[core, ios, macos] Refactor composite stop types and conversions

1 files changed, 35 insertions, 0 deletions

diff --git a/include/mbgl/style/function/composite_exponential_stops.hpp b/include/mbgl/style/function/composite_exponential_stops.hpp
new file mode 100644
index 0000000000..f1ad32a04d
--- /dev/null
+++ b/include/mbgl/style/function/composite_exponential_stops.hpp
@@ -0,0 +1,35 @@
+#pragma once
+
+#include <mbgl/style/function/exponential_stops.hpp>
+
+#include <map>
+
+namespace mbgl {
+namespace style {
+
+template <class T>
+class CompositeExponentialStops {
+public:
+    using Stops = std::map<float, std::map<float, T>>;
+
+    Stops stops;
+    float base = 1.0f;
+
+    CompositeExponentialStops() = default;
+    CompositeExponentialStops(Stops stops_, float base_ = 1.0f)
+        : stops(std::move(stops_)),
+          base(base_) {
+    }
+
+    ExponentialStops<T> innerStops(const std::map<float, T>& stops_) const {
+        return ExponentialStops<T>(stops_, base);
+    }
+
+    friend bool operator==(const CompositeExponentialStops& lhs,
+                           const CompositeExponentialStops& rhs) {
+        return lhs.stops == rhs.stops && lhs.base == rhs.base;
+    }
+};
+
+} // namespace style
+} // namespace mbgl