External GridDefinition read fix

core/src/main/java/org/locationtech/proj4j/InvalidValueException.java

@@ -28,4 +28,8 @@ public class InvalidValueException extends Proj4jException {
 	public InvalidValueException(String message) {
 		super(message);
 	}
+
+	public InvalidValueException(String message, Exception cause) {
+		super(message, cause);
+	}
 }

core/src/main/java/org/locationtech/proj4j/Proj4jException.java

@@ -34,4 +34,8 @@ public Proj4jException() {
 	public Proj4jException(String message) {
 		super(message);
 	}
+
+	public Proj4jException(String message, Exception cause) {
+		super(message, cause);
+	}
 }

core/src/main/java/org/locationtech/proj4j/datum/Grid.java

@@ -376,7 +376,7 @@ private static DataInputStream resolveGridDefinition(String gridName) throws IOE
         // search path for grid definition files, but for now we only check the
         // working directory and the classpath (in that order.)
         File file = new File(gridName);
-        if (file.exists()) return new DataInputStream(new FileInputStream(file));
+        if (file.exists()) return new DataInputStream(new BufferedInputStream(new FileInputStream(file)));
         InputStream resource = Grid.class.getResourceAsStream("/proj4/nad/" + gridName);
         if (resource != null) return new DataInputStream(new BufferedInputStream(resource));
 

core/src/main/java/org/locationtech/proj4j/parser/Proj4Parser.java

@@ -205,7 +205,7 @@ private void parseDatum(Map params, DatumParameters datumParam) {
             try {
                 datumParam.setGrids(Grid.fromNadGrids(nadgrids));
             } catch (IOException e) {
-                throw new InvalidValueException("Unknown nadgrid: " + nadgrids);
+                throw new InvalidValueException("Unknown nadgrid: " + nadgrids, e);
             }
         }
     }

core/src/test/java/org/locationtech/proj4j/datum/NTV2Test.java

@@ -24,6 +24,8 @@
 import org.locationtech.proj4j.CoordinateTransformFactory;
 import org.locationtech.proj4j.ProjCoordinate;
 
+import java.net.URISyntaxException;
+
 /**
  * Using grid shifts for Catalonia
  * @see https://geoinquiets.cat/
@@ -77,4 +79,18 @@ public void gridShiftNTV2Inverse() {
         Assert.assertTrue(expected2.areXOrdinatesEqual(result2, 0.001) &&
                           expected2.areYOrdinatesEqual(result2, 0.001));
     }
+
+    @Test
+    public void nadGridExternalTest() throws URISyntaxException {
+        String path = this.getClass().getResource("/proj4/nad/100800401.gsb").toURI().getPath();
+        CRSFactory crsFactory = new CRSFactory();
+
+        CoordinateReferenceSystem tmercWithNadGridV2 =
+                crsFactory.createFromParameters("EPSG:2100",
+                        "+proj=tmerc +lat_0=0 +lon_0=24 +k=0.9996 +x_0=500000 +y_0=0 +ellps=GRS80 +towgs84=-199.87,74.79,246.62,0,0,0,0 +units=m +nadgrids="
+                                + path + " +no_defs"
+                );
+
+        Assert.assertEquals(Datum.TYPE_GRIDSHIFT, tmercWithNadGridV2.getDatum().getTransformType());
+    }
 }