Fix writeRaw(String, offset, len) to copy only the requested slice

Use getChars(offset, offset+len) instead of toCharArray() which copies
the entire string unnecessarily.

Author: komamitsu

msgpack-jackson3/src/main/java/org/msgpack/jackson/dataformat/MessagePackGenerator.java

@@ -677,8 +677,9 @@ public JsonGenerator writeRaw(String text) throws JacksonException
     public JsonGenerator writeRaw(String text, int offset, int len) throws JacksonException
     {
         try {
-            char[] chars = text.toCharArray();
-            writeCharArrayTextValue(chars, offset, len);
+            char[] chars = new char[len];
+            text.getChars(offset, offset + len, chars, 0);
+            writeCharArrayTextValue(chars, 0, len);
         }
         catch (IOException e) {
             throw _wrapIOFailure(e);

msgpack-jackson3/src/test/java/org/msgpack/jackson/dataformat/MessagePackGeneratorTest.java

@@ -996,6 +996,22 @@ public void testGeneratorReusableAfterRootContainerClose()
         assertEquals(2, unpacker.unpackInt());
     }
 
+    @Test
+    public void testWriteRawStringWithOffset()
+            throws IOException
+    {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        JsonGenerator generator = factory.createGenerator(baos, JsonEncoding.UTF8);
+        generator.writeStartArray();
+        generator.writeRaw("XXhelloXX", 2, 5); // "hello"
+        generator.writeEndArray();
+        generator.close();
+
+        MessageUnpacker unpacker = MessagePack.newDefaultUnpacker(baos.toByteArray());
+        unpacker.unpackArrayHeader();
+        assertEquals("hello", unpacker.unpackString());
+    }
+
     @Test
     public void testWriteStringCharArrayWithOffset()
             throws IOException