netwerk/base/src/nsBaseContentStream.h

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   4  *
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   6  * 1.1 (the "License"); you may not use this file except in compliance with
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  15  * The Original Code is mozilla.org code.
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  17  * The Initial Developer of the Original Code is Google Inc.
  18  * Portions created by the Initial Developer are Copyright (C) 2005
  19  * the Initial Developer. All Rights Reserved.
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  21  * Contributor(s):
  22  *  Darin Fisher <darin@meer.net>
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  36  * ***** END LICENSE BLOCK ***** */
  37
  38 #ifndef nsBaseContentStream_h__
  39 #define nsBaseContentStream_h__
  40
  41 #include "nsIAsyncInputStream.h"
  42 #include "nsIEventTarget.h"
  43 #include "nsCOMPtr.h"
  44
  45 //-----------------------------------------------------------------------------
  46 // nsBaseContentStream is designed to be subclassed with the intention of being
  47 // used to satisfy the nsBaseChannel::OpenContentStream method.
  48 //
  49 // The subclass typically overrides the default Available, ReadSegments and
  50 // CloseWithStatus methods.  By default, Read is implemented in terms of
  51 // ReadSegments, and Close is implemented in terms of CloseWithStatus.  If
  52 // CloseWithStatus is overriden, then the subclass will usually want to call
  53 // the base class' CloseWithStatus method before returning.
  54 //
  55 // If the stream is non-blocking, then readSegments may return the exception
  56 // NS_BASE_STREAM_WOULD_BLOCK if there is no data available and the stream is
  57 // not at the "end-of-file" or already closed.  This error code must not be
  58 // returned from the Available implementation.  When the caller receives this
  59 // error code, he may choose to call the stream's AsyncWait method, in which
  60 // case the base stream will have a non-null PendingCallback.  When the stream
  61 // has data or encounters an error, it should be sure to dispatch a pending
  62 // callback if one exists (see DispatchCallback).  The implementation of the
  63 // base stream's CloseWithStatus (and Close) method will ensure that any
  64 // pending callback is dispatched.  It is the responsibility of the subclass
  65 // to ensure that the pending callback is dispatched when it wants to have its
  66 // ReadSegments method called again.
  67
  68 class nsBaseContentStream : public nsIAsyncInputStream
  69 {
  70 public:
  71   NS_DECL_ISUPPORTS
  72   NS_DECL_NSIINPUTSTREAM
  73   NS_DECL_NSIASYNCINPUTSTREAM
  74
  75   nsBaseContentStream(PRBool nonBlocking)
  76     : mStatus(NS_OK)
  77     , mNonBlocking(nonBlocking) {
  78   }
  79
  80   nsresult Status() { return mStatus; }
  81   PRBool IsNonBlocking() { return mNonBlocking; }
  82   PRBool IsClosed() { return NS_FAILED(mStatus); }
  83
  84   // Called to test if the stream has a pending callback.
  85   PRBool HasPendingCallback() { return mCallback != nsnull; }
  86
  87   // The current dispatch target (may be null) for the pending callback if any.
  88   nsIEventTarget *CallbackTarget() { return mCallbackTarget; }
  89
  90   // Called to dispatch a pending callback.  If there is no pending callback,
  91   // then this function does nothing.  Pass true to this function to cause the
  92   // callback to occur asynchronously; otherwise, the callback will happen
  93   // before this function returns.
  94   void DispatchCallback(PRBool async = PR_TRUE);
  95
  96   // Helper function to make code more self-documenting.
  97   void DispatchCallbackSync() { DispatchCallback(PR_FALSE); }
  98
  99 protected:
 100   virtual ~nsBaseContentStream() {}
 101
 102 private:
 103   // Called from the base stream's AsyncWait method when a pending callback
 104   // is installed on the stream.
 105   virtual void OnCallbackPending() {}
 106
 107 private:
 108   nsCOMPtr<nsIInputStreamCallback> mCallback;
 109   nsCOMPtr<nsIEventTarget>         mCallbackTarget;
 110   nsresult                         mStatus;
 111   PRPackedBool                     mNonBlocking;
 112 };
 113
 114 #endif // nsBaseContentStream_h__