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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 */
* 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"
#include "mozilla/Attributes.h"
{ /* 669a9795-6ff7-4ed4-9150-c34ce2971b63 */ \
0x669a9795, 0x6ff7, 0x4ed4, { \
0x91, 0x50, 0xc3, 0x4c, 0xe2, 0x97, 0x1b, 0x63 \
} \
class nsSegmentedBuffer;
class nsStorageStream final : public nsIStorageStream, public nsIOutputStream {
friend class nsStorageInputStream;
nsSegmentedBuffer* mSegmentedBuffer;
mSegmentSize; // All segments, except possibly the last, are of this size
// Must be power-of-2
uint32_t mSegmentSizeLog2; // log2(mSegmentSize)
bool mWriteInProgress; // true, if an un-Close'ed output stream exists
int32_t 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
uint32_t mLogicalLength; // Number of bytes written to stream
nsresult Seek(int32_t aPosition);
uint32_t SegNum(uint32_t aPosition) { return aPosition >> mSegmentSizeLog2; }
uint32_t SegOffset(uint32_t aPosition) {
return aPosition & (mSegmentSize - 1);
#endif // _nsStorageStream_h_