1 files changed, 95 insertions, 0 deletions
diff --git a/dom/xhr/XMLHttpRequestString.h b/dom/xhr/XMLHttpRequestString.h
index b6b12483f..5709c1aa2 100644
--- a/dom/xhr/XMLHttpRequestString.h
+++ b/dom/xhr/XMLHttpRequestString.h
@@ -7,6 +7,9 @@
 #ifndef mozilla_dom_XMLHttpRequestString_h
 #define mozilla_dom_XMLHttpRequestString_h
 
+#include "mozilla/Mutex.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/DOMString.h"
 #include "nsString.h"
 
 namespace mozilla {
@@ -155,6 +158,98 @@ private:
   MutexAutoLock mLock;
 };
 
+class XMLHttpRequestStringBuffer final
+{
+  friend class XMLHttpRequestStringWriterHelper;
+  friend class XMLHttpRequestStringSnapshotReaderHelper;
+
+public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(XMLHttpRequestStringBuffer)
+  NS_DECL_OWNINGTHREAD
+
+  XMLHttpRequestStringBuffer()
+    : mMutex("XMLHttpRequestStringBuffer::mMutex")
+  {
+  }
+
+  uint32_t
+  Length()
+  {
+    MutexAutoLock lock(mMutex);
+    return mData.Length();
+  }
+
+  uint32_t
+  UnsafeLength() const
+  {
+    return mData.Length();
+  }
+
+  void
+  Append(const nsAString& aString)
+  {
+    NS_ASSERT_OWNINGTHREAD(XMLHttpRequestStringBuffer);
+
+    MutexAutoLock lock(mMutex);
+    mData.Append(aString);
+  }
+
+  MOZ_MUST_USE bool
+  GetAsString(nsAString& aString)
+  {
+    MutexAutoLock lock(mMutex);
+    return aString.Assign(mData, mozilla::fallible);
+  }
+
+  size_t
+  SizeOfThis(MallocSizeOf aMallocSizeOf) const
+  {
+    return mData.SizeOfExcludingThisIfUnshared(aMallocSizeOf);
+  }
+
+  MOZ_MUST_USE bool
+  GetAsString(DOMString& aString, uint32_t aLength)
+  {
+    MutexAutoLock lock(mMutex);
+    MOZ_ASSERT(aLength <= mData.Length());
+    nsStringBuffer* buf = nsStringBuffer::FromString(mData);
+    if (buf) {
+      // We have to use SetEphemeralStringBuffer, because once we release our
+      // mutex mData can get mutated from some other thread while the DOMString
+      // is still alive.
+      aString.SetEphemeralStringBuffer(buf, aLength);
+      return true;
+    }
+
+    // We can get here if mData is empty.  In that case it won't have an
+    // nsStringBuffer....
+    MOZ_ASSERT(mData.IsEmpty());
+    return aString.AsAString().Assign(mData.BeginReading(), aLength,
+                                      mozilla::fallible);
+  }
+
+  void
+  CreateSnapshot(XMLHttpRequestStringSnapshot& aSnapshot)
+  {
+    MutexAutoLock lock(mMutex);
+    aSnapshot.Set(this, mData.Length());
+  }
+
+private:
+  ~XMLHttpRequestStringBuffer()
+  {}
+
+  nsString& UnsafeData()
+  {
+    return mData;
+  }
+
+  Mutex mMutex;
+
+  // The following member variable is protected by mutex.
+  nsString mData;
+};
+
 } // dom namespace
 } // mozilla namespace