From 6b9fdc6ad3ac84cf8b8543b6e46b0ca8c4d61860 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 31 Jul 2021 17:14:21 +0100
Subject: Build a basic hacky semaphore for compilers that don't support
 std::binary_semaphore yet

---
 test/Jamfile.jam   |  2 +-
 test/semaphore.cpp | 37 +++++++++++++++++++++++++++++++++++++
 test/semaphore.h   | 27 +++++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 1 deletion(-)
 create mode 100644 test/semaphore.cpp
 create mode 100644 test/semaphore.h

diff --git a/test/Jamfile.jam b/test/Jamfile.jam
index 8486a14..1f0dac3 100644
--- a/test/Jamfile.jam
+++ b/test/Jamfile.jam
@@ -9,7 +9,7 @@ project : requirements
 
 lib testdb :
 	[ glob-tree *.sql : bin ]
-	[ glob testdb-*.cpp ] :
+	[ glob *.cpp : test-*.cpp ] :
 	<link>static
 	;
 
diff --git a/test/semaphore.cpp b/test/semaphore.cpp
new file mode 100644
index 0000000..09124ee
--- /dev/null
+++ b/test/semaphore.cpp
@@ -0,0 +1,37 @@
+#include "semaphore.h"
+
+#ifndef __cpp_lib_semaphore
+#	include <thread>
+
+semaphore::semaphore(unsigned int v_) : v {v_} { }
+
+void
+semaphore::release(unsigned int n)
+{
+	std::lock_guard lk {m};
+	v += n;
+}
+
+void
+semaphore::acquire()
+{
+	while (!try_dec()) { }
+}
+
+bool
+semaphore::try_dec()
+{
+	std::lock_guard lk {m};
+	if (v) {
+		v--;
+		m.unlock();
+		return true;
+	}
+	else {
+		m.unlock();
+		std::this_thread::sleep_for(std::chrono::milliseconds(100));
+		return false;
+	}
+}
+
+#endif
diff --git a/test/semaphore.h b/test/semaphore.h
new file mode 100644
index 0000000..f2e9355
--- /dev/null
+++ b/test/semaphore.h
@@ -0,0 +1,27 @@
+#ifndef MYGRATE_TEST_SEMAPHORE_H
+#define MYGRATE_TEST_SEMAPHORE_H
+
+#if __has_include(<semaphore>)
+#	include <semaphore>
+#endif
+
+#ifdef __cpp_lib_semaphore
+using semaphore = std::binary_semaphore;
+#else
+#	include <mutex>
+class semaphore {
+public:
+	semaphore(unsigned int v_);
+
+	void release(unsigned int n = 1);
+
+	void acquire();
+
+private:
+	bool try_dec();
+	unsigned int v;
+	std::mutex m;
+};
+#endif
+
+#endif
-- 
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