Implement barriers for Threaded Fork

This commit introduces a concept of a barrier, where all threads must
synchronise before continuing. Threaded Fork uses this to ensure that all
input is consumed by each sink exactly once.

Fixes #695.

1 files changed, 35 insertions, 0 deletions

diff --git a/src/lib/utils/barrier.cpp b/src/lib/utils/barrier.cpp
new file mode 100644
index 000000000..eb2ab978c
--- /dev/null
+++ b/src/lib/utils/barrier.cpp
@@ -0,0 +1,35 @@
+/*
+* Barrier
+* (C) 2016 Joel Low
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/internal/barrier.h>
+
+#if defined(BOTAN_TARGET_OS_HAS_THREADS)
+
+namespace Botan {
+
+void Barrier::wait(unsigned delta)
+    {
+    lock_guard_type<mutex_type> lock(m_mutex);
+    m_value += delta;
+    }
+
+void Barrier::sync()
+    {
+    std::unique_lock<mutex_type> lock(m_mutex);
+    --m_value;
+    if(m_value > 0)
+        m_cond.wait(lock, [this] { return m_value <= 0; });
+    else
+        {
+        m_value = 0;
+        m_cond.notify_all();
+        }
+    }
+
+}
+
+#endif