[Java] Reduce processing and allocation when dealing with empty var data strings.

Author: mjpt777

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/java/JavaGenerator.java

@@ -791,7 +791,11 @@ private void generateDataDecodeMethods(
  indent + " final int headerLength = %3$d;\n" +
  indent + " final int limit = parentMessage.limit();\n" +
  indent + " final int dataLength = (int)%4$s;\n" +
- indent + " parentMessage.limit(limit + headerLength + dataLength);\n" +
+ indent + " parentMessage.limit(limit + headerLength + dataLength);\n\n" +
+ indent + " if (0 == dataLength)\n" +
+ indent + " {\n" +
+ indent + " return \"\";\n" +
+ indent + " }\n\n" +
  indent + " final byte[] tmp = new byte[dataLength];\n" +
  indent + " buffer.getBytes(limit + headerLength, tmp, 0, dataLength);\n\n" +
  indent + " final String value;\n" +
@@ -884,7 +888,7 @@ private void generateDataEncodeMethods(
  indent + " final byte[] bytes;\n" +
  indent + " try\n" +
  indent + " {\n" +
- indent + " bytes = value.getBytes(\"%3$s\");\n" +
+ indent + " bytes = value.isEmpty() ? new byte[0] : value.getBytes(\"%3$s\");\n" +
  indent + " }\n" +
  indent + " catch (final java.io.UnsupportedEncodingException ex)\n" +
  indent + " {\n" +