Merge pull request #1813 from rouault/rfc4_network

[RFC4_dev] Add networking capabilities

15 files changed, 1370 insertions, 44 deletions

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index ae721d46..a7aac755 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -10,6 +10,7 @@ proj_add_gie_test("GDA" "gie/GDA.gie")
 proj_add_gie_test("4D-API-cs2cs-style" "gie/4D-API_cs2cs-style.gie")
 proj_add_gie_test("DHDN_ETRS89" "gie/DHDN_ETRS89.gie")
 proj_add_gie_test("Unitconvert" "gie/unitconvert.gie")
+proj_add_gie_test("geotiff_grids" "gie/geotiff_grids.gie")
 
 # GIGS tests. Uncommented tests are expected to fail due to issues with
 # various projections. Should be investigated further and fixed.
diff --git a/test/cli/ntv2_out.dist b/test/cli/ntv2_out.dist
index 9a97f9cf..650a69d8 100644
--- a/test/cli/ntv2_out.dist
+++ b/test/cli/ntv2_out.dist
@@ -9,3 +9,6 @@ Try with NTv2 and NTv1 together ... falls back to NTv1
 99d00'00.000"W 65d00'00.000"N 0.0	99d0'1.5885"W	65d0'1.3482"N 0.000
 111d00'00.000"W 46d00'00.000"N 0.0	111d0'3.1897"W	45d59'59.7489"N 0.000
 111d00'00.000"W 47d30'00.000"N 0.0	111d0'2.7989"W	47d29'59.9896"N 0.000
+##############################################################
+Switching between NTv2 subgrids
+-112.5839956 49.4914451 0	-112.58307487	49.49145197 0.00000000
diff --git a/test/cli/test27 b/test/cli/test27
index bfc1cb0a..5825ed80 100755
--- a/test/cli/test27
+++ b/test/cli/test27
@@ -34,7 +34,7 @@ echo "Running ${0} using ${EXE}:"
 echo "============================================"
 
 OUT=proj_out27
-INIT_FILE=${PROJ_LIB}/nad27
+INIT_FILE=nad27
 #
 echo "doing tests into file ${OUT}, please wait"
 #
diff --git a/test/cli/test83 b/test/cli/test83
index cfb1365e..8c1293d0 100755
--- a/test/cli/test83
+++ b/test/cli/test83
@@ -35,7 +35,7 @@ echo "Running ${0} using ${EXE}:"
 echo "============================================"
 
 OUT=proj_out83
-INIT_FILE=${PROJ_LIB}/nad83
+INIT_FILE=nad83
 #
 echo "doing tests into file ${OUT}, please wait"
 #
diff --git a/test/cli/testdatumfile b/test/cli/testdatumfile
index 29a40876..9bd12ce4 100755
--- a/test/cli/testdatumfile
+++ b/test/cli/testdatumfile
@@ -27,7 +27,11 @@ echo "Running ${0} using ${EXE}:"
 echo "============================================"
 
 mkdir "dir with \" space"
-cp ${PROJ_LIB}/conus "dir with \" space/myconus"
+if test -f "${PROJ_LIB}/conus"; then
+    cp "${PROJ_LIB}/conus" "dir with \" space/myconus"
+else
+    cp "`dirname $0`/../../data/conus" "dir with \" space/myconus"
+fi
 
 OUT=td_out
 #EXE=../src/cs2cs
diff --git a/test/cli/testntv2 b/test/cli/testntv2
index 73371dbe..2a31304e 100755
--- a/test/cli/testntv2
+++ b/test/cli/testntv2
@@ -52,6 +52,14 @@ $EXE +proj=latlong +ellps=clrk66 +nadgrids=ntv2_0.gsb,ntv1_can.dat,conus \
 111d00'00.000"W 46d00'00.000"N 0.0
 111d00'00.000"W 47d30'00.000"N 0.0
 EOF
+
+echo "##############################################################" >> ${OUT}
+echo Switching between NTv2 subgrids >> ${OUT}
+# Initial guess is in ALraymnd, going to parent CAwest afterwards
+$EXE +proj=latlong +datum=NAD83 +to +proj=latlong +ellps=clrk66 +nadgrids=ntv2_0.gsb -E -d 8 >>${OUT} <<EOF
+-112.5839956 49.4914451 0
+EOF
+
 #
 ##############################################################################
 # Done! 
diff --git a/test/gie/4D-API_cs2cs-style.gie b/test/gie/4D-API_cs2cs-style.gie
index 8d541823..3e4b9d2c 100644
--- a/test/gie/4D-API_cs2cs-style.gie
+++ b/test/gie/4D-API_cs2cs-style.gie
@@ -442,7 +442,6 @@ Test bugfix of https://github.com/OSGeo/proj.4/issues/1002
 -------------------------------------------------------------------------------
 operation   +proj=latlong +ellps=WGS84 +geoidgrids=tests/test_nodata.gtx
 -------------------------------------------------------------------------------
-ignore      pjd_err_failed_to_load_grid
 accept      4.05        52.1        0
 expect      4.05        52.1        -10
 -------------------------------------------------------------------------------
@@ -452,7 +451,6 @@ Test null grid with vgridshift
 -------------------------------------------------------------------------------
 operation   proj=vgridshift  grids=tests/test_nodata.gtx,null  ellps=GRS80
 -------------------------------------------------------------------------------
-ignore      pjd_err_failed_to_load_grid
 accept      4.05        52.1        0
 expect      4.05        52.1        -10
 
diff --git a/test/gie/Makefile.am b/test/gie/Makefile.am
index 44facd87..ff333a14 100644
--- a/test/gie/Makefile.am
+++ b/test/gie/Makefile.am
@@ -9,7 +9,8 @@ EXTRA_DIST = 4D-API_cs2cs-style.gie \
 	ellipsoid.gie \
 	more_builtins.gie \
 	unitconvert.gie \
-	DHDN_ETRS89.gie
+	DHDN_ETRS89.gie \
+	geotiff_grids.gie
 
 PROJ_LIB ?= ../../data
 
@@ -40,4 +41,7 @@ unitconvert: unitconvert.gie
 DHDN_ETRS89: DHDN_ETRS89.gie
 	PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
 
-check-local: 4D-API-cs2cs-style GDA axisswap builtins deformation ellipsoid more_builtins unitconvert DHDN_ETRS89
+geotiff_grids: geotiff_grids.gie
+	PROJ_LIB=$(PROJ_LIB) $(GIEEXE) $<
+
+check-local: 4D-API-cs2cs-style GDA axisswap builtins deformation ellipsoid more_builtins unitconvert DHDN_ETRS89 geotiff_grids
diff --git a/test/gie/geotiff_grids.gie b/test/gie/geotiff_grids.gie
new file mode 100644
index 00000000..920fcf28
--- /dev/null
+++ b/test/gie/geotiff_grids.gie
@@ -0,0 +1,306 @@
+
+-------------------------------------------------------------------------------
+===============================================================================
+Test GeoTIFF grids
+===============================================================================
+
+<gie>
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_pixelispoint.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_pixelisarea.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_deflate.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_deflate_floatingpointpredictor.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_uint16.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_uint16_with_scale_offset.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_int16.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_int32.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_uint32.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_float64.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+# The overview should be ignored
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_with_overview.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_in_second_channel.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_bigtiff.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_bigendian.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_bigendian_bigtiff.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_bottomup_with_scale.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_bottomup_with_matrix.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_with_subgrid.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.5        52.5        0
+expect      4.5        52.5        11.5
+
+# In subgrid
+accept      5.5        53.5        0
+expect      5.5        53.5        110.0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_nodata.tif +multiplier=1
+-------------------------------------------------------------------------------
+accept      4.05        52.1        0
+expect      4.05        52.1        10
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_invalid_channel_type.tif +multiplier=1
+-------------------------------------------------------------------------------
+expect      failure errno failed_to_load_grid
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=vgridshift +grids=tests/test_vgrid_unsupported_byte.tif +multiplier=1
+-------------------------------------------------------------------------------
+expect      failure errno failed_to_load_grid
+-------------------------------------------------------------------------------
+
+
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_separate.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_strip.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_tiled.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_tiled_separate.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_positive_west.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_lon_shift_first.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_radian.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_degree.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+# The overview should be ignored
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_with_overview.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_extra_ifd_with_other_info.tif
+-------------------------------------------------------------------------------
+tolerance   2 mm
+accept      4.5        52.5        0
+expect      5.875      55.375      0
+-------------------------------------------------------------------------------
+
+# Subset of NTv2_0.gsb
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_with_subgrid.tif
+-------------------------------------------------------------------------------
+# In subgrid ALbanff, of parent CAwest
+accept     -115.5416667      51.1666667        0
+expect     -115.5427092888   51.1666899972     0
+
+# In subgrid ONtronto, of parent CAeast
+accept     -80.5041667       44.5458333        0
+expect     -80.50401615833   44.5458827236     0
+-------------------------------------------------------------------------------
+
+# Subset of NTv2_0.gsb
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_hgrid_with_subgrid_no_grid_name.tif
+-------------------------------------------------------------------------------
+# In subgrid ALbanff, of parent CAwest
+accept     -115.5416667      51.1666667        0
+expect     -115.5427092888   51.1666899972     0
+
+# In subgrid ONtronto, of parent CAeast
+accept     -80.5041667       44.5458333        0
+expect     -80.50401615833   44.5458827236     0
+-------------------------------------------------------------------------------
+
+-------------------------------------------------------------------------------
+operation   +proj=hgridshift +grids=tests/test_vgrid.tif
+-------------------------------------------------------------------------------
+expect      failure errno failed_to_load_grid
+-------------------------------------------------------------------------------
+
+
+# IGNF:LAMBE to IGNF:LAMB93 using xyzgridshift operation
+-------------------------------------------------------------------------------
+operation   +proj=pipeline
+                +step +inv +proj=lcc +lat_1=46.8 +lat_0=46.8 +lon_0=0
+                    +k_0=0.99987742 +x_0=600000 +y_0=2200000 +ellps=clrk80ign +pm=paris
+                +step +proj=push +v_3
+                +step +proj=cart +ellps=clrk80ign
+                +step +proj=xyzgridshift +grids=tests/subset_of_gr3df97a.tif +grid_ref=output_crs +ellps=GRS80
+                +step +proj=cart +ellps=GRS80 +inv
+                +step +proj=pop +v_3
+                +step +proj=lcc +lat_0=46.5 +lon_0=3 +lat_1=49 +lat_2=44
+                    +x_0=700000 +y_0=6600000 +ellps=GRS80
+-------------------------------------------------------------------------------
+tolerance 1 mm
+
+accept    814149.529   1887019.768   0
+expect    860690.804   6319036.849   0
+# If using ntf_r93.gsb, one gets: 860690.805   6319036.850
+
+roundtrip 1
+-------------------------------------------------------------------------------
+
+
+</gie>
diff --git a/test/unit/CMakeLists.txt b/test/unit/CMakeLists.txt
index 841d72b3..0dcafc85 100644
--- a/test/unit/CMakeLists.txt
+++ b/test/unit/CMakeLists.txt
@@ -147,3 +147,23 @@ target_link_libraries(gie_self_tests
 add_test(NAME gie_self_tests COMMAND gie_self_tests)
 set_property(TEST gie_self_tests
         PROPERTY ENVIRONMENT "PROJ_LIB=${PROJECT_BINARY_DIR}/data")
+
+
+add_executable(test_network
+  main.cpp
+  test_network.cpp)
+if(CURL_FOUND)
+  include_directories(${CURL_INCLUDE_DIR})
+  target_link_libraries(test_network ${CURL_LIBRARY})
+endif()
+target_link_libraries(test_network
+  GTest::gtest
+  ${PROJ_LIBRARIES})
+add_test(NAME test_network COMMAND test_network)
+if(MSVC)
+    set_property(TEST test_network
+        PROPERTY ENVIRONMENT "PROJ_LIB=${PROJECT_BINARY_DIR}/data\\;${PROJECT_SOURCE_DIR}/data;PROJ_SOURCE_DATA=${PROJECT_SOURCE_DIR}/data")
+else()
+    set_property(TEST test_network
+        PROPERTY ENVIRONMENT "PROJ_LIB=${PROJECT_BINARY_DIR}/data:${PROJECT_SOURCE_DIR}/data;PROJ_SOURCE_DATA=${PROJECT_SOURCE_DIR}/data")
+endif()
diff --git a/test/unit/Makefile.am b/test/unit/Makefile.am
index 57a03ca8..ce11ae4e 100644
--- a/test/unit/Makefile.am
+++ b/test/unit/Makefile.am
@@ -17,6 +17,7 @@ noinst_PROGRAMS += proj_context_test
 noinst_PROGRAMS += test_cpp_api
 noinst_PROGRAMS += gie_self_tests
 noinst_PROGRAMS += include_proj_h_from_c
+noinst_PROGRAMS += test_network
 
 pj_transform_test_SOURCES = pj_transform_test.cpp main.cpp
 pj_transform_test_LDADD = ../../src/libproj.la @GTEST_LIBS@
@@ -62,4 +63,11 @@ gie_self_tests-check: gie_self_tests
 
 include_proj_h_from_c_SOURCES = include_proj_h_from_c.c
 
-check-local: pj_transform_test-check pj_phi2_test-check proj_errno_string_test-check proj_angular_io_test-check proj_context_test-check test_cpp_api-check gie_self_tests-check
+test_network_SOURCES = test_network.cpp main.cpp
+test_network_CXXFLAGS = @CURL_CFLAGS@ @CURL_ENABLED_FLAGS@
+test_network_LDADD = ../../src/libproj.la @GTEST_LIBS@ @CURL_LIBS@
+
+test_network-check: test_network
+	PROJ_LIB=$(PROJ_LIB) PROJ_SOURCE_DATA=$(PROJ_LIB) ./test_network
+
+check-local: pj_transform_test-check pj_phi2_test-check proj_errno_string_test-check proj_angular_io_test-check proj_context_test-check test_cpp_api-check gie_self_tests-check test_network-check
diff --git a/test/unit/pj_transform_test.cpp b/test/unit/pj_transform_test.cpp
index b3a061b4..5ca8dcce 100644
--- a/test/unit/pj_transform_test.cpp
+++ b/test/unit/pj_transform_test.cpp
@@ -614,4 +614,95 @@ TEST(proj_api_h, pj_set_finder) {
     pj_set_finder(nullptr);
 }
 
+// ---------------------------------------------------------------------------
+
+TEST(proj_api_h, default_fileapi) {
+    auto ctx = pj_ctx_alloc();
+    auto fid = pj_open_lib(ctx, "proj.db", "rb");
+    ASSERT_NE(fid, nullptr);
+    char header[6];
+    ASSERT_EQ(pj_ctx_fread(ctx, header, 1, 6, fid), 6U);
+    ASSERT_TRUE(memcmp(header, "SQLite", 6) == 0);
+    ASSERT_EQ(pj_ctx_ftell(ctx, fid), 6);
+    ASSERT_EQ(pj_ctx_fseek(ctx, fid, 0, SEEK_SET), 0);
+    ASSERT_EQ(pj_ctx_ftell(ctx, fid), 0);
+    pj_ctx_fclose(ctx, fid);
+    pj_ctx_free(ctx);
+}
+
+// ---------------------------------------------------------------------------
+
+struct Spy {
+    bool gotInMyFOpen = false;
+    bool gotInMyFRead = false;
+    bool gotInMyFSeek = false;
+    bool gotInMyFTell = false;
+    bool gotInMyFClose = false;
+};
+
+struct MyFile {
+    FILE *fp;
+    Spy *spy;
+};
+
+static PAFile myFOpen(projCtx ctx, const char *filename, const char *access) {
+    FILE *fp = fopen(filename, access);
+    if (!fp)
+        return nullptr;
+    MyFile *myF = new MyFile;
+    myF->spy = (Spy *)pj_ctx_get_app_data(ctx);
+    myF->spy->gotInMyFOpen = true;
+    myF->fp = fp;
+    return reinterpret_cast<PAFile>(myF);
+}
+
+static size_t myFRead(void *buffer, size_t size, size_t nmemb, PAFile file) {
+    MyFile *myF = reinterpret_cast<MyFile *>(file);
+    myF->spy->gotInMyFRead = true;
+    return fread(buffer, size, nmemb, myF->fp);
+}
+
+static int myFSeek(PAFile file, long offset, int whence) {
+    MyFile *myF = reinterpret_cast<MyFile *>(file);
+    myF->spy->gotInMyFSeek = true;
+    return fseek(myF->fp, offset, whence);
+}
+
+static long myFTell(PAFile file) {
+    MyFile *myF = reinterpret_cast<MyFile *>(file);
+    myF->spy->gotInMyFTell = true;
+    return ftell(myF->fp);
+}
+
+static void myFClose(PAFile file) {
+    MyFile *myF = reinterpret_cast<MyFile *>(file);
+    myF->spy->gotInMyFClose = true;
+    fclose(myF->fp);
+    delete myF;
+}
+
+TEST(proj_api_h, custom_fileapi) {
+    auto ctx = pj_ctx_alloc();
+    Spy spy;
+    pj_ctx_set_app_data(ctx, &spy);
+    projFileAPI myAPI = {myFOpen, myFRead, myFSeek, myFTell, myFClose};
+    pj_ctx_set_fileapi(ctx, &myAPI);
+    EXPECT_EQ(pj_ctx_get_fileapi(ctx), &myAPI);
+    auto fid = pj_open_lib(ctx, "proj.db", "rb");
+    ASSERT_NE(fid, nullptr);
+    char header[6];
+    ASSERT_EQ(pj_ctx_fread(ctx, header, 1, 6, fid), 6U);
+    ASSERT_TRUE(memcmp(header, "SQLite", 6) == 0);
+    ASSERT_EQ(pj_ctx_ftell(ctx, fid), 6);
+    ASSERT_EQ(pj_ctx_fseek(ctx, fid, 0, SEEK_SET), 0);
+    ASSERT_EQ(pj_ctx_ftell(ctx, fid), 0);
+    pj_ctx_fclose(ctx, fid);
+    pj_ctx_free(ctx);
+    EXPECT_TRUE(spy.gotInMyFOpen);
+    EXPECT_TRUE(spy.gotInMyFRead);
+    EXPECT_TRUE(spy.gotInMyFSeek);
+    EXPECT_TRUE(spy.gotInMyFTell);
+    EXPECT_TRUE(spy.gotInMyFClose);
+}
+
 } // namespace
diff --git a/test/unit/test_factory.cpp b/test/unit/test_factory.cpp
index 93b2ef34..e342dad9 100644
--- a/test/unit/test_factory.cpp
+++ b/test/unit/test_factory.cpp
@@ -1617,34 +1617,34 @@ class FactoryWithTmpDatabase : public ::testing::Test {
                 DatabaseContext::create(m_ctxt), "OTHER");
             auto res = factoryOTHER->createFromCRSCodesWithIntermediates(
                 "NS_SOURCE", "SOURCE", "NS_TARGET", "TARGET", false, false,
-                false, {});
+                false, false, {});
             EXPECT_EQ(res.size(), 1U);
             EXPECT_TRUE(res.empty() ||
                         nn_dynamic_pointer_cast<ConcatenatedOperation>(res[0]));
 
             res = factoryOTHER->createFromCRSCodesWithIntermediates(
                 "NS_SOURCE", "SOURCE", "NS_TARGET", "TARGET", false, false,
-                false, {std::make_pair(std::string("NS_PIVOT"),
-                                       std::string("PIVOT"))});
+                false, false, {std::make_pair(std::string("NS_PIVOT"),
+                                              std::string("PIVOT"))});
             EXPECT_EQ(res.size(), 1U);
             EXPECT_TRUE(res.empty() ||
                         nn_dynamic_pointer_cast<ConcatenatedOperation>(res[0]));
 
             res = factoryOTHER->createFromCRSCodesWithIntermediates(
                 "NS_SOURCE", "SOURCE", "NS_TARGET", "TARGET", false, false,
-                false, {std::make_pair(std::string("NS_PIVOT"),
-                                       std::string("NOT_EXISTING"))});
+                false, false, {std::make_pair(std::string("NS_PIVOT"),
+                                              std::string("NOT_EXISTING"))});
             EXPECT_EQ(res.size(), 0U);
 
             res = factoryOTHER->createFromCRSCodesWithIntermediates(
                 "NS_SOURCE", "SOURCE", "NS_TARGET", "TARGET", false, false,
-                false,
+                false, false,
                 {std::make_pair(std::string("BAD_NS"), std::string("PIVOT"))});
             EXPECT_EQ(res.size(), 0U);
 
             res = factoryOTHER->createFromCRSCodesWithIntermediates(
                 "NS_TARGET", "TARGET", "NS_SOURCE", "SOURCE", false, false,
-                false, {});
+                false, false, {});
             EXPECT_EQ(res.size(), 1U);
             EXPECT_TRUE(res.empty() ||
                         nn_dynamic_pointer_cast<ConcatenatedOperation>(res[0]));
@@ -1654,7 +1654,7 @@ class FactoryWithTmpDatabase : public ::testing::Test {
                 DatabaseContext::create(m_ctxt), std::string());
             auto res = factory->createFromCRSCodesWithIntermediates(
                 "NS_SOURCE", "SOURCE", "NS_TARGET", "TARGET", false, false,
-                false, {});
+                false, false, {});
             EXPECT_EQ(res.size(), 1U);
             EXPECT_TRUE(res.empty() ||
                         nn_dynamic_pointer_cast<ConcatenatedOperation>(res[0]));
@@ -1833,7 +1833,7 @@ TEST(factory, AuthorityFactory_createFromCoordinateReferenceSystemCodes) {
     {
         // Test removal of superseded transform
         auto list = factory->createFromCoordinateReferenceSystemCodes(
-            "EPSG", "4179", "EPSG", "4258", false, false, true);
+            "EPSG", "4179", "EPSG", "4258", false, false, false, true);
         ASSERT_EQ(list.size(), 2U);
         // Romania has a larger area than Poland (given our approx formula)
         EXPECT_EQ(list[0]->getEPSGCode(), 15994); // Romania - 3m
@@ -1851,12 +1851,12 @@ TEST(
 
     {
         auto res = factory->createFromCoordinateReferenceSystemCodes(
-            "EPSG", "4326", "EPSG", "32631", false, false, false);
+            "EPSG", "4326", "EPSG", "32631", false, false, false, false);
         ASSERT_EQ(res.size(), 1U);
     }
     {
         auto res = factory->createFromCoordinateReferenceSystemCodes(
-            "EPSG", "4209", "EPSG", "4326", false, false, false);
+            "EPSG", "4209", "EPSG", "4326", false, false, false, false);
         EXPECT_TRUE(!res.empty());
         for (const auto &conv : res) {
             EXPECT_TRUE(conv->sourceCRS()->getEPSGCode() == 4209);
@@ -1889,7 +1889,8 @@ TEST_F(FactoryWithTmpDatabase,
         DatabaseContext::create(m_ctxt), std::string());
     {
         auto res = factoryGeneral->createFromCoordinateReferenceSystemCodes(
-            "OTHER", "OTHER_4326", "OTHER", "OTHER_32631", false, false, false);
+            "OTHER", "OTHER_4326", "OTHER", "OTHER_32631", false, false, false,
+            false);
         ASSERT_EQ(res.size(), 1U);
     }
 
@@ -1897,7 +1898,8 @@ TEST_F(FactoryWithTmpDatabase,
         AuthorityFactory::create(DatabaseContext::create(m_ctxt), "EPSG");
     {
         auto res = factoryEPSG->createFromCoordinateReferenceSystemCodes(
-            "OTHER", "OTHER_4326", "OTHER", "OTHER_32631", false, false, false);
+            "OTHER", "OTHER_4326", "OTHER", "OTHER_32631", false, false, false,
+            false);
         ASSERT_EQ(res.size(), 1U);
     }
 
@@ -1919,17 +1921,17 @@ TEST_F(FactoryWithTmpDatabase,
         << last_error();
     {
         auto res = factoryGeneral->createFromCoordinateReferenceSystemCodes(
-            "EPSG", "4326", "OTHER", "OTHER_4326", false, false, false);
+            "EPSG", "4326", "OTHER", "OTHER_4326", false, false, false, false);
         ASSERT_EQ(res.size(), 1U);
     }
     {
         auto res = factoryEPSG->createFromCoordinateReferenceSystemCodes(
-            "EPSG", "4326", "OTHER", "OTHER_4326", false, false, false);
+            "EPSG", "4326", "OTHER", "OTHER_4326", false, false, false, false);
         ASSERT_EQ(res.size(), 0U);
     }
     {
         auto res = factoryOTHER->createFromCoordinateReferenceSystemCodes(
-            "EPSG", "4326", "OTHER", "OTHER_4326", false, false, false);
+            "EPSG", "4326", "OTHER", "OTHER_4326", false, false, false, false);
         ASSERT_EQ(res.size(), 1U);
     }
 }
@@ -1982,7 +1984,7 @@ TEST_F(FactoryWithTmpDatabase,
     auto factoryOTHER =
         AuthorityFactory::create(DatabaseContext::create(m_ctxt), "OTHER");
     auto res = factoryOTHER->createFromCoordinateReferenceSystemCodes(
-        "EPSG", "4326", "EPSG", "4326", false, false, false);
+        "EPSG", "4326", "EPSG", "4326", false, false, false, false);
     ASSERT_EQ(res.size(), 3U);
     EXPECT_EQ(*(res[0]->name()->description()), "TRANSFORMATION_1M");
     EXPECT_EQ(*(res[1]->name()->description()), "TRANSFORMATION_10M");
@@ -2001,7 +2003,7 @@ TEST_F(
     auto factory = AuthorityFactory::create(DatabaseContext::create(m_ctxt),
                                             std::string());
     auto res = factory->createFromCRSCodesWithIntermediates(
-        "EPSG", "4326", "EPSG", "4326", false, false, false, {});
+        "EPSG", "4326", "EPSG", "4326", false, false, false, false, {});
     EXPECT_EQ(res.size(), 0U);
 }
 
@@ -2085,7 +2087,7 @@ TEST_F(FactoryWithTmpDatabase, AuthorityFactory_proj_based_transformation) {
     auto factoryOTHER =
         AuthorityFactory::create(DatabaseContext::create(m_ctxt), "OTHER");
     auto res = factoryOTHER->createFromCoordinateReferenceSystemCodes(
-        "EPSG", "4326", "EPSG", "4326", false, false, false);
+        "EPSG", "4326", "EPSG", "4326", false, false, false, false);
     ASSERT_EQ(res.size(), 1U);
     EXPECT_EQ(res[0]->nameStr(), "My PROJ string based op");
     EXPECT_EQ(res[0]->exportToPROJString(PROJStringFormatter::create().get()),
@@ -2146,7 +2148,7 @@ TEST_F(FactoryWithTmpDatabase, AuthorityFactory_wkt_based_transformation) {
     auto factoryOTHER =
         AuthorityFactory::create(DatabaseContext::create(m_ctxt), "OTHER");
     auto res = factoryOTHER->createFromCoordinateReferenceSystemCodes(
-        "EPSG", "4326", "EPSG", "4326", false, false, false);
+        "EPSG", "4326", "EPSG", "4326", false, false, false, false);
     ASSERT_EQ(res.size(), 1U);
     EXPECT_EQ(res[0]->nameStr(), "My WKT string based op");
     EXPECT_EQ(res[0]->exportToPROJString(PROJStringFormatter::create().get()),
@@ -2180,9 +2182,10 @@ TEST_F(FactoryWithTmpDatabase,
 
     auto factoryOTHER =
         AuthorityFactory::create(DatabaseContext::create(m_ctxt), "OTHER");
-    EXPECT_THROW(factoryOTHER->createFromCoordinateReferenceSystemCodes(
-                     "EPSG", "4326", "EPSG", "4326", false, false, false),
-                 FactoryException);
+    EXPECT_THROW(
+        factoryOTHER->createFromCoordinateReferenceSystemCodes(
+            "EPSG", "4326", "EPSG", "4326", false, false, false, false),
+        FactoryException);
 }
 
 // ---------------------------------------------------------------------------
@@ -2207,9 +2210,10 @@ TEST_F(FactoryWithTmpDatabase,
 
     auto factoryOTHER =
         AuthorityFactory::create(DatabaseContext::create(m_ctxt), "OTHER");
-    EXPECT_THROW(factoryOTHER->createFromCoordinateReferenceSystemCodes(
-                     "EPSG", "4326", "EPSG", "4326", false, false, false),
-                 FactoryException);
+    EXPECT_THROW(
+        factoryOTHER->createFromCoordinateReferenceSystemCodes(
+            "EPSG", "4326", "EPSG", "4326", false, false, false, false),
+        FactoryException);
 }
 
 // ---------------------------------------------------------------------------
@@ -2262,7 +2266,7 @@ TEST_F(FactoryWithTmpDatabase, lookForGridInfo) {
     bool openLicense = false;
     bool gridAvailable = false;
     EXPECT_TRUE(DatabaseContext::create(m_ctxt)->lookForGridInfo(
-        "PROJ_fake_grid", fullFilename, packageName, url, directDownload,
+        "PROJ_fake_grid", false, fullFilename, packageName, url, directDownload,
         openLicense, gridAvailable));
     EXPECT_TRUE(fullFilename.empty());
     EXPECT_TRUE(packageName.empty());
diff --git a/test/unit/test_network.cpp b/test/unit/test_network.cpp
new file mode 100644
index 00000000..5cd32f68
--- /dev/null
+++ b/test/unit/test_network.cpp
@@ -0,0 +1,879 @@
+/******************************************************************************
+ *
+ * Project:  PROJ
+ * Purpose:  Test networking
+ * Author:   Even Rouault <even dot rouault at spatialys dot com>
+ *
+ ******************************************************************************
+ * Copyright (c) 2019, 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 <memory>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "proj_internal.h"
+#include <proj.h>
+
+#ifdef CURL_ENABLED
+#include <curl/curl.h>
+#endif
+
+namespace {
+
+// ---------------------------------------------------------------------------
+
+#ifdef CURL_ENABLED
+
+static bool networkAccessOK = false;
+
+static size_t noop_curl_write_func(void *, size_t, size_t nmemb, void *) {
+    return nmemb;
+}
+
+TEST(networking, initial_check) {
+    CURL *hCurlHandle = curl_easy_init();
+    if (!hCurlHandle)
+        return;
+    curl_easy_setopt(hCurlHandle, CURLOPT_URL,
+                     "https://cdn.proj.org/ntf_r93.tif");
+
+    curl_easy_setopt(hCurlHandle, CURLOPT_RANGE, "0-1");
+    curl_easy_setopt(hCurlHandle, CURLOPT_WRITEFUNCTION, noop_curl_write_func);
+
+    curl_easy_perform(hCurlHandle);
+
+    long response_code = 0;
+    curl_easy_getinfo(hCurlHandle, CURLINFO_HTTP_CODE, &response_code);
+
+    curl_easy_cleanup(hCurlHandle);
+
+    networkAccessOK = (response_code == 206);
+    if (!networkAccessOK) {
+        fprintf(stderr, "network access not working");
+    }
+}
+
+#endif
+
+// ---------------------------------------------------------------------------
+
+static void silent_logger(void *, int, const char *) {}
+
+// ---------------------------------------------------------------------------
+
+TEST(networking, basic) {
+    const char *pipeline =
+        "+proj=pipeline "
+        "+step +proj=unitconvert +xy_in=deg +xy_out=rad "
+        "+step +proj=hgridshift +grids=https://cdn.proj.org/ntf_r93.tif "
+        "+step +proj=unitconvert +xy_in=rad +xy_out=deg";
+
+    // network access disabled by default
+    auto ctx = proj_context_create();
+    proj_log_func(ctx, nullptr, silent_logger);
+    auto P = proj_create(ctx, pipeline);
+    ASSERT_EQ(P, nullptr);
+    proj_context_destroy(ctx);
+
+#ifdef CURL_ENABLED
+    // enable through env variable
+    ctx = proj_context_create();
+    putenv(const_cast<char *>("PROJ_NETWORK=ON"));
+    P = proj_create(ctx, pipeline);
+    if (networkAccessOK) {
+        ASSERT_NE(P, nullptr);
+    }
+    proj_destroy(P);
+    proj_context_destroy(ctx);
+    putenv(const_cast<char *>("PROJ_NETWORK="));
+#endif
+
+    // still disabled
+    ctx = proj_context_create();
+    proj_log_func(ctx, nullptr, silent_logger);
+    P = proj_create(ctx, pipeline);
+    ASSERT_EQ(P, nullptr);
+    proj_context_destroy(ctx);
+
+    // enable through API
+    ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+    P = proj_create(ctx, pipeline);
+#ifdef CURL_ENABLED
+    if (networkAccessOK) {
+        ASSERT_NE(P, nullptr);
+    } else {
+        ASSERT_EQ(P, nullptr);
+        proj_context_destroy(ctx);
+        return;
+    }
+    double lon = 2;
+    double lat = 49;
+    proj_trans_generic(P, PJ_FWD, &lon, sizeof(double), 1, &lat, sizeof(double),
+                       1, nullptr, 0, 0, nullptr, 0, 0);
+    EXPECT_NEAR(lon, 1.9992776848, 1e-10);
+    EXPECT_NEAR(lat, 48.9999322600, 1e-10);
+
+    proj_destroy(P);
+#else
+    ASSERT_EQ(P, nullptr);
+#endif
+    proj_context_destroy(ctx);
+}
+
+// ---------------------------------------------------------------------------
+
+#ifdef CURL_ENABLED
+
+TEST(networking, curl_invalid_resource) {
+    auto ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+    proj_log_func(ctx, nullptr, silent_logger);
+    auto P = proj_create(
+        ctx, "+proj=hgridshift +grids=https://i_do_not.exist/my.tif");
+    proj_context_destroy(ctx);
+    ASSERT_EQ(P, nullptr);
+}
+#endif
+
+// ---------------------------------------------------------------------------
+
+struct Event {
+    virtual ~Event();
+    std::string type{};
+    PJ_CONTEXT *ctx = nullptr;
+};
+
+Event::~Event() = default;
+
+struct OpenEvent : public Event {
+    OpenEvent() { type = "OpenEvent"; }
+
+    std::string url{};
+    unsigned long long offset = 0;
+    size_t size_to_read = 0;
+    std::vector<unsigned char> response{};
+    std::string errorMsg{};
+    int file_id = 0;
+};
+
+struct CloseEvent : public Event {
+    CloseEvent() { type = "CloseEvent"; }
+
+    int file_id = 0;
+};
+
+struct GetHeaderValueEvent : public Event {
+    GetHeaderValueEvent() { type = "GetHeaderValueEvent"; }
+
+    int file_id = 0;
+    std::string key{};
+    std::string value{};
+};
+
+struct ReadRangeEvent : public Event {
+    ReadRangeEvent() { type = "ReadRangeEvent"; }
+
+    unsigned long long offset = 0;
+    size_t size_to_read = 0;
+    std::vector<unsigned char> response{};
+    std::string errorMsg{};
+    int file_id = 0;
+};
+
+struct File {};
+
+struct ExchangeWithCallback {
+    std::vector<std::unique_ptr<Event>> events{};
+    size_t nextEvent = 0;
+    bool error = false;
+    std::map<int, PROJ_NETWORK_HANDLE *> mapIdToHandle{};
+
+    bool allConsumedAndNoError() const {
+        return nextEvent == events.size() && !error;
+    }
+};
+
+static PROJ_NETWORK_HANDLE *open_cbk(PJ_CONTEXT *ctx, const char *url,
+                                     unsigned long long offset,
+                                     size_t size_to_read, void *buffer,
+                                     size_t *out_size_read,
+                                     size_t error_string_max_size,
+                                     char *out_error_string, void *user_data) {
+    auto exchange = static_cast<ExchangeWithCallback *>(user_data);
+    if (exchange->error)
+        return nullptr;
+    if (exchange->nextEvent >= exchange->events.size()) {
+        fprintf(stderr, "unexpected call to open(%s, %ld, %ld)\n", url,
+                (long)offset, (long)size_to_read);
+        exchange->error = true;
+        return nullptr;
+    }
+    auto openEvent =
+        dynamic_cast<OpenEvent *>(exchange->events[exchange->nextEvent].get());
+    if (!openEvent) {
+        fprintf(stderr, "unexpected call to open(%s, %ld, %ld). "
+                        "Was expecting a %s event\n",
+                url, (long)offset, (long)size_to_read,
+                exchange->events[exchange->nextEvent]->type.c_str());
+        exchange->error = true;
+        return nullptr;
+    }
+    exchange->nextEvent++;
+    if (openEvent->ctx != ctx || openEvent->url != url ||
+        openEvent->offset != offset ||
+        openEvent->size_to_read != size_to_read) {
+        fprintf(stderr, "wrong call to open(%s, %ld, %ld). Was expecting "
+                        "open(%s, %ld, %ld)\n",
+                url, (long)offset, (long)size_to_read, openEvent->url.c_str(),
+                (long)openEvent->offset, (long)openEvent->size_to_read);
+        exchange->error = true;
+        return nullptr;
+    }
+    if (!openEvent->errorMsg.empty()) {
+        snprintf(out_error_string, error_string_max_size, "%s",
+                 openEvent->errorMsg.c_str());
+        return nullptr;
+    }
+
+    memcpy(buffer, openEvent->response.data(), openEvent->response.size());
+    *out_size_read = openEvent->response.size();
+    auto handle = reinterpret_cast<PROJ_NETWORK_HANDLE *>(new File());
+    exchange->mapIdToHandle[openEvent->file_id] = handle;
+    return handle;
+}
+
+static void close_cbk(PJ_CONTEXT *ctx, PROJ_NETWORK_HANDLE *handle,
+                      void *user_data) {
+    auto exchange = static_cast<ExchangeWithCallback *>(user_data);
+    if (exchange->error)
+        return;
+    if (exchange->nextEvent >= exchange->events.size()) {
+        fprintf(stderr, "unexpected call to close()\n");
+        exchange->error = true;
+        return;
+    }
+    auto closeEvent =
+        dynamic_cast<CloseEvent *>(exchange->events[exchange->nextEvent].get());
+    if (!closeEvent) {
+        fprintf(stderr, "unexpected call to close(). "
+                        "Was expecting a %s event\n",
+                exchange->events[exchange->nextEvent]->type.c_str());
+        exchange->error = true;
+        return;
+    }
+    if (closeEvent->ctx != ctx) {
+        fprintf(stderr, "close() called with bad context\n");
+        exchange->error = true;
+        return;
+    }
+    if (exchange->mapIdToHandle[closeEvent->file_id] != handle) {
+        fprintf(stderr, "close() called with bad handle\n");
+        exchange->error = true;
+        return;
+    }
+    exchange->nextEvent++;
+    delete reinterpret_cast<File *>(handle);
+}
+
+static const char *get_header_value_cbk(PJ_CONTEXT *ctx,
+                                        PROJ_NETWORK_HANDLE *handle,
+                                        const char *header_name,
+                                        void *user_data) {
+    auto exchange = static_cast<ExchangeWithCallback *>(user_data);
+    if (exchange->error)
+        return nullptr;
+    if (exchange->nextEvent >= exchange->events.size()) {
+        fprintf(stderr, "unexpected call to get_header_value()\n");
+        exchange->error = true;
+        return nullptr;
+    }
+    auto getHeaderValueEvent = dynamic_cast<GetHeaderValueEvent *>(
+        exchange->events[exchange->nextEvent].get());
+    if (!getHeaderValueEvent) {
+        fprintf(stderr, "unexpected call to get_header_value(). "
+                        "Was expecting a %s event\n",
+                exchange->events[exchange->nextEvent]->type.c_str());
+        exchange->error = true;
+        return nullptr;
+    }
+    if (getHeaderValueEvent->ctx != ctx) {
+        fprintf(stderr, "get_header_value() called with bad context\n");
+        exchange->error = true;
+        return nullptr;
+    }
+    if (getHeaderValueEvent->key != header_name) {
+        fprintf(stderr, "wrong call to get_header_value(%s). Was expecting "
+                        "get_header_value(%s)\n",
+                header_name, getHeaderValueEvent->key.c_str());
+        exchange->error = true;
+        return nullptr;
+    }
+    if (exchange->mapIdToHandle[getHeaderValueEvent->file_id] != handle) {
+        fprintf(stderr, "get_header_value() called with bad handle\n");
+        exchange->error = true;
+        return nullptr;
+    }
+    exchange->nextEvent++;
+    return getHeaderValueEvent->value.c_str();
+}
+
+static size_t read_range_cbk(PJ_CONTEXT *ctx, PROJ_NETWORK_HANDLE *handle,
+                             unsigned long long offset, size_t size_to_read,
+                             void *buffer, size_t error_string_max_size,
+                             char *out_error_string, void *user_data) {
+    auto exchange = static_cast<ExchangeWithCallback *>(user_data);
+    if (exchange->error)
+        return 0;
+    if (exchange->nextEvent >= exchange->events.size()) {
+        fprintf(stderr, "unexpected call to read_range(%ld, %ld)\n",
+                (long)offset, (long)size_to_read);
+        exchange->error = true;
+        return 0;
+    }
+    auto readRangeEvent = dynamic_cast<ReadRangeEvent *>(
+        exchange->events[exchange->nextEvent].get());
+    if (!readRangeEvent) {
+        fprintf(stderr, "unexpected call to read_range(). "
+                        "Was expecting a %s event\n",
+                exchange->events[exchange->nextEvent]->type.c_str());
+        exchange->error = true;
+        return 0;
+    }
+    if (exchange->mapIdToHandle[readRangeEvent->file_id] != handle) {
+        fprintf(stderr, "read_range() called with bad handle\n");
+        exchange->error = true;
+        return 0;
+    }
+    if (readRangeEvent->ctx != ctx || readRangeEvent->offset != offset ||
+        readRangeEvent->size_to_read != size_to_read) {
+        fprintf(stderr, "wrong call to read_range(%ld, %ld). Was expecting "
+                        "read_range(%ld, %ld)\n",
+                (long)offset, (long)size_to_read, (long)readRangeEvent->offset,
+                (long)readRangeEvent->size_to_read);
+        exchange->error = true;
+        return 0;
+    }
+    exchange->nextEvent++;
+    if (!readRangeEvent->errorMsg.empty()) {
+        snprintf(out_error_string, error_string_max_size, "%s",
+                 readRangeEvent->errorMsg.c_str());
+        return 0;
+    }
+    memcpy(buffer, readRangeEvent->response.data(),
+           readRangeEvent->response.size());
+    return readRangeEvent->response.size();
+}
+
+TEST(networking, custom) {
+    auto ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+    ExchangeWithCallback exchange;
+    ASSERT_TRUE(proj_context_set_network_callbacks(ctx, open_cbk, close_cbk,
+                                                   get_header_value_cbk,
+                                                   read_range_cbk, &exchange));
+
+    {
+        std::unique_ptr<OpenEvent> event(new OpenEvent());
+        event->ctx = ctx;
+        event->url = "https://foo/my.tif";
+        event->offset = 0;
+        event->size_to_read = 16384;
+        event->response.resize(16384);
+        event->file_id = 1;
+
+        const char *proj_source_data = getenv("PROJ_SOURCE_DATA");
+        ASSERT_TRUE(proj_source_data != nullptr);
+        std::string filename(proj_source_data);
+        filename += "/tests/egm96_15_uncompressed_truncated.tif";
+        FILE *f = fopen(filename.c_str(), "rb");
+        ASSERT_TRUE(f != nullptr);
+        ASSERT_EQ(fread(&event->response[0], 1, 956, f), 956U);
+        fclose(f);
+        exchange.events.emplace_back(std::move(event));
+    }
+    {
+        std::unique_ptr<GetHeaderValueEvent> event(new GetHeaderValueEvent());
+        event->ctx = ctx;
+        event->key = "Content-Range";
+        event->value = "dummy"; // dummy value: not used
+        event->file_id = 1;
+        exchange.events.emplace_back(std::move(event));
+    }
+    {
+        std::unique_ptr<CloseEvent> event(new CloseEvent());
+        event->ctx = ctx;
+        event->file_id = 1;
+        exchange.events.emplace_back(std::move(event));
+    }
+
+    auto P = proj_create(
+        ctx, "+proj=vgridshift +grids=https://foo/my.tif +multiplier=1");
+
+    ASSERT_NE(P, nullptr);
+    ASSERT_TRUE(exchange.allConsumedAndNoError());
+
+    {
+        std::unique_ptr<OpenEvent> event(new OpenEvent());
+        event->ctx = ctx;
+        event->url = "https://foo/my.tif";
+        event->offset = 524288;
+        event->size_to_read = 278528;
+        event->response.resize(278528);
+        event->file_id = 2;
+        float f = 1.25;
+        for (size_t i = 0; i < 278528 / sizeof(float); i++) {
+            memcpy(&event->response[i * sizeof(float)], &f, sizeof(float));
+        }
+        exchange.events.emplace_back(std::move(event));
+    }
+
+    {
+        double lon = 2 / 180. * M_PI;
+        double lat = 49 / 180. * M_PI;
+        double z = 0;
+        ASSERT_EQ(proj_trans_generic(P, PJ_FWD, &lon, sizeof(double), 1, &lat,
+                                     sizeof(double), 1, &z, sizeof(double), 1,
+                                     nullptr, 0, 0),
+                  1U);
+        EXPECT_EQ(z, 1.25);
+    }
+
+    ASSERT_TRUE(exchange.allConsumedAndNoError());
+
+    {
+        std::unique_ptr<ReadRangeEvent> event(new ReadRangeEvent());
+        event->ctx = ctx;
+        event->offset = 3670016;
+        event->size_to_read = 278528;
+        event->response.resize(278528);
+        event->file_id = 2;
+        float f = 2.25;
+        for (size_t i = 0; i < 278528 / sizeof(float); i++) {
+            memcpy(&event->response[i * sizeof(float)], &f, sizeof(float));
+        }
+        exchange.events.emplace_back(std::move(event));
+    }
+
+    {
+        double lon = 2 / 180. * M_PI;
+        double lat = -49 / 180. * M_PI;
+        double z = 0;
+        ASSERT_EQ(proj_trans_generic(P, PJ_FWD, &lon, sizeof(double), 1, &lat,
+                                     sizeof(double), 1, &z, sizeof(double), 1,
+                                     nullptr, 0, 0),
+                  1U);
+        EXPECT_EQ(z, 2.25);
+    }
+    {
+        std::unique_ptr<CloseEvent> event(new CloseEvent());
+        event->ctx = ctx;
+        event->file_id = 2;
+        exchange.events.emplace_back(std::move(event));
+    }
+    proj_destroy(P);
+
+    ASSERT_TRUE(exchange.allConsumedAndNoError());
+
+    // Once again ! No network access
+
+    P = proj_create(ctx,
+                    "+proj=vgridshift +grids=https://foo/my.tif +multiplier=1");
+    ASSERT_NE(P, nullptr);
+
+    {
+        double lon = 2 / 180. * M_PI;
+        double lat = 49 / 180. * M_PI;
+        double z = 0;
+        ASSERT_EQ(proj_trans_generic(P, PJ_FWD, &lon, sizeof(double), 1, &lat,
+                                     sizeof(double), 1, &z, sizeof(double), 1,
+                                     nullptr, 0, 0),
+                  1U);
+        EXPECT_EQ(z, 1.25);
+    }
+
+    proj_destroy(P);
+
+    ASSERT_TRUE(exchange.allConsumedAndNoError());
+
+    proj_context_destroy(ctx);
+}
+
+// ---------------------------------------------------------------------------
+
+TEST(networking, getfilesize) {
+    auto ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+    ExchangeWithCallback exchange;
+    ASSERT_TRUE(proj_context_set_network_callbacks(ctx, open_cbk, close_cbk,
+                                                   get_header_value_cbk,
+                                                   read_range_cbk, &exchange));
+
+    {
+        std::unique_ptr<OpenEvent> event(new OpenEvent());
+        event->ctx = ctx;
+        event->url = "https://foo/getfilesize.tif";
+        event->offset = 0;
+        event->size_to_read = 16384;
+        event->response.resize(16384);
+        event->file_id = 1;
+
+        const char *proj_source_data = getenv("PROJ_SOURCE_DATA");
+        ASSERT_TRUE(proj_source_data != nullptr);
+        std::string filename(proj_source_data);
+        filename += "/tests/test_vgrid_single_strip_truncated.tif";
+        FILE *f = fopen(filename.c_str(), "rb");
+        ASSERT_TRUE(f != nullptr);
+        ASSERT_EQ(fread(&event->response[0], 1, 550, f), 550U);
+        fclose(f);
+        exchange.events.emplace_back(std::move(event));
+    }
+    {
+        std::unique_ptr<GetHeaderValueEvent> event(new GetHeaderValueEvent());
+        event->ctx = ctx;
+        event->key = "Content-Range";
+        event->value = "bytes 0-16383/4153510";
+        event->file_id = 1;
+        exchange.events.emplace_back(std::move(event));
+    }
+    {
+        std::unique_ptr<CloseEvent> event(new CloseEvent());
+        event->ctx = ctx;
+        event->file_id = 1;
+        exchange.events.emplace_back(std::move(event));
+    }
+
+    auto P = proj_create(
+        ctx,
+        "+proj=vgridshift +grids=https://foo/getfilesize.tif +multiplier=1");
+
+    ASSERT_NE(P, nullptr);
+    ASSERT_TRUE(exchange.allConsumedAndNoError());
+
+    proj_destroy(P);
+
+    P = proj_create(
+        ctx,
+        "+proj=vgridshift +grids=https://foo/getfilesize.tif +multiplier=1");
+
+    ASSERT_NE(P, nullptr);
+    ASSERT_TRUE(exchange.allConsumedAndNoError());
+
+    proj_destroy(P);
+
+    proj_context_destroy(ctx);
+}
+
+// ---------------------------------------------------------------------------
+
+TEST(networking, simul_open_error) {
+    auto ctx = proj_context_create();
+    proj_log_func(ctx, nullptr, silent_logger);
+    proj_context_set_enable_network(ctx, true);
+    ExchangeWithCallback exchange;
+    ASSERT_TRUE(proj_context_set_network_callbacks(ctx, open_cbk, close_cbk,
+                                                   get_header_value_cbk,
+                                                   read_range_cbk, &exchange));
+
+    {
+        std::unique_ptr<OpenEvent> event(new OpenEvent());
+        event->ctx = ctx;
+        event->url = "https://foo/open_error.tif";
+        event->offset = 0;
+        event->size_to_read = 16384;
+        event->errorMsg = "Cannot open file";
+        event->file_id = 1;
+
+        exchange.events.emplace_back(std::move(event));
+    }
+
+    auto P = proj_create(
+        ctx,
+        "+proj=vgridshift +grids=https://foo/open_error.tif +multiplier=1");
+
+    ASSERT_EQ(P, nullptr);
+    ASSERT_TRUE(exchange.allConsumedAndNoError());
+
+    proj_context_destroy(ctx);
+}
+
+// ---------------------------------------------------------------------------
+
+TEST(networking, simul_read_range_error) {
+    auto ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+    ExchangeWithCallback exchange;
+    ASSERT_TRUE(proj_context_set_network_callbacks(ctx, open_cbk, close_cbk,
+                                                   get_header_value_cbk,
+                                                   read_range_cbk, &exchange));
+
+    {
+        std::unique_ptr<OpenEvent> event(new OpenEvent());
+        event->ctx = ctx;
+        event->url = "https://foo/read_range_error.tif";
+        event->offset = 0;
+        event->size_to_read = 16384;
+        event->response.resize(16384);
+        event->file_id = 1;
+
+        const char *proj_source_data = getenv("PROJ_SOURCE_DATA");
+        ASSERT_TRUE(proj_source_data != nullptr);
+        std::string filename(proj_source_data);
+        filename += "/tests/egm96_15_uncompressed_truncated.tif";
+        FILE *f = fopen(filename.c_str(), "rb");
+        ASSERT_TRUE(f != nullptr);
+        ASSERT_EQ(fread(&event->response[0], 1, 956, f), 956U);
+        fclose(f);
+        exchange.events.emplace_back(std::move(event));
+    }
+    {
+        std::unique_ptr<GetHeaderValueEvent> event(new GetHeaderValueEvent());
+        event->ctx = ctx;
+        event->key = "Content-Range";
+        event->value = "dummy"; // dummy value: not used
+        event->file_id = 1;
+        exchange.events.emplace_back(std::move(event));
+    }
+    {
+        std::unique_ptr<CloseEvent> event(new CloseEvent());
+        event->ctx = ctx;
+        event->file_id = 1;
+        exchange.events.emplace_back(std::move(event));
+    }
+
+    auto P = proj_create(ctx, "+proj=vgridshift "
+                              "+grids=https://foo/read_range_error.tif "
+                              "+multiplier=1");
+
+    ASSERT_NE(P, nullptr);
+    ASSERT_TRUE(exchange.allConsumedAndNoError());
+
+    {
+        std::unique_ptr<OpenEvent> event(new OpenEvent());
+        event->ctx = ctx;
+        event->url = "https://foo/read_range_error.tif";
+        event->offset = 524288;
+        event->size_to_read = 278528;
+        event->response.resize(278528);
+        event->file_id = 2;
+        float f = 1.25;
+        for (size_t i = 0; i < 278528 / sizeof(float); i++) {
+            memcpy(&event->response[i * sizeof(float)], &f, sizeof(float));
+        }
+        exchange.events.emplace_back(std::move(event));
+    }
+
+    {
+        double lon = 2 / 180. * M_PI;
+        double lat = 49 / 180. * M_PI;
+        double z = 0;
+        ASSERT_EQ(proj_trans_generic(P, PJ_FWD, &lon, sizeof(double), 1, &lat,
+                                     sizeof(double), 1, &z, sizeof(double), 1,
+                                     nullptr, 0, 0),
+                  1U);
+        EXPECT_EQ(z, 1.25);
+    }
+
+    ASSERT_TRUE(exchange.allConsumedAndNoError());
+
+    {
+        std::unique_ptr<ReadRangeEvent> event(new ReadRangeEvent());
+        event->ctx = ctx;
+        event->offset = 3670016;
+        event->size_to_read = 278528;
+        event->errorMsg = "read range error";
+        event->file_id = 2;
+        exchange.events.emplace_back(std::move(event));
+    }
+
+    {
+        double lon = 2 / 180. * M_PI;
+        double lat = -49 / 180. * M_PI;
+        double z = 0;
+        proj_log_func(ctx, nullptr, silent_logger);
+        ASSERT_EQ(proj_trans_generic(P, PJ_FWD, &lon, sizeof(double), 1, &lat,
+                                     sizeof(double), 1, &z, sizeof(double), 1,
+                                     nullptr, 0, 0),
+                  1U);
+        EXPECT_EQ(z, HUGE_VAL);
+    }
+    {
+        std::unique_ptr<CloseEvent> event(new CloseEvent());
+        event->ctx = ctx;
+        event->file_id = 2;
+        exchange.events.emplace_back(std::move(event));
+    }
+    proj_destroy(P);
+
+    ASSERT_TRUE(exchange.allConsumedAndNoError());
+
+    proj_context_destroy(ctx);
+}
+
+// ---------------------------------------------------------------------------
+
+#ifdef CURL_ENABLED
+
+TEST(networking, curl_hgridshift) {
+    auto ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+
+    // NAD83 to NAD83(HARN) in West-Virginia. Using wvhpgn.tif
+    auto P = proj_create_crs_to_crs(ctx, "EPSG:4269", "EPSG:4152", nullptr);
+    ASSERT_NE(P, nullptr);
+
+    PJ_COORD c;
+    c.xyz.x = 40;  // lat
+    c.xyz.y = -80; // lon
+    c.xyz.z = 0;
+    c = proj_trans(P, PJ_FWD, c);
+
+    proj_assign_context(P, ctx); // (dummy) test context reassignment
+
+    proj_destroy(P);
+    proj_context_destroy(ctx);
+
+    EXPECT_NEAR(c.xyz.x, 39.99999839, 1e-8);
+    EXPECT_NEAR(c.xyz.y, -79.99999807, 1e-8);
+    EXPECT_NEAR(c.xyz.z, 0, 1e-2);
+}
+
+#endif
+
+// ---------------------------------------------------------------------------
+
+#ifdef CURL_ENABLED
+
+TEST(networking, curl_vgridshift) {
+    auto ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+
+    // WGS84 to EGM2008 height. Using egm08_25.tif
+    auto P =
+        proj_create_crs_to_crs(ctx, "EPSG:4326", "EPSG:4326+3855", nullptr);
+    ASSERT_NE(P, nullptr);
+
+    PJ_COORD c;
+    c.xyz.x = -30; // lat
+    c.xyz.y = 150; // lon
+    c.xyz.z = 0;
+    c = proj_trans(P, PJ_FWD, c);
+
+    proj_assign_context(P, ctx); // (dummy) test context reassignment
+
+    proj_destroy(P);
+    proj_context_destroy(ctx);
+
+    EXPECT_NEAR(c.xyz.x, -30, 1e-8);
+    EXPECT_NEAR(c.xyz.y, 150, 1e-8);
+    EXPECT_NEAR(c.xyz.z, -31.89, 1e-2);
+}
+
+#endif
+
+// ---------------------------------------------------------------------------
+
+#ifdef CURL_ENABLED
+
+TEST(networking, curl_vgridshift_vertcon) {
+    auto ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+
+    // NGVD29 to NAVD88 height. Using vertcone.tif
+    auto P = proj_create_crs_to_crs(ctx, "EPSG:4269+7968", "EPSG:4269+5703",
+                                    nullptr);
+    ASSERT_NE(P, nullptr);
+
+    PJ_COORD c;
+    c.xyz.x = 40;  // lat
+    c.xyz.y = -80; // lon
+    c.xyz.z = 0;
+    c = proj_trans(P, PJ_FWD, c);
+
+    proj_destroy(P);
+    proj_context_destroy(ctx);
+
+    EXPECT_NEAR(c.xyz.x, 40, 1e-8);
+    EXPECT_NEAR(c.xyz.y, -80, 1e-8);
+    EXPECT_NEAR(c.xyz.z, -0.15, 1e-2);
+}
+
+#endif
+
+// ---------------------------------------------------------------------------
+
+#ifdef CURL_ENABLED
+
+TEST(networking, network_endpoint_env_variable) {
+    putenv(const_cast<char *>("PROJ_NETWORK_ENDPOINT=http://0.0.0.0/"));
+    auto ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+
+    // NAD83 to NAD83(HARN) in West-Virginia. Using wvhpgn.tif
+    auto P = proj_create_crs_to_crs(ctx, "EPSG:4269", "EPSG:4152", nullptr);
+    ASSERT_NE(P, nullptr);
+
+    PJ_COORD c;
+    c.xyz.x = 40;  // lat
+    c.xyz.y = -80; // lon
+    c.xyz.z = 0;
+    c = proj_trans(P, PJ_FWD, c);
+    putenv(const_cast<char *>("PROJ_NETWORK_ENDPOINT="));
+
+    proj_destroy(P);
+    proj_context_destroy(ctx);
+
+    EXPECT_EQ(c.xyz.x, HUGE_VAL);
+}
+
+#endif
+
+// ---------------------------------------------------------------------------
+
+#ifdef CURL_ENABLED
+
+TEST(networking, network_endpoint_api) {
+    auto ctx = proj_context_create();
+    proj_context_set_enable_network(ctx, true);
+    proj_context_set_url_endpoint(ctx, "http://0.0.0.0");
+
+    // NAD83 to NAD83(HARN) in West-Virginia. Using wvhpgn.tif
+    auto P = proj_create_crs_to_crs(ctx, "EPSG:4269", "EPSG:4152", nullptr);
+    ASSERT_NE(P, nullptr);
+
+    PJ_COORD c;
+    c.xyz.x = 40;  // lat
+    c.xyz.y = -80; // lon
+    c.xyz.z = 0;
+    c = proj_trans(P, PJ_FWD, c);
+
+    proj_destroy(P);
+    proj_context_destroy(ctx);
+
+    EXPECT_EQ(c.xyz.x, HUGE_VAL);
+}
+
+#endif
+
+} // namespace
diff --git a/test/unit/test_operation.cpp b/test/unit/test_operation.cpp
index 9cde8822..753878c5 100644
--- a/test/unit/test_operation.cpp
+++ b/test/unit/test_operation.cpp
@@ -4789,7 +4789,7 @@ TEST(operation, geogCRS_to_geogCRS_context_concatenated_operation) {
 
     EXPECT_TRUE(nn_dynamic_pointer_cast<ConcatenatedOperation>(list[0]) !=
                 nullptr);
-    auto grids = list[0]->gridsNeeded(DatabaseContext::create());
+    auto grids = list[0]->gridsNeeded(DatabaseContext::create(), false);
     EXPECT_EQ(grids.size(), 1U);
 }
 
@@ -6402,7 +6402,7 @@ TEST(operation, transformation_height_to_PROJ_string) {
     EXPECT_EQ(transf->exportToPROJString(PROJStringFormatter::create().get()),
               "+proj=vgridshift +grids=egm08_25.gtx +multiplier=1");
 
-    auto grids = transf->gridsNeeded(DatabaseContext::create());
+    auto grids = transf->gridsNeeded(DatabaseContext::create(), false);
     ASSERT_EQ(grids.size(), 1U);
     auto gridDesc = *(grids.begin());
     EXPECT_EQ(gridDesc.shortName, "egm08_25.gtx");
@@ -6702,7 +6702,7 @@ TEST(operation, compoundCRS_with_boundGeogCRS_and_boundVerticalCRS_to_geogCRS) {
               "+step +proj=unitconvert +xy_in=rad +xy_out=deg "
               "+step +proj=axisswap +order=2,1");
 
-    auto grids = op->gridsNeeded(DatabaseContext::create());
+    auto grids = op->gridsNeeded(DatabaseContext::create(), false);
     EXPECT_EQ(grids.size(), 1U);
 
     auto opInverse = CoordinateOperationFactory::create()->createOperation(
@@ -8128,8 +8128,8 @@ TEST(operation, isPROJInstantiable) {
         auto transformation = Transformation::createGeocentricTranslations(
             PropertyMap(), GeographicCRS::EPSG_4269, GeographicCRS::EPSG_4326,
             1.0, 2.0, 3.0, {});
-        EXPECT_TRUE(
-            transformation->isPROJInstantiable(DatabaseContext::create()));
+        EXPECT_TRUE(transformation->isPROJInstantiable(
+            DatabaseContext::create(), false));
     }
 
     // Missing grid
@@ -8137,8 +8137,8 @@ TEST(operation, isPROJInstantiable) {
         auto transformation = Transformation::createNTv2(
             PropertyMap(), GeographicCRS::EPSG_4807, GeographicCRS::EPSG_4326,
             "foo.gsb", std::vector<PositionalAccuracyNNPtr>());
-        EXPECT_FALSE(
-            transformation->isPROJInstantiable(DatabaseContext::create()));
+        EXPECT_FALSE(transformation->isPROJInstantiable(
+            DatabaseContext::create(), false));
     }
 
     // Unsupported method
@@ -8149,8 +8149,8 @@ TEST(operation, isPROJInstantiable) {
                          PropertyMap(), std::vector<OperationParameterNNPtr>{}),
             std::vector<GeneralParameterValueNNPtr>{},
             std::vector<PositionalAccuracyNNPtr>{});
-        EXPECT_FALSE(
-            transformation->isPROJInstantiable(DatabaseContext::create()));
+        EXPECT_FALSE(transformation->isPROJInstantiable(
+            DatabaseContext::create(), false));
     }
 }