gecko-dev/content/media/FileBlockCache.cpp

343 строки
11 KiB
C++
Исходник Обычный вид История

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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/. */
#include "mozilla/XPCOM.h"
#include "FileBlockCache.h"
#include "VideoUtils.h"
namespace mozilla {
nsresult FileBlockCache::Open(PRFileDesc* aFD)
{
NS_ASSERTION(NS_IsMainThread(), "Only call on main thread");
NS_ENSURE_TRUE(aFD != nullptr, NS_ERROR_FAILURE);
{
MonitorAutoLock mon(mFileMonitor);
mFD = aFD;
}
{
MonitorAutoLock mon(mDataMonitor);
nsresult res = NS_NewThread(getter_AddRefs(mThread),
nullptr,
MEDIA_THREAD_STACK_SIZE);
mIsOpen = NS_SUCCEEDED(res);
return res;
}
}
FileBlockCache::FileBlockCache()
: mFileMonitor("nsMediaCache.Writer.IO.Monitor"),
mFD(nullptr),
mFDCurrentPos(0),
mDataMonitor("nsMediaCache.Writer.Data.Monitor"),
mIsWriteScheduled(false),
mIsOpen(false)
{
MOZ_COUNT_CTOR(FileBlockCache);
}
FileBlockCache::~FileBlockCache()
{
NS_ASSERTION(!mIsOpen, "Should Close() FileBlockCache before destroying");
{
// Note, mThread will be shutdown by the time this runs, so we won't
// block while taking mFileMonitor.
MonitorAutoLock mon(mFileMonitor);
if (mFD) {
PR_Close(mFD);
mFD = nullptr;
}
}
MOZ_COUNT_DTOR(FileBlockCache);
}
void FileBlockCache::Close()
{
NS_ASSERTION(NS_IsMainThread(), "Only call on main thread");
MonitorAutoLock mon(mDataMonitor);
mIsOpen = false;
if (mThread) {
// We must shut down the thread in another runnable. This is called
// while we're shutting down the media cache, and nsIThread::Shutdown()
// can cause events to run before it completes, which could end up
// opening more streams, while the media cache is shutting down and
// releasing memory etc! Also note we close mFD in the destructor so
// as to not disturb any IO that's currently running.
nsCOMPtr<nsIRunnable> event = new ShutdownThreadEvent(mThread);
mThread = nullptr;
NS_DispatchToMainThread(event);
}
}
nsresult FileBlockCache::WriteBlock(PRUint32 aBlockIndex, const PRUint8* aData)
{
MonitorAutoLock mon(mDataMonitor);
if (!mIsOpen)
return NS_ERROR_FAILURE;
// Check if we've already got a pending write scheduled for this block.
mBlockChanges.EnsureLengthAtLeast(aBlockIndex + 1);
bool blockAlreadyHadPendingChange = mBlockChanges[aBlockIndex] != nullptr;
mBlockChanges[aBlockIndex] = new BlockChange(aData);
if (!blockAlreadyHadPendingChange || !mChangeIndexList.Contains(aBlockIndex)) {
// We either didn't already have a pending change for this block, or we
// did but we didn't have an entry for it in mChangeIndexList (we're in the process
// of writing it and have removed the block's index out of mChangeIndexList
// in Run() but not finished writing the block to file yet). Add the blocks
// index to the end of mChangeIndexList to ensure the block is written as
// as soon as possible.
mChangeIndexList.PushBack(aBlockIndex);
}
NS_ASSERTION(mChangeIndexList.Contains(aBlockIndex), "Must have entry for new block");
EnsureWriteScheduled();
return NS_OK;
}
void FileBlockCache::EnsureWriteScheduled()
{
mDataMonitor.AssertCurrentThreadOwns();
if (!mIsWriteScheduled) {
mThread->Dispatch(this, NS_DISPATCH_NORMAL);
mIsWriteScheduled = true;
}
}
nsresult FileBlockCache::Seek(PRInt64 aOffset)
{
mFileMonitor.AssertCurrentThreadOwns();
if (mFDCurrentPos != aOffset) {
PROffset64 result = PR_Seek64(mFD, aOffset, PR_SEEK_SET);
if (result != aOffset) {
NS_WARNING("Failed to seek media cache file");
return NS_ERROR_FAILURE;
}
mFDCurrentPos = result;
}
return NS_OK;
}
nsresult FileBlockCache::ReadFromFile(PRInt32 aOffset,
PRUint8* aDest,
PRInt32 aBytesToRead,
PRInt32& aBytesRead)
{
mFileMonitor.AssertCurrentThreadOwns();
nsresult res = Seek(aOffset);
if (NS_FAILED(res)) return res;
aBytesRead = PR_Read(mFD, aDest, aBytesToRead);
if (aBytesRead <= 0)
return NS_ERROR_FAILURE;
mFDCurrentPos += aBytesRead;
return NS_OK;
}
nsresult FileBlockCache::WriteBlockToFile(PRInt32 aBlockIndex,
const PRUint8* aBlockData)
{
mFileMonitor.AssertCurrentThreadOwns();
nsresult rv = Seek(aBlockIndex * BLOCK_SIZE);
if (NS_FAILED(rv)) return rv;
PRInt32 amount = PR_Write(mFD, aBlockData, BLOCK_SIZE);
if (amount < BLOCK_SIZE) {
NS_WARNING("Failed to write media cache block!");
return NS_ERROR_FAILURE;
}
mFDCurrentPos += BLOCK_SIZE;
return NS_OK;
}
nsresult FileBlockCache::MoveBlockInFile(PRInt32 aSourceBlockIndex,
PRInt32 aDestBlockIndex)
{
mFileMonitor.AssertCurrentThreadOwns();
PRUint8 buf[BLOCK_SIZE];
PRInt32 bytesRead = 0;
if (NS_FAILED(ReadFromFile(aSourceBlockIndex * BLOCK_SIZE,
buf,
BLOCK_SIZE,
bytesRead))) {
return NS_ERROR_FAILURE;
}
return WriteBlockToFile(aDestBlockIndex, buf);
}
nsresult FileBlockCache::Run()
{
MonitorAutoLock mon(mDataMonitor);
NS_ASSERTION(!NS_IsMainThread(), "Don't call on main thread");
NS_ASSERTION(!mChangeIndexList.IsEmpty(), "Only dispatch when there's work to do");
NS_ASSERTION(mIsWriteScheduled, "Should report write running or scheduled.");
while (!mChangeIndexList.IsEmpty()) {
if (!mIsOpen) {
// We've been closed, abort, discarding unwritten changes.
mIsWriteScheduled = false;
return NS_ERROR_FAILURE;
}
// Process each pending change. We pop the index out of the change
// list, but leave the BlockChange in mBlockChanges until the change
// is written to file. This is so that any read which happens while
// we drop mDataMonitor to write will refer to the data's source in
// memory, rather than the not-yet up to date data written to file.
// This also ensures we will insert a new index into mChangeIndexList
// when this happens.
// Hold a reference to the change, in case another change
// overwrites the mBlockChanges entry for this block while we drop
// mDataMonitor to take mFileMonitor.
PRInt32 blockIndex = mChangeIndexList.PopFront();
nsRefPtr<BlockChange> change = mBlockChanges[blockIndex];
NS_ABORT_IF_FALSE(change,
"Change index list should only contain entries for blocks with changes");
{
MonitorAutoUnlock unlock(mDataMonitor);
MonitorAutoLock lock(mFileMonitor);
if (change->IsWrite()) {
WriteBlockToFile(blockIndex, change->mData.get());
} else if (change->IsMove()) {
MoveBlockInFile(change->mSourceBlockIndex, blockIndex);
}
}
// If a new change has not been made to the block while we dropped
// mDataMonitor, clear reference to the old change. Otherwise, the old
// reference has been cleared already.
if (mBlockChanges[blockIndex] == change) {
mBlockChanges[blockIndex] = nullptr;
}
}
mIsWriteScheduled = false;
return NS_OK;
}
nsresult FileBlockCache::Read(PRInt64 aOffset,
PRUint8* aData,
PRInt32 aLength,
PRInt32* aBytes)
{
MonitorAutoLock mon(mDataMonitor);
if (!mFD || (aOffset / BLOCK_SIZE) > PR_INT32_MAX)
return NS_ERROR_FAILURE;
PRInt32 bytesToRead = aLength;
PRInt64 offset = aOffset;
PRUint8* dst = aData;
while (bytesToRead > 0) {
PRInt32 blockIndex = static_cast<PRInt32>(offset / BLOCK_SIZE);
PRInt32 start = offset % BLOCK_SIZE;
PRInt32 amount = NS_MIN(BLOCK_SIZE - start, bytesToRead);
// If the block is not yet written to file, we can just read from
// the memory buffer, otherwise we need to read from file.
PRInt32 bytesRead = 0;
nsRefPtr<BlockChange> change = mBlockChanges[blockIndex];
if (change && change->IsWrite()) {
// Block isn't yet written to file. Read from memory buffer.
const PRUint8* blockData = change->mData.get();
memcpy(dst, blockData + start, amount);
bytesRead = amount;
} else {
if (change && change->IsMove()) {
// The target block is the destination of a not-yet-completed move
// action, so read from the move's source block from file. Note we
// *don't* follow a chain of moves here, as a move's source index
// is resolved when MoveBlock() is called, and the move's source's
// block could be have itself been subject to a move (or write)
// which happened *after* this move was recorded.
blockIndex = mBlockChanges[blockIndex]->mSourceBlockIndex;
}
// Block has been written to file, either as the source block of a move,
// or as a stable (all changes made) block. Read the data directly
// from file.
nsresult res;
{
MonitorAutoUnlock unlock(mDataMonitor);
MonitorAutoLock lock(mFileMonitor);
res = ReadFromFile(blockIndex * BLOCK_SIZE + start,
dst,
amount,
bytesRead);
}
NS_ENSURE_SUCCESS(res,res);
}
dst += bytesRead;
offset += bytesRead;
bytesToRead -= bytesRead;
}
*aBytes = aLength - bytesToRead;
return NS_OK;
}
nsresult FileBlockCache::MoveBlock(PRInt32 aSourceBlockIndex, PRInt32 aDestBlockIndex)
{
NS_ASSERTION(NS_IsMainThread(), "Only call on main thread");
MonitorAutoLock mon(mDataMonitor);
if (!mIsOpen)
return NS_ERROR_FAILURE;
mBlockChanges.EnsureLengthAtLeast(NS_MAX(aSourceBlockIndex, aDestBlockIndex) + 1);
// The source block's contents may be the destination of another pending
// move, which in turn can be the destination of another pending move,
// etc. Resolve the final source block, so that if one of the blocks in
// the chain of moves is overwritten, we don't lose the reference to the
// contents of the destination block.
PRInt32 sourceIndex = aSourceBlockIndex;
BlockChange* sourceBlock = nullptr;
while ((sourceBlock = mBlockChanges[sourceIndex]) &&
sourceBlock->IsMove()) {
sourceIndex = sourceBlock->mSourceBlockIndex;
}
if (mBlockChanges[aDestBlockIndex] == nullptr ||
!mChangeIndexList.Contains(aDestBlockIndex)) {
// Only add another entry to the change index list if we don't already
// have one for this block. We won't have an entry when either there's
// no pending change for this block, or if there is a pending change for
// this block and we're in the process of writing it (we've popped the
// block's index out of mChangeIndexList in Run() but not finished writing
// the block to file yet.
mChangeIndexList.PushBack(aDestBlockIndex);
}
// If the source block hasn't yet been written to file then the dest block
// simply contains that same write. Resolve this as a write instead.
if (sourceBlock && sourceBlock->IsWrite()) {
mBlockChanges[aDestBlockIndex] = new BlockChange(sourceBlock->mData.get());
} else {
mBlockChanges[aDestBlockIndex] = new BlockChange(sourceIndex);
}
EnsureWriteScheduled();
NS_ASSERTION(mChangeIndexList.Contains(aDestBlockIndex),
"Should have scheduled block for change");
return NS_OK;
}
} // End namespace mozilla.