PDFBOX-6083: catch length 0 case + plus test

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1929152 13f79535-47bb-0310-9956-ffa450edef68

Author: THausherr

io/src/main/java/org/apache/pdfbox/io/RandomAccessRead.java

@@ -189,7 +189,7 @@ default void readFully(byte[] b, int offset, int length) throws IOException
             throw new EOFException("Premature end of buffer reached");
         }
         int bytesReadTotal = 0;
-        do
+        while (bytesReadTotal < length)
         {
             int bytesReadNow = read(b, offset + bytesReadTotal, length - bytesReadTotal);
             if (bytesReadNow <= 0)
@@ -198,6 +198,5 @@ default void readFully(byte[] b, int offset, int length) throws IOException
             }
             bytesReadTotal += bytesReadNow;
         }
-        while (bytesReadTotal < length);
     }
 }

io/src/test/java/org/apache/pdfbox/io/RandomAccessReadBufferedFileTest.java

@@ -296,4 +296,17 @@ void testReadFullyAcrossBuffers() throws IOException
             Assertions.assertArrayEquals(expectedBytes, b);
         }
     }
+
+    @Test
+    void testReadFullyNothing() throws IOException, URISyntaxException
+    {
+        try (RandomAccessRead randomAccessSource = new RandomAccessReadBufferedFile(
+                new File(getClass().getResource("RandomAccessReadFile1.txt").toURI())))
+        {
+            assertEquals(0, randomAccessSource.getPosition());
+            byte[] b = new byte[0];
+            randomAccessSource.readFully(b);
+            assertEquals(0, randomAccessSource.getPosition());
+        }
+    }
 }