1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
3 /* This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
8 * The storage stream provides an internal buffer that can be filled by a
9 * client using a single output stream. One or more independent input streams
10 * can be created to read the data out non-destructively. The implementation
11 * uses a segmented buffer internally to avoid realloc'ing of large buffers,
12 * with the attendant performance loss and heap fragmentation.
15 #ifndef _nsStorageStream_h_
16 #define _nsStorageStream_h_
18 #include "nsIStorageStream.h"
19 #include "nsIOutputStream.h"
20 #include "mozilla/Attributes.h"
21 #include "mozilla/Mutex.h"
23 #define NS_STORAGESTREAM_CID \
24 { /* 669a9795-6ff7-4ed4-9150-c34ce2971b63 */ \
25 0x669a9795, 0x6ff7, 0x4ed4, { \
26 0x91, 0x50, 0xc3, 0x4c, 0xe2, 0x97, 0x1b, 0x63 \
30 #define NS_STORAGESTREAM_CONTRACTID "@mozilla.org/storagestream;1"
32 class nsSegmentedBuffer
;
34 class nsStorageStream final
: public nsIStorageStream
, public nsIOutputStream
{
38 NS_DECL_THREADSAFE_ISUPPORTS
39 NS_DECL_NSISTORAGESTREAM
40 NS_DECL_NSIOUTPUTSTREAM
42 friend class nsStorageInputStream
;
47 mozilla::Mutex mMutex
{"nsStorageStream"};
48 nsSegmentedBuffer
* mSegmentedBuffer
MOZ_GUARDED_BY(mMutex
) = nullptr;
49 // All segments, except possibly the last, are of this size. Must be
51 uint32_t mSegmentSize
MOZ_GUARDED_BY(mMutex
) = 0;
53 uint32_t mSegmentSizeLog2
MOZ_GUARDED_BY(mMutex
) = 0;
54 // true, if an un-Close'ed output stream exists
55 bool mWriteInProgress
MOZ_GUARDED_BY(mMutex
) = false;
56 // Last segment # in use, -1 initially
57 int32_t mLastSegmentNum
MOZ_GUARDED_BY(mMutex
) = -1;
58 // Pointer to next byte to be written
59 char* mWriteCursor
MOZ_GUARDED_BY(mMutex
) = nullptr;
60 // Pointer to one byte after end of segment containing the write cursor
61 char* mSegmentEnd
MOZ_GUARDED_BY(mMutex
) = nullptr;
62 // Maximum number of bytes which may be written to the stream
63 uint32_t mMaxLogicalLength
MOZ_GUARDED_BY(mMutex
) = 0;
64 // Number of bytes written to stream
65 uint32_t mLogicalLength
MOZ_GUARDED_BY(mMutex
) = 0;
66 // number of input streams actively reading a segment.
67 uint32_t mActiveSegmentBorrows
MOZ_GUARDED_BY(mMutex
) = 0;
69 nsresult
SetLengthLocked(uint32_t aLength
) MOZ_REQUIRES(mMutex
);
70 nsresult
Seek(int32_t aPosition
) MOZ_REQUIRES(mMutex
);
71 uint32_t SegNum(uint32_t aPosition
) MOZ_REQUIRES(mMutex
) {
72 return aPosition
>> mSegmentSizeLog2
;
74 uint32_t SegOffset(uint32_t aPosition
) MOZ_REQUIRES(mMutex
) {
75 return aPosition
& (mSegmentSize
- 1);
79 #endif // _nsStorageStream_h_