fixes bug 287750 "provide methods to test if streams are buffered" r=biesi sr=bzbarsky

xpcom/build/dlldeps.cpp

@@ -112,6 +112,8 @@ void XXXNeverCalled()
     NS_NewInputStreamReadyEvent(nsnull, nsnull, nsnull);
     NS_NewOutputStreamReadyEvent(nsnull, nsnull, nsnull);
     NS_AsyncCopy(nsnull, nsnull, nsnull, NS_ASYNCCOPY_VIA_READSEGMENTS, 0, nsnull, nsnull);
+    NS_InputStreamIsBuffered(nsnull);
+    NS_OutputStreamIsBuffered(nsnull);
     PL_DHashStubEnumRemove(nsnull, nsnull, nsnull, nsnull);
     nsIDHashKey::HashKey(nsnull);
     nsFixedSizeAllocator a;

xpcom/io/nsStreamUtils.cpp

@@ -1,3 +1,4 @@
+/* vim:set ts=4 sw=4 sts=4 et cin: */
 /* ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  *
@@ -581,3 +582,49 @@ NS_AsyncCopy(nsIInputStream         *source,
 
     return rv;
 }
+
+//-----------------------------------------------------------------------------
+
+static NS_METHOD
+TestInputStream(nsIInputStream *inStr,
+                void *closure,
+                const char *buffer,
+                PRUint32 offset,
+                PRUint32 count,
+                PRUint32 *countWritten)
+{
+    PRBool *result = NS_REINTERPRET_CAST(PRBool *, closure);
+    *result = PR_TRUE;
+    return NS_ERROR_ABORT;  // don't call me anymore
+}
+
+NS_COM PRBool
+NS_InputStreamIsBuffered(nsIInputStream *stream)
+{
+    PRBool result = PR_FALSE;
+    PRUint32 n;
+    stream->ReadSegments(TestInputStream, &result, 1, &n);
+    return result;
+}
+
+static NS_METHOD
+TestOutputStream(nsIOutputStream *outStr,
+                 void *closure,
+                 char *buffer,
+                 PRUint32 offset,
+                 PRUint32 count,
+                 PRUint32 *countRead)
+{
+    PRBool *result = NS_REINTERPRET_CAST(PRBool *, closure);
+    *result = PR_TRUE;
+    return NS_ERROR_ABORT;  // don't call me anymore
+}
+
+NS_COM PRBool
+NS_OutputStreamIsBuffered(nsIOutputStream *stream)
+{
+    PRBool result = PR_FALSE;
+    PRUint32 n;
+    stream->WriteSegments(TestOutputStream, &result, 1, &n);
+    return result;
+}

xpcom/io/nsStreamUtils.h

@@ -108,4 +108,36 @@ NS_AsyncCopy(nsIInputStream         *aSource,
              nsAsyncCopyCallbackFun  aCallbackFun = nsnull,
              void                   *aCallbackClosure = nsnull);
 
+/**
+ * This function tests whether or not the input stream is buffered.  A buffered
+ * input stream is one that implements readSegments.  The test for this is to
+ * simply call readSegments, without actually consuming any data from the
+ * stream, to verify that it functions.
+ *
+ * NOTE: If the stream is non-blocking and has no data available yet, then this
+ * test will fail.  In that case, we return false even though the test is not 
+ * really conclusive.
+ *
+ * @param aInputStream
+ *        The input stream to test.
+ */
+extern NS_COM PRBool
+NS_InputStreamIsBuffered(nsIInputStream *aInputStream);
+
+/**
+ * This function tests whether or not the output stream is buffered.  A
+ * buffered output stream is one that implements writeSegments.  The test for
+ * this is to simply call writeSegments, without actually writing any data into
+ * the stream, to verify that it functions.
+ *
+ * NOTE: If the stream is non-blocking and has no available space yet, then
+ * this test will fail.  In that case, we return false even though the test is
+ * not really conclusive.
+ *
+ * @param aOutputStream
+ *        The output stream to test.
+ */
+extern NS_COM PRBool
+NS_OutputStreamIsBuffered(nsIOutputStream *aOutputStream);
+
 #endif // !nsStreamUtils_h__