The Tor Browser: xpcom/io/nsStorageStream.h@97036ab72558

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

     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/. */

     6 /*

     7  * The storage stream provides an internal buffer that can be filled by a

     8  * client using a single output stream.  One or more independent input streams

     9  * can be created to read the data out non-destructively.  The implementation

    10  * uses a segmented buffer internally to avoid realloc'ing of large buffers,

    11  * with the attendant performance loss and heap fragmentation.

    12  */

    14 #ifndef _nsStorageStream_h_

    15 #define _nsStorageStream_h_

    17 #include "nsIStorageStream.h"

    18 #include "nsIOutputStream.h"

    19 #include "nsMemory.h"

    20 #include "mozilla/Attributes.h"

    22 #define NS_STORAGESTREAM_CID                       \

    23 { /* 669a9795-6ff7-4ed4-9150-c34ce2971b63 */       \

    24   0x669a9795,                                      \

    25   0x6ff7,                                          \

    26   0x4ed4,                                          \

    27   {0x91, 0x50, 0xc3, 0x4c, 0xe2, 0x97, 0x1b, 0x63} \

    28 }

    30 #define NS_STORAGESTREAM_CONTRACTID "@mozilla.org/storagestream;1"

    32 class nsSegmentedBuffer;

    34 class nsStorageStream MOZ_FINAL : public nsIStorageStream,

    35                                   public nsIOutputStream

    36 {

    37 public:

    38     nsStorageStream();

    40     NS_DECL_THREADSAFE_ISUPPORTS

    41     NS_DECL_NSISTORAGESTREAM

    42     NS_DECL_NSIOUTPUTSTREAM

    44     friend class nsStorageInputStream;

    46 private:

    47     ~nsStorageStream();

    49     nsSegmentedBuffer* mSegmentedBuffer;

    50     uint32_t           mSegmentSize;       // All segments, except possibly the last, are of this size

    51                                            //   Must be power-of-2

    52     uint32_t           mSegmentSizeLog2;   // log2(mSegmentSize)

    53     bool               mWriteInProgress;   // true, if an un-Close'ed output stream exists

    54     int32_t            mLastSegmentNum;    // Last segment # in use, -1 initially

    55     char*              mWriteCursor;       // Pointer to next byte to be written

    56     char*              mSegmentEnd;        // Pointer to one byte after end of segment

    57                                            //   containing the write cursor

    58     uint32_t           mLogicalLength;     // Number of bytes written to stream

    60     NS_METHOD Seek(int32_t aPosition);

    61     uint32_t SegNum(uint32_t aPosition)    {return aPosition >> mSegmentSizeLog2;}

    62     uint32_t SegOffset(uint32_t aPosition) {return aPosition & (mSegmentSize - 1);}

    63 };

    65 #endif //  _nsStorageStream_h_

The Tor Browser / file revision

xpcom/io/nsStorageStream.h@97036ab72558

xpcom/io/nsStorageStream.h