uhd: added header with misc atomic wrappers

2 files changed, 145 insertions, 1 deletions

diff --git a/host/include/uhd/utils/CMakeLists.txt b/host/include/uhd/utils/CMakeLists.txt
index 5a434fd9a..de91993fe 100644
--- a/host/include/uhd/utils/CMakeLists.txt
+++ b/host/include/uhd/utils/CMakeLists.txt
@@ -1,5 +1,5 @@
 #
-# Copyright 2010-2011 Ettus Research LLC
+# Copyright 2010-2012 Ettus Research LLC
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -19,6 +19,7 @@ INSTALL(FILES
     algorithm.hpp
     assert_has.hpp
     assert_has.ipp
+    atomic.hpp
     byteswap.hpp
     byteswap.ipp
     csv.hpp
diff --git a/host/include/uhd/utils/atomic.hpp b/host/include/uhd/utils/atomic.hpp
new file mode 100644
index 000000000..f9bc728cc
--- /dev/null
+++ b/host/include/uhd/utils/atomic.hpp
@@ -0,0 +1,143 @@
+//
+// Copyright 2012 Ettus Research LLC
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+#ifndef INCLUDED_UHD_UTILS_ATOMIC_HPP
+#define INCLUDED_UHD_UTILS_ATOMIC_HPP
+
+#include <uhd/config.hpp>
+#include <uhd/types/time_spec.hpp>
+#include <boost/thread/thread.hpp>
+#include <boost/interprocess/detail/atomic.hpp>
+
+namespace uhd{
+
+    //! A 32-bit integer that can be atomically accessed
+    class UHD_API atomic_uint32_t{
+    public:
+
+        //! Create a new atomic 32-bit integer, initialized to zero
+        UHD_INLINE atomic_uint32_t(void){
+            this->write(0);
+        }
+
+        //! Compare with cmp, swap with newval if same, return old value
+        UHD_INLINE boost::uint32_t cas(boost::uint32_t newval, boost::uint32_t cmp){
+            return boost::interprocess::detail::atomic_cas32(&_num, newval, cmp);
+        }
+
+        //! Sets the atomic integer to a new value
+        UHD_INLINE void write(const boost::uint32_t newval){
+            boost::interprocess::detail::atomic_write32(&_num, newval);
+        }
+
+        //! Gets the current value of the atomic integer
+        UHD_INLINE boost::uint32_t read(void){
+            return boost::interprocess::detail::atomic_read32(&_num);
+        }
+
+        //! Increment by 1 and return the old value
+        UHD_INLINE boost::uint32_t inc(void){
+            return boost::interprocess::detail::atomic_inc32(&_num);
+        }
+
+        //! Decrement by 1 and return the old value
+        UHD_INLINE boost::uint32_t dec(void){
+            return boost::interprocess::detail::atomic_dec32(&_num);
+        }
+
+    private: volatile boost::uint32_t _num;
+    };
+
+    /*!
+     * A reusable barrier to sync multiple threads.
+     * All threads spin on wait() until count is reset.
+     */
+    class UHD_API reusable_barrier{
+    public:
+
+        //! Resize the barrier for N threads
+        void resize(const size_t size){
+            _size = size;
+            _count.write(size);
+        }
+
+        //! Wait on the barrier condition
+        UHD_INLINE void wait(void){
+            _count.dec();
+            _count.cas(_size, 0);
+            while (_count.read() != _size){
+                boost::this_thread::interruption_point();
+                boost::this_thread::yield();
+            }
+        }
+
+    private:
+        size_t _size;
+        atomic_uint32_t _count;
+    };
+
+    /*!
+     * Spin-wait on a condition with a timeout.
+     * \param cond an atomic variable to compare
+     * \param value compare to atomic for true/false
+     * \param timeout the timeout in seconds
+     * \return true for cond == value, false for timeout
+     */
+    UHD_INLINE bool spin_wait_with_timeout(
+        atomic_uint32_t &cond,
+        boost::uint32_t value,
+        const double timeout
+    ){
+        if (cond.read() == value) return true;
+        const time_spec_t exit_time = time_spec_t::get_system_time() + time_spec_t(timeout);
+        while (cond.read() != value){
+            if (time_spec_t::get_system_time() > exit_time) return false;
+            boost::this_thread::interruption_point();
+            boost::this_thread::yield();
+        }
+        return true;
+    }
+
+    /*!
+     * Claimer class to provide synchronization for multi-thread access.
+     * Claiming enables buffer classes to be used with a buffer queue.
+     */
+    class simple_claimer{
+    public:
+        simple_claimer(void){
+            this->release();
+        }
+
+        UHD_INLINE void release(void){
+            _locked.write(0);
+        }
+
+        UHD_INLINE bool claim_with_wait(const double timeout){
+            if (spin_wait_with_timeout(_locked, 0, timeout)){
+                _locked.write(1);
+                return true;
+            }
+            return false;
+        }
+
+    private:
+        atomic_uint32_t _locked;
+    };
+
+} //namespace uhd
+
+#endif /* INCLUDED_UHD_UTILS_ATOMIC_HPP */