diff --git a/include/buffer.h b/include/buffer.h
index 1835ba5..27fcd4c 100644
--- a/include/buffer.h
+++ b/include/buffer.h
@@ -3,6 +3,7 @@
 #include <cstddef>
 #include <tuple>
 #include <vector>
+#include <type_traits>
 
 #include "export.h"
 #include "def.h"
@@ -35,6 +36,16 @@ public:
     void *       data()       noexcept;
     void const * data() const noexcept;
 
+    template <typename T>
+    auto data() noexcept -> std::enable_if_t<!std::is_const_v<T>, T*> {
+        return static_cast<T*>(data());
+    }
+
+    template <typename T>
+    auto data() const noexcept -> std::enable_if_t<std::is_const_v<T>, T*> {
+        return static_cast<T*>(data());
+    }
+
     std::size_t size() const noexcept;
 
     std::tuple<void*, std::size_t> to_tuple() {
diff --git a/include/circ_queue.h b/include/circ_queue.h
index 5d5b04f..58da813 100644
--- a/include/circ_queue.h
+++ b/include/circ_queue.h
@@ -99,27 +99,19 @@ public:
         });
     }
 
-    static auto pop(queue* que) noexcept {
-        std::tuple<queue*, T> ret;
-        if (que == nullptr) {
-            return ret;
+    T pop() noexcept {
+        if (elems_ == nullptr) {
+            return {};
         }
-        if (que->elems_ == nullptr) {
-            return ret;
-        }
-        for (unsigned k = 0; que->elems_->cursor() == que->cursor_;) {
+        T item;
+        for (unsigned k = 0;;) {
+            if (elems_->pop(cursor_, [&item](void* p) {
+                ::new (&item) T(std::move(*static_cast<T*>(p)));
+            })) {
+                return item;
+            }
             ipc::sleep(k);
         }
-        if (!que->elems_->pop(que->cursor_, [&ret](void* p) {
-            ::new (&std::get<1>(ret)) T(std::move(*static_cast<T*>(p)));
-        })) {
-            return ret;
-        }
-        return ret;
-    }
-
-    T pop() noexcept {
-        return std::get<1>(pop(this));
     }
 };
 
diff --git a/src/ipc.cpp b/src/ipc.cpp
index 6c06907..ae1c641 100644
--- a/src/ipc.cpp
+++ b/src/ipc.cpp
@@ -183,10 +183,9 @@ static buff_t recv(handle_t h) {
     auto& rc = recv_cache();
     while (1) {
         // pop a new message
-        auto tp = que->pop(que);
-        auto& msg = std::get<1>(tp);
-        if (msg.que_ == std::get<0>(tp)) return {};
+        auto msg = que->pop();
         if (msg.id_ == 0) return {};
+        if (msg.que_ == que) continue; // pop next
         // msg.remain_ may minus & abs(msg.remain_) < data_length
         std::size_t remain = static_cast<std::size_t>(
                              static_cast<int>(data_length) + msg.remain_);
diff --git a/test/test_ipc.cpp b/test/test_ipc.cpp
index f6c1031..768250b 100644
--- a/test/test_ipc.cpp
+++ b/test/test_ipc.cpp
@@ -30,6 +30,7 @@ std::vector<ipc::buff_t> datas__;
 constexpr int DataMin   = 2;
 constexpr int DataMax   = 256;
 constexpr int LoopCount = 100000;
+//constexpr int LoopCount = 10000;
 
 } // internal-linkage
 
@@ -439,10 +440,11 @@ void Unit::test_channel_rtt() {
         for (std::size_t i = 0;; ++i) {
             auto dd = cc.recv();
             if (dd.size() < 2) return;
-//            std::cout << "recving: " << i << "-[" << dd.size() << "]" << std::endl;
+            //std::cout << "recving: " << i << "-[" << dd.size() << "]" << std::endl;
             while (!cc.send(ipc::buff_t('a'))) {
                 cc.wait_for_recv(1);
             }
+            //std::cout << "sent ack." << std::endl;
         }
     }};
 
@@ -451,12 +453,13 @@ void Unit::test_channel_rtt() {
         cc.wait_for_recv(1);
         sw.start();
         for (std::size_t i = 0; i < LoopCount; ++i) {
-//            std::cout << "sending: " << i << "-[" << datas__[i].size() << "]" << std::endl;
+            //std::cout << "sending: " << i << "-[" << datas__[i].size() << "]" << std::endl;
             cc.send(datas__[i]);
             /*auto dd = */cc.recv();
-//            if (dd.size() != 1 || dd[0] != 'a') {
-//                QVERIFY(false);
-//            }
+            //if (dd.size() != 1 || dd.data<char>()[0] != 'a') {
+            //    std::cout << "recv ack fail: " << i << "-[" << dd.size() << "]" << std::endl;
+            //    QVERIFY(false);
+            //}
         }
         cc.send(ipc::buff_t('\0'));
         t1.join();