C API: add proj_dynamic_datum_get_frame_reference_epoch()

2 files changed, 37 insertions, 0 deletions

diff --git a/src/iso19111/c_api.cpp b/src/iso19111/c_api.cpp
index c152df88..cad76431 100644
--- a/src/iso19111/c_api.cpp
+++ b/src/iso19111/c_api.cpp
@@ -8163,6 +8163,40 @@ PJ *proj_crs_get_datum_forced(PJ_CONTEXT *ctx, const PJ *crs) {
 
 // ---------------------------------------------------------------------------
 
+/** \brief Returns the frame reference epoch of a dynamic geodetic or vertical
+ * reference frame.
+ *
+ * @param ctx PROJ context, or NULL for default context
+ * @param datum Object of type DynamicGeodeticReferenceFrame or
+ * DynamicVerticalReferenceFrame (must not be NULL)
+ * @return the frame reference epoch as decimal year, or -1 in case of error.
+ *
+ * @since 7.2
+ */
+double proj_dynamic_datum_get_frame_reference_epoch(PJ_CONTEXT *ctx,
+                                                    const PJ *datum) {
+    SANITIZE_CTX(ctx);
+    if (!datum) {
+        proj_log_error(ctx, __FUNCTION__, "missing required input");
+        return -1;
+    }
+    auto dgrf = dynamic_cast<const DynamicGeodeticReferenceFrame *>(
+        datum->iso_obj.get());
+    auto dvrf = dynamic_cast<const DynamicVerticalReferenceFrame *>(
+        datum->iso_obj.get());
+    if (!dgrf && !dvrf) {
+        proj_log_error(ctx, __FUNCTION__, "Object is not a "
+                                          "DynamicGeodeticReferenceFrame or "
+                                          "DynamicVerticalReferenceFrame");
+        return -1;
+    }
+    const auto &frameReferenceEpoch =
+        dgrf ? dgrf->frameReferenceEpoch() : dvrf->frameReferenceEpoch();
+    return frameReferenceEpoch.value();
+}
+
+// ---------------------------------------------------------------------------
+
 /** \brief Returns the coordinate system of a SingleCRS.
  *
  * The returned object must be unreferenced with proj_destroy() after
diff --git a/src/proj.h b/src/proj.h
index 92966526..b758663a 100644
--- a/src/proj.h
+++ b/src/proj.h
@@ -1263,6 +1263,9 @@ PJ PROJ_DLL *proj_datum_ensemble_get_member(PJ_CONTEXT *ctx,
                                             const PJ *datum_ensemble,
                                             int member_index);
 
+double PROJ_DLL proj_dynamic_datum_get_frame_reference_epoch(PJ_CONTEXT *ctx,
+                                                     const PJ *datum);
+
 PJ PROJ_DLL *proj_crs_get_coordinate_system(PJ_CONTEXT *ctx, const PJ *crs);
 
 PJ_COORDINATE_SYSTEM_TYPE PROJ_DLL proj_cs_get_type(PJ_CONTEXT *ctx,