From 22fe281b639187960a9ca92c58676ad55bcc0769 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Tue, 17 Nov 2015 22:21:09 +0000
Subject: Add a portable semaphore class with timeout support

---
 libadhocutil/Jamfile.jam                 |  5 +++-
 libadhocutil/semaphore.cpp               | 40 +++++++++++++++++++++++++++++
 libadhocutil/semaphore.h                 | 29 +++++++++++++++++++++
 libadhocutil/unittests/Jamfile.jam       | 11 ++++++++
 libadhocutil/unittests/testSemaphore.cpp | 44 ++++++++++++++++++++++++++++++++
 5 files changed, 128 insertions(+), 1 deletion(-)
 create mode 100644 libadhocutil/semaphore.cpp
 create mode 100644 libadhocutil/semaphore.h
 create mode 100644 libadhocutil/unittests/testSemaphore.cpp

diff --git a/libadhocutil/Jamfile.jam b/libadhocutil/Jamfile.jam
index 861509a..c82dade 100644
--- a/libadhocutil/Jamfile.jam
+++ b/libadhocutil/Jamfile.jam
@@ -1,7 +1,8 @@
 import package ;
 import lex ;
 
-lib boost_utf : : <name>boost_unit_test_framework ;
+lib boost_system ;
+lib boost_thread ;
 lib Ice : ;
 lib IceUtil ;
 lib pthread ;
@@ -15,6 +16,8 @@ lib adhocutil :
 	:
 	<include>.
 	<library>iceall
+	<library>boost_system
+	<library>boost_thread
 	<library>curl
 	<library>dl
 	<cflags>-fvisibility=hidden
diff --git a/libadhocutil/semaphore.cpp b/libadhocutil/semaphore.cpp
new file mode 100644
index 0000000..0500445
--- /dev/null
+++ b/libadhocutil/semaphore.cpp
@@ -0,0 +1,40 @@
+#include "semaphore.h"
+
+namespace AdHoc {
+	Semaphore::Semaphore(unsigned int initial) : count(initial)
+	{
+	}
+
+	void
+	Semaphore::notify()
+	{
+		boost::mutex::scoped_lock lock(mutex);
+		++count;
+		condition.notify_one();
+	}
+
+	void
+	Semaphore::wait()
+	{
+		boost::mutex::scoped_lock lock(mutex);
+		while (!count) {
+			condition.wait(lock);
+		}
+		--count;
+	}
+
+	bool
+	Semaphore::wait(unsigned int timeout)
+	{
+		const boost::system_time expiry = boost::get_system_time() + boost::posix_time::milliseconds(timeout);
+		boost::mutex::scoped_lock lock(mutex);
+		while (!count) {
+			if (!condition.timed_wait(lock, expiry)) {
+				return false;
+			}
+		}
+		--count;
+		return true;
+	}
+}
+
diff --git a/libadhocutil/semaphore.h b/libadhocutil/semaphore.h
new file mode 100644
index 0000000..de10333
--- /dev/null
+++ b/libadhocutil/semaphore.h
@@ -0,0 +1,29 @@
+#ifndef ADHOCUTIL_SEMAPHORE_H
+#define ADHOCUTIL_SEMAPHORE_H
+
+// Borrowed from StackOverflow
+// http://stackoverflow.com/questions/4792449/c0x-has-no-semaphores-how-to-synchronize-threads
+
+#include <boost/thread/condition.hpp>
+#include <boost/thread/mutex.hpp>
+#include "visibility.h"
+
+namespace AdHoc {
+	/// A portable semaphore with timeout support
+	class DLL_PUBLIC Semaphore {
+		public:
+			Semaphore(unsigned int initial = 0);
+
+			void notify();
+			void wait();
+			bool wait(unsigned int);
+
+		private:
+			boost::mutex mutex;
+			boost::condition_variable condition;
+			unsigned long count;
+	};
+}
+
+#endif
+
diff --git a/libadhocutil/unittests/Jamfile.jam b/libadhocutil/unittests/Jamfile.jam
index 0961f31..334b47e 100644
--- a/libadhocutil/unittests/Jamfile.jam
+++ b/libadhocutil/unittests/Jamfile.jam
@@ -164,6 +164,17 @@ run
 	testFactory
 	;
 
+run
+	testSemaphore.cpp
+	: : :
+	<define>BOOST_TEST_DYN_LINK
+	<library>..//adhocutil
+	<library>boost_utf
+	<library>boost_system
+	:
+	testSemaphore
+	;
+
 run
 	testException.cpp
 	: : :
diff --git a/libadhocutil/unittests/testSemaphore.cpp b/libadhocutil/unittests/testSemaphore.cpp
new file mode 100644
index 0000000..b5e435e
--- /dev/null
+++ b/libadhocutil/unittests/testSemaphore.cpp
@@ -0,0 +1,44 @@
+#define BOOST_TEST_MODULE Semaphore
+#include <boost/test/unit_test.hpp>
+
+#include <thread>
+#include <semaphore.h>
+
+BOOST_AUTO_TEST_CASE( addRemoveOne )
+{
+	AdHoc::Semaphore s;
+	s.notify();
+	s.wait();
+}
+
+BOOST_AUTO_TEST_CASE( addRemoveSome )
+{
+	AdHoc::Semaphore s;
+	s.notify();
+	s.notify();
+	s.notify();
+	s.wait();
+	s.wait();
+	s.wait();
+}
+
+BOOST_AUTO_TEST_CASE( addRemoveTimeOut )
+{
+	AdHoc::Semaphore s;
+	s.notify();
+	s.wait();
+	BOOST_REQUIRE_EQUAL(false, s.wait(100));
+	BOOST_REQUIRE_EQUAL(false, s.wait(0));
+}
+
+BOOST_AUTO_TEST_CASE( addRemoveWait )
+{
+	AdHoc::Semaphore s;
+	s.notify();
+	s.wait();
+	std::thread th([&s]() { usleep(100000); s.notify(); });
+	BOOST_REQUIRE_EQUAL(false, s.wait(1));
+	s.wait();
+	th.join();
+}
+
-- 
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