C API: add a proj_coordoperation_get_method_info() method

3 files changed, 62 insertions, 31 deletions

diff --git a/src/c_api.cpp b/src/c_api.cpp
index 539675e2..230b4492 100644
--- a/src/c_api.cpp
+++ b/src/c_api.cpp
@@ -1914,19 +1914,10 @@ void proj_free_string_list(PROJ_STRING_LIST list) {
  *
  * @param ctx PROJ context, or NULL for default context
  * @param crs Objet of type DerivedCRS or BoundCRSs (must not be NULL)
- * @param out_method_name Pointer to a string value to store the method
- * (projection) name. or NULL
- * @param out_method_auth_name Pointer to a string value to store the method
- * authority name. or NULL
- * @param out_method_code Pointer to a string value to store the method
- * code. or NULL
  * @return Object of type SingleOperation that must be unreferenced with
  * proj_obj_unref(), or NULL in case of error.
  */
-PJ_OBJ *proj_obj_crs_get_coordoperation(PJ_CONTEXT *ctx, const PJ_OBJ *crs,
-                                        const char **out_method_name,
-                                        const char **out_method_auth_name,
-                                        const char **out_method_code) {
+PJ_OBJ *proj_obj_crs_get_coordoperation(PJ_CONTEXT *ctx, const PJ_OBJ *crs) {
     SANITIZE_CTX(ctx);
     assert(crs);
     SingleOperationPtr co;
@@ -1945,7 +1936,41 @@ PJ_OBJ *proj_obj_crs_get_coordoperation(PJ_CONTEXT *ctx, const PJ_OBJ *crs,
         }
     }
 
-    const auto &method = co->method();
+    return PJ_OBJ::create(NN_NO_CHECK(co));
+}
+
+// ---------------------------------------------------------------------------
+
+/** \brief Return informatin on the operation method of the SingleOperation.
+ *
+ * @param ctx PROJ context, or NULL for default context
+ * @param coordoperation Objet of type SingleOperation (typically a Conversion
+ * or Transformation) (must not be NULL)
+ * @param out_method_name Pointer to a string value to store the method
+ * (projection) name. or NULL
+ * @param out_method_auth_name Pointer to a string value to store the method
+ * authority name. or NULL
+ * @param out_method_code Pointer to a string value to store the method
+ * code. or NULL
+ * @return TRUE in case of success.
+ */
+int proj_coordoperation_get_method_info(PJ_CONTEXT *ctx,
+                                        const PJ_OBJ *coordoperation,
+                                        const char **out_method_name,
+                                        const char **out_method_auth_name,
+                                        const char **out_method_code) {
+    SANITIZE_CTX(ctx);
+    assert(coordoperation);
+
+    auto singleOp =
+        dynamic_cast<const SingleOperation *>(coordoperation->obj.get());
+    if (!singleOp) {
+        proj_log_error(ctx, __FUNCTION__,
+                       "Object is not a DerivedCRS or BoundCRS");
+        return false;
+    }
+
+    const auto &method = singleOp->method();
     const auto &method_ids = method->identifiers();
     if (out_method_name) {
         *out_method_name = method->name()->description()->c_str();
@@ -1964,7 +1989,7 @@ PJ_OBJ *proj_obj_crs_get_coordoperation(PJ_CONTEXT *ctx, const PJ_OBJ *crs,
             *out_method_code = nullptr;
         }
     }
-    return PJ_OBJ::create(NN_NO_CHECK(co));
+    return true;
 }
 
 // ---------------------------------------------------------------------------
diff --git a/src/proj.h b/src/proj.h
index 295ecc23..7dbd23c1 100644
--- a/src/proj.h
+++ b/src/proj.h
@@ -872,10 +872,13 @@ int PROJ_DLL proj_obj_prime_meridian_get_parameters(PJ_CONTEXT *ctx,
                                                const char **out_unit_name);
 
 PJ_OBJ PROJ_DLL *proj_obj_crs_get_coordoperation(PJ_CONTEXT *ctx,
-                                                 const PJ_OBJ *crs,
-                                             const char **out_method_name,
-                                             const char **out_method_auth_name,
-                                             const char **out_method_code);
+                                                 const PJ_OBJ *crs);
+
+int PROJ_DLL proj_coordoperation_get_method_info(PJ_CONTEXT *ctx,
+                                                 const PJ_OBJ *coordoperation,
+                                                 const char **out_method_name,
+                                                 const char **out_method_auth_name,
+                                                 const char **out_method_code);
 
 int PROJ_DLL proj_coordoperation_is_instanciable(PJ_CONTEXT *ctx,
                                                  const PJ_OBJ *coordoperation);
diff --git a/test/unit/test_c_api.cpp b/test/unit/test_c_api.cpp
index cb355892..a49e9501 100644
--- a/test/unit/test_c_api.cpp
+++ b/test/unit/test_c_api.cpp
@@ -422,8 +422,7 @@ TEST_F(CApi, proj_obj_crs_create_bound_crs_to_WGS84) {
     ObjectKeeper keeper_hub_crs(hub_crs);
     ASSERT_NE(hub_crs, nullptr);
 
-    auto transf =
-        proj_obj_crs_get_coordoperation(m_ctxt, res, nullptr, nullptr, nullptr);
+    auto transf = proj_obj_crs_get_coordoperation(m_ctxt, res);
     ObjectKeeper keeper_transf(transf);
     ASSERT_NE(transf, nullptr);
 
@@ -998,24 +997,30 @@ TEST_F(CApi, conversion) {
     ASSERT_NE(crs, nullptr);
     ObjectKeeper keeper(crs);
 
+    // invalid object type
+    EXPECT_FALSE(proj_coordoperation_get_method_info(m_ctxt, crs, nullptr,
+                                                     nullptr, nullptr));
+
     {
-        auto conv = proj_obj_crs_get_coordoperation(m_ctxt, crs, nullptr,
-                                                    nullptr, nullptr);
+        auto conv = proj_obj_crs_get_coordoperation(m_ctxt, crs);
         ASSERT_NE(conv, nullptr);
         ObjectKeeper keeper_conv(conv);
 
-        ASSERT_EQ(proj_obj_crs_get_coordoperation(m_ctxt, conv, nullptr,
-                                                  nullptr, nullptr),
-                  nullptr);
+        ASSERT_EQ(proj_obj_crs_get_coordoperation(m_ctxt, conv), nullptr);
     }
 
+    auto conv = proj_obj_crs_get_coordoperation(m_ctxt, crs);
+    ASSERT_NE(conv, nullptr);
+    ObjectKeeper keeper_conv(conv);
+
+    EXPECT_TRUE(proj_coordoperation_get_method_info(m_ctxt, conv, nullptr,
+                                                    nullptr, nullptr));
+
     const char *methodName = nullptr;
     const char *methodAuthorityName = nullptr;
     const char *methodCode = nullptr;
-    auto conv = proj_obj_crs_get_coordoperation(
-        m_ctxt, crs, &methodName, &methodAuthorityName, &methodCode);
-    ASSERT_NE(conv, nullptr);
-    ObjectKeeper keeper_conv(conv);
+    EXPECT_TRUE(proj_coordoperation_get_method_info(
+        m_ctxt, conv, &methodName, &methodAuthorityName, &methodCode));
 
     ASSERT_NE(methodName, nullptr);
     ASSERT_NE(methodAuthorityName, nullptr);
@@ -1069,8 +1074,7 @@ TEST_F(CApi, transformation_from_boundCRS) {
     ASSERT_NE(crs, nullptr);
     ObjectKeeper keeper(crs);
 
-    auto transf =
-        proj_obj_crs_get_coordoperation(m_ctxt, crs, nullptr, nullptr, nullptr);
+    auto transf = proj_obj_crs_get_coordoperation(m_ctxt, crs);
     ASSERT_NE(transf, nullptr);
     ObjectKeeper keeper_transf(transf);
 }
@@ -2536,8 +2540,7 @@ TEST_F(CApi, proj_obj_convert_conversion_to_other_method) {
                 m_ctxt, projCRS, EPSG_CODE_METHOD_MERCATOR_VARIANT_B, nullptr),
             nullptr);
 
-        auto conv_in_proj = proj_obj_crs_get_coordoperation(
-            m_ctxt, projCRS, nullptr, nullptr, nullptr);
+        auto conv_in_proj = proj_obj_crs_get_coordoperation(m_ctxt, projCRS);
         ObjectKeeper keeper_conv_in_proj(conv_in_proj);
         ASSERT_NE(conv_in_proj, nullptr);