Merge pull request #145 from dorodnic/context-lifetime

Let multiple users share ownership over rs_context object

src/context.cpp

@@ -5,8 +5,9 @@
 #include "uvc.h"
 #include "r200.h"
 #include "f200.h"
+#include <mutex>
 
-rs_context::rs_context() : rs_context(0)
+rs_context::rs_context()
 {
     context = rsimpl::uvc::create_context();
 
@@ -27,18 +28,31 @@ rs_context::rs_context() : rs_context(0)
     }
 }
 
-// Enforce singleton semantics on rs_context
+// Enforce singleton semantics on rs_context
+rs_context* rs_context::instance = nullptr;
+int rs_context::ref_count = 0;
+std::mutex rs_context::instance_lock;
 
-bool rs_context::singleton_alive = false;
+rs_context* rs_context::acquire_instance()
+{
+    std::lock_guard<std::mutex> lock(instance_lock);
+    if (ref_count++ == 0)
+    {
+        instance = new rs_context();
+    }
+    return instance;
+}
 
-rs_context::rs_context(int)
+void rs_context::release_instance()
 {
-    if(singleton_alive) throw std::runtime_error("rs_context has singleton semantics, only one may exist at a time");
-    singleton_alive = true;
+    std::lock_guard<std::mutex> lock(instance_lock);
+    if (--ref_count == 0)
+    {
+        delete instance;
+    }
 }
 
 rs_context::~rs_context()
 {
-    assert(singleton_alive);
-    singleton_alive = false;
+    assert(ref_count == 0);
 }

src/context.h

@@ -15,9 +15,13 @@ struct rs_context
 
                                                     rs_context();
                                                     ~rs_context();
+
+    static rs_context*                              acquire_instance();
+    static void                                     release_instance();
 private:
-                                                    rs_context(int);
-    static bool                                     singleton_alive;
+    static int                                      ref_count;
+    static std::mutex                               instance_lock;
+    static rs_context*                              instance;
 };
 
 #endif

src/rs.cpp

@@ -45,14 +45,14 @@ namespace rsimpl
 rs_context * rs_create_context(int api_version, rs_error ** error) try
 {
     if (api_version != RS_API_VERSION) throw std::runtime_error("api version mismatch");
-    return new rs_context();
+    return rs_context::acquire_instance();
 }
 HANDLE_EXCEPTIONS_AND_RETURN(nullptr, api_version)
 
 void rs_delete_context(rs_context * context, rs_error ** error) try
 {
     VALIDATE_NOT_NULL(context);
-    delete context;
+    rs_context::release_instance();
 }
 HANDLE_EXCEPTIONS_AND_RETURN(, context)
 

unit-tests/unit-tests-common.h

@@ -77,6 +77,8 @@ class safe_context
         }
     }
 
+    bool operator == (const safe_context& other) const { return context == other.context; }
+
     operator rs_context * () const { return context; }
 };
 

unit-tests/unit-tests-offline.cpp

@@ -378,5 +378,6 @@ TEST_CASE( "rs_create_context() returns a valid context", "[offline] [validation
 TEST_CASE( "rs_context has singleton semantics", "[offline] [validation]" )
 {
     safe_context ctx;
-    REQUIRE(rs_create_context(RS_API_VERSION, require_error("rs_context has singleton semantics, only one may exist at a time")) == nullptr);
+    safe_context second_ctx;
+    REQUIRE(second_ctx == ctx);
 }