1 files changed, 365 insertions, 0 deletions
diff --git a/dom/media/FileBlockCache.cpp b/dom/media/FileBlockCache.cpp
new file mode 100644
index 000000000..ce6a34cce
--- /dev/null
+++ b/dom/media/FileBlockCache.cpp
@@ -0,0 +1,365 @@
+/* -*- 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/SharedThreadPool.h"
+#include "FileBlockCache.h"
+#include "VideoUtils.h"
+#include "prio.h"
+#include <algorithm>
+
+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,
+                                SharedThreadPool::kStackSize);
+    mIsOpen = NS_SUCCEEDED(res);
+    return res;
+  }
+}
+
+FileBlockCache::FileBlockCache()
+  : mFileMonitor("MediaCache.Writer.IO.Monitor"),
+    mFD(nullptr),
+    mFDCurrentPos(0),
+    mDataMonitor("MediaCache.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) {
+      PRStatus prrc;
+      prrc = PR_Close(mFD);
+      if (prrc != PR_SUCCESS) {
+        NS_WARNING("PR_Close() failed.");
+      }
+      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<nsIThread> mainThread = do_GetMainThread();
+    if (mainThread) {
+      nsCOMPtr<nsIRunnable> event = new ShutdownThreadEvent(mThread);
+      mainThread->Dispatch(event.forget(), NS_DISPATCH_NORMAL);
+    } else {
+      // we're on Mainthread already, *and* the event queues are already
+      // shut down, so no events should occur - certainly not creations of
+      // new streams.
+      mThread->Shutdown();
+    }
+  }
+}
+
+template<typename Container, typename Value>
+bool
+ContainerContains(const Container& aContainer, const Value& value)
+{
+  return std::find(aContainer.begin(), aContainer.end(), value)
+         != aContainer.end();
+}
+
+nsresult FileBlockCache::WriteBlock(uint32_t aBlockIndex, const uint8_t* 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 || !ContainerContains(mChangeIndexList, 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.push_back(aBlockIndex);
+  }
+  NS_ASSERTION(ContainerContains(mChangeIndexList, 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(int64_t aOffset)
+{
+  mFileMonitor.AssertCurrentThreadOwns();
+
+  if (mFDCurrentPos != aOffset) {
+    int64_t 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(int64_t aOffset,
+                                      uint8_t* aDest,
+                                      int32_t aBytesToRead,
+                                      int32_t& 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(int32_t aBlockIndex,
+                                          const uint8_t* aBlockData)
+{
+  mFileMonitor.AssertCurrentThreadOwns();
+
+  nsresult rv = Seek(BlockIndexToOffset(aBlockIndex));
+  if (NS_FAILED(rv)) return rv;
+
+  int32_t 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(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::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::Read(int64_t aOffset,
+                              uint8_t* aData,
+                              int32_t aLength,
+                              int32_t* aBytes)
+{
+  MonitorAutoLock mon(mDataMonitor);
+
+  if (!mFD || (aOffset / BLOCK_SIZE) > INT32_MAX)
+    return NS_ERROR_FAILURE;
+
+  int32_t bytesToRead = aLength;
+  int64_t offset = aOffset;
+  uint8_t* dst = aData;
+  while (bytesToRead > 0) {
+    int32_t blockIndex = static_cast<int32_t>(offset / BLOCK_SIZE);
+    int32_t start = offset % BLOCK_SIZE;
+    int32_t amount = std::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.
+    int32_t bytesRead = 0;
+    RefPtr<BlockChange> change = mBlockChanges[blockIndex];
+    if (change && change->IsWrite()) {
+      // Block isn't yet written to file. Read from memory buffer.
+      const uint8_t* 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(BlockIndexToOffset(blockIndex) + start,
+                           dst,
+                           amount,
+                           bytesRead);
+      }
+      NS_ENSURE_SUCCESS(res,res);
+    }
+    dst += bytesRead;
+    offset += bytesRead;
+    bytesToRead -= bytesRead;
+  }
+  *aBytes = aLength - bytesToRead;
+  return NS_OK;
+}
+
+nsresult FileBlockCache::MoveBlock(int32_t aSourceBlockIndex, int32_t aDestBlockIndex)
+{
+  NS_ASSERTION(NS_IsMainThread(), "Only call on main thread");
+  MonitorAutoLock mon(mDataMonitor);
+
+  if (!mIsOpen)
+    return NS_ERROR_FAILURE;
+
+  mBlockChanges.EnsureLengthAtLeast(std::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.
+  int32_t sourceIndex = aSourceBlockIndex;
+  BlockChange* sourceBlock = nullptr;
+  while ((sourceBlock = mBlockChanges[sourceIndex]) &&
+          sourceBlock->IsMove()) {
+    sourceIndex = sourceBlock->mSourceBlockIndex;
+  }
+
+  if (mBlockChanges[aDestBlockIndex] == nullptr ||
+      !ContainerContains(mChangeIndexList, 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.push_back(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(ContainerContains(mChangeIndexList, aDestBlockIndex),
+    "Should have scheduled block for change");
+
+  return NS_OK;
+}
+
+} // End namespace mozilla.