Task #5441: COBALT RSP raw support: improve LCS/Stream StringStream. Fixes...

Task #5441: COBALT RSP raw support: improve LCS/Stream StringStream. Fixes tTABTranspose, which exposed the deadlock introduced in r38093. StringStream is still broken wrt thread-safety and remaining data (but a little less than it was), but not used in operations, only for tests. It sucks, but it'll have to do for now.

LCS/Stream/src/StringStream.cc

 //# StringStream.cc: 
 //#
-//# Copyright (C) 2008
+//# Copyright (C) 2008, 2017
 //# ASTRON (Netherlands Institute for Radio Astronomy)
 //# P.O.Box 2, 7990 AA Dwingeloo, The Netherlands
 //#
@@ -40,21 +40,25 @@ size_t StringStream::tryRead(void *ptr, size_t size)
 {
   Cancellation::point(); // keep behaviour consistent with real I/O streams
 
-  {
-    ScopedLock sl(itsMutex);
-// still wrong for !USE_THREADS wrt stringstream exception vs EndOfStreamException, but !USE_THREADS is obsolete anyway
+// NOTE: still wrong for !USE_THREADS and wrt less than size bytes avail and stringstream error vs EndOfStreamException, but !USE_THREADS is obsolete anyway. Need CondVar instead of Semaphore and drop !USE_THREADS.
 #ifdef USE_THREADS
-    if (!dataWritten.down(size)) {
-      // stream closed and avail < size
-      size_t avail = dataWritten.getValue();
-      if (avail == 0) // size > 0
-        THROW(EndOfStreamException, "Stream has been closed");
-
-      size = avail;
-      dataWritten.down(size);
-    }
+  if (!dataWritten.down(size)) {
+    ScopedLock sl(itsMutex);
+    size_t avail = dataWritten.getValue();
+    if (avail == 0) // size > 0
+      THROW(EndOfStreamException, "Stream has been closed");
+
+    size = avail;
+    dataWritten.down(size);
+
+    itsBuffer.read(static_cast<char*>(ptr), size);
+
+    return size;
+  }
 #endif
 
+  {
+    ScopedLock sl(itsMutex);
     itsBuffer.read(static_cast<char*>(ptr), size);
   }
 
@@ -89,29 +93,30 @@ size_t StringStream::tryReadv(const struct iovec *iov, int iovcnt)
     size += iov[i].iov_len;
   }
 
-  {
-    ScopedLock sl(itsMutex);
-// still wrong for !USE_THREADS wrt stringstream exception vs EndOfStreamException, but !USE_THREADS is obsolete anyway
+// NOTE: still wrong for !USE_THREADS and wrt less than size bytes avail and stringstream error vs EndOfStreamException, but !USE_THREADS is obsolete anyway. Need CondVar instead of Semaphore and drop !USE_THREADS.
 #ifdef USE_THREADS
-    if (!dataWritten.down(size)) {
-      // stream closed and avail < size
-      size_t avail = dataWritten.getValue();
-      if (avail == 0) // size > 0
-        THROW(EndOfStreamException, "Stream has been closed");
-
-      size = avail;
-      dataWritten.down(size);
-
-      for (int i = 0; i < iovcnt && avail > 0; i++) {
-        size_t len = avail < iov[i].iov_len ? avail : iov[i].iov_len;
-        itsBuffer.read(static_cast<char*>(iov[i].iov_base), len);
-        avail -= len;
-      }
-
-      return size;
+  if (!dataWritten.down(size)) {
+    ScopedLock sl(itsMutex);
+    // stream closed and avail < size
+    size_t avail = dataWritten.getValue();
+    if (avail == 0) // size > 0
+      THROW(EndOfStreamException, "Stream has been closed");
+
+    size = avail;
+    dataWritten.down(size);
+
+    for (int i = 0; i < iovcnt && avail > 0; i++) {
+      size_t len = avail < iov[i].iov_len ? avail : iov[i].iov_len;
+      itsBuffer.read(static_cast<char*>(iov[i].iov_base), len);
+      avail -= len;
     }
+
+    return size;
+  }
 #endif
 
+  {
+    ScopedLock sl(itsMutex);
     for (int i = 0; i < iovcnt; i++) {
       itsBuffer.read(static_cast<char*>(iov[i].iov_base), iov[i].iov_len);
     }