Restrict the 1-argument ArrayView constructor to types with .size() and .data()
Before this change, the argument still needed those methods, but not
having them resulted in a compilation error. Now, it results in this
constructor being removed from the overload set.
This currently makes no difference, but I'm about to publish a CL that
breaks without this.
Review-Url: https://codereview.webrtc.org/2312473002
Cr-Commit-Position: refs/heads/master@{#14068}
diff --git a/webrtc/base/array_view.h b/webrtc/base/array_view.h
index 783e717..725a2d7 100644
--- a/webrtc/base/array_view.h
+++ b/webrtc/base/array_view.h
@@ -11,10 +11,37 @@
#ifndef WEBRTC_BASE_ARRAY_VIEW_H_
#define WEBRTC_BASE_ARRAY_VIEW_H_
+#include <type_traits>
+
#include "webrtc/base/checks.h"
namespace rtc {
+namespace internal {
+
+// (Internal; please don't use outside this file.) Determines if the given
+// class has zero-argument .data() and .size() methods whose return values are
+// convertible to T* and size_t, respectively.
+template <typename DS, typename T>
+class HasDataAndSize {
+ private:
+ template <
+ typename C,
+ typename std::enable_if<
+ std::is_convertible<decltype(std::declval<C>().data()), T*>::value &&
+ std::is_convertible<decltype(std::declval<C>().size()),
+ size_t>::value>::type* = nullptr>
+ static int Test(int);
+
+ template <typename>
+ static char Test(...);
+
+ public:
+ static constexpr bool value = std::is_same<decltype(Test<DS>(0)), int>::value;
+};
+
+} // namespace internal
+
// Many functions read from or write to arrays. The obvious way to do this is
// to use two arguments, a pointer to the first element and an element count:
//
@@ -95,7 +122,9 @@
// or ArrayView<const T>, const std::vector<T> to ArrayView<const T>, and
// rtc::Buffer to ArrayView<uint8_t> (with the same const behavior as
// std::vector).
- template <typename U>
+ template <typename U,
+ typename std::enable_if<
+ internal::HasDataAndSize<U, T>::value>::type* = nullptr>
ArrayView(U& u) : ArrayView(u.data(), u.size()) {}
// Indexing, size, and iteration. These allow mutation even if the ArrayView