param segmentSize
  26      *        Size of each segment. Must be a power of two.
  27      * @param maxSize
  28      *        Maximum total size of this stream. length will always be less
  29      *        than or equal to this value. Passing UINT32_MAX is safe.
  30      */
  31     void init(in uint32_t segmentSize, in uint32_t maxSize);
  32
  33     /**
  34      * Get a reference to the one and only output stream for this instance.
  35      * The zero-based startPosition argument is used is used to set the initial
  36      * write cursor position.  The startPosition cannot be set larger than the
  37      * current buffer length.  Calling this method has the side-effect of
  38      * truncating the internal buffer to startPosition bytes.
  39      */
  40     nsIOutputStream getOutputStream(in int32_t startPosition);
  41
  42     /**
  43      * Create a new input stream to read data (written by the singleton output
  44      * stream) from the internal buffer.  Multiple, independent input streams
  45      * can be created.
  46      */
  47     nsIInputStream newInputStream(in int32_t startPosition);
  48
  49     /**
  50      * The length attribute indicates the total number of bytes stored in the
  51      * nsIStorageStream internal buffer, regardless of any consumption by input
  52      * streams.  Assigning to the length field can be used to truncate the
  53      * buffer data, but can not be used when either the instance's output
  54      * stream is in use.
  55      *
  56      * @See #writeInProgress */
  57     attribute uint32_t length;
  58
  59     /**
  60      * True, when output stream has not yet been Close'ed
  61      */
  62     readonly attribute boolean writeInProgress;
  63 };
  64
  65 %{C++
  66 // Factory method
  67 nsresult
  68 NS_NewStorageStream(uint32_t segmentSize, uint32_t maxSize, nsIStorageStream **result);
  69 %}