Fix a bug where we would improperly calculate if the FIFO was

full by adding a reserve feature to the packet fifo which allows
us to reserve space in the fifo if only part of a packet was
copied into the fifo.

dev/ns_gige.cc:
    use the new reserve feature in the fifo to properly determine
    when we're full.  assert that adding a packet to the fifo suceeds.
dev/pktfifo.hh:
    add the ability to reserve space in the fifo.  This is useful for
    partial writing of packets into the fifo.

--HG--
extra : convert_revision : 83f871f34fac237bb464c9513cf6490b5c62420e

1 files changed, 15 insertions, 5 deletions

diff --git a/dev/pktfifo.hh b/dev/pktfifo.hh
index a54a49996..0b2e95e2a 100644
--- a/dev/pktfifo.hh
+++ b/dev/pktfifo.hh
@@ -43,6 +43,7 @@ class PacketFifo
     std::list<PacketPtr> fifo;
     int _maxsize;
     int _size;
+    int _reserved;
 
   public:
     explicit PacketFifo(int max) : _maxsize(max), _size(0) {}
@@ -50,18 +51,27 @@ class PacketFifo
 
     int maxsize() const { return _maxsize; }
     int packets() const { return fifo.size(); }
-    int size() const { return _size; }
-    int avail() const { return _maxsize - _size; }
-    bool empty() const { return _size == 0; }
-    bool full() const { return _size >= _maxsize; }
+    int size() const { return _size + _reserved; }
+    int avail() const { return maxsize() - size(); }
+    bool empty() const { return size() == 0; }
+    bool full() const { return size() >= maxsize(); }
+
+    int reserve(int len = 0)
+    {
+        _reserved += len;
+        assert(avail() >= 0);
+        return _reserved;
+    }
 
     bool push(PacketPtr ptr)
     {
-        if (avail() < ptr->length)
+        assert(_reserved <= ptr->length);
+        if (avail() < ptr->length - _reserved)
             return false;
 
         _size += ptr->length;
         fifo.push_back(ptr);
+        _reserved = 0;
         return true;
     }