gecko/xpcom/io/nsStorageStream.h
2012-05-21 12:12:37 +01:00

66 lines
2.5 KiB
C++

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* 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 "nsMemory.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"
#define NS_STORAGESTREAM_CLASSNAME "Storage Stream"
class nsSegmentedBuffer;
class nsStorageStream : public nsIStorageStream,
public nsIOutputStream
{
public:
nsStorageStream();
NS_DECL_ISUPPORTS
NS_DECL_NSISTORAGESTREAM
NS_DECL_NSIOUTPUTSTREAM
friend class nsStorageInputStream;
private:
~nsStorageStream();
nsSegmentedBuffer* mSegmentedBuffer;
PRUint32 mSegmentSize; // All segments, except possibly the last, are of this size
// Must be power-of-2
PRUint32 mSegmentSizeLog2; // log2(mSegmentSize)
bool mWriteInProgress; // true, if an un-Close'ed output stream exists
PRInt32 mLastSegmentNum; // Last segment # in use, -1 initially
char* mWriteCursor; // Pointer to next byte to be written
char* mSegmentEnd; // Pointer to one byte after end of segment
// containing the write cursor
PRUint32 mLogicalLength; // Number of bytes written to stream
NS_METHOD Seek(PRInt32 aPosition);
PRUint32 SegNum(PRUint32 aPosition) {return aPosition >> mSegmentSizeLog2;}
PRUint32 SegOffset(PRUint32 aPosition) {return aPosition & (mSegmentSize - 1);}
};
#endif // _nsStorageStream_h_