2 files changed, 37 insertions, 5 deletions
diff --git a/src/surveyor.cpp b/src/surveyor.cpp
index bd19b8a..6a789eb 100644
--- a/src/surveyor.cpp
+++ b/src/surveyor.cpp
@@ -31,13 +31,17 @@ xs::surveyor_t::surveyor_t (class ctx_t *parent_, uint32_t tid_, int sid_) :
     xsurveyor_t (parent_, tid_, sid_),
     receiving_responses (false),
     survey_id (generate_random ()),
-    timeout (0)
+    timeout (0),
+    has_prefetched (false)
 {
     options.type = XS_SURVEYOR;
+
+    prefetched.init ();
 }
 
 xs::surveyor_t::~surveyor_t ()
 {
+    prefetched.close ();
 }
 
 int xs::surveyor_t::xsend (msg_t *msg_, int flags_)
@@ -90,6 +94,13 @@ int xs::surveyor_t::xrecv (msg_t *msg_, int flags_)
         return -1;
     }
 
+    //  If we have a message prefetched we can return it straight away.
+    if (has_prefetched) {
+        msg_->move (prefetched);
+        has_prefetched = false;
+        return 0;
+    }
+
     //  Get the first part of the response -- the survey ID.
     rc = xsurveyor_t::xrecv (msg_, flags_);
     if (rc != 0) {
@@ -128,9 +139,26 @@ int xs::surveyor_t::xrecv (msg_t *msg_, int flags_)
 
 bool xs::surveyor_t::xhas_in ()
 {
-    //  TODO: We need a prefetched_message here...
-    xs_assert (false);
-    return false;
+    //  When no survey is underway, POLLIN is never signaled.
+    if (!receiving_responses)
+        return false;
+
+    //  If there's already a message prefetches signal POLLIN.
+    if (has_prefetched)
+        return true;
+
+    //  Try to prefetch a message.
+    int rc = xrecv (&prefetched, XS_DONTWAIT);
+
+    //  No message available.
+    if (rc != 0 && errno == EAGAIN)
+        return false;
+
+    errno_assert (rc == 0);
+
+    //  We have a message prefetched. We can signal POLLIN now.
+    has_prefetched = true;
+    return true;
 }
 
 bool xs::surveyor_t::xhas_out ()
diff --git a/src/surveyor.hpp b/src/surveyor.hpp
index e79dab0..1661d9c 100644
--- a/src/surveyor.hpp
+++ b/src/surveyor.hpp
@@ -23,12 +23,12 @@
 
 #include "xsurveyor.hpp"
 #include "stdint.hpp"
+#include "msg.hpp"
 
 namespace xs
 {
 
     class ctx_t;
-    class msg_t;
     class io_thread_t;
     class socket_base_t;
 
@@ -57,6 +57,10 @@ namespace xs
         //  The time instant when the current survey expires.
         uint64_t timeout;
 
+        //  Inbound message prefetched during polling.
+        bool has_prefetched;
+        msg_t prefetched;
+
         surveyor_t (const surveyor_t&);
         const surveyor_t &operator = (const surveyor_t&);
     };