Add Threaded_Fork, which acts like a normal Fork filter except that

each subchain of filters will run in its own thread.

Written and contributed by Joel Low.

A thread on botan-devel contains the original patch and some
discussion:
  http://lists.randombit.net/pipermail/botan-devel/2013-January/001699.html

3 files changed, 77 insertions, 1 deletions

diff --git a/src/utils/info.txt b/src/utils/info.txt
index 5bf1b9a54..cc056fc69 100644
--- a/src/utils/info.txt
+++ b/src/utils/info.txt
@@ -8,6 +8,7 @@ calendar.cpp
 charset.cpp
 cpuid.cpp
 parsing.cpp
+semaphore.cpp
 version.cpp
 zero_mem.cpp
 </source>
@@ -17,6 +18,7 @@ assert.h
 bit_ops.h
 prefetch.h
 rounding.h
+semaphore.h
 stl_util.h
 xor_buf.h
 </header:internal>
@@ -27,13 +29,14 @@ calendar.h
 charset.h
 cpuid.h
 exceptn.h
+get_byte.h
 loadstor.h
 mem_ops.h
 parsing.h
 rotate.h
+semaphore.h
 types.h
 version.h
-get_byte.h
 </header:public>
 
 <libs>
diff --git a/src/utils/semaphore.cpp b/src/utils/semaphore.cpp
new file mode 100644
index 000000000..f4f5b2b53
--- /dev/null
+++ b/src/utils/semaphore.cpp
@@ -0,0 +1,39 @@
+/*
+* Semaphore
+* by Pierre Gaston (http://p9as.blogspot.com/2012/06/c11-semaphores.html)
+* modified by Joel Low for Botan
+*
+*/
+
+#include <botan/internal/semaphore.h>
+
+namespace Botan {
+
+void Semaphore::release(size_t n)
+   {
+   for(size_t i = 0; i != n; ++i)
+      {
+      std::lock_guard<std::mutex> lock(m_mutex);
+
+      ++m_value;
+
+      if(m_value <= 0)
+         {
+         ++m_wakeups;
+         m_cond.notify_one();
+         }
+      }
+   }
+
+void Semaphore::acquire()
+   {
+   std::unique_lock<std::mutex> lock(m_mutex);
+   --m_value;
+   if(m_value < 0)
+      {
+      m_cond.wait(lock, [this] { return m_wakeups > 0; });
+      --m_wakeups;
+      }
+   }
+
+}
diff --git a/src/utils/semaphore.h b/src/utils/semaphore.h
new file mode 100644
index 000000000..c3ce73680
--- /dev/null
+++ b/src/utils/semaphore.h
@@ -0,0 +1,34 @@
+/*
+* Semaphore
+* by Pierre Gaston (http://p9as.blogspot.com/2012/06/c11-semaphores.html)
+* modified by Joel Low for Botan
+*
+*/
+
+#ifndef BOTAN_SEMAPHORE_H__
+#define BOTAN_SEMAPHORE_H__
+
+#include <mutex>
+#include <condition_variable>
+
+namespace Botan {
+
+class Semaphore
+   {
+   public:
+      Semaphore(int value = 0) : m_value(value), m_wakeups(0) {}
+
+      void acquire();
+
+      void release(size_t n = 1);
+
+   private:
+      int m_value;
+      int m_wakeups;
+      std::mutex m_mutex;
+      std::condition_variable m_cond;
+   };
+
+}
+
+#endif