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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/*
* The storage stream provides an internal buffer that can be filled by a
* client using a single output stream. One or more independent input streams
* can be created to read the data out non-destructively. The implementation
* uses a segmented buffer internally to avoid realloc'ing of large buffers,
* with the attendant performance loss and heap fragmentation.
*/
#ifndef _nsStorageStream_h_
#define _nsStorageStream_h_
#include "nsIStorageStream.h"
#include "nsIOutputStream.h"
#include "mozilla/Attributes.h"
#include "mozilla/Mutex.h"
#define NS_STORAGESTREAM_CID \
{ /* 669a9795-6ff7-4ed4-9150-c34ce2971b63 */ \
0x669a9795, 0x6ff7, 0x4ed4, { \
0x91, 0x50, 0xc3, 0x4c, 0xe2, 0x97, 0x1b, 0x63 \
} \
}
#define NS_STORAGESTREAM_CONTRACTID "@mozilla.org/storagestream;1"
class nsSegmentedBuffer;
class nsStorageStream final : public nsIStorageStream, public nsIOutputStream {
public:
nsStorageStream();
NS_DECL_THREADSAFE_ISUPPORTS
NS_DECL_NSISTORAGESTREAM
NS_DECL_NSIOUTPUTSTREAM
friend class nsStorageInputStream;
private:
~nsStorageStream();
mozilla::Mutex mMutex{"nsStorageStream"};
nsSegmentedBuffer* mSegmentedBuffer MOZ_GUARDED_BY(mMutex) = nullptr;
// All segments, except possibly the last, are of this size. Must be
// power-of-2
uint32_t mSegmentSize MOZ_GUARDED_BY(mMutex) = 0;
// log2(mSegmentSize)
uint32_t mSegmentSizeLog2 MOZ_GUARDED_BY(mMutex) = 0;
// true, if an un-Close'ed output stream exists
bool mWriteInProgress MOZ_GUARDED_BY(mMutex) = false;
// Last segment # in use, -1 initially
int32_t mLastSegmentNum MOZ_GUARDED_BY(mMutex) = -1;
// Pointer to next byte to be written
char* mWriteCursor MOZ_GUARDED_BY(mMutex) = nullptr;
// Pointer to one byte after end of segment containing the write cursor
char* mSegmentEnd MOZ_GUARDED_BY(mMutex) = nullptr;
// Number of bytes written to stream
uint32_t mLogicalLength MOZ_GUARDED_BY(mMutex) = 0;
// number of input streams actively reading a segment.
uint32_t mActiveSegmentBorrows MOZ_GUARDED_BY(mMutex) = 0;
nsresult SetLengthLocked(uint32_t aLength) MOZ_REQUIRES(mMutex);
nsresult Seek(int32_t aPosition) MOZ_REQUIRES(mMutex);
uint32_t SegNum(uint32_t aPosition) MOZ_REQUIRES(mMutex) {
return aPosition >> mSegmentSizeLog2;
}
uint32_t SegOffset(uint32_t aPosition) MOZ_REQUIRES(mMutex) {
return aPosition & (mSegmentSize - 1);
}
};
#endif // _nsStorageStream_h_
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