Fix #18, starting 2.5.x backport

Author: cowtowncoder

release-notes/VERSION

@@ -4,6 +4,11 @@ Project: jackson-dataformat-cbor
 === Releases ===
 ------------------------------------------------------------------------
 
+2.5.6 (not released)
+
+#18: Correct parsing of zero length byte strings
+ (reported, fix suggested by philipa@github)
+
 2.5.5 (07-Dec-2015)
 2.5.4 (09-Jun-2015)
 2.5.3 (24-Apr-2015)

src/main/java/com/fasterxml/jackson/dataformat/cbor/CBORParser.java

@@ -18,6 +18,8 @@
 
 public final class CBORParser extends ParserMinimalBase
 {
+    private final static byte[] NO_BYTES = new byte[0];
+    
     /**
      * Enumeration that defines all togglable features for CBOR generators.
      */
@@ -1726,6 +1728,9 @@ protected byte[] _finishBytes(int len) throws IOException
     {
         // First, simple: non-chunked
         if (len >= 0) {
+            if (len == 0) {
+                return NO_BYTES;
+            }
             byte[] b = new byte[len];
             if (_inputPtr >= _inputEnd) {
                 loadMoreGuaranteed();

src/test/java/com/fasterxml/jackson/dataformat/cbor/ParserBinaryTest.java

@@ -20,6 +20,7 @@ public Bytes() { }
     private final ObjectMapper MAPPER = cborMapper();
 
     public void testSmallBinaryValues() throws Exception {
+        _testBinary(0);
         _testBinary(1);
         _testBinary(20);
         _testBinary(100);