Problem: some context options have no getter

Solution: add one so that class-based bindings can easily use them

doc/zmq_ctx_get.txt

@@ -64,6 +64,24 @@ zero if the "block forever on context termination" gambit was disabled by
 setting ZMQ_BLOCKY to false on all new contexts.
 
 
+ZMQ_THREAD_SCHED_POLICY: Get scheduling policy for I/O threads
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The 'ZMQ_THREAD_SCHED_POLICY' argument returns the scheduling policy for
+internal context's thread pool.
+
+
+ZMQ_THREAD_PRIORITY: Get scheduling priority for I/O threads
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The 'ZMQ_THREAD_PRIORITY' argument returns the scheduling priority for
+internal context's thread pool.
+
+
+ZMQ_THREAD_NAME_PREFIX: Get name prefix for I/O threads
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The 'ZMQ_THREAD_NAME_PREFIX' argument gets the numeric prefix of each thread
+created for the internal context's thread pool.
+
+
 ZMQ_MSG_T_SIZE: Get the zmq_msg_t size at runtime
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 The 'ZMQ_MSG_T_SIZE' argument returns the size of the zmq_msg_t structure at

src/ctx.cpp

@@ -271,8 +271,7 @@ int zmq::ctx_t::get (int option_)
     else if (option_ == ZMQ_ZERO_COPY_RECV) {
         rc = _zero_copy;
     } else {
-        errno = EINVAL;
-        rc = -1;
+        rc = thread_ctx_t::get (option_);
     }
     return rc;
 }
@@ -467,6 +466,25 @@ int zmq::thread_ctx_t::set (int option_, int optval_)
     return rc;
 }
 
+int zmq::thread_ctx_t::get (int option_)
+{
+    int rc = 0;
+    if (option_ == ZMQ_THREAD_PRIORITY) {
+        scoped_lock_t locker (_opt_sync);
+        rc = _thread_priority;
+    } else if (option_ == ZMQ_THREAD_SCHED_POLICY) {
+        scoped_lock_t locker (_opt_sync);
+        rc = _thread_sched_policy;
+    } else if (option_ == ZMQ_THREAD_NAME_PREFIX) {
+        scoped_lock_t locker (_opt_sync);
+        rc = atoi (_thread_name_prefix.c_str ());
+    } else {
+        errno = EINVAL;
+        rc = -1;
+    }
+    return rc;
+}
+
 void zmq::ctx_t::send_command (uint32_t tid_, const command_t &command_)
 {
     _slots[tid_]->send (command_);

src/ctx.hpp

@@ -70,6 +70,7 @@ class thread_ctx_t
     void start_thread (thread_t &thread_, thread_fn *tfn_, void *arg_) const;
 
     int set (int option_, int optval_);
+    int get (int option_);
 
   protected:
     //  Synchronisation of access to context options.

tests/test_ctx_options.cpp

@@ -92,6 +92,8 @@ void test_ctx_thread_opts (void *ctx_)
     // as of ZMQ 4.2.3 this has an effect only on POSIX systems (nothing happens on Windows, but still it should return success):
     rc = zmq_ctx_set (ctx_, ZMQ_THREAD_SCHED_POLICY, TEST_POLICY);
     assert (rc == 0);
+    rc = zmq_ctx_get (ctx_, ZMQ_THREAD_SCHED_POLICY);
+    assert (rc == TEST_POLICY);
 
 
     // test priority:
@@ -110,6 +112,8 @@ void test_ctx_thread_opts (void *ctx_)
           ctx_, ZMQ_THREAD_PRIORITY,
           1 /* any positive value different than the default will be ok */);
         assert (rc == 0);
+        rc = zmq_ctx_get (ctx_, ZMQ_THREAD_PRIORITY);
+        assert (rc == 1);
     }
 
 
@@ -143,6 +147,8 @@ void test_ctx_thread_opts (void *ctx_)
 
     rc = zmq_ctx_set (ctx_, ZMQ_THREAD_NAME_PREFIX, 1234);
     assert (rc == 0);
+    rc = zmq_ctx_get (ctx_, ZMQ_THREAD_NAME_PREFIX);
+    assert (rc == 1234);
 #endif
 }