Merge pull request #1839 from rouault/rfc4_utf8

[RFC4_dev] Use Win32 Unicode APIs and expect all strings to be UTF-8 (fixes #1765)

9 files changed, 470 insertions, 20 deletions

diff --git a/test/cli/ntv2_out.dist b/test/cli/ntv2_out.dist
index 650a69d8..ce866f37 100644
--- a/test/cli/ntv2_out.dist
+++ b/test/cli/ntv2_out.dist
@@ -12,3 +12,11 @@ Try with NTv2 and NTv1 together ... falls back to NTv1
 ##############################################################
 Switching between NTv2 subgrids
 -112.5839956 49.4914451 0	-112.58307487	49.49145197 0.00000000
+##############################################################
+Interpolating very close (and sometimes a bit outside) to the edges a NTv2 subgrid (#209)
+-115.58333333 51.25000000 0	-115.58228512	51.24997866 0.00000000
+-115.58333333 51.25000010 0	-115.58228512	51.24997876 0.00000000
+-115.58333334 51.25000000 0	-115.58228513	51.24997866 0.00000000
+-115.49166667 51.07500000 0	-115.49062909	51.07497666 0.00000000
+-115.49166668 51.07500000 0	-115.49062910	51.07497666 0.00000000
+-115.49166667 51.07499990 0	-115.49062909	51.07497656 0.00000000
diff --git a/test/cli/td_out.dist b/test/cli/td_out.dist
index 82b64321..76c6e6ec 100644
--- a/test/cli/td_out.dist
+++ b/test/cli/td_out.dist
@@ -21,7 +21,7 @@ edge or even a wee bit outside (#141).
 -5.5001 52.0	-5.500100000000	52.000000000000 0.000000000000
 -5.5 52.0	-5.498893534472	52.000109529716 0.000000000000
 -5.5000000000001 52.0000000000001	-5.498893534472	52.000109529717 0.000000000000
--5.4999 51.9999	-5.498793541695	52.000009529743 0.000000000000
+-5.4999 51.9999	-5.498793593803	52.000009531513 0.000000000000
 -5.5001 52.0	-5.500100000000	52.000000000000 0.000000000000
 ##############################################################
 NAD27 -> NAD83: 1st through ntv1, 2nd through conus
diff --git a/test/cli/testntv2 b/test/cli/testntv2
index 2a31304e..d15ad7aa 100755
--- a/test/cli/testntv2
+++ b/test/cli/testntv2
@@ -60,6 +60,17 @@ $EXE +proj=latlong +datum=NAD83 +to +proj=latlong +ellps=clrk66 +nadgrids=ntv2_0
 -112.5839956 49.4914451 0
 EOF
 
+echo "##############################################################" >> ${OUT}
+echo "Interpolating very close (and sometimes a bit outside) to the edges a NTv2 subgrid (#209)" >> ${OUT}
+$EXE +proj=latlong +datum=NAD83 +to +proj=latlong +ellps=clrk66 +nadgrids=ntv2_0.gsb -E -d 8 >>${OUT} <<EOF
+-115.58333333 51.25000000 0
+-115.58333333 51.25000010 0
+-115.58333334 51.25000000 0
+-115.49166667 51.07500000 0
+-115.49166668 51.07500000 0
+-115.49166667 51.07499990 0
+EOF
+
 #
 ##############################################################################
 # Done! 
diff --git a/test/gie/geotiff_grids.gie b/test/gie/geotiff_grids.gie
index 85c0cbe9..62a5b16d 100644
--- a/test/gie/geotiff_grids.gie
+++ b/test/gie/geotiff_grids.gie
@@ -277,6 +277,20 @@ accept     -80.5041667       44.5458333        0
 expect     -80.50401615833   44.5458827236     0
 -------------------------------------------------------------------------------
 
+# Check a nested grid of a nested grid only based on spatial extent analysis
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_with_two_level_of_subgrids_no_grid_name.tif
+-------------------------------------------------------------------------------
+accept      -45.0              22.5
+accept      -44.9983333334     22.5013888889
+
+# Check a nested grid of a nested grid only based on spatial extent analysis
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_hgrid_with_two_level_of_subgrids_no_grid_name.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      -45.0              22.5             0
+accept      -45.0              22.5             5
+
 -------------------------------------------------------------------------------
 operation   +proj=hgridshift +grids=tests/test_vgrid.tif
 -------------------------------------------------------------------------------
diff --git a/test/unit/CMakeLists.txt b/test/unit/CMakeLists.txt
index e1eefcf0..e14d4c70 100644
--- a/test/unit/CMakeLists.txt
+++ b/test/unit/CMakeLists.txt
@@ -128,14 +128,20 @@ add_executable(proj_test_cpp_api
   test_operation.cpp
   test_datum.cpp
   test_factory.cpp
-  test_c_api.cpp)
+  test_c_api.cpp
+  test_grids.cpp)
 target_link_libraries(proj_test_cpp_api
   GTest::gtest
   ${PROJ_LIBRARIES}
   ${SQLITE3_LIBRARY})
 add_test(NAME proj_test_cpp_api COMMAND proj_test_cpp_api)
-set_property(TEST proj_test_cpp_api
-        PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data")
+if(MSVC)
+    set_property(TEST proj_test_cpp_api
+            PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data\\;${PROJECT_SOURCE_DIR}/data")
+else()
+    set_property(TEST proj_test_cpp_api
+            PROPERTY ENVIRONMENT "PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES;PROJ_LIB=${PROJECT_BINARY_DIR}/data:${PROJECT_SOURCE_DIR}/data")
+endif()
 
 
 add_executable(gie_self_tests
diff --git a/test/unit/Makefile.am b/test/unit/Makefile.am
index 7ffb06ae..b7a26d4e 100644
--- a/test/unit/Makefile.am
+++ b/test/unit/Makefile.am
@@ -49,7 +49,7 @@ proj_context_test_LDADD = ../../src/libproj.la @GTEST_LIBS@
 proj_context_test-check: proj_context_test
 	PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES ./proj_context_test
 
-test_cpp_api_SOURCES = test_util.cpp test_common.cpp test_crs.cpp test_metadata.cpp test_io.cpp test_operation.cpp test_datum.cpp test_factory.cpp test_c_api.cpp main.cpp
+test_cpp_api_SOURCES = test_util.cpp test_common.cpp test_crs.cpp test_metadata.cpp test_io.cpp test_operation.cpp test_datum.cpp test_factory.cpp test_c_api.cpp test_grids.cpp main.cpp
 test_cpp_api_LDADD = ../../src/libproj.la @GTEST_LIBS@ @SQLITE3_LIBS@
 
 test_cpp_api-check: test_cpp_api
diff --git a/test/unit/test_c_api.cpp b/test/unit/test_c_api.cpp
index f87f6589..8871f679 100644
--- a/test/unit/test_c_api.cpp
+++ b/test/unit/test_c_api.cpp
@@ -4434,4 +4434,26 @@ TEST_F(CApi, proj_create_derived_geographic_crs) {
                                   "+o_lat_p=-2 +lon_0=3 +datum=WGS84 +no_defs "
                                   "+type=crs"));
 }
+
+// ---------------------------------------------------------------------------
+
+TEST_F(CApi, proj_context_set_sqlite3_vfs_name) {
+
+    PJ_CONTEXT *ctx = proj_context_create();
+    proj_log_func(ctx, nullptr, [](void *, int, const char *) -> void {});
+
+    // Set a dummy VFS and check it is taken into account
+    // (failure to open proj.db)
+    proj_context_set_sqlite3_vfs_name(ctx, "dummy_vfs_name");
+    ASSERT_EQ(proj_create(ctx, "EPSG:4326"), nullptr);
+
+    // Restore default VFS
+    proj_context_set_sqlite3_vfs_name(ctx, nullptr);
+    PJ *crs_4326 = proj_create(ctx, "EPSG:4326");
+    ASSERT_NE(crs_4326, nullptr);
+    proj_destroy(crs_4326);
+
+    proj_context_destroy(ctx);
+}
+
 } // namespace
diff --git a/test/unit/test_grids.cpp b/test/unit/test_grids.cpp
new file mode 100644
index 00000000..5240949e
--- /dev/null
+++ b/test/unit/test_grids.cpp
@@ -0,0 +1,227 @@
+/******************************************************************************
+ *
+ * Project:  PROJ
+ * Purpose:  Test grids.hpp
+ * Author:   Even Rouault <even dot rouault at spatialys dot com>
+ *
+ ******************************************************************************
+ * Copyright (c) 2020, Even Rouault <even dot rouault at spatialys dot com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ ****************************************************************************/
+
+#include "gtest_include.h"
+
+#include "grids.hpp"
+
+#include "proj_internal.h" // M_PI
+
+namespace {
+
+// ---------------------------------------------------------------------------
+
+class GridTest : public ::testing::Test {
+
+    static void DummyLogFunction(void *, int, const char *) {}
+
+  protected:
+    void SetUp() override {
+        m_ctxt = proj_context_create();
+        proj_log_func(m_ctxt, nullptr, DummyLogFunction);
+        m_ctxt2 = proj_context_create();
+        proj_log_func(m_ctxt2, nullptr, DummyLogFunction);
+    }
+
+    void TearDown() override {
+        proj_context_destroy(m_ctxt);
+        proj_context_destroy(m_ctxt2);
+    }
+
+    PJ_CONTEXT *m_ctxt = nullptr;
+    PJ_CONTEXT *m_ctxt2 = nullptr;
+};
+
+// ---------------------------------------------------------------------------
+
+TEST_F(GridTest, VerticalShiftGridSet_null) {
+    auto gridSet = NS_PROJ::VerticalShiftGridSet::open(m_ctxt, "null");
+    ASSERT_NE(gridSet, nullptr);
+    auto grid = gridSet->gridAt(0.0, 0.0);
+    ASSERT_NE(grid, nullptr);
+    EXPECT_EQ(grid->width(), 3);
+    EXPECT_EQ(grid->height(), 3);
+    EXPECT_EQ(grid->extentAndRes().westLon, -M_PI);
+    EXPECT_TRUE(grid->isNullGrid());
+    EXPECT_FALSE(grid->hasChanged());
+    float out = -1.0f;
+    EXPECT_TRUE(grid->valueAt(0, 0, out));
+    EXPECT_EQ(out, 0.0f);
+    EXPECT_FALSE(grid->isNodata(0.0f, 0.0));
+    gridSet->reassign_context(m_ctxt2);
+    gridSet->reopen(m_ctxt2);
+}
+
+// ---------------------------------------------------------------------------
+
+TEST_F(GridTest, VerticalShiftGridSet_gtx) {
+    ASSERT_EQ(NS_PROJ::VerticalShiftGridSet::open(m_ctxt, "foobar"), nullptr);
+    auto gridSet =
+        NS_PROJ::VerticalShiftGridSet::open(m_ctxt, "tests/test_nodata.gtx");
+    ASSERT_NE(gridSet, nullptr);
+    ASSERT_EQ(gridSet->gridAt(-100, -100), nullptr);
+    auto grid = gridSet->gridAt(4.15 / 180 * M_PI, 52.15 / 180 * M_PI);
+    ASSERT_NE(grid, nullptr);
+    EXPECT_TRUE(grid->isNodata(-88.8888f, 1.0));
+    gridSet->reassign_context(m_ctxt2);
+    gridSet->reopen(m_ctxt2);
+    grid = gridSet->gridAt(4.15 / 180 * M_PI, 52.15 / 180 * M_PI);
+    EXPECT_NE(grid, nullptr);
+}
+
+// ---------------------------------------------------------------------------
+
+TEST_F(GridTest, HorizontalShiftGridSet_null) {
+    auto gridSet = NS_PROJ::HorizontalShiftGridSet::open(m_ctxt, "null");
+    ASSERT_NE(gridSet, nullptr);
+    auto grid = gridSet->gridAt(0.0, 0.0);
+    ASSERT_NE(grid, nullptr);
+    EXPECT_EQ(grid->width(), 3);
+    EXPECT_EQ(grid->height(), 3);
+    EXPECT_EQ(grid->extentAndRes().westLon, -M_PI);
+    EXPECT_TRUE(grid->isNullGrid());
+    EXPECT_FALSE(grid->hasChanged());
+    float out1 = -1.0f;
+    float out2 = -1.0f;
+    EXPECT_TRUE(grid->valueAt(0, 0, false, out1, out2));
+    EXPECT_EQ(out1, 0.0f);
+    EXPECT_EQ(out2, 0.0f);
+    gridSet->reassign_context(m_ctxt2);
+    gridSet->reopen(m_ctxt2);
+}
+
+// ---------------------------------------------------------------------------
+
+TEST_F(GridTest, HorizontalShiftGridSet_gtiff) {
+    auto gridSet =
+        NS_PROJ::HorizontalShiftGridSet::open(m_ctxt, "tests/test_hgrid.tif");
+    ASSERT_NE(gridSet, nullptr);
+    EXPECT_EQ(gridSet->format(), "gtiff");
+    EXPECT_TRUE(gridSet->name().find("tests/test_hgrid.tif") !=
+                std::string::npos)
+        << gridSet->name();
+    EXPECT_EQ(gridSet->grids().size(), 1U);
+    ASSERT_EQ(gridSet->gridAt(-100, -100), nullptr);
+    auto grid = gridSet->gridAt(5.5 / 180 * M_PI, 53.5 / 180 * M_PI);
+    ASSERT_NE(grid, nullptr);
+    EXPECT_EQ(grid->width(), 4);
+    EXPECT_EQ(grid->height(), 4);
+    EXPECT_EQ(grid->extentAndRes().westLon, 4.0 / 180 * M_PI);
+    EXPECT_FALSE(grid->isNullGrid());
+    EXPECT_FALSE(grid->hasChanged());
+    float out1 = -1.0f;
+    float out2 = -1.0f;
+    EXPECT_TRUE(grid->valueAt(0, 3, false, out1, out2));
+    EXPECT_EQ(out1, static_cast<float>(14400.0 / 3600. / 180 * M_PI));
+    EXPECT_EQ(out2, static_cast<float>(900.0 / 3600. / 180 * M_PI));
+    gridSet->reassign_context(m_ctxt2);
+    gridSet->reopen(m_ctxt2);
+    grid = gridSet->gridAt(5.5 / 180 * M_PI, 53.5 / 180 * M_PI);
+    EXPECT_NE(grid, nullptr);
+}
+
+// ---------------------------------------------------------------------------
+
+TEST_F(GridTest, GenericShiftGridSet_null) {
+    auto gridSet = NS_PROJ::GenericShiftGridSet::open(m_ctxt, "null");
+    ASSERT_NE(gridSet, nullptr);
+    auto grid = gridSet->gridAt(0.0, 0.0);
+    ASSERT_NE(grid, nullptr);
+    EXPECT_EQ(grid->width(), 3);
+    EXPECT_EQ(grid->height(), 3);
+    EXPECT_EQ(grid->extentAndRes().westLon, -M_PI);
+    EXPECT_TRUE(grid->isNullGrid());
+    EXPECT_FALSE(grid->hasChanged());
+    float out = -1.0f;
+    EXPECT_TRUE(grid->valueAt(0, 0, 0, out));
+    EXPECT_EQ(out, 0.0f);
+    EXPECT_EQ(grid->unit(0), "");
+    EXPECT_EQ(grid->description(0), "");
+    EXPECT_EQ(grid->metadataItem("foo"), "");
+    EXPECT_EQ(grid->samplesPerPixel(), 0);
+    gridSet->reassign_context(m_ctxt2);
+    gridSet->reopen(m_ctxt2);
+}
+
+// ---------------------------------------------------------------------------
+
+TEST_F(GridTest, GenericShiftGridSet_gtiff) {
+    ASSERT_EQ(NS_PROJ::GenericShiftGridSet::open(m_ctxt, "foobar"), nullptr);
+    auto gridSet = NS_PROJ::GenericShiftGridSet::open(
+        m_ctxt, "tests/nkgrf03vel_realigned_extract.tif");
+    ASSERT_NE(gridSet, nullptr);
+    ASSERT_EQ(gridSet->gridAt(-100, -100), nullptr);
+    auto grid = gridSet->gridAt(21.3333333 / 180 * M_PI, 63.0 / 180 * M_PI);
+    ASSERT_NE(grid, nullptr);
+    EXPECT_EQ(grid->width(), 5);
+    EXPECT_EQ(grid->height(), 5);
+    EXPECT_EQ(grid->extentAndRes().westLon, 21.0 / 180 * M_PI);
+    EXPECT_FALSE(grid->isNullGrid());
+    EXPECT_FALSE(grid->hasChanged());
+    float out = -1.0f;
+    EXPECT_FALSE(grid->valueAt(0, 0, grid->samplesPerPixel(), out));
+    EXPECT_EQ(grid->metadataItem("area_of_use"), "Nordic and Baltic countries");
+    EXPECT_EQ(grid->metadataItem("non_existing"), std::string());
+    EXPECT_EQ(grid->metadataItem("non_existing", 1), std::string());
+    EXPECT_EQ(grid->metadataItem("non_existing", 10), std::string());
+    gridSet->reassign_context(m_ctxt2);
+    gridSet->reopen(m_ctxt2);
+    grid = gridSet->gridAt(21.3333333 / 180 * M_PI, 63.0 / 180 * M_PI);
+    EXPECT_NE(grid, nullptr);
+}
+
+// ---------------------------------------------------------------------------
+
+TEST_F(GridTest, GenericShiftGridSet_gtiff_with_subgrid) {
+    auto gridSet = NS_PROJ::GenericShiftGridSet::open(
+        m_ctxt, "tests/test_hgrid_with_subgrid.tif");
+    ASSERT_NE(gridSet, nullptr);
+    ASSERT_EQ(gridSet->gridAt(-100, -100), nullptr);
+    auto grid =
+        gridSet->gridAt(-115.5416667 / 180 * M_PI, 51.1666667 / 180 * M_PI);
+    ASSERT_NE(grid, nullptr);
+    EXPECT_EQ(grid->width(), 11);
+    EXPECT_EQ(grid->height(), 21);
+    EXPECT_EQ(grid->metadataItem("grid_name"), "ALbanff");
+}
+
+// ---------------------------------------------------------------------------
+
+TEST_F(GridTest,
+       GenericShiftGridSet_gtiff_with_two_level_of_subgrids_no_grid_name) {
+    auto gridSet = NS_PROJ::GenericShiftGridSet::open(
+        m_ctxt, "tests/test_hgrid_with_two_level_of_subgrids_no_grid_name.tif");
+    ASSERT_NE(gridSet, nullptr);
+    ASSERT_EQ(gridSet->gridAt(-100, -100), nullptr);
+    auto grid = gridSet->gridAt(-45.5 / 180 * M_PI, 22.5 / 180 * M_PI);
+    ASSERT_NE(grid, nullptr);
+    EXPECT_EQ(grid->width(), 8);
+    EXPECT_EQ(grid->height(), 8);
+}
+
+} // namespace
diff --git a/test/unit/test_network.cpp b/test/unit/test_network.cpp
index 4e66d8c5..688e61e5 100644
--- a/test/unit/test_network.cpp
+++ b/test/unit/test_network.cpp
@@ -1574,27 +1574,45 @@ TEST(networking, download_whole_files) {
 
     proj_cleanup();
     unlink("proj_test_tmp/cache.db");
-    unlink("proj_test_tmp/ntf_r93.tif");
+    unlink("proj_test_tmp/dvr90.tif");
     rmdir("proj_test_tmp");
 
     putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY="));
     putenv(const_cast<char *>("PROJ_USER_WRITABLE_DIRECTORY=./proj_test_tmp"));
-    putenv(const_cast<char *>("PROJ_FULL_FILE_CHUNK_SIZE=30000"));
+    putenv(const_cast<char *>("PROJ_FULL_FILE_CHUNK_SIZE=100000"));
     auto ctx = proj_context_create();
     proj_context_set_enable_network(ctx, true);
 
-    ASSERT_TRUE(proj_is_download_needed(ctx, "ntf_r93.gsb", false));
+    ASSERT_TRUE(proj_is_download_needed(ctx, "dvr90.gtx", false));
 
-    ASSERT_TRUE(
-        proj_download_file(ctx, "ntf_r93.gsb", false, nullptr, nullptr));
+    ASSERT_TRUE(proj_download_file(ctx, "dvr90.gtx", false, nullptr, nullptr));
 
-    FILE *f = fopen("proj_test_tmp/ntf_r93.tif", "rb");
+    FILE *f = fopen("proj_test_tmp/dvr90.tif", "rb");
     ASSERT_NE(f, nullptr);
-    fseek(f, 0, SEEK_END);
-    ASSERT_EQ(ftell(f), 93581);
     fclose(f);
 
-    ASSERT_FALSE(proj_is_download_needed(ctx, "ntf_r93.gsb", false));
+    proj_context_set_enable_network(ctx, false);
+
+    const char *pipeline =
+        "+proj=pipeline "
+        "+step +proj=unitconvert +xy_in=deg +xy_out=rad "
+        "+step +proj=vgridshift +grids=dvr90.gtx +multiplier=1 "
+        "+step +proj=unitconvert +xy_in=rad +xy_out=deg";
+
+    auto P = proj_create(ctx, pipeline);
+    ASSERT_NE(P, nullptr);
+
+    double lon = 12;
+    double lat = 56;
+    double z = 0;
+    proj_trans_generic(P, PJ_FWD, &lon, sizeof(double), 1, &lat, sizeof(double),
+                       1, &z, sizeof(double), 1, nullptr, 0, 0);
+    EXPECT_NEAR(z, 36.5909996032715, 1e-10);
+    proj_destroy(P);
+
+    proj_context_set_enable_network(ctx, true);
+
+    ASSERT_FALSE(proj_is_download_needed(ctx, "dvr90.gtx", false));
 
     {
         sqlite3 *hDB = nullptr;
@@ -1613,7 +1631,7 @@ TEST(networking, download_whole_files) {
     }
 
     // If we ignore TTL settings, then no network access will be done
-    ASSERT_FALSE(proj_is_download_needed(ctx, "ntf_r93.gsb", true));
+    ASSERT_FALSE(proj_is_download_needed(ctx, "dvr90.gtx", true));
 
     {
         sqlite3 *hDB = nullptr;
@@ -1633,7 +1651,7 @@ TEST(networking, download_whole_files) {
     }
 
     // Should recheck from the CDN, update last_checked and do nothing
-    ASSERT_FALSE(proj_is_download_needed(ctx, "ntf_r93.gsb", false));
+    ASSERT_FALSE(proj_is_download_needed(ctx, "dvr90.gtx", false));
 
     {
         sqlite3 *hDB = nullptr;
@@ -1662,10 +1680,10 @@ TEST(networking, download_whole_files) {
         sqlite3_close(hDB);
     }
 
-    ASSERT_TRUE(proj_is_download_needed(ctx, "ntf_r93.gsb", false));
+    ASSERT_TRUE(proj_is_download_needed(ctx, "dvr90.gtx", false));
 
     // Redo download with a progress callback this time.
-    unlink("proj_test_tmp/ntf_r93.tif");
+    unlink("proj_test_tmp/dvr90.tif");
 
     const auto cbk = [](PJ_CONTEXT *l_ctx, double pct, void *user_data) -> int {
         auto vect = static_cast<std::vector<std::pair<PJ_CONTEXT *, double>> *>(
@@ -1675,7 +1693,7 @@ TEST(networking, download_whole_files) {
     };
 
     std::vector<std::pair<PJ_CONTEXT *, double>> vectPct;
-    ASSERT_TRUE(proj_download_file(ctx, "ntf_r93.gsb", false, cbk, &vectPct));
+    ASSERT_TRUE(proj_download_file(ctx, "dvr90.gtx", false, cbk, &vectPct));
     ASSERT_EQ(vectPct.size(), 3U);
     ASSERT_EQ(vectPct.back().first, ctx);
     ASSERT_EQ(vectPct.back().second, 1.0);
@@ -1685,7 +1703,151 @@ TEST(networking, download_whole_files) {
     putenv(const_cast<char *>("PROJ_USER_WRITABLE_DIRECTORY="));
     putenv(const_cast<char *>("PROJ_FULL_FILE_CHUNK_SIZE="));
     unlink("proj_test_tmp/cache.db");
-    unlink("proj_test_tmp/ntf_r93.tif");
+    unlink("proj_test_tmp/dvr90.tif");
+    rmdir("proj_test_tmp");
+}
+
+// ---------------------------------------------------------------------------
+
+TEST(networking, file_api) {
+    if (!networkAccessOK) {
+        return;
+    }
+
+    proj_cleanup();
+    unlink("proj_test_tmp/cache.db");
+    unlink("proj_test_tmp/dvr90.tif");
+    rmdir("proj_test_tmp");
+
+    putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY="));
+    putenv(const_cast<char *>("PROJ_USER_WRITABLE_DIRECTORY=./proj_test_tmp"));
+    putenv(const_cast<char *>("PROJ_FULL_FILE_CHUNK_SIZE=30000"));
+    auto ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+
+    struct UserData {
+        bool in_open = false;
+        bool in_read = false;
+        bool in_write = false;
+        bool in_seek = false;
+        bool in_tell = false;
+        bool in_close = false;
+        bool in_exists = false;
+        bool in_mkdir = false;
+        bool in_unlink = false;
+        bool in_rename = false;
+    };
+
+    struct PROJ_FILE_API api;
+    api.version = 1;
+    api.open_cbk = [](PJ_CONTEXT *, const char *filename,
+                      PROJ_OPEN_ACCESS access,
+                      void *user_data) -> PROJ_FILE_HANDLE * {
+        static_cast<UserData *>(user_data)->in_open = true;
+        return reinterpret_cast<PROJ_FILE_HANDLE *>(fopen(
+            filename,
+            access == PROJ_OPEN_ACCESS_READ_ONLY
+                ? "rb"
+                : access == PROJ_OPEN_ACCESS_READ_UPDATE ? "r+b" : "w+b"));
+    };
+    api.read_cbk = [](PJ_CONTEXT *, PROJ_FILE_HANDLE *handle, void *buffer,
+                      size_t sizeBytes, void *user_data) -> size_t {
+        static_cast<UserData *>(user_data)->in_read = true;
+        return fread(buffer, 1, sizeBytes, reinterpret_cast<FILE *>(handle));
+    };
+    api.write_cbk = [](PJ_CONTEXT *, PROJ_FILE_HANDLE *handle,
+                       const void *buffer, size_t sizeBytes,
+                       void *user_data) -> size_t {
+        static_cast<UserData *>(user_data)->in_write = true;
+        return fwrite(buffer, 1, sizeBytes, reinterpret_cast<FILE *>(handle));
+    };
+    api.seek_cbk = [](PJ_CONTEXT *, PROJ_FILE_HANDLE *handle, long long offset,
+                      int whence, void *user_data) -> int {
+        static_cast<UserData *>(user_data)->in_seek = true;
+        return fseek(reinterpret_cast<FILE *>(handle),
+                     static_cast<long>(offset), whence) == 0;
+    };
+    api.tell_cbk = [](PJ_CONTEXT *, PROJ_FILE_HANDLE *handle,
+                      void *user_data) -> unsigned long long {
+        static_cast<UserData *>(user_data)->in_tell = true;
+        return ftell(reinterpret_cast<FILE *>(handle));
+    };
+    api.close_cbk = [](PJ_CONTEXT *, PROJ_FILE_HANDLE *handle,
+                       void *user_data) -> void {
+        static_cast<UserData *>(user_data)->in_close = true;
+        fclose(reinterpret_cast<FILE *>(handle));
+    };
+    api.exists_cbk = [](PJ_CONTEXT *, const char *filename,
+                        void *user_data) -> int {
+        static_cast<UserData *>(user_data)->in_exists = true;
+        struct stat buf;
+        return stat(filename, &buf) == 0;
+    };
+    api.mkdir_cbk = [](PJ_CONTEXT *, const char *filename,
+                       void *user_data) -> int {
+        static_cast<UserData *>(user_data)->in_mkdir = true;
+#ifdef _WIN32
+        return mkdir(filename) == 0;
+#else
+        return mkdir(filename, 0755) == 0;
+#endif
+    };
+    api.unlink_cbk = [](PJ_CONTEXT *, const char *filename,
+                        void *user_data) -> int {
+        static_cast<UserData *>(user_data)->in_unlink = true;
+        return unlink(filename) == 0;
+    };
+    api.rename_cbk = [](PJ_CONTEXT *, const char *oldPath, const char *newPath,
+                        void *user_data) -> int {
+        static_cast<UserData *>(user_data)->in_rename = true;
+        return rename(oldPath, newPath) == 0;
+    };
+
+    UserData userData;
+    ASSERT_TRUE(proj_context_set_fileapi(ctx, &api, &userData));
+
+    ASSERT_TRUE(proj_is_download_needed(ctx, "dvr90.gtx", false));
+
+    ASSERT_TRUE(proj_download_file(ctx, "dvr90.gtx", false, nullptr, nullptr));
+
+    ASSERT_TRUE(userData.in_open);
+    ASSERT_FALSE(userData.in_read);
+    ASSERT_TRUE(userData.in_write);
+    ASSERT_TRUE(userData.in_close);
+    ASSERT_TRUE(userData.in_exists);
+    ASSERT_TRUE(userData.in_mkdir);
+    ASSERT_TRUE(userData.in_unlink);
+    ASSERT_TRUE(userData.in_rename);
+
+    proj_context_set_enable_network(ctx, false);
+
+    const char *pipeline =
+        "+proj=pipeline "
+        "+step +proj=unitconvert +xy_in=deg +xy_out=rad "
+        "+step +proj=vgridshift +grids=dvr90.gtx +multiplier=1 "
+        "+step +proj=unitconvert +xy_in=rad +xy_out=deg";
+
+    auto P = proj_create(ctx, pipeline);
+    ASSERT_NE(P, nullptr);
+
+    double lon = 12;
+    double lat = 56;
+    double z = 0;
+    proj_trans_generic(P, PJ_FWD, &lon, sizeof(double), 1, &lat, sizeof(double),
+                       1, &z, sizeof(double), 1, nullptr, 0, 0);
+    EXPECT_NEAR(z, 36.5909996032715, 1e-10);
+
+    proj_destroy(P);
+
+    ASSERT_TRUE(userData.in_read);
+    ASSERT_TRUE(userData.in_seek);
+
+    proj_context_destroy(ctx);
+    putenv(const_cast<char *>("PROJ_IGNORE_USER_WRITABLE_DIRECTORY=YES"));
+    putenv(const_cast<char *>("PROJ_USER_WRITABLE_DIRECTORY="));
+    putenv(const_cast<char *>("PROJ_FULL_FILE_CHUNK_SIZE="));
+    unlink("proj_test_tmp/cache.db");
+    unlink("proj_test_tmp/dvr90.tif");
     rmdir("proj_test_tmp");
 }