diff --git a/mozilla/base/src/nsByteBuffer.cpp b/mozilla/base/src/nsByteBuffer.cpp
index a27f8cbf2c9..bd3c9b72467 100644
--- a/mozilla/base/src/nsByteBuffer.cpp
+++ b/mozilla/base/src/nsByteBuffer.cpp
@@ -31,7 +31,7 @@ public:
   virtual PRInt32 GetBufferSize() const;
   virtual char* GetBuffer() const;
   virtual PRBool Grow(PRInt32 aNewSize);
-  virtual PRInt32 Fill(PRInt32* aErrorCode, nsIInputStream* aStream,
+  virtual PRInt32 Fill(nsresult* aErrorCode, nsIInputStream* aStream,
                        PRInt32 aKeep);
 
   char* mBuffer;
@@ -94,14 +94,14 @@ PRBool ByteBufferImpl::Grow(PRInt32 aNewSize)
   return PR_FALSE;
 }
 
-PRInt32 ByteBufferImpl::Fill(PRInt32* aErrorCode, nsIInputStream* aStream,
+PRInt32 ByteBufferImpl::Fill(nsresult* aErrorCode, nsIInputStream* aStream,
                              PRInt32 aKeep)
 {
   NS_PRECONDITION(nsnull != aStream, "null stream");
   NS_PRECONDITION(PRUint32(aKeep) <= PRUint32(mLength), "illegal keep count");
   if ((nsnull == aStream) || (PRUint32(aKeep) > PRUint32(mLength))) {
     // whoops
-    *aErrorCode = NS_INPUTSTREAM_ILLEGAL_ARGS;
+    *aErrorCode = NS_BASE_STREAM_ILLEGAL_ARGS;
     return -1;
   }
 
@@ -113,10 +113,13 @@ PRInt32 ByteBufferImpl::Fill(PRInt32* aErrorCode, nsIInputStream* aStream,
   // Read in some new data
   mLength = aKeep;
   PRInt32 amount = mSpace - aKeep;
-  PRInt32 nb = aStream->Read(aErrorCode, mBuffer, aKeep, amount);
-  if (nb > 0) {
+  PRInt32 nb;
+  *aErrorCode = aStream->Read(mBuffer, aKeep, amount, &nb);
+  if (NS_SUCCEEDED(*aErrorCode)) {
     mLength += nb;
   }
+  else
+    nb = 0;
   return nb;
 }
 
diff --git a/mozilla/base/src/nsIBaseStream.h b/mozilla/base/src/nsIBaseStream.h
index 8578d81676a..06efd0fad4f 100644
--- a/mozilla/base/src/nsIBaseStream.h
+++ b/mozilla/base/src/nsIBaseStream.h
@@ -31,12 +31,27 @@
 class nsIBaseStream : public nsISupports {
 public:
 
-  /** Return the number of bytes in the stream */
-  virtual PRInt32 GetLength() = 0;
-
-  /** Close the stream. */
-  virtual void Close() = 0;
+    /** Close the stream. */
+    NS_IMETHOD
+    Close(void) = 0;
 };
 
+/** Error codes */
+//@{ 
+// XXX fix up the values so they are not total hacks... MMP
+/// End of file
+#define NS_BASE_STREAM_EOF            0x80001001
+/// Stream closed
+#define NS_BASE_STREAM_CLOSED         0x80001002
+/// Error from the operating system
+#define NS_BASE_STREAM_OSERROR        0x80001003
+/// Illegal arguments
+#define NS_BASE_STREAM_ILLEGAL_ARGS   0x80001004
+/// For unichar streams
+#define NS_BASE_STREAM_NO_CONVERTER   0x80001005
+/// For unichar streams
+#define NS_BASE_STREAM_BAD_CONVERSION 0x80001006
+//@}
+
 
 #endif /* nsInputStream_h___ */
diff --git a/mozilla/base/src/nsIByteBuffer.h b/mozilla/base/src/nsIByteBuffer.h
index 74561b69a47..43a04c29342 100644
--- a/mozilla/base/src/nsIByteBuffer.h
+++ b/mozilla/base/src/nsIByteBuffer.h
@@ -44,7 +44,7 @@ public:
 
   /** Fill the buffer with data from aStream.  Don't grow the buffer, only
    *  read until length of buffer equals buffer size. */
-  virtual PRInt32 Fill(PRInt32* aErrorCode, nsIInputStream* aStream,
+  virtual PRInt32 Fill(nsresult* aErrorCode, nsIInputStream* aStream,
                        PRInt32 aKeep) = 0;
 };
 
diff --git a/mozilla/base/src/nsIInputStream.h b/mozilla/base/src/nsIInputStream.h
index abfc50f4512..37c942927f3 100644
--- a/mozilla/base/src/nsIInputStream.h
+++ b/mozilla/base/src/nsIInputStream.h
@@ -27,34 +27,28 @@
 /** Abstract byte input stream */
 class nsIInputStream : public nsIBaseStream {
 public:
-  /** Read data from the stream.
-   *  @param aErrorCode the error code if an error occurs
-   *  @param aBuf the buffer into which the data is read
-   *  @param aOffset the start offset of the data
-   *  @param aCount the maximum number of bytes to read
-   *  @return number of bytes read or -1 if error
-   */   
-  virtual PRInt32 Read(PRInt32* aErrorCode,
-                       char* aBuf,
-                       PRInt32 aOffset,
-                       PRInt32 aCount) = 0;
+
+    /** Return the number of bytes in the stream
+     *  @param aLength out parameter to hold the length
+     *         of the stream. if an error occurs, the length
+     *         will be undefined
+     *  @return error status
+     */
+    NS_IMETHOD
+    GetLength(PRInt32 *aLength) = 0;
+
+    /** Read data from the stream.
+     *  @param aErrorCode the error code if an error occurs
+     *  @param aBuf the buffer into which the data is read
+     *  @param aOffset the start offset of the data
+     *  @param aCount the maximum number of bytes to read
+     *  @param aReadCount out parameter to hold the number of
+     *         bytes read, eof if 0. if an error occurs, the
+     *         read count will be undefined
+     *  @return error status
+     */   
+    NS_IMETHOD
+    Read(char* aBuf, PRInt32 aOffset, PRInt32 aCount, PRInt32 *aReadCount) = 0; 
 };
 
-/** Error codes */
-//@{ 
-// XXX fix up the values to work with nsqresult
-/// End of file
-#define NS_INPUTSTREAM_EOF 1
-/// Stream closed
-#define NS_INPUTSTREAM_CLOSED 2
-/// Error from the operating system
-#define NS_INPUTSTREAM_OSERROR 3
-/// Illegal arguments
-#define NS_INPUTSTREAM_ILLEGAL_ARGS 4
-/// For unichar streams
-#define NS_INPUTSTREAM_NO_CONVERTER 5
-/// For unichar streams
-#define NS_INPUTSTREAM_BAD_CONVERSION 6
-//@}
-
 #endif /* nsInputStream_h___ */
diff --git a/mozilla/base/src/nsIOutputStream.h b/mozilla/base/src/nsIOutputStream.h
index 3f89f03a4a3..ad032f52767 100644
--- a/mozilla/base/src/nsIOutputStream.h
+++ b/mozilla/base/src/nsIOutputStream.h
@@ -25,20 +25,21 @@
 { 0x7f13b870, 0xe95f, 0x11d1, \
   {0xbe, 0xae, 0x00, 0x80, 0x5f, 0x8a, 0x66, 0xdc} }
 
-/** Abstract byte input stream */
+/** Abstract byte output stream */
 class nsIOutputStream : public nsIBaseStream {
 public:
-  /** Write data into the stream.
-   *  @param aErrorCode the error code if an error occurs
-   *  @param aBuf the buffer into which the data is read
-   *  @param aOffset the start offset of the data
-   *  @param aCount the maximum number of bytes to read
-   *  @return number of bytes read or -1 if error
-   */   
-  virtual PRInt32 Write(PRInt32* aErrorCode,
-                        const char* aBuf,
-                        PRInt32 aOffset,
-                        PRInt32 aCount) = 0;
+
+    /** Write data into the stream.
+     *  @param aBuf the buffer into which the data is read
+     *  @param aOffset the start offset of the data
+     *  @param aCount the maximum number of bytes to read
+     *  @param aWriteCount out parameter to hold the number of
+     *         bytes written. if an error occurs, the writecount
+     *         is undefined
+     *  @return error status
+     */   
+    NS_IMETHOD
+    Write(const char* aBuf, PRInt32 aOffset, PRInt32 aCount, PRInt32 *aWriteCount) = 0; 
 };
 
 
diff --git a/mozilla/base/src/nsIUnicharBuffer.h b/mozilla/base/src/nsIUnicharBuffer.h
index 17bf8e74a3a..a5f57d7886b 100644
--- a/mozilla/base/src/nsIUnicharBuffer.h
+++ b/mozilla/base/src/nsIUnicharBuffer.h
@@ -33,7 +33,7 @@ public:
   virtual PRInt32 GetBufferSize() const = 0;
   virtual PRUnichar* GetBuffer() const = 0;
   virtual PRBool Grow(PRInt32 aNewSize) = 0;
-  virtual PRInt32 Fill(PRInt32* aErrorCode, nsIUnicharInputStream* aStream,
+  virtual PRInt32 Fill(nsresult* aErrorCode, nsIUnicharInputStream* aStream,
                        PRInt32 aKeep) = 0;
 };
 
diff --git a/mozilla/base/src/nsIUnicharInputStream.h b/mozilla/base/src/nsIUnicharInputStream.h
index 250dd07f17b..ecd21b775d4 100644
--- a/mozilla/base/src/nsIUnicharInputStream.h
+++ b/mozilla/base/src/nsIUnicharInputStream.h
@@ -42,11 +42,11 @@ enum nsCharSetID {
  */
 class nsIUnicharInputStream : public nsISupports {
 public:
-  virtual PRInt32 Read(PRInt32* aErrorCode,
-                       PRUnichar* aBuf,
-                       PRInt32 aOffset,
-                       PRInt32 aCount) = 0;
-  virtual void Close() = 0;
+  NS_IMETHOD Read(PRUnichar* aBuf,
+                  PRInt32 aOffset,
+                  PRInt32 aCount,
+                  PRInt32 *aReadCount) = 0;
+  NS_IMETHOD Close() = 0;
 };
 
 /**
diff --git a/mozilla/base/src/nsUnicharBuffer.cpp b/mozilla/base/src/nsUnicharBuffer.cpp
index 8c001afe069..6bedaaf6255 100644
--- a/mozilla/base/src/nsUnicharBuffer.cpp
+++ b/mozilla/base/src/nsUnicharBuffer.cpp
@@ -31,7 +31,7 @@ public:
   virtual PRInt32 GetBufferSize() const;
   virtual PRUnichar* GetBuffer() const;
   virtual PRBool Grow(PRInt32 aNewSize);
-  virtual PRInt32 Fill(PRInt32* aErrorCode, nsIUnicharInputStream* aStream,
+  virtual PRInt32 Fill(nsresult* aErrorCode, nsIUnicharInputStream* aStream,
                        PRInt32 aKeep);
 
   PRUnichar* mBuffer;
@@ -94,7 +94,7 @@ PRBool UnicharBufferImpl::Grow(PRInt32 aNewSize)
   return PR_FALSE;
 }
 
-PRInt32 UnicharBufferImpl::Fill(PRInt32* aErrorCode,
+PRInt32 UnicharBufferImpl::Fill(nsresult* aErrorCode,
                                 nsIUnicharInputStream* aStream,
                                 PRInt32 aKeep)
 {
@@ -102,7 +102,7 @@ PRInt32 UnicharBufferImpl::Fill(PRInt32* aErrorCode,
   NS_PRECONDITION(PRUint32(aKeep) < PRUint32(mLength), "illegal keep count");
   if ((nsnull == aStream) || (PRUint32(aKeep) >= PRUint32(mLength))) {
     // whoops
-    *aErrorCode = NS_INPUTSTREAM_ILLEGAL_ARGS;
+    *aErrorCode = NS_BASE_STREAM_ILLEGAL_ARGS;
     return -1;
   }
 
@@ -115,10 +115,13 @@ PRInt32 UnicharBufferImpl::Fill(PRInt32* aErrorCode,
   // Read in some new data
   mLength = aKeep;
   PRInt32 amount = mSpace - aKeep;
-  PRInt32 nb = aStream->Read(aErrorCode, mBuffer, aKeep, amount);
-  if (nb > 0) {
+  PRInt32 nb;
+  *aErrorCode = aStream->Read(mBuffer, aKeep, amount, &nb);
+  if (NS_SUCCEEDED(*aErrorCode)) {
     mLength += nb;
   }
+  else
+    nb = 0;
   return nb;
 }
 
diff --git a/mozilla/base/src/nsUnicharInputStream.cpp b/mozilla/base/src/nsUnicharInputStream.cpp
index 6f1534af003..b724da7f262 100644
--- a/mozilla/base/src/nsUnicharInputStream.cpp
+++ b/mozilla/base/src/nsUnicharInputStream.cpp
@@ -36,11 +36,11 @@ public:
 
   NS_DECL_ISUPPORTS
 
-  virtual PRInt32 Read(PRInt32* aErrorCode,
-                       PRUnichar* aBuf,
-                       PRInt32 aOffset,
-                       PRInt32 aCount);
-  virtual void Close();
+  NS_IMETHOD Read(PRUnichar* aBuf,
+                  PRInt32 aOffset,
+                  PRInt32 aCount,
+                  PRInt32 *aReadCount);
+  NS_IMETHOD Close();
 
   nsString* mString;
   PRInt32 mPos;
@@ -62,12 +62,13 @@ StringUnicharInputStream::~StringUnicharInputStream()
   }
 }
 
-PRInt32 StringUnicharInputStream::Read(PRInt32* aErrorCode,
-                                       PRUnichar* aBuf,
-                                       PRInt32 aOffset,
-                                       PRInt32 aCount)
+nsresult StringUnicharInputStream::Read(PRUnichar* aBuf,
+                                        PRInt32 aOffset,
+                                        PRInt32 aCount,
+                                        PRInt32 *aReadCount)
 {
   if (mPos >= mLen) {
+    *aReadCount = 0;
     return -1;
   }
   const PRUnichar* us = mString->GetUnicode();
@@ -77,15 +78,17 @@ PRInt32 StringUnicharInputStream::Read(PRInt32* aErrorCode,
   }
   nsCRT::memcpy(aBuf + aOffset, us + mPos, sizeof(PRUnichar) * amount);
   mPos += amount;
-  return amount;
+  *aReadCount = amount;
+  return NS_OK;
 }
 
-void StringUnicharInputStream::Close()
+nsresult StringUnicharInputStream::Close()
 {
   mPos = mLen;
   if (nsnull != mString) {
     delete mString;
   }
+  return NS_OK;
 }
 
 NS_IMPL_ISUPPORTS(StringUnicharInputStream, kIUnicharInputStreamIID);
@@ -163,7 +166,7 @@ NS_NewB2UConverter(nsIB2UConverter** aInstancePtrResult,
     return NS_ERROR_NO_AGGREGATION;
   }
   if (eCharSetID_IsoLatin1 != aCharSet) {
-    return NS_INPUTSTREAM_NO_CONVERTER;
+    return NS_BASE_STREAM_NO_CONVERTER;
   }
   IsoLatin1Converter* it = new IsoLatin1Converter();
   if (nsnull == it) {
@@ -182,14 +185,14 @@ public:
   ~ConverterInputStream();
 
   NS_DECL_ISUPPORTS
-  virtual PRInt32 Read(PRInt32* aErrorCode,
-                       PRUnichar* aBuf,
-                       PRInt32 aOffset,
-                       PRInt32 aCount);
-  virtual void Close();
+  NS_IMETHOD Read(PRUnichar* aBuf,
+                  PRInt32 aOffset,
+                  PRInt32 aCount,
+                  PRInt32 *aReadCount);
+  NS_IMETHOD Close();
 
 protected:
-  PRInt32 Fill(PRInt32* aErrorCode);
+  PRInt32 Fill(nsresult * aErrorCode);
 
   nsIInputStream* mInput;
   nsIB2UConverter* mConverter;
@@ -224,7 +227,7 @@ ConverterInputStream::~ConverterInputStream()
   Close();
 }
 
-void ConverterInputStream::Close()
+nsresult ConverterInputStream::Close()
 {
   if (nsnull != mInput) {
     mInput->Release();
@@ -242,19 +245,23 @@ void ConverterInputStream::Close()
     mUnicharData->Release();
     mUnicharData = nsnull;
   }
+
+  return NS_OK;
 }
 
-PRInt32 ConverterInputStream::Read(PRInt32* aErrorCode,
-                                   PRUnichar* aBuf,
-                                   PRInt32 aOffset,
-                                   PRInt32 aCount)
+nsresult ConverterInputStream::Read(PRUnichar* aBuf,
+                                    PRInt32 aOffset,
+                                    PRInt32 aCount,
+                                    PRInt32 *aReadCount)
 {
   PRInt32 rv = mUnicharDataLength - mUnicharDataOffset;
+  nsresult errorCode;
   if (0 == rv) {
     // Fill the unichar buffer
-    rv = Fill(aErrorCode);
+    rv = Fill(&errorCode);
     if (rv <= 0) {
-      return rv;
+      *aReadCount = 0;
+      return errorCode;
     }
   }
   if (rv > aCount) {
@@ -263,14 +270,15 @@ PRInt32 ConverterInputStream::Read(PRInt32* aErrorCode,
   nsCRT::memcpy(aBuf + aOffset, mUnicharData->GetBuffer() + mUnicharDataOffset,
                 rv * sizeof(PRUnichar));
   mUnicharDataOffset += rv;
-  return rv;
+  *aReadCount = rv;
+  return NS_OK;
 }
 
-PRInt32 ConverterInputStream::Fill(PRInt32* aErrorCode)
+PRInt32 ConverterInputStream::Fill(nsresult * aErrorCode)
 {
   if (nsnull == mInput) {
     // We already closed the stream!
-    *aErrorCode = NS_INPUTSTREAM_CLOSED;
+    *aErrorCode = NS_BASE_STREAM_CLOSED;
     return -1;
   }
 
diff --git a/mozilla/base/src/nscore.h b/mozilla/base/src/nscore.h
index 337781679a3..87ad079890e 100644
--- a/mozilla/base/src/nscore.h
+++ b/mozilla/base/src/nscore.h
@@ -107,4 +107,10 @@ typedef PRUcs2 PRUnichar;
 #define NS_GFX NS_IMPORT
 #endif
 
+#ifdef _IMPL_NS_PLUGIN
+#define NS_PLUGIN NS_EXPORT
+#else
+#define NS_PLUGIN NS_IMPORT
+#endif
+
 #endif /* nscore_h___ */
diff --git a/mozilla/base/tests/CvtURL.cpp b/mozilla/base/tests/CvtURL.cpp
index 365b687431a..f3f50f47626 100644
--- a/mozilla/base/tests/CvtURL.cpp
+++ b/mozilla/base/tests/CvtURL.cpp
@@ -75,9 +75,10 @@ int main(int argc, char** argv)
   PRInt32 count = 0;
   for (;;) {
     PRUnichar buf[1000];
-    PRInt32 nb = uin->Read(&ec, buf, 0, 1000);
-    if (nb <= 0) {
-      if (nb < 0) {
+    PRInt32 nb;
+    ec = uin->Read(buf, 0, 1000, &nb);
+    if (ec < 0) {
+      if (ec != NS_BASE_STREAM_EOF) {
         printf("i/o error: %d\n", ec);
       }
       break;
diff --git a/mozilla/xpcom/ds/nsByteBuffer.cpp b/mozilla/xpcom/ds/nsByteBuffer.cpp
index a27f8cbf2c9..bd3c9b72467 100644
--- a/mozilla/xpcom/ds/nsByteBuffer.cpp
+++ b/mozilla/xpcom/ds/nsByteBuffer.cpp
@@ -31,7 +31,7 @@ public:
   virtual PRInt32 GetBufferSize() const;
   virtual char* GetBuffer() const;
   virtual PRBool Grow(PRInt32 aNewSize);
-  virtual PRInt32 Fill(PRInt32* aErrorCode, nsIInputStream* aStream,
+  virtual PRInt32 Fill(nsresult* aErrorCode, nsIInputStream* aStream,
                        PRInt32 aKeep);
 
   char* mBuffer;
@@ -94,14 +94,14 @@ PRBool ByteBufferImpl::Grow(PRInt32 aNewSize)
   return PR_FALSE;
 }
 
-PRInt32 ByteBufferImpl::Fill(PRInt32* aErrorCode, nsIInputStream* aStream,
+PRInt32 ByteBufferImpl::Fill(nsresult* aErrorCode, nsIInputStream* aStream,
                              PRInt32 aKeep)
 {
   NS_PRECONDITION(nsnull != aStream, "null stream");
   NS_PRECONDITION(PRUint32(aKeep) <= PRUint32(mLength), "illegal keep count");
   if ((nsnull == aStream) || (PRUint32(aKeep) > PRUint32(mLength))) {
     // whoops
-    *aErrorCode = NS_INPUTSTREAM_ILLEGAL_ARGS;
+    *aErrorCode = NS_BASE_STREAM_ILLEGAL_ARGS;
     return -1;
   }
 
@@ -113,10 +113,13 @@ PRInt32 ByteBufferImpl::Fill(PRInt32* aErrorCode, nsIInputStream* aStream,
   // Read in some new data
   mLength = aKeep;
   PRInt32 amount = mSpace - aKeep;
-  PRInt32 nb = aStream->Read(aErrorCode, mBuffer, aKeep, amount);
-  if (nb > 0) {
+  PRInt32 nb;
+  *aErrorCode = aStream->Read(mBuffer, aKeep, amount, &nb);
+  if (NS_SUCCEEDED(*aErrorCode)) {
     mLength += nb;
   }
+  else
+    nb = 0;
   return nb;
 }
 
diff --git a/mozilla/xpcom/ds/nsIByteBuffer.h b/mozilla/xpcom/ds/nsIByteBuffer.h
index 74561b69a47..43a04c29342 100644
--- a/mozilla/xpcom/ds/nsIByteBuffer.h
+++ b/mozilla/xpcom/ds/nsIByteBuffer.h
@@ -44,7 +44,7 @@ public:
 
   /** Fill the buffer with data from aStream.  Don't grow the buffer, only
    *  read until length of buffer equals buffer size. */
-  virtual PRInt32 Fill(PRInt32* aErrorCode, nsIInputStream* aStream,
+  virtual PRInt32 Fill(nsresult* aErrorCode, nsIInputStream* aStream,
                        PRInt32 aKeep) = 0;
 };
 
diff --git a/mozilla/xpcom/ds/nsIUnicharBuffer.h b/mozilla/xpcom/ds/nsIUnicharBuffer.h
index 17bf8e74a3a..a5f57d7886b 100644
--- a/mozilla/xpcom/ds/nsIUnicharBuffer.h
+++ b/mozilla/xpcom/ds/nsIUnicharBuffer.h
@@ -33,7 +33,7 @@ public:
   virtual PRInt32 GetBufferSize() const = 0;
   virtual PRUnichar* GetBuffer() const = 0;
   virtual PRBool Grow(PRInt32 aNewSize) = 0;
-  virtual PRInt32 Fill(PRInt32* aErrorCode, nsIUnicharInputStream* aStream,
+  virtual PRInt32 Fill(nsresult* aErrorCode, nsIUnicharInputStream* aStream,
                        PRInt32 aKeep) = 0;
 };
 
diff --git a/mozilla/xpcom/ds/nsUnicharBuffer.cpp b/mozilla/xpcom/ds/nsUnicharBuffer.cpp
index 8c001afe069..6bedaaf6255 100644
--- a/mozilla/xpcom/ds/nsUnicharBuffer.cpp
+++ b/mozilla/xpcom/ds/nsUnicharBuffer.cpp
@@ -31,7 +31,7 @@ public:
   virtual PRInt32 GetBufferSize() const;
   virtual PRUnichar* GetBuffer() const;
   virtual PRBool Grow(PRInt32 aNewSize);
-  virtual PRInt32 Fill(PRInt32* aErrorCode, nsIUnicharInputStream* aStream,
+  virtual PRInt32 Fill(nsresult* aErrorCode, nsIUnicharInputStream* aStream,
                        PRInt32 aKeep);
 
   PRUnichar* mBuffer;
@@ -94,7 +94,7 @@ PRBool UnicharBufferImpl::Grow(PRInt32 aNewSize)
   return PR_FALSE;
 }
 
-PRInt32 UnicharBufferImpl::Fill(PRInt32* aErrorCode,
+PRInt32 UnicharBufferImpl::Fill(nsresult* aErrorCode,
                                 nsIUnicharInputStream* aStream,
                                 PRInt32 aKeep)
 {
@@ -102,7 +102,7 @@ PRInt32 UnicharBufferImpl::Fill(PRInt32* aErrorCode,
   NS_PRECONDITION(PRUint32(aKeep) < PRUint32(mLength), "illegal keep count");
   if ((nsnull == aStream) || (PRUint32(aKeep) >= PRUint32(mLength))) {
     // whoops
-    *aErrorCode = NS_INPUTSTREAM_ILLEGAL_ARGS;
+    *aErrorCode = NS_BASE_STREAM_ILLEGAL_ARGS;
     return -1;
   }
 
@@ -115,10 +115,13 @@ PRInt32 UnicharBufferImpl::Fill(PRInt32* aErrorCode,
   // Read in some new data
   mLength = aKeep;
   PRInt32 amount = mSpace - aKeep;
-  PRInt32 nb = aStream->Read(aErrorCode, mBuffer, aKeep, amount);
-  if (nb > 0) {
+  PRInt32 nb;
+  *aErrorCode = aStream->Read(mBuffer, aKeep, amount, &nb);
+  if (NS_SUCCEEDED(*aErrorCode)) {
     mLength += nb;
   }
+  else
+    nb = 0;
   return nb;
 }
 
diff --git a/mozilla/xpcom/io/nsIBaseStream.h b/mozilla/xpcom/io/nsIBaseStream.h
index 8578d81676a..06efd0fad4f 100644
--- a/mozilla/xpcom/io/nsIBaseStream.h
+++ b/mozilla/xpcom/io/nsIBaseStream.h
@@ -31,12 +31,27 @@
 class nsIBaseStream : public nsISupports {
 public:
 
-  /** Return the number of bytes in the stream */
-  virtual PRInt32 GetLength() = 0;
-
-  /** Close the stream. */
-  virtual void Close() = 0;
+    /** Close the stream. */
+    NS_IMETHOD
+    Close(void) = 0;
 };
 
+/** Error codes */
+//@{ 
+// XXX fix up the values so they are not total hacks... MMP
+/// End of file
+#define NS_BASE_STREAM_EOF            0x80001001
+/// Stream closed
+#define NS_BASE_STREAM_CLOSED         0x80001002
+/// Error from the operating system
+#define NS_BASE_STREAM_OSERROR        0x80001003
+/// Illegal arguments
+#define NS_BASE_STREAM_ILLEGAL_ARGS   0x80001004
+/// For unichar streams
+#define NS_BASE_STREAM_NO_CONVERTER   0x80001005
+/// For unichar streams
+#define NS_BASE_STREAM_BAD_CONVERSION 0x80001006
+//@}
+
 
 #endif /* nsInputStream_h___ */
diff --git a/mozilla/xpcom/io/nsIInputStream.h b/mozilla/xpcom/io/nsIInputStream.h
index abfc50f4512..37c942927f3 100644
--- a/mozilla/xpcom/io/nsIInputStream.h
+++ b/mozilla/xpcom/io/nsIInputStream.h
@@ -27,34 +27,28 @@
 /** Abstract byte input stream */
 class nsIInputStream : public nsIBaseStream {
 public:
-  /** Read data from the stream.
-   *  @param aErrorCode the error code if an error occurs
-   *  @param aBuf the buffer into which the data is read
-   *  @param aOffset the start offset of the data
-   *  @param aCount the maximum number of bytes to read
-   *  @return number of bytes read or -1 if error
-   */   
-  virtual PRInt32 Read(PRInt32* aErrorCode,
-                       char* aBuf,
-                       PRInt32 aOffset,
-                       PRInt32 aCount) = 0;
+
+    /** Return the number of bytes in the stream
+     *  @param aLength out parameter to hold the length
+     *         of the stream. if an error occurs, the length
+     *         will be undefined
+     *  @return error status
+     */
+    NS_IMETHOD
+    GetLength(PRInt32 *aLength) = 0;
+
+    /** Read data from the stream.
+     *  @param aErrorCode the error code if an error occurs
+     *  @param aBuf the buffer into which the data is read
+     *  @param aOffset the start offset of the data
+     *  @param aCount the maximum number of bytes to read
+     *  @param aReadCount out parameter to hold the number of
+     *         bytes read, eof if 0. if an error occurs, the
+     *         read count will be undefined
+     *  @return error status
+     */   
+    NS_IMETHOD
+    Read(char* aBuf, PRInt32 aOffset, PRInt32 aCount, PRInt32 *aReadCount) = 0; 
 };
 
-/** Error codes */
-//@{ 
-// XXX fix up the values to work with nsqresult
-/// End of file
-#define NS_INPUTSTREAM_EOF 1
-/// Stream closed
-#define NS_INPUTSTREAM_CLOSED 2
-/// Error from the operating system
-#define NS_INPUTSTREAM_OSERROR 3
-/// Illegal arguments
-#define NS_INPUTSTREAM_ILLEGAL_ARGS 4
-/// For unichar streams
-#define NS_INPUTSTREAM_NO_CONVERTER 5
-/// For unichar streams
-#define NS_INPUTSTREAM_BAD_CONVERSION 6
-//@}
-
 #endif /* nsInputStream_h___ */
diff --git a/mozilla/xpcom/io/nsIOutputStream.h b/mozilla/xpcom/io/nsIOutputStream.h
index 3f89f03a4a3..ad032f52767 100644
--- a/mozilla/xpcom/io/nsIOutputStream.h
+++ b/mozilla/xpcom/io/nsIOutputStream.h
@@ -25,20 +25,21 @@
 { 0x7f13b870, 0xe95f, 0x11d1, \
   {0xbe, 0xae, 0x00, 0x80, 0x5f, 0x8a, 0x66, 0xdc} }
 
-/** Abstract byte input stream */
+/** Abstract byte output stream */
 class nsIOutputStream : public nsIBaseStream {
 public:
-  /** Write data into the stream.
-   *  @param aErrorCode the error code if an error occurs
-   *  @param aBuf the buffer into which the data is read
-   *  @param aOffset the start offset of the data
-   *  @param aCount the maximum number of bytes to read
-   *  @return number of bytes read or -1 if error
-   */   
-  virtual PRInt32 Write(PRInt32* aErrorCode,
-                        const char* aBuf,
-                        PRInt32 aOffset,
-                        PRInt32 aCount) = 0;
+
+    /** Write data into the stream.
+     *  @param aBuf the buffer into which the data is read
+     *  @param aOffset the start offset of the data
+     *  @param aCount the maximum number of bytes to read
+     *  @param aWriteCount out parameter to hold the number of
+     *         bytes written. if an error occurs, the writecount
+     *         is undefined
+     *  @return error status
+     */   
+    NS_IMETHOD
+    Write(const char* aBuf, PRInt32 aOffset, PRInt32 aCount, PRInt32 *aWriteCount) = 0; 
 };
 
 
diff --git a/mozilla/xpcom/io/nsIUnicharInputStream.h b/mozilla/xpcom/io/nsIUnicharInputStream.h
index 250dd07f17b..ecd21b775d4 100644
--- a/mozilla/xpcom/io/nsIUnicharInputStream.h
+++ b/mozilla/xpcom/io/nsIUnicharInputStream.h
@@ -42,11 +42,11 @@ enum nsCharSetID {
  */
 class nsIUnicharInputStream : public nsISupports {
 public:
-  virtual PRInt32 Read(PRInt32* aErrorCode,
-                       PRUnichar* aBuf,
-                       PRInt32 aOffset,
-                       PRInt32 aCount) = 0;
-  virtual void Close() = 0;
+  NS_IMETHOD Read(PRUnichar* aBuf,
+                  PRInt32 aOffset,
+                  PRInt32 aCount,
+                  PRInt32 *aReadCount) = 0;
+  NS_IMETHOD Close() = 0;
 };
 
 /**
diff --git a/mozilla/xpcom/io/nsUnicharInputStream.cpp b/mozilla/xpcom/io/nsUnicharInputStream.cpp
index 6f1534af003..b724da7f262 100644
--- a/mozilla/xpcom/io/nsUnicharInputStream.cpp
+++ b/mozilla/xpcom/io/nsUnicharInputStream.cpp
@@ -36,11 +36,11 @@ public:
 
   NS_DECL_ISUPPORTS
 
-  virtual PRInt32 Read(PRInt32* aErrorCode,
-                       PRUnichar* aBuf,
-                       PRInt32 aOffset,
-                       PRInt32 aCount);
-  virtual void Close();
+  NS_IMETHOD Read(PRUnichar* aBuf,
+                  PRInt32 aOffset,
+                  PRInt32 aCount,
+                  PRInt32 *aReadCount);
+  NS_IMETHOD Close();
 
   nsString* mString;
   PRInt32 mPos;
@@ -62,12 +62,13 @@ StringUnicharInputStream::~StringUnicharInputStream()
   }
 }
 
-PRInt32 StringUnicharInputStream::Read(PRInt32* aErrorCode,
-                                       PRUnichar* aBuf,
-                                       PRInt32 aOffset,
-                                       PRInt32 aCount)
+nsresult StringUnicharInputStream::Read(PRUnichar* aBuf,
+                                        PRInt32 aOffset,
+                                        PRInt32 aCount,
+                                        PRInt32 *aReadCount)
 {
   if (mPos >= mLen) {
+    *aReadCount = 0;
     return -1;
   }
   const PRUnichar* us = mString->GetUnicode();
@@ -77,15 +78,17 @@ PRInt32 StringUnicharInputStream::Read(PRInt32* aErrorCode,
   }
   nsCRT::memcpy(aBuf + aOffset, us + mPos, sizeof(PRUnichar) * amount);
   mPos += amount;
-  return amount;
+  *aReadCount = amount;
+  return NS_OK;
 }
 
-void StringUnicharInputStream::Close()
+nsresult StringUnicharInputStream::Close()
 {
   mPos = mLen;
   if (nsnull != mString) {
     delete mString;
   }
+  return NS_OK;
 }
 
 NS_IMPL_ISUPPORTS(StringUnicharInputStream, kIUnicharInputStreamIID);
@@ -163,7 +166,7 @@ NS_NewB2UConverter(nsIB2UConverter** aInstancePtrResult,
     return NS_ERROR_NO_AGGREGATION;
   }
   if (eCharSetID_IsoLatin1 != aCharSet) {
-    return NS_INPUTSTREAM_NO_CONVERTER;
+    return NS_BASE_STREAM_NO_CONVERTER;
   }
   IsoLatin1Converter* it = new IsoLatin1Converter();
   if (nsnull == it) {
@@ -182,14 +185,14 @@ public:
   ~ConverterInputStream();
 
   NS_DECL_ISUPPORTS
-  virtual PRInt32 Read(PRInt32* aErrorCode,
-                       PRUnichar* aBuf,
-                       PRInt32 aOffset,
-                       PRInt32 aCount);
-  virtual void Close();
+  NS_IMETHOD Read(PRUnichar* aBuf,
+                  PRInt32 aOffset,
+                  PRInt32 aCount,
+                  PRInt32 *aReadCount);
+  NS_IMETHOD Close();
 
 protected:
-  PRInt32 Fill(PRInt32* aErrorCode);
+  PRInt32 Fill(nsresult * aErrorCode);
 
   nsIInputStream* mInput;
   nsIB2UConverter* mConverter;
@@ -224,7 +227,7 @@ ConverterInputStream::~ConverterInputStream()
   Close();
 }
 
-void ConverterInputStream::Close()
+nsresult ConverterInputStream::Close()
 {
   if (nsnull != mInput) {
     mInput->Release();
@@ -242,19 +245,23 @@ void ConverterInputStream::Close()
     mUnicharData->Release();
     mUnicharData = nsnull;
   }
+
+  return NS_OK;
 }
 
-PRInt32 ConverterInputStream::Read(PRInt32* aErrorCode,
-                                   PRUnichar* aBuf,
-                                   PRInt32 aOffset,
-                                   PRInt32 aCount)
+nsresult ConverterInputStream::Read(PRUnichar* aBuf,
+                                    PRInt32 aOffset,
+                                    PRInt32 aCount,
+                                    PRInt32 *aReadCount)
 {
   PRInt32 rv = mUnicharDataLength - mUnicharDataOffset;
+  nsresult errorCode;
   if (0 == rv) {
     // Fill the unichar buffer
-    rv = Fill(aErrorCode);
+    rv = Fill(&errorCode);
     if (rv <= 0) {
-      return rv;
+      *aReadCount = 0;
+      return errorCode;
     }
   }
   if (rv > aCount) {
@@ -263,14 +270,15 @@ PRInt32 ConverterInputStream::Read(PRInt32* aErrorCode,
   nsCRT::memcpy(aBuf + aOffset, mUnicharData->GetBuffer() + mUnicharDataOffset,
                 rv * sizeof(PRUnichar));
   mUnicharDataOffset += rv;
-  return rv;
+  *aReadCount = rv;
+  return NS_OK;
 }
 
-PRInt32 ConverterInputStream::Fill(PRInt32* aErrorCode)
+PRInt32 ConverterInputStream::Fill(nsresult * aErrorCode)
 {
   if (nsnull == mInput) {
     // We already closed the stream!
-    *aErrorCode = NS_INPUTSTREAM_CLOSED;
+    *aErrorCode = NS_BASE_STREAM_CLOSED;
     return -1;
   }
 
diff --git a/mozilla/xpcom/tests/CvtURL.cpp b/mozilla/xpcom/tests/CvtURL.cpp
index 365b687431a..f3f50f47626 100644
--- a/mozilla/xpcom/tests/CvtURL.cpp
+++ b/mozilla/xpcom/tests/CvtURL.cpp
@@ -75,9 +75,10 @@ int main(int argc, char** argv)
   PRInt32 count = 0;
   for (;;) {
     PRUnichar buf[1000];
-    PRInt32 nb = uin->Read(&ec, buf, 0, 1000);
-    if (nb <= 0) {
-      if (nb < 0) {
+    PRInt32 nb;
+    ec = uin->Read(buf, 0, 1000, &nb);
+    if (ec < 0) {
+      if (ec != NS_BASE_STREAM_EOF) {
         printf("i/o error: %d\n", ec);
       }
       break;