nsStorageStream.cpp
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim:set ts=4 sts=4 sw=4 cin et: */
/* 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.
*/
#include "nsAlgorithm.h"
#include "nsStorageStream.h"
#include "nsSegmentedBuffer.h"
#include "nsStreamUtils.h"
#include "nsCOMPtr.h"
#include "nsIInputStream.h"
#include "nsISeekableStream.h"
#include "prlog.h"
#include "mozilla/Attributes.h"
#include "mozilla/Likely.h"
#include "mozilla/MathAlgorithms.h"
#if defined(PR_LOGGING)
//
// Log module for StorageStream logging...
//
// To enable logging (see prlog.h for full details):
//
// set NSPR_LOG_MODULES=StorageStreamLog:5
// set NSPR_LOG_FILE=nspr.log
//
// this enables PR_LOG_DEBUG level information and places all output in
// the file nspr.log
//
static PRLogModuleInfo*
GetStorageStreamLog()
{
static PRLogModuleInfo *sLog;
if (!sLog)
sLog = PR_NewLogModule("nsStorageStream");
return sLog;
}
#endif
#ifdef LOG
#undef LOG
#endif
#define LOG(args) PR_LOG(GetStorageStreamLog(), PR_LOG_DEBUG, args)
nsStorageStream::nsStorageStream()
: mSegmentedBuffer(0), mSegmentSize(0), mWriteInProgress(false),
mLastSegmentNum(-1), mWriteCursor(0), mSegmentEnd(0), mLogicalLength(0)
{
LOG(("Creating nsStorageStream [%p].\n", this));
}
nsStorageStream::~nsStorageStream()
{
delete mSegmentedBuffer;
}
NS_IMPL_ISUPPORTS2(nsStorageStream,
nsIStorageStream,
nsIOutputStream)
NS_IMETHODIMP
nsStorageStream::Init(uint32_t segmentSize, uint32_t maxSize,
nsIMemory *segmentAllocator)
{
mSegmentedBuffer = new nsSegmentedBuffer();
if (!mSegmentedBuffer)
return NS_ERROR_OUT_OF_MEMORY;
mSegmentSize = segmentSize;
mSegmentSizeLog2 = mozilla::FloorLog2(segmentSize);
// Segment size must be a power of two
if (mSegmentSize != ((uint32_t)1 << mSegmentSizeLog2))
return NS_ERROR_INVALID_ARG;
return mSegmentedBuffer->Init(segmentSize, maxSize, segmentAllocator);
}
NS_IMETHODIMP
nsStorageStream::GetOutputStream(int32_t aStartingOffset,
nsIOutputStream * *aOutputStream)
{
if (NS_WARN_IF(!aOutputStream))
return NS_ERROR_INVALID_ARG;
if (NS_WARN_IF(!mSegmentedBuffer))
return NS_ERROR_NOT_INITIALIZED;
if (mWriteInProgress)
return NS_ERROR_NOT_AVAILABLE;
nsresult rv = Seek(aStartingOffset);
if (NS_FAILED(rv)) return rv;
// Enlarge the last segment in the buffer so that it is the same size as
// all the other segments in the buffer. (It may have been realloc'ed
// smaller in the Close() method.)
if (mLastSegmentNum >= 0)
if (mSegmentedBuffer->ReallocLastSegment(mSegmentSize)) {
// Need to re-Seek, since realloc changed segment base pointer
rv = Seek(aStartingOffset);
if (NS_FAILED(rv)) return rv;
}
NS_ADDREF(this);
*aOutputStream = static_cast<nsIOutputStream*>(this);
mWriteInProgress = true;
return NS_OK;
}
NS_IMETHODIMP
nsStorageStream::Close()
{
if (NS_WARN_IF(!mSegmentedBuffer))
return NS_ERROR_NOT_INITIALIZED;
mWriteInProgress = false;
int32_t segmentOffset = SegOffset(mLogicalLength);
// Shrink the final segment in the segmented buffer to the minimum size
// needed to contain the data, so as to conserve memory.
if (segmentOffset)
mSegmentedBuffer->ReallocLastSegment(segmentOffset);
mWriteCursor = 0;
mSegmentEnd = 0;
LOG(("nsStorageStream [%p] Close mWriteCursor=%x mSegmentEnd=%x\n",
this, mWriteCursor, mSegmentEnd));
return NS_OK;
}
NS_IMETHODIMP
nsStorageStream::Flush()
{
return NS_OK;
}
NS_IMETHODIMP
nsStorageStream::Write(const char *aBuffer, uint32_t aCount, uint32_t *aNumWritten)
{
if (NS_WARN_IF(!aNumWritten) || NS_WARN_IF(!aBuffer))
return NS_ERROR_INVALID_ARG;
if (NS_WARN_IF(!mSegmentedBuffer))
return NS_ERROR_NOT_INITIALIZED;
const char* readCursor;
uint32_t count, availableInSegment, remaining;
nsresult rv = NS_OK;
LOG(("nsStorageStream [%p] Write mWriteCursor=%x mSegmentEnd=%x aCount=%d\n",
this, mWriteCursor, mSegmentEnd, aCount));
remaining = aCount;
readCursor = aBuffer;
// If no segments have been created yet, create one even if we don't have
// to write any data; this enables creating an input stream which reads from
// the very end of the data for any amount of data in the stream (i.e.
// this stream contains N bytes of data and newInputStream(N) is called),
// even for N=0 (with the caveat that we require .write("", 0) be called to
// initialize internal buffers).
bool firstTime = mSegmentedBuffer->GetSegmentCount() == 0;
while (remaining || MOZ_UNLIKELY(firstTime)) {
firstTime = false;
availableInSegment = mSegmentEnd - mWriteCursor;
if (!availableInSegment) {
mWriteCursor = mSegmentedBuffer->AppendNewSegment();
if (!mWriteCursor) {
mSegmentEnd = 0;
rv = NS_ERROR_OUT_OF_MEMORY;
goto out;
}
mLastSegmentNum++;
mSegmentEnd = mWriteCursor + mSegmentSize;
availableInSegment = mSegmentEnd - mWriteCursor;
LOG(("nsStorageStream [%p] Write (new seg) mWriteCursor=%x mSegmentEnd=%x\n",
this, mWriteCursor, mSegmentEnd));
}
count = XPCOM_MIN(availableInSegment, remaining);
memcpy(mWriteCursor, readCursor, count);
remaining -= count;
readCursor += count;
mWriteCursor += count;
LOG(("nsStorageStream [%p] Writing mWriteCursor=%x mSegmentEnd=%x count=%d\n",
this, mWriteCursor, mSegmentEnd, count));
};
out:
*aNumWritten = aCount - remaining;
mLogicalLength += *aNumWritten;
LOG(("nsStorageStream [%p] Wrote mWriteCursor=%x mSegmentEnd=%x numWritten=%d\n",
this, mWriteCursor, mSegmentEnd, *aNumWritten));
return rv;
}
NS_IMETHODIMP
nsStorageStream::WriteFrom(nsIInputStream *inStr, uint32_t count, uint32_t *_retval)
{
return NS_ERROR_NOT_IMPLEMENTED;
}
NS_IMETHODIMP
nsStorageStream::WriteSegments(nsReadSegmentFun reader, void * closure, uint32_t count, uint32_t *_retval)
{
return NS_ERROR_NOT_IMPLEMENTED;
}
NS_IMETHODIMP
nsStorageStream::IsNonBlocking(bool *aNonBlocking)
{
*aNonBlocking = false;
return NS_OK;
}
NS_IMETHODIMP
nsStorageStream::GetLength(uint32_t *aLength)
{
*aLength = mLogicalLength;
return NS_OK;
}
// Truncate the buffer by deleting the end segments
NS_IMETHODIMP
nsStorageStream::SetLength(uint32_t aLength)
{
if (NS_WARN_IF(!mSegmentedBuffer))
return NS_ERROR_NOT_INITIALIZED;
if (mWriteInProgress)
return NS_ERROR_NOT_AVAILABLE;
if (aLength > mLogicalLength)
return NS_ERROR_INVALID_ARG;
int32_t newLastSegmentNum = SegNum(aLength);
int32_t segmentOffset = SegOffset(aLength);
if (segmentOffset == 0)
newLastSegmentNum--;
while (newLastSegmentNum < mLastSegmentNum) {
mSegmentedBuffer->DeleteLastSegment();
mLastSegmentNum--;
}
mLogicalLength = aLength;
return NS_OK;
}
NS_IMETHODIMP
nsStorageStream::GetWriteInProgress(bool *aWriteInProgress)
{
*aWriteInProgress = mWriteInProgress;
return NS_OK;
}
NS_METHOD
nsStorageStream::Seek(int32_t aPosition)
{
if (NS_WARN_IF(!mSegmentedBuffer))
return NS_ERROR_NOT_INITIALIZED;
// An argument of -1 means "seek to end of stream"
if (aPosition == -1)
aPosition = mLogicalLength;
// Seeking beyond the buffer end is illegal
if ((uint32_t)aPosition > mLogicalLength)
return NS_ERROR_INVALID_ARG;
// Seeking backwards in the write stream results in truncation
SetLength(aPosition);
// Special handling for seek to start-of-buffer
if (aPosition == 0) {
mWriteCursor = 0;
mSegmentEnd = 0;
LOG(("nsStorageStream [%p] Seek mWriteCursor=%x mSegmentEnd=%x\n",
this, mWriteCursor, mSegmentEnd));
return NS_OK;
}
// Segment may have changed, so reset pointers
mWriteCursor = mSegmentedBuffer->GetSegment(mLastSegmentNum);
NS_ASSERTION(mWriteCursor, "null mWriteCursor");
mSegmentEnd = mWriteCursor + mSegmentSize;
// Adjust write cursor for current segment offset. This test is necessary
// because SegNum may reference the next-to-be-allocated segment, in which
// case we need to be pointing at the end of the last segment.
int32_t segmentOffset = SegOffset(aPosition);
if (segmentOffset == 0 && (SegNum(aPosition) > (uint32_t) mLastSegmentNum))
mWriteCursor = mSegmentEnd;
else
mWriteCursor += segmentOffset;
LOG(("nsStorageStream [%p] Seek mWriteCursor=%x mSegmentEnd=%x\n",
this, mWriteCursor, mSegmentEnd));
return NS_OK;
}
////////////////////////////////////////////////////////////////////////////////
// There can be many nsStorageInputStreams for a single nsStorageStream
class nsStorageInputStream MOZ_FINAL : public nsIInputStream
, public nsISeekableStream
{
public:
nsStorageInputStream(nsStorageStream *aStorageStream, uint32_t aSegmentSize)
: mStorageStream(aStorageStream), mReadCursor(0),
mSegmentEnd(0), mSegmentNum(0),
mSegmentSize(aSegmentSize), mLogicalCursor(0),
mStatus(NS_OK)
{
NS_ADDREF(mStorageStream);
}
NS_DECL_THREADSAFE_ISUPPORTS
NS_DECL_NSIINPUTSTREAM
NS_DECL_NSISEEKABLESTREAM
private:
~nsStorageInputStream()
{
NS_IF_RELEASE(mStorageStream);
}
protected:
NS_METHOD Seek(uint32_t aPosition);
friend class nsStorageStream;
private:
nsStorageStream* mStorageStream;
uint32_t mReadCursor; // Next memory location to read byte, or 0
uint32_t mSegmentEnd; // One byte past end of current buffer segment
uint32_t mSegmentNum; // Segment number containing read cursor
uint32_t mSegmentSize; // All segments, except the last, are of this size
uint32_t mLogicalCursor; // Logical offset into stream
nsresult mStatus;
uint32_t SegNum(uint32_t aPosition) {return aPosition >> mStorageStream->mSegmentSizeLog2;}
uint32_t SegOffset(uint32_t aPosition) {return aPosition & (mSegmentSize - 1);}
};
NS_IMPL_ISUPPORTS2(nsStorageInputStream,
nsIInputStream,
nsISeekableStream)
NS_IMETHODIMP
nsStorageStream::NewInputStream(int32_t aStartingOffset, nsIInputStream* *aInputStream)
{
if (NS_WARN_IF(!mSegmentedBuffer))
return NS_ERROR_NOT_INITIALIZED;
nsStorageInputStream *inputStream = new nsStorageInputStream(this, mSegmentSize);
if (!inputStream)
return NS_ERROR_OUT_OF_MEMORY;
NS_ADDREF(inputStream);
nsresult rv = inputStream->Seek(aStartingOffset);
if (NS_FAILED(rv)) {
NS_RELEASE(inputStream);
return rv;
}
*aInputStream = inputStream;
return NS_OK;
}
NS_IMETHODIMP
nsStorageInputStream::Close()
{
mStatus = NS_BASE_STREAM_CLOSED;
return NS_OK;
}
NS_IMETHODIMP
nsStorageInputStream::Available(uint64_t *aAvailable)
{
if (NS_FAILED(mStatus))
return mStatus;
*aAvailable = mStorageStream->mLogicalLength - mLogicalCursor;
return NS_OK;
}
NS_IMETHODIMP
nsStorageInputStream::Read(char* aBuffer, uint32_t aCount, uint32_t *aNumRead)
{
return ReadSegments(NS_CopySegmentToBuffer, aBuffer, aCount, aNumRead);
}
NS_IMETHODIMP
nsStorageInputStream::ReadSegments(nsWriteSegmentFun writer, void * closure, uint32_t aCount, uint32_t *aNumRead)
{
*aNumRead = 0;
if (mStatus == NS_BASE_STREAM_CLOSED)
return NS_OK;
if (NS_FAILED(mStatus))
return mStatus;
uint32_t count, availableInSegment, remainingCapacity, bytesConsumed;
nsresult rv;
remainingCapacity = aCount;
while (remainingCapacity) {
availableInSegment = mSegmentEnd - mReadCursor;
if (!availableInSegment) {
uint32_t available = mStorageStream->mLogicalLength - mLogicalCursor;
if (!available)
goto out;
mSegmentNum++;
mReadCursor = 0;
mSegmentEnd = XPCOM_MIN(mSegmentSize, available);
availableInSegment = mSegmentEnd;
}
const char *cur = mStorageStream->mSegmentedBuffer->GetSegment(mSegmentNum);
count = XPCOM_MIN(availableInSegment, remainingCapacity);
rv = writer(this, closure, cur + mReadCursor, aCount - remainingCapacity,
count, &bytesConsumed);
if (NS_FAILED(rv) || (bytesConsumed == 0))
break;
remainingCapacity -= bytesConsumed;
mReadCursor += bytesConsumed;
mLogicalCursor += bytesConsumed;
};
out:
*aNumRead = aCount - remainingCapacity;
bool isWriteInProgress = false;
if (NS_FAILED(mStorageStream->GetWriteInProgress(&isWriteInProgress)))
isWriteInProgress = false;
if (*aNumRead == 0 && isWriteInProgress)
return NS_BASE_STREAM_WOULD_BLOCK;
return NS_OK;
}
NS_IMETHODIMP
nsStorageInputStream::IsNonBlocking(bool *aNonBlocking)
{
// TODO: This class should implement nsIAsyncInputStream so that callers
// have some way of dealing with NS_BASE_STREAM_WOULD_BLOCK errors.
*aNonBlocking = true;
return NS_OK;
}
NS_IMETHODIMP
nsStorageInputStream::Seek(int32_t aWhence, int64_t aOffset)
{
if (NS_FAILED(mStatus))
return mStatus;
int64_t pos = aOffset;
switch (aWhence) {
case NS_SEEK_SET:
break;
case NS_SEEK_CUR:
pos += mLogicalCursor;
break;
case NS_SEEK_END:
pos += mStorageStream->mLogicalLength;
break;
default:
NS_NOTREACHED("unexpected whence value");
return NS_ERROR_UNEXPECTED;
}
if (pos == int64_t(mLogicalCursor))
return NS_OK;
return Seek(pos);
}
NS_IMETHODIMP
nsStorageInputStream::Tell(int64_t *aResult)
{
if (NS_FAILED(mStatus))
return mStatus;
*aResult = mLogicalCursor;
return NS_OK;
}
NS_IMETHODIMP
nsStorageInputStream::SetEOF()
{
NS_NOTREACHED("nsStorageInputStream::SetEOF");
return NS_ERROR_NOT_IMPLEMENTED;
}
NS_METHOD
nsStorageInputStream::Seek(uint32_t aPosition)
{
uint32_t length = mStorageStream->mLogicalLength;
if (aPosition > length)
return NS_ERROR_INVALID_ARG;
if (length == 0)
return NS_OK;
mSegmentNum = SegNum(aPosition);
mReadCursor = SegOffset(aPosition);
uint32_t available = length - aPosition;
mSegmentEnd = mReadCursor + XPCOM_MIN(mSegmentSize - mReadCursor, available);
mLogicalCursor = aPosition;
return NS_OK;
}
nsresult
NS_NewStorageStream(uint32_t segmentSize, uint32_t maxSize, nsIStorageStream **result)
{
nsStorageStream* storageStream = new nsStorageStream();
if (!storageStream) return NS_ERROR_OUT_OF_MEMORY;
NS_ADDREF(storageStream);
nsresult rv = storageStream->Init(segmentSize, maxSize, nullptr);
if (NS_FAILED(rv)) {
NS_RELEASE(storageStream);
return rv;
}
*result = storageStream;
return NS_OK;
}
// Undefine LOG, so that other .cpp files (or their includes) won't complain
// about it already being defined, when we build in unified mode.
#undef LOG
