nsresult FileBlockCache::Run()
{
MonitorAutoLock mon(mDataMonitor);
NS_ASSERTION(!NS_IsMainThread(), "Don't call on main thread");
NS_ASSERTION(!mChangeIndexList.empty(), "Only dispatch when there's work to do");
NS_ASSERTION(mIsWriteScheduled, "Should report write running or scheduled.");
while (!mChangeIndexList.empty()) {
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.
int32_t blockIndex = mChangeIndexList.front();
mChangeIndexList.pop_front();
RefPtr<BlockChange> change = mBlockChanges[blockIndex];
MOZ_ASSERT(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::MoveBlockInFile(int32_t aSourceBlockIndex,
int32_t aDestBlockIndex)
{
mFileMonitor.AssertCurrentThreadOwns();
uint8_t buf[BLOCK_SIZE];
int32_t bytesRead = 0;
if (NS_FAILED(ReadFromFile(BlockIndexToOffset(aSourceBlockIndex),
buf,
BLOCK_SIZE,
bytesRead))) {
return NS_ERROR_FAILURE;
}
return WriteBlockToFile(aDestBlockIndex, buf);
}
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);
}
