- Simplified the usage of span now with implicit constructors as it should be.

- Added overload for generic containers that have size and data members like vector.
- Removed unnecessary uses of make_span.

lib/include/srslte/adt/span.h

@@ -33,12 +33,53 @@ namespace srslte {
 
 /// The class template span describes an object that can refer to a contiguous sequence of objects with the first
 /// element of the sequence at position zero.
-/// It is encouraged to use the make_span() helper functions for creating new spans instead of using the constructors
-/// directly. This way is more explicit in code and makes the developer think first to make sure the lifetime of the
-/// sequence outlasts the new created span.
 template <typename T>
 class span
 {
+  /// Helper traits used by SFINAE expressions in constructors.
+
+  template <typename... Ts>
+  struct make_void {
+    typedef void type;
+  };
+  template <typename... Ts>
+  using void_t = typename make_void<Ts...>::type;
+
+  template <typename U>
+  struct is_span : std::false_type {};
+  template <typename U>
+  struct is_span<span<U> > : std::true_type {};
+
+  template <typename U>
+  struct is_std_array : std::false_type {};
+  template <typename U, std::size_t N>
+  struct is_std_array<std::array<U, N> > : std::true_type {};
+
+  template <typename U>
+  using remove_cvref_t = typename std::remove_cv<typename std::remove_reference<U>::type>::type;
+
+  template <class Container, class U, class = void>
+  struct is_container_compatible : public std::false_type {};
+  template <class Container, class U>
+  struct is_container_compatible<
+      Container,
+      U,
+      void_t<
+          // Check if the container type has data and size members.
+          decltype(std::declval<Container>().data()),
+          decltype(std::declval<Container>().size()),
+          // Container should not be a span.
+          typename std::enable_if<!is_span<remove_cvref_t<Container> >::value, int>::type,
+          // Container should not be a std::array.
+          typename std::enable_if<!is_std_array<remove_cvref_t<Container> >::value, int>::type,
+          // Container should not be an array.
+          typename std::enable_if<!std::is_array<remove_cvref_t<Container> >::value, int>::type,
+          // Check type compatibility between the contained type and the span type.
+          typename std::enable_if<
+              std::is_convertible<typename std::remove_pointer<decltype(std::declval<Container>().data())>::type (*)[],
+                                  U (*)[]>::value,
+              int>::type> > : public std::true_type {};
+
 public:
   /// Member types.
   using element_type     = T;
@@ -56,10 +97,10 @@ public:
   constexpr span() noexcept = default;
 
   /// Constructs a span that is a view over the range [ptr, ptr + len).
-  constexpr explicit span(pointer ptr, size_type len) noexcept : ptr(ptr), len(len) {}
+  constexpr span(pointer ptr, size_type len) noexcept : ptr(ptr), len(len) {}
 
   /// Constructs a span that is a view over the range [first, last).
-  constexpr explicit span(pointer first, pointer last) noexcept : ptr(first), len(last - first) {}
+  constexpr span(pointer first, pointer last) noexcept : ptr(first), len(last - first) {}
 
   /// Constructs a span that is a view over the array arr.
   template <std::size_t N>
@@ -80,6 +121,18 @@ public:
   constexpr span(const std::array<U, N>& arr) noexcept : ptr(arr.data()), len(N)
   {}
 
+  /// Constructs a span that is a view over the container c.
+  template <typename Container,
+            typename std::enable_if<is_container_compatible<Container, element_type>::value, int>::type = 0>
+  constexpr span(Container& c) noexcept : ptr(c.data()), len(c.size())
+  {}
+
+  /// Constructs a span that is a view over the container c.
+  template <typename Container,
+            typename std::enable_if<is_container_compatible<const Container, element_type>::value, int>::type = 0>
+  constexpr span(const Container& c) noexcept : ptr(c.data()), len(c.size())
+  {}
+
   template <typename U, typename std::enable_if<std::is_convertible<U (*)[], element_type (*)[]>::value, int>::type = 0>
   constexpr span(const span<U>& other) noexcept : ptr(other.data()), len(other.size())
   {}
@@ -156,7 +209,7 @@ public:
   span<element_type> subspan(size_type offset, size_type count) const
   {
     assert(count <= size() - offset && "size out of bounds!");
-    return span{data() + offset, count};
+    return {data() + offset, count};
   }
 
   /// Returns true if the input span has the same elements as this.
@@ -179,40 +232,6 @@ inline bool operator!=(span<T> lhs, span<T> rhs)
   return not lhs.equals(rhs);
 }
 
-///
-/// Helpers to construct span objects from different types of contiguous containers.
-///
-
-template <typename T, std::size_t N>
-inline span<T> make_span(T (&arr)[N])
-{
-  return span<T>{arr};
-}
-
-template <typename T, std::size_t N>
-inline span<T> make_span(std::array<T, N>& arr)
-{
-  return span<T>{arr};
-}
-
-template <typename T, std::size_t N>
-inline span<const T> make_span(const std::array<T, N>& arr)
-{
-  return span<const T>{arr};
-}
-
-template <typename T>
-inline span<T> make_span(std::vector<T>& v)
-{
-  return span<T>{v.data(), v.size()};
-}
-
-template <typename T>
-inline span<const T> make_span(const std::vector<T>& v)
-{
-  return span<const T>{v.data(), v.size()};
-}
-
 } // namespace srslte
 
 #endif // SRSLTE_SPAN_H

lib/test/adt/span_test.cc

@@ -27,7 +27,7 @@ int test_span_access()
   std::array<int, 7> values{1, 2, 3, 4, 5, 6, 7};
 
   {
-    auto view = srslte::make_span(values);
+    srslte::span<int> view = values;
 
     // access operators
     TESTASSERT(view.size() == 7);
@@ -56,7 +56,7 @@ int test_span_conversion()
 
   {
     // TEST: changing individual values
-    auto v = srslte::make_span(values), v2 = srslte::make_span(values2);
+    srslte::span<int> v = values, v2 = values2;
     TESTASSERT(v == v2);
 
     v[0] = 3;
@@ -68,7 +68,7 @@ int test_span_conversion()
 
   {
     // TEST: const context
-    const auto v = srslte::make_span(values), v2 = srslte::make_span(values2);
+    const srslte::span<int> v = values, v2 = values2;
     TESTASSERT(v != v2);
     TESTASSERT(v[0] == 3);
     TESTASSERT(v2[0] == 2);
@@ -78,8 +78,8 @@ int test_span_conversion()
 
   {
     // TEST: raw arrays
-    int  carray[] = {2, 3, 4, 5, 6, 7, 8};
-    auto v = srslte::make_span(values), v2 = srslte::make_span(carray);
+    int               carray[] = {2, 3, 4, 5, 6, 7, 8};
+    srslte::span<int> v = values, v2 = carray;
     TESTASSERT(v == v2);
     TESTASSERT(v2.size() == v.size());
   }

srsenb/test/upper/rrc_mobility_test.cc

@@ -430,7 +430,7 @@ int test_s1ap_mobility(mobility_test_params test_params)
                                     0x01, 0x48, 0x04, 0xbc, 0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x02, 0xa0, 0x07, 0xa0,
                                     0x10, 0x00, 0x01, 0x00, 0x05, 0x00, 0xa7, 0xd0, 0xc1, 0xf6, 0xaf, 0x3e, 0x12, 0xcc,
                                     0x86, 0x0d, 0x30, 0x00, 0x0b, 0x5a, 0x02, 0x17, 0x86, 0x00, 0x05, 0xa0, 0x20};
-  test_helpers::copy_msg_to_buffer(pdu, srslte::make_span(ho_cmd_rrc_container));
+  test_helpers::copy_msg_to_buffer(pdu, ho_cmd_rrc_container);
   TESTASSERT(s1ap.last_enb_status.rnti != tester.rnti);
   tester.rrc.ho_preparation_complete(tester.rnti, true, std::move(pdu));
   TESTASSERT(s1ap.last_enb_status.status_present);

srsenb/test/upper/test_helpers.h

@@ -228,7 +228,7 @@ int bring_rrc_to_reconf_state(srsenb::rrc& rrc, srslte::timer_handler& timers, u
 
   // Send RRCConnectionRequest
   uint8_t rrc_conn_request[] = {0x40, 0x12, 0xf6, 0xfb, 0xe2, 0xc6};
-  copy_msg_to_buffer(pdu, srslte::make_span(rrc_conn_request));
+  copy_msg_to_buffer(pdu, rrc_conn_request);
   rrc.write_pdu(rnti, 0, std::move(pdu));
   timers.step_all();
   rrc.tti_clock();
@@ -237,7 +237,7 @@ int bring_rrc_to_reconf_state(srsenb::rrc& rrc, srslte::timer_handler& timers, u
   uint8_t rrc_conn_setup_complete[] = {0x20, 0x00, 0x40, 0x2e, 0x90, 0x50, 0x49, 0xe8, 0x06, 0x0e, 0x82, 0xa2,
                                        0x17, 0xec, 0x13, 0xe2, 0x0f, 0x00, 0x02, 0x02, 0x5e, 0xdf, 0x7c, 0x58,
                                        0x05, 0xc0, 0xc0, 0x00, 0x08, 0x04, 0x03, 0xa0, 0x23, 0x23, 0xc0};
-  copy_msg_to_buffer(pdu, srslte::make_span(rrc_conn_setup_complete));
+  copy_msg_to_buffer(pdu, rrc_conn_setup_complete);
   rrc.write_pdu(rnti, 1, std::move(pdu));
   timers.step_all();
   rrc.tti_clock();
@@ -267,7 +267,7 @@ int bring_rrc_to_reconf_state(srsenb::rrc& rrc, srslte::timer_handler& timers, u
 
   // Send SecurityModeComplete
   uint8_t sec_mode_complete[] = {0x28, 0x00};
-  copy_msg_to_buffer(pdu, srslte::make_span(sec_mode_complete));
+  copy_msg_to_buffer(pdu, sec_mode_complete);
   rrc.write_pdu(rnti, 1, std::move(pdu));
   timers.step_all();
   rrc.tti_clock();
@@ -275,14 +275,14 @@ int bring_rrc_to_reconf_state(srsenb::rrc& rrc, srslte::timer_handler& timers, u
   // send UE cap info
   uint8_t ue_cap_info[] = {0x38, 0x01, 0x01, 0x0c, 0x98, 0x00, 0x00, 0x18, 0x00, 0x0f,
                            0x30, 0x20, 0x80, 0x00, 0x01, 0x00, 0x0e, 0x01, 0x00, 0x00};
-  copy_msg_to_buffer(pdu, srslte::make_span(ue_cap_info));
+  copy_msg_to_buffer(pdu, ue_cap_info);
   rrc.write_pdu(rnti, 1, std::move(pdu));
   timers.step_all();
   rrc.tti_clock();
 
   // RRCConnectionReconfiguration was sent. Send RRCConnectionReconfigurationComplete
   uint8_t rrc_conn_reconf_complete[] = {0x10, 0x00};
-  copy_msg_to_buffer(pdu, srslte::make_span(rrc_conn_reconf_complete));
+  copy_msg_to_buffer(pdu, rrc_conn_reconf_complete);
   rrc.write_pdu(rnti, 1, std::move(pdu));
   timers.step_all();
   rrc.tti_clock();