Make KJ_MAP support raw arrays as input.

c++/src/kj/array-test.c++

@@ -333,6 +333,16 @@ TEST(Array, Map) {
   EXPECT_STREQ("bcde", str(bar).cStr());
 }
 
+TEST(Array, MapRawArray) {
+  uint foo[4] = {1, 2, 3, 4};
+  Array<uint> bar = KJ_MAP(i, foo) -> uint { return i * i; };
+  ASSERT_EQ(4, bar.size());
+  EXPECT_EQ(1, bar[0]);
+  EXPECT_EQ(4, bar[1]);
+  EXPECT_EQ(9, bar[2]);
+  EXPECT_EQ(16, bar[3]);
+}
+
 TEST(Array, ReleaseAsBytesOrChars) {
   {
     Array<char> chars = kj::heapArray<char>("foo", 3);

c++/src/kj/array.h

@@ -501,7 +501,8 @@ private:
 // KJ_MAP
 
 #define KJ_MAP(elementName, array) \
-  ::kj::_::Mapper<KJ_DECLTYPE_REF(array)>(array) * [&](decltype(*(array).begin()) elementName)
+  ::kj::_::Mapper<KJ_DECLTYPE_REF(array)>(array) * \
+  [&](typename ::kj::_::Mapper<KJ_DECLTYPE_REF(array)>::Element elementName)
 // Applies some function to every element of an array, returning an Array of the results,  with
 // nice syntax.  Example:
 //
@@ -523,6 +524,22 @@ struct Mapper {
     }
     return builder.finish();
   }
+  typedef decltype(*(array).begin()) Element;
+};
+
+template <typename T, size_t s>
+struct Mapper<T(&)[s]> {
+  T* array;
+  Mapper(T* array): array(array) {}
+  template <typename Func>
+  auto operator*(Func&& func) -> Array<decltype(func(*array))> {
+    auto builder = heapArrayBuilder<decltype(func(*array))>(s);
+    for (size_t i = 0; i < s; i++) {
+      builder.add(func(array[i]));
+    }
+    return builder.finish();
+  }
+  typedef decltype(*array)& Element;
 };
 
 }  // namespace _ (private)