Implement vector::shrink_to_fit()

Author: jszuppe

include/boost/compute/container/vector.hpp

@@ -477,7 +477,22 @@ class vector
 
     void shrink_to_fit(command_queue &queue)
     {
-        (void) queue;
+        pointer old_data = m_data;
+        m_data = pointer(); // null pointer
+        if(m_size > 0)
+        {
+            // allocate new buffer
+            m_data = m_allocator.allocate(m_size);
+
+            // copy old values to the new buffer
+            ::boost::compute::copy(old_data, old_data + m_size, m_data, queue);
+        }
+
+        if(capacity() > 0)
+        {
+            // free old memory
+            m_allocator.deallocate(old_data, capacity());
+        }
     }
 
     void shrink_to_fit()

test/test_vector.cpp

@@ -472,4 +472,31 @@ BOOST_AUTO_TEST_CASE(swap_ctor_custom_alloc)
     CHECK_RANGE_EQUAL(int, 4, b, (11, 12, 13, 14));
 }
 
+BOOST_AUTO_TEST_CASE(shrink_to_fit)
+{
+    bc::vector<bc::int_> int_vector(5, context);
+    BOOST_CHECK_EQUAL(int_vector.size(), 5);
+    BOOST_CHECK(int_vector.capacity() >= 5);
+
+    int_vector.reserve(15);
+    BOOST_CHECK_EQUAL(int_vector.size(), 5);
+    BOOST_CHECK(int_vector.capacity() >= 15);
+
+    int_vector.shrink_to_fit();
+    BOOST_CHECK_EQUAL(int_vector.size(), 5);
+    BOOST_CHECK_EQUAL(int_vector.capacity(), 5);
+
+    int_vector.clear();
+    BOOST_CHECK_EQUAL(int_vector.size(), 0);
+    BOOST_CHECK_EQUAL(int_vector.capacity(), 5);
+
+    int_vector.shrink_to_fit();
+    BOOST_CHECK_EQUAL(int_vector.size(), 0);
+    BOOST_CHECK_EQUAL(int_vector.capacity(), 0);
+
+    int_vector.reserve(15);
+    BOOST_CHECK_EQUAL(int_vector.size(), 0);
+    BOOST_CHECK(int_vector.capacity() >= 15);
+}
+
 BOOST_AUTO_TEST_SUITE_END()