GDALBuildVRT(): in -separate mode, add support for sources such as ME…

…M dataset or non-materialized VRT files Similar to 13cfbf8 that applied only to non-separate mode
linhnv2801 · Mar 29, 2022 · 5dccc51 · 5dccc51
1 parent 67d0d23
commit 5dccc51
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Showing 2 changed files with 73 additions and 15 deletions.
diff --git a/apps/gdalbuildvrt_lib.cpp b/apps/gdalbuildvrt_lib.cpp
@@ -950,19 +950,34 @@ void VRTBuilder::CreateVRTSeparate(VRTDatasetH hVRTDS)
 
         GDALAddBand(hVRTDS, psDatasetProperties->firstBandType, nullptr);
 
-        GDALProxyPoolDatasetH hProxyDS =
-            GDALProxyPoolDatasetCreate(dsFileName,
-                                        psDatasetProperties->nRasterXSize,
-                                        psDatasetProperties->nRasterYSize,
-                                        GA_ReadOnly, TRUE, pszProjectionRef,
-                                        psDatasetProperties->adfGeoTransform);
-        reinterpret_cast<GDALProxyPoolDataset*>(hProxyDS)->
-                                        SetOpenOptions( papszOpenOptions );
-
-        GDALProxyPoolDatasetAddSrcBandDescription(hProxyDS,
-                                            psDatasetProperties->firstBandType,
-                                            psDatasetProperties->nBlockXSize,
-                                            psDatasetProperties->nBlockYSize);
+
+        GDALDatasetH hSourceDS;
+        bool bDropRef = false;
+        if( nSrcDSCount == nInputFiles &&
+            GDALGetDatasetDriver(pahSrcDS[i]) != nullptr &&
+            ( dsFileName[0] == '\0' || // could be a unnamed VRT file
+              EQUAL(GDALGetDescription(GDALGetDatasetDriver(pahSrcDS[i])), "MEM")) )
+        {
+            hSourceDS = pahSrcDS[i];
+        }
+        else
+        {
+            bDropRef = true;
+            GDALProxyPoolDatasetH hProxyDS =
+                GDALProxyPoolDatasetCreate(dsFileName,
+                                            psDatasetProperties->nRasterXSize,
+                                            psDatasetProperties->nRasterYSize,
+                                            GA_ReadOnly, TRUE, pszProjectionRef,
+                                            psDatasetProperties->adfGeoTransform);
+            hSourceDS = static_cast<GDALDatasetH>(hProxyDS);
+            reinterpret_cast<GDALProxyPoolDataset*>(hProxyDS)->
+                                            SetOpenOptions( papszOpenOptions );
+
+            GDALProxyPoolDatasetAddSrcBandDescription(hProxyDS,
+                                                psDatasetProperties->firstBandType,
+                                                psDatasetProperties->nBlockXSize,
+                                                psDatasetProperties->nBlockYSize);
+        }
 
         VRTSourcedRasterBandH hVRTBand =
                 static_cast<VRTSourcedRasterBandH>(GDALGetRasterBand(hVRTDS, iBand));
@@ -1015,7 +1030,7 @@ void VRTBuilder::CreateVRTSeparate(VRTDatasetH hVRTDS)
         if( pszResampling )
             poSimpleSource->SetResampling(pszResampling);
         poVRTBand->ConfigureSource( poSimpleSource,
-                                    static_cast<GDALRasterBand*>(GDALGetRasterBand(static_cast<GDALDatasetH>(hProxyDS), 1)),
+                                    static_cast<GDALRasterBand*>(GDALGetRasterBand(hSourceDS, 1)),
                                     FALSE,
                                     dfSrcXOff, dfSrcYOff,
                                     dfSrcXSize, dfSrcYSize,
@@ -1030,7 +1045,10 @@ void VRTBuilder::CreateVRTSeparate(VRTDatasetH hVRTDS)
 
         poVRTBand->AddSource( poSimpleSource );
 
-        GDALDereferenceDataset(hProxyDS);
+        if( bDropRef )
+        {
+            GDALDereferenceDataset(hSourceDS);
+        }
 
         iBand ++;
     }

diff --git a/autotest/utilities/test_gdalbuildvrt_lib.py b/autotest/utilities/test_gdalbuildvrt_lib.py
@@ -155,6 +155,46 @@ def get_vrt_of_vrt():
     scenario_1()
     scenario_2()
 
+
+###############################################################################
+# Test BuildVRT() with sources that can't be opened by name, in separate mode
+
+def test_gdalbuildvrt_lib_mem_sources_separate():
+
+    def create_sources():
+        src1_ds = gdal.GetDriverByName('MEM').Create('i_have_a_name_but_nobody_can_open_me_through_it', 1, 1)
+        src1_ds.SetGeoTransform([2,1,0,49,0,-1])
+        src1_ds.GetRasterBand(1).Fill(100)
+
+        src2_ds = gdal.GetDriverByName('MEM').Create('', 1, 1)
+        src2_ds.SetGeoTransform([2,1,0,49,0,-1])
+        src2_ds.GetRasterBand(1).Fill(200)
+
+        return src1_ds, src2_ds
+
+    def scenario_1():
+        src1_ds, src2_ds = create_sources()
+        vrt_ds = gdal.BuildVRT('', [src1_ds, src2_ds], options = '-separate')
+        vals = struct.unpack('B' * 2, vrt_ds.ReadRaster())
+        assert vals == (100, 200)
+
+        vrt_of_vrt_ds = gdal.BuildVRT('', [vrt_ds])
+        vals = struct.unpack('B' * 2, vrt_of_vrt_ds.ReadRaster())
+        assert vals == (100, 200)
+
+    # Alternate scenario where the Python objects of sources and intermediate
+    # VRT are no longer alive when the VRT of VRT is accessed
+    def scenario_2():
+        def get_vrt_of_vrt():
+            src1_ds, src2_ds = create_sources()
+            return gdal.BuildVRT('', [ gdal.BuildVRT('', [src1_ds, src2_ds], options = '-separate') ])
+        vrt_of_vrt_ds = get_vrt_of_vrt()
+        vals = struct.unpack('B' * 2, vrt_of_vrt_ds.ReadRaster())
+        assert vals == (100, 200)
+
+    scenario_1()
+    scenario_2()
+
 ###############################################################################
 # Test BuildVRT() with virtual overviews