Bug 1355406 - Change the type of MediaCacheStream::mPartialBlockBuffer to UniquePtr<uint8_t[]>. r=jya

UniquePtr<uint8_t[]> has the same alignment as UniquePtr<int64_t[]> for the
underlying buffer. It also allows us to remove some reinterpret_casts.

MozReview-Commit-ID: 8V1lZdayFQv

--HG--
extra : rebase_source : 61f1943b9f3e464b47865fb0fff2742125f4c688
extra : intermediate-source : 329adb8a4414f32e2f83ba79af06d288d7b25705
extra : source : ba967b187b9dbc8f402db90272f55b9ee9d92692

dom/media/MediaCache.cpp

@@ -389,7 +389,6 @@ MediaCacheStream::MediaCacheStream(ChannelMediaResource* aClient,
     mPinCount(0),
     mCurrentMode(MODE_PLAYBACK),
     mMetadataInPartialBlockBuffer(false),
-    mPartialBlockBuffer(MakeUnique<int64_t[]>(BLOCK_SIZE/sizeof(int64_t))),
     mIsPrivateBrowsing(aIsPrivateBrowsing)
 {
 }
@@ -1798,13 +1797,12 @@ MediaCacheStream::NotifyDataReceived(int64_t aSize, const char* aData,
     if (blockOffset + chunkSize == BLOCK_SIZE) {
       // We have a whole block now to write it out.
       auto data1 = MakeSpan<const uint8_t>(
-        reinterpret_cast<uint8_t*>(mPartialBlockBuffer.get()), blockOffset);
+        mPartialBlockBuffer.get(), blockOffset);
       auto data2 = MakeSpan<const uint8_t>(
         reinterpret_cast<const uint8_t*>(data), chunkSize);
       gMediaCache->AllocateAndWriteBlock(this, mode, data1, data2);
     } else {
-      memcpy(reinterpret_cast<char*>(mPartialBlockBuffer.get()) + blockOffset,
-             data, chunkSize);
+      memcpy(mPartialBlockBuffer.get() + blockOffset, data, chunkSize);
     }
 
     mChannelOffset += chunkSize;
@@ -1843,9 +1841,8 @@ MediaCacheStream::FlushPartialBlockInternal(bool aNotifyAll,
                aNotifyAll ? "yes" : "no"));
 
     // Write back the partial block
-    uint8_t* p = reinterpret_cast<uint8_t*>(mPartialBlockBuffer.get());
-    memset(p + blockOffset, 0, BLOCK_SIZE - blockOffset);
-    auto data = MakeSpan<const uint8_t>(p, BLOCK_SIZE);
+    memset(mPartialBlockBuffer.get() + blockOffset, 0, BLOCK_SIZE - blockOffset);
+    auto data = MakeSpan<const uint8_t>(mPartialBlockBuffer.get(), BLOCK_SIZE);
     gMediaCache->AllocateAndWriteBlock(this,
       mMetadataInPartialBlockBuffer ? MODE_METADATA : MODE_PLAYBACK, data);
   }
@@ -2266,7 +2263,7 @@ MediaCacheStream::Read(char* aBuffer, uint32_t aCount, uint32_t* aBytes)
         bytes = std::min(bytes, int64_t(INT32_MAX));
         MOZ_ASSERT(bytes >= 0 && bytes <= aCount, "Bytes out of range.");
         memcpy(aBuffer,
-          reinterpret_cast<char*>(streamWithPartialBlock->mPartialBlockBuffer.get()) + offsetInStreamBlock, bytes);
+          streamWithPartialBlock->mPartialBlockBuffer.get() + offsetInStreamBlock, bytes);
         if (mCurrentMode == MODE_METADATA) {
           streamWithPartialBlock->mMetadataInPartialBlockBuffer = true;
         }
@@ -2366,7 +2363,7 @@ MediaCacheStream::ReadFromCache(char* aBuffer, int64_t aOffset, int64_t aCount)
       bytes = std::min(toCopy, int64_t(INT32_MAX));
       MOZ_ASSERT(bytes >= 0 && bytes <= toCopy, "Bytes out of range.");
       memcpy(aBuffer + count,
-        reinterpret_cast<char*>(mPartialBlockBuffer.get()) + offsetInStreamBlock, bytes);
+        mPartialBlockBuffer.get() + offsetInStreamBlock, bytes);
     } else {
       if (cacheBlock < 0) {
         // We expect all blocks to be cached! Fail!

dom/media/MediaCache.h

@@ -508,10 +508,9 @@ private:
   // to wait here so we can write back a complete block. The first
   // mChannelOffset%BLOCK_SIZE bytes have been filled in with good data,
   // the rest are garbage.
-  // Use int64_t so that the data is well-aligned.
   // Heap allocate this buffer since the exact power-of-2 will cause allocation
   // slop when combined with the rest of the object members.
-  UniquePtr<int64_t[]> mPartialBlockBuffer;
+  UniquePtr<uint8_t[]> mPartialBlockBuffer = MakeUnique<uint8_t[]>(BLOCK_SIZE);
 
   // True if associated with a private browsing window.
   const bool mIsPrivateBrowsing;