xpcom/io/nsStorageStream.h

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   2  * ***** BEGIN LICENSE BLOCK *****
   3  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   4  *
   5  * The contents of this file are subject to the Mozilla Public License Version
   6  * 1.1 (the "License"); you may not use this file except in compliance with
   7  * the License. You may obtain a copy of the License at
   8  * http://www.mozilla.org/MPL/
   9  *
  10  * Software distributed under the License is distributed on an "AS IS" basis,
  11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  12  * for the specific language governing rights and limitations under the
  13  * License.
  14  *
  15  * The Original Code is Mozilla Communicator client code, released
  16  * March 31, 1998.
  17  *
  18  * The Initial Developer of the Original Code is
  19  * Netscape Communications Corporation.
  20  * Portions created by the Initial Developer are Copyright (C) 1998-1999
  21  * the Initial Developer. All Rights Reserved.
  22  *
  23  * Contributor(s):
  24  *
  25  * Alternatively, the contents of this file may be used under the terms of
  26  * either of the GNU General Public License Version 2 or later (the "GPL"),
  27  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  28  * in which case the provisions of the GPL or the LGPL are applicable instead
  29  * of those above. If you wish to allow use of your version of this file only
  30  * under the terms of either the GPL or the LGPL, and not to allow others to
  31  * use your version of this file under the terms of the MPL, indicate your
  32  * decision by deleting the provisions above and replace them with the notice
  33  * and other provisions required by the GPL or the LGPL. If you do not delete
  34  * the provisions above, a recipient may use your version of this file under
  35  * the terms of any one of the MPL, the GPL or the LGPL.
  36  *
  37  * ***** END LICENSE BLOCK ***** */
  38
  39 /*
  40  * The storage stream provides an internal buffer that can be filled by a
  41  * client using a single output stream.  One or more independent input streams
  42  * can be created to read the data out non-destructively.  The implementation
  43  * uses a segmented buffer internally to avoid realloc'ing of large buffers,
  44  * with the attendant performance loss and heap fragmentation.
  45  */
  46
  47 #ifndef _nsStorageStream_h_
  48 #define _nsStorageStream_h_
  49
  50 #include "nsIStorageStream.h"
  51 #include "nsIOutputStream.h"
  52 #include "nsMemory.h"
  53
  54 #define NS_STORAGESTREAM_CID                       \
  55 { /* 669a9795-6ff7-4ed4-9150-c34ce2971b63 */       \
  56   0x669a9795,                                      \
  57   0x6ff7,                                          \
  58   0x4ed4,                                          \
  59   {0x91, 0x50, 0xc3, 0x4c, 0xe2, 0x97, 0x1b, 0x63} \
  60 }
  61
  62 #define NS_STORAGESTREAM_CONTRACTID "@mozilla.org/storagestream;1"
  63 #define NS_STORAGESTREAM_CLASSNAME "Storage Stream"
  64
  65 class nsSegmentedBuffer;
  66
  67 class nsStorageStream : public nsIStorageStream,
  68                         public nsIOutputStream
  69 {
  70 public:
  71     nsStorageStream();
  72
  73     NS_DECL_ISUPPORTS
  74     NS_DECL_NSISTORAGESTREAM
  75     NS_DECL_NSIOUTPUTSTREAM
  76
  77     friend class nsStorageInputStream;
  78
  79 private:
  80     ~nsStorageStream();
  81
  82     nsSegmentedBuffer* mSegmentedBuffer;
  83     PRUint32           mSegmentSize;       // All segments, except possibly the last, are of this size
  84                                            //   Must be power-of-2
  85     PRUint32           mSegmentSizeLog2;   // log2(mSegmentSize)
  86     PRBool             mWriteInProgress;   // true, if an un-Close'ed output stream exists
  87     PRInt32            mLastSegmentNum;    // Last segment # in use, -1 initially
  88     char*              mWriteCursor;       // Pointer to next byte to be written
  89     char*              mSegmentEnd;        // Pointer to one byte after end of segment
  90                                            //   containing the write cursor
  91     PRUint32           mLogicalLength;     // Number of bytes written to stream
  92
  93     NS_METHOD Seek(PRInt32 aPosition);
  94     PRUint32 SegNum(PRUint32 aPosition)    {return aPosition >> mSegmentSizeLog2;}
  95     PRUint32 SegOffset(PRUint32 aPosition) {return aPosition & (mSegmentSize - 1);}
  96 };
  97
  98 #endif //  _nsStorageStream_h_