Bug 799234 - Fix seeking within a single stream's range within a multiplexed stream. r=biesi,amarchesini

--HG--
extra : rebase_source : 73658a2351a9a0a9476f6d1f4f6e5d8a77413eb5

xpcom/io/nsMultiplexInputStream.cpp

@@ -87,10 +87,22 @@ nsMultiplexInputStream::GetCount(uint32_t *aCount)
     return NS_OK;
 }
 
+static bool
+SeekableStreamAtBeginning(nsIInputStream *aStream)
+{
+    int64_t streamPos;
+    nsCOMPtr<nsISeekableStream> stream = do_QueryInterface(aStream);
+    if (stream && NS_SUCCEEDED(stream->Tell(&streamPos)) && streamPos != 0) {
+        return false;
+    }
+    return true;
+}
+
 /* void appendStream (in nsIInputStream stream); */
 NS_IMETHODIMP
 nsMultiplexInputStream::AppendStream(nsIInputStream *aStream)
 {
+    NS_ASSERTION(SeekableStreamAtBeginning(aStream), "Appended stream not at beginning.");
     return mStreams.AppendElement(aStream) ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
 }
 
@@ -98,6 +110,7 @@ nsMultiplexInputStream::AppendStream(nsIInputStream *aStream)
 NS_IMETHODIMP
 nsMultiplexInputStream::InsertStream(nsIInputStream *aStream, uint32_t aIndex)
 {
+    NS_ASSERTION(SeekableStreamAtBeginning(aStream), "Inserted stream not at beginning.");
     bool result = mStreams.InsertElementAt(aIndex, aStream);
     NS_ENSURE_TRUE(result, NS_ERROR_OUT_OF_MEMORY);
     if (mCurrentStream > aIndex ||
@@ -378,23 +391,27 @@ nsMultiplexInputStream::Seek(int32_t aWhence, int64_t aOffset)
                 remaining = 0;
             }
             else if (remaining > streamPos) {
+                if (i < oldCurrentStream) {
+                    // We're already at end so no need to seek this stream
+                    remaining -= streamPos;
+                    NS_ASSERTION(remaining >= 0, "Remaining invalid");
+                }
+                else {
                     uint64_t avail;
                     rv = mStreams[i]->Available(&avail);
                     NS_ENSURE_SUCCESS(rv, rv);
 
-                int64_t newPos;
-                if (remaining < (streamPos + (int64_t) avail)) {
-                    newPos = remaining - streamPos;
-                    remaining = 0;
-                } else {
-                    newPos = streamPos + (int64_t)avail;
-                    remaining -= streamPos + avail;
-                }
-                rv = stream->Seek(NS_SEEK_CUR, newPos);
+                    int64_t newPos = NS_MIN(remaining, streamPos + (int64_t)avail);
+
+                    rv = stream->Seek(NS_SEEK_SET, newPos);
                     NS_ENSURE_SUCCESS(rv, rv);
 
                     mCurrentStream = i;
                     mStartedReadingCurrent = true;
+
+                    remaining -= newPos;
+                    NS_ASSERTION(remaining >= 0, "Remaining invalid");
+                }
             }
             else {
                 NS_ASSERTION(remaining == streamPos, "Huh?");

xpcom/tests/unit/test_seek_multiplex.js

@@ -13,7 +13,6 @@ const data = "0123456789";
 const count = 10;
 
 function test_multiplex_streams() {
-  try {
   var MultiplexStream = CC("@mozilla.org/io/multiplex-input-stream;1",
                            "nsIMultiplexInputStream");
   do_check_eq(1, 1);
@@ -39,7 +38,14 @@ function test_multiplex_streams() {
   var readData = sis.read(20);
   do_check_eq(readData, data + data);
   // -- Tests for NS_SEEK_SET
-    // Seek accross stream.
+  // Seek to a non-zero, non-stream-boundary offset.
+  seekable.seek(Ci.nsISeekableStream.NS_SEEK_SET, 2);
+  do_check_eq(seekable.tell(), 2);
+  do_check_eq(seekable.available(), 98);
+  seekable.seek(Ci.nsISeekableStream.NS_SEEK_SET, 9);
+  do_check_eq(seekable.tell(), 9);
+  do_check_eq(seekable.available(), 91);
+  // Seek across stream boundary.
   seekable.seek(Ci.nsISeekableStream.NS_SEEK_SET, 35);
   do_check_eq(seekable.tell(), 35);
   do_check_eq(seekable.available(), 65);
@@ -54,7 +60,7 @@ function test_multiplex_streams() {
   do_check_eq(readData, data);
   do_check_eq(seekable.tell(), 50);
   do_check_eq(seekable.available(), 50);
-    // Rewind and read accross streams.
+  // Rewind and read across streams.
   seekable.seek(Ci.nsISeekableStream.NS_SEEK_SET, 39);
   do_check_eq(seekable.tell(), 39);
   do_check_eq(seekable.available(), 61);
@@ -66,7 +72,7 @@ function test_multiplex_streams() {
   seekable.seek(Ci.nsISeekableStream.NS_SEEK_SET, 0);
   do_check_eq(seekable.tell(), 0);
   do_check_eq(seekable.available(), 100);
-    // Seek to some randome location
+  // Seek to some random location
   seekable.seek(Ci.nsISeekableStream.NS_SEEK_SET, 50);
   // -- Tests for NS_SEEK_CUR
   // Positive seek.
@@ -93,7 +99,7 @@ function test_multiplex_streams() {
   readData = sis.read(5);
   do_check_eq(readData, data.slice(5));
   do_check_eq(seekable.tell(), data.length * count);
-    // Read accros streams.
+  // Read across streams.
   seekable.seek(Ci.nsISeekableStream.NS_SEEK_END, -15);
   do_check_eq(seekable.tell(), data.length * count - 15);
   readData = sis.read(15);
@@ -115,7 +121,7 @@ function test_multiplex_streams() {
   do_check_eq(seekable.tell(), 0);
   seekable.seek(Ci.nsISeekableStream.NS_SEEK_CUR, -15);
   do_check_eq(seekable.tell(), 0);
-    // Seek too far: shoul be clamped.
+  // Seek too far: should be clamped.
   seekable.seek(Ci.nsISeekableStream.NS_SEEK_SET, 0);
   do_check_eq(seekable.tell(), 0);
   seekable.seek(Ci.nsISeekableStream.NS_SEEK_CUR, 3 * data.length * count);
@@ -124,16 +130,12 @@ function test_multiplex_streams() {
   do_check_eq(seekable.tell(), 100);
   seekable.seek(Ci.nsISeekableStream.NS_SEEK_CUR, -2 * data.length * count);
   do_check_eq(seekable.tell(), 0);
-  } catch(e) {
-    dump(e + "\n");
-  }
 }
 
 function test_multiplex_bug797871() {
 
   var data = "1234567890123456789012345678901234567890";
 
-  try {
   var MultiplexStream = CC("@mozilla.org/io/multiplex-input-stream;1",
                            "nsIMultiplexInputStream");
   do_check_eq(1, 1);
@@ -162,9 +164,6 @@ function test_multiplex_bug797871() {
 
   seekable.seek(Ci.nsISeekableStream.NS_SEEK_SET, 20);
   do_check_eq(seekable.tell(), 20);
-  } catch(e) {
-    do_note_exception(e, "exception in test_multiplex_bug797871");
-  }
 }
 
 function run_test() {