PDFBOX-5981: don't return -1 for length 0

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1924772 13f79535-47bb-0310-9956-ffa450edef68

Author: THausherr

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

@@ -115,6 +115,10 @@ public int read() throws IOException
     public int read(byte[] b, int offset, int length) throws IOException
     {
         checkClosed();
+        if (length == 0)
+        {
+            return 0;
+        }
         int maxAvailBytes = Math.min(available(), length);
         if (maxAvailBytes == 0)
         {

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

@@ -240,4 +240,27 @@ void TestEmptyStream() throws IOException
             assertTrue(sequenceRandomAccessRead.isEOF());
         }
     }
+
+    @Test
+    void testPDFBox5981() throws IOException
+    {
+        RandomAccessReadBuffer r1 = new RandomAccessReadBuffer(new byte[2448]);
+        RandomAccessReadBuffer r2 = new RandomAccessReadBuffer(new byte[2412]);
+        RandomAccessReadBuffer r3 = new RandomAccessReadBuffer(new byte[2417]);
+        RandomAccessReadBuffer r4 = new RandomAccessReadBuffer(new byte[2433]);
+        RandomAccessReadBuffer r5 = new RandomAccessReadBuffer(new byte[2432]);
+        RandomAccessReadBuffer r6 = new RandomAccessReadBuffer(new byte[2416]);
+        RandomAccessReadBuffer r7 = new RandomAccessReadBuffer(new byte[2417]);
+        RandomAccessReadBuffer r8 = new RandomAccessReadBuffer(new byte[2266]);
+
+        try (SequenceRandomAccessRead srar = new SequenceRandomAccessRead(List.of(r1, r2, r3, r4, r5, r6, r7, r8));
+             RandomAccessInputStream rais = new RandomAccessInputStream(srar))
+        {
+            int rc = rais.read(new byte[0], 0, 0);
+            assertEquals(0, rc);
+            byte[] result = rais.readAllBytes();
+            assertEquals(19241, result.length);
+            assertEquals(srar.length(), result.length);
+        }
+    }
 }