1 files changed, 79 insertions, 0 deletions
diff --git a/netwerk/base/nsBaseContentStream.h b/netwerk/base/nsBaseContentStream.h
new file mode 100644
index 0000000000..13a3766857
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+++ b/netwerk/base/nsBaseContentStream.h
@@ -0,0 +1,79 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#ifndef nsBaseContentStream_h__
+#define nsBaseContentStream_h__
+
+#include "nsIAsyncInputStream.h"
+#include "nsIEventTarget.h"
+#include "nsCOMPtr.h"
+
+//-----------------------------------------------------------------------------
+// nsBaseContentStream is designed to be subclassed with the intention of being
+// used to satisfy the nsBaseChannel::OpenContentStream method.
+//
+// The subclass typically overrides the default Available, ReadSegments and
+// CloseWithStatus methods.  By default, Read is implemented in terms of
+// ReadSegments, and Close is implemented in terms of CloseWithStatus.  If
+// CloseWithStatus is overriden, then the subclass will usually want to call
+// the base class' CloseWithStatus method before returning.
+//
+// If the stream is non-blocking, then readSegments may return the exception
+// NS_BASE_STREAM_WOULD_BLOCK if there is no data available and the stream is
+// not at the "end-of-file" or already closed.  This error code must not be
+// returned from the Available implementation.  When the caller receives this
+// error code, he may choose to call the stream's AsyncWait method, in which
+// case the base stream will have a non-null PendingCallback.  When the stream
+// has data or encounters an error, it should be sure to dispatch a pending
+// callback if one exists (see DispatchCallback).  The implementation of the
+// base stream's CloseWithStatus (and Close) method will ensure that any
+// pending callback is dispatched.  It is the responsibility of the subclass
+// to ensure that the pending callback is dispatched when it wants to have its
+// ReadSegments method called again.
+
+class nsBaseContentStream : public nsIAsyncInputStream {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIINPUTSTREAM
+  NS_DECL_NSIASYNCINPUTSTREAM
+
+  explicit nsBaseContentStream(bool nonBlocking)
+      : mStatus(NS_OK), mNonBlocking(nonBlocking) {}
+
+  nsresult Status() { return mStatus; }
+  bool IsNonBlocking() { return mNonBlocking; }
+  bool IsClosed() { return NS_FAILED(mStatus); }
+
+  // Called to test if the stream has a pending callback.
+  bool HasPendingCallback() { return mCallback != nullptr; }
+
+  // The current dispatch target (may be null) for the pending callback if any.
+  nsIEventTarget* CallbackTarget() { return mCallbackTarget; }
+
+  // Called to dispatch a pending callback.  If there is no pending callback,
+  // then this function does nothing.  Pass true to this function to cause the
+  // callback to occur asynchronously; otherwise, the callback will happen
+  // before this function returns.
+  void DispatchCallback(bool async = true);
+
+  // Helper function to make code more self-documenting.
+  void DispatchCallbackSync() { DispatchCallback(false); }
+
+ protected:
+  virtual ~nsBaseContentStream() = default;
+
+ private:
+  // Called from the base stream's AsyncWait method when a pending callback
+  // is installed on the stream.
+  virtual void OnCallbackPending() {}
+
+ private:
+  nsCOMPtr<nsIInputStreamCallback> mCallback;
+  nsCOMPtr<nsIEventTarget> mCallbackTarget;
+  nsresult mStatus;
+  bool mNonBlocking;
+};
+
+#endif  // nsBaseContentStream_h__