1 files changed, 506 insertions, 0 deletions
diff --git a/dom/media/FileBlockCache.cpp b/dom/media/FileBlockCache.cpp
new file mode 100644
index 0000000000..3989c05833
--- /dev/null
+++ b/dom/media/FileBlockCache.cpp
@@ -0,0 +1,506 @@
+/* -*- 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 "FileBlockCache.h"
+#include "MediaCache.h"
+#include "VideoUtils.h"
+#include "prio.h"
+#include <algorithm>
+#include "nsAnonymousTemporaryFile.h"
+#include "nsIThreadManager.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/ScopeExit.h"
+#include "nsXULAppAPI.h"
+
+namespace mozilla {
+
+#undef LOG
+LazyLogModule gFileBlockCacheLog("FileBlockCache");
+#define LOG(x, ...) \
+  MOZ_LOG(gFileBlockCacheLog, LogLevel::Debug, ("%p " x, this, ##__VA_ARGS__))
+
+static void CloseFD(PRFileDesc* aFD) {
+  PRStatus prrc;
+  prrc = PR_Close(aFD);
+  if (prrc != PR_SUCCESS) {
+    NS_WARNING("PR_Close() failed.");
+  }
+}
+
+void FileBlockCache::SetCacheFile(PRFileDesc* aFD) {
+  LOG("SetCacheFile aFD=%p", aFD);
+  if (!aFD) {
+    // Failed to get a temporary file. Shutdown.
+    Close();
+    return;
+  }
+  {
+    MutexAutoLock lock(mFileMutex);
+    mFD = aFD;
+  }
+  {
+    MutexAutoLock lock(mDataMutex);
+    LOG("SetFileCache mBackgroundET=%p, mIsWriteScheduled %d",
+        mBackgroundET.get(), mIsWriteScheduled);
+    if (mBackgroundET) {
+      // Still open, complete the initialization.
+      mInitialized = true;
+      if (mIsWriteScheduled) {
+        // A write was scheduled while waiting for FD. We need to run/dispatch a
+        // task to service the request.
+        nsCOMPtr<nsIRunnable> event = mozilla::NewRunnableMethod(
+            "FileBlockCache::SetCacheFile -> PerformBlockIOs", this,
+            &FileBlockCache::PerformBlockIOs);
+        mBackgroundET->Dispatch(event.forget(), NS_DISPATCH_EVENT_MAY_BLOCK);
+      }
+      return;
+    }
+  }
+  // We've been closed while waiting for the file descriptor.
+  // Close the file descriptor we've just received, if still there.
+  MutexAutoLock lock(mFileMutex);
+  if (mFD) {
+    CloseFD(mFD);
+    mFD = nullptr;
+  }
+}
+
+nsresult FileBlockCache::Init() {
+  LOG("Init()");
+  MutexAutoLock mon(mDataMutex);
+  MOZ_ASSERT(!mBackgroundET);
+  nsresult rv = NS_CreateBackgroundTaskQueue("FileBlockCache",
+                                             getter_AddRefs(mBackgroundET));
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  if (XRE_IsParentProcess()) {
+    RefPtr<FileBlockCache> self = this;
+    rv = mBackgroundET->Dispatch(
+        NS_NewRunnableFunction("FileBlockCache::Init",
+                               [self] {
+                                 PRFileDesc* fd = nullptr;
+                                 nsresult rv =
+                                     NS_OpenAnonymousTemporaryFile(&fd);
+                                 if (NS_SUCCEEDED(rv)) {
+                                   self->SetCacheFile(fd);
+                                 } else {
+                                   self->Close();
+                                 }
+                               }),
+        NS_DISPATCH_EVENT_MAY_BLOCK);
+  } else {
+    // We must request a temporary file descriptor from the parent process.
+    RefPtr<FileBlockCache> self = this;
+    rv = dom::ContentChild::GetSingleton()->AsyncOpenAnonymousTemporaryFile(
+        [self](PRFileDesc* aFD) { self->SetCacheFile(aFD); });
+  }
+
+  if (NS_FAILED(rv)) {
+    Close();
+  }
+
+  return rv;
+}
+
+void FileBlockCache::Flush() {
+  LOG("Flush()");
+  MutexAutoLock mon(mDataMutex);
+  MOZ_ASSERT(mBackgroundET);
+
+  // Dispatch a task so we won't clear the arrays while PerformBlockIOs() is
+  // dropping the data lock and cause InvalidArrayIndex.
+  RefPtr<FileBlockCache> self = this;
+  mBackgroundET->Dispatch(
+      NS_NewRunnableFunction("FileBlockCache::Flush", [self]() {
+        MutexAutoLock mon(self->mDataMutex);
+        // Just discard pending changes, assume MediaCache won't read from
+        // blocks it hasn't written to.
+        self->mChangeIndexList.clear();
+        self->mBlockChanges.Clear();
+      }));
+}
+
+size_t FileBlockCache::GetMaxBlocks(size_t aCacheSizeInKB) const {
+  // We look up the cache size every time. This means dynamic changes
+  // to the pref are applied.
+  // Ensure we can divide BLOCK_SIZE by 1024.
+  static_assert(MediaCacheStream::BLOCK_SIZE % 1024 == 0,
+                "BLOCK_SIZE should be a multiple of 1024");
+  // Ensure BLOCK_SIZE/1024 is at least 2.
+  static_assert(MediaCacheStream::BLOCK_SIZE / 1024 >= 2,
+                "BLOCK_SIZE / 1024 should be at least 2");
+  // Ensure we can convert BLOCK_SIZE/1024 to a uint32_t without truncation.
+  static_assert(MediaCacheStream::BLOCK_SIZE / 1024 <= int64_t(UINT32_MAX),
+                "BLOCK_SIZE / 1024 should be at most UINT32_MAX");
+  // Since BLOCK_SIZE is a strict multiple of 1024,
+  // aCacheSizeInKB * 1024 / BLOCK_SIZE == aCacheSizeInKB / (BLOCK_SIZE /
+  // 1024), but the latter formula avoids a potential overflow from `* 1024`.
+  // And because BLOCK_SIZE/1024 is at least 2, the maximum cache size
+  // INT32_MAX*2 will give a maxBlocks that can fit in an int32_t.
+  constexpr size_t blockSizeKb = size_t(MediaCacheStream::BLOCK_SIZE / 1024);
+  const size_t maxBlocks = aCacheSizeInKB / blockSizeKb;
+  return std::max(maxBlocks, size_t(1));
+}
+
+FileBlockCache::FileBlockCache()
+    : mFileMutex("MediaCache.Writer.IO.Mutex"),
+      mFD(nullptr),
+      mFDCurrentPos(0),
+      mDataMutex("MediaCache.Writer.Data.Mutex"),
+      mIsWriteScheduled(false),
+      mIsReading(false) {}
+
+FileBlockCache::~FileBlockCache() { Close(); }
+
+void FileBlockCache::Close() {
+  LOG("Close()");
+
+  nsCOMPtr<nsISerialEventTarget> thread;
+  {
+    MutexAutoLock mon(mDataMutex);
+    if (!mBackgroundET) {
+      return;
+    }
+    thread.swap(mBackgroundET);
+  }
+
+  PRFileDesc* fd;
+  {
+    MutexAutoLock lock(mFileMutex);
+    fd = mFD;
+    mFD = nullptr;
+  }
+
+  // Let the thread close the FD, and then trigger its own shutdown.
+  // Note that mBackgroundET is now empty, so no other task will be posted
+  // there. Also mBackgroundET and mFD are empty and therefore can be reused
+  // immediately.
+  nsresult rv = thread->Dispatch(NS_NewRunnableFunction("FileBlockCache::Close",
+                                                        [thread, fd] {
+                                                          if (fd) {
+                                                            CloseFD(fd);
+                                                          }
+                                                          // No need to shutdown
+                                                          // background task
+                                                          // queues.
+                                                        }),
+                                 NS_DISPATCH_EVENT_MAY_BLOCK);
+  NS_ENSURE_SUCCESS_VOID(rv);
+}
+
+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,
+                                    Span<const uint8_t> aData1,
+                                    Span<const uint8_t> aData2) {
+  MutexAutoLock mon(mDataMutex);
+
+  if (!mBackgroundET) {
+    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(aData1, aData2);
+
+  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() {
+  mDataMutex.AssertCurrentThreadOwns();
+  MOZ_ASSERT(mBackgroundET);
+
+  if (mIsWriteScheduled || mIsReading) {
+    return;
+  }
+  mIsWriteScheduled = true;
+  if (!mInitialized) {
+    // We're still waiting on a file descriptor. When it arrives,
+    // the write will be scheduled.
+    return;
+  }
+  nsCOMPtr<nsIRunnable> event = mozilla::NewRunnableMethod(
+      "FileBlockCache::EnsureWriteScheduled -> PerformBlockIOs", this,
+      &FileBlockCache::PerformBlockIOs);
+  mBackgroundET->Dispatch(event.forget(), NS_DISPATCH_EVENT_MAY_BLOCK);
+}
+
+nsresult FileBlockCache::Seek(int64_t aOffset) {
+  mFileMutex.AssertCurrentThreadOwns();
+
+  if (mFDCurrentPos != aOffset) {
+    MOZ_ASSERT(mFD);
+    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) {
+  LOG("ReadFromFile(offset=%" PRIu64 ", len=%u)", aOffset, aBytesToRead);
+  mFileMutex.AssertCurrentThreadOwns();
+  MOZ_ASSERT(mFD);
+
+  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) {
+  LOG("WriteBlockToFile(index=%u)", aBlockIndex);
+
+  mFileMutex.AssertCurrentThreadOwns();
+  MOZ_ASSERT(mFD);
+
+  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) {
+  LOG("MoveBlockInFile(src=%u, dest=%u)", aSourceBlockIndex, aDestBlockIndex);
+
+  mFileMutex.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);
+}
+
+void FileBlockCache::PerformBlockIOs() {
+  MutexAutoLock mon(mDataMutex);
+  MOZ_ASSERT(mBackgroundET->IsOnCurrentThread());
+  NS_ASSERTION(mIsWriteScheduled, "Should report write running or scheduled.");
+
+  LOG("Run() mFD=%p mBackgroundET=%p", mFD, mBackgroundET.get());
+
+  while (!mChangeIndexList.empty()) {
+    if (!mBackgroundET) {
+      // We've been closed, abort, discarding unwritten changes.
+      mIsWriteScheduled = false;
+      return;
+    }
+
+    if (mIsReading) {
+      // We're trying to read; postpone all writes. (Reader will resume writes.)
+      mIsWriteScheduled = false;
+      return;
+    }
+
+    // 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 mDataMutex 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
+    // mDataMutex to take mFileMutex.
+    int32_t blockIndex = mChangeIndexList.front();
+    RefPtr<BlockChange> change = mBlockChanges[blockIndex];
+    MOZ_ASSERT(change,
+               "Change index list should only contain entries for blocks "
+               "with changes");
+    {
+      MutexAutoUnlock unlock(mDataMutex);
+      MutexAutoLock lock(mFileMutex);
+      if (!mFD) {
+        // We may be here if mFD has been reset because we're closing, so we
+        // don't care anymore about writes.
+        return;
+      }
+      if (change->IsWrite()) {
+        WriteBlockToFile(blockIndex, change->mData.get());
+      } else if (change->IsMove()) {
+        MoveBlockInFile(change->mSourceBlockIndex, blockIndex);
+      }
+    }
+    mChangeIndexList.pop_front();  // MonitorAutoUnlock above
+    // If a new change has not been made to the block while we dropped
+    // mDataMutex, clear reference to the old change. Otherwise, the old
+    // reference has been cleared already.
+    if (mBlockChanges[blockIndex] == change) {  // MonitorAutoUnlock above
+      mBlockChanges[blockIndex] = nullptr;      // MonitorAutoUnlock above
+    }
+  }
+
+  mIsWriteScheduled = false;
+}
+
+nsresult FileBlockCache::Read(int64_t aOffset, uint8_t* aData, int32_t aLength,
+                              int32_t* aBytes) {
+  MutexAutoLock mon(mDataMutex);
+
+  if (!mBackgroundET || (aOffset / BLOCK_SIZE) > INT32_MAX) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mIsReading = true;
+  auto exitRead = MakeScopeExit([&] {
+    mDataMutex.AssertCurrentThreadOwns();
+    mIsReading = false;
+    if (!mChangeIndexList.empty()) {
+      // mReading has stopped or prevented pending writes, resume them.
+      EnsureWriteScheduled();
+    }
+  });
+
+  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;
+    MOZ_ASSERT(!mBlockChanges.IsEmpty());
+    MOZ_ASSERT(blockIndex >= 0 &&
+               static_cast<uint32_t>(blockIndex) < mBlockChanges.Length());
+    RefPtr<BlockChange> change = mBlockChanges.SafeElementAt(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 = change->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;
+      {
+        MutexAutoUnlock unlock(mDataMutex);
+        MutexAutoLock lock(mFileMutex);
+        if (!mFD) {
+          // Not initialized yet, or closed.
+          return NS_ERROR_FAILURE;
+        }
+        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) {
+  MutexAutoLock mon(mDataMutex);
+
+  if (!mBackgroundET) {
+    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.
+
+// avoid redefined macro in unified build
+#undef LOG