ReadBufferDataHandle: ensure pages are fully read

Reading bytes with `DataHandle#read(bytes[], off, len)` results in *up
to* `len` bytes being read into the provided array.
In ReadBufferHandleDataHandle the number of read bytes was not checked,
this lead to partially filled pages resulting in read errors. Now the
reading is repeated until the page is either full or EOF is reached.

And adapt to changes in ReadBufferDataHandle.

Author: gab1one

src/main/java/org/scijava/io/handle/ReadBufferDataHandle.java

@@ -167,7 +167,17 @@ private byte[] readPage(final int pageID, final int slotID) throws IOException {
 		if (handle().offset() != startOfPage) {
 			handle().seek(startOfPage);
 		}
-		handle().read(page);
+
+		// NB: we read repeatedly until the page is full or EOF is reached
+		// handle().read(..) might read less bytes than requested
+		int off = 0;
+		while (off < pageSize) {
+			final int read = handle().read(page, off, pageSize - off);
+			if (read == -1) { // EOF
+				break;
+			}
+			off += read;
+		}
 		return page;
 	}
 

src/test/java/org/scijava/io/handle/ReadBufferDataHandleMockTest.java

@@ -1,21 +1,25 @@
 
 package org.scijava.io.handle;
 
-import org.junit.Before;
-import org.junit.Test;
-
 import static org.junit.Assert.assertEquals;
 import static org.mockito.AdditionalMatchers.aryEq;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyLong;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.doAnswer;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
 
+import java.io.IOException;
+
+import org.junit.Before;
+import org.junit.Test;
 import org.scijava.io.location.DummyLocation;
 import org.scijava.io.location.Location;
 
-import static org.mockito.Mockito.*;
-
-import java.io.IOException;
-
 public class ReadBufferDataHandleMockTest {
 
 	private DataHandle<Location> mock;
@@ -59,34 +63,40 @@ public void testBufferingSequence() throws IOException {
 
 		// set length of stubbed handle
 		when(mock.length()).thenReturn(30l);
+		byte[] value = new byte[10];
+		when(mock.read(aryEq(value), eq(0), eq(10))).thenReturn(10);
+		when(mock.read(aryEq(value), anyInt(), anyInt())).thenReturn(10);
 
 		// read the first byte
 		buf.read();
 		verify(mock, times(0)).seek(0);
 		// buffer should read a whole page
-		verify(mock).read(aryEq(byteArrayLen10));
+		verify(mock).read(aryEq(byteArrayLen10), eq(0), eq(10));
 
 		buf.seek(0);
 		// ensure seek was not called again
 		verify(mock, times(0)).seek(0);
 
+		when(mock.offset()).thenReturn(10l);
+
 		// read over the edge of the current page
 		buf.read(new byte[12]);
 		verify(mock, times(0)).seek(anyLong());
-		verify(mock, times(2)).read(aryEq(byteArrayLen10));
+		verify(mock, times(2)).read(aryEq(byteArrayLen10), eq(0), eq(10));
 
 		assertEquals(12, buf.offset());
 
 		// read the last page
+		when(mock.offset()).thenReturn(20l);
 		buf.read(new byte[12]);
 		verify(mock, times(0)).seek(anyLong());
-		verify(mock, times(3)).read(aryEq(byteArrayLen10));
+		verify(mock, times(3)).read(aryEq(byteArrayLen10), eq(0), eq(10));
 
 		// first page should no longer be buffered, must be reread in
 		buf.seek(0);
 		buf.read();
 		verify(mock).seek(0);
-		verify(mock, times(4)).read(aryEq(byteArrayLen10));
+		verify(mock, times(4)).read(aryEq(byteArrayLen10), eq(0), eq(10));
 	}
 
 	/**
@@ -99,19 +109,21 @@ public void testSkipForward() throws IOException {
 
 		// set length of stubbed handle
 		when(mock.length()).thenReturn(40l);
+		when(mock.read(any(), anyInt(), anyInt())).thenReturn(10);
 
 		// read the first byte
 		buf.read();
 		verify(mock, times(0)).seek(anyLong());
-		verify(mock).read(aryEq(byteArrayLen10));
+		verify(mock, times(1)).read(aryEq(byteArrayLen10), eq(0), eq(10));
 
 		// skip the second page
 		buf.seek(30l);
 		buf.read();
 
 		// read the third page
 		verify(mock).seek(30l);
-		verify(mock, times(2)).read(aryEq(byteArrayLen10));
+		verify(mock, times(2)).read(aryEq(byteArrayLen10), eq(0), eq(10));
+		when(mock.offset()).thenReturn(40l);
 
 		// go back to already buffered page
 		buf.seek(0l);
@@ -123,6 +135,6 @@ public void testSkipForward() throws IOException {
 		buf.seek(35);
 		buf.read();
 		verify(mock, times(1)).seek(anyLong());
-		verify(mock, times(2)).read(any());
+		verify(mock, times(2)).read(any(), anyInt(), anyInt());
 	}
 }