[Java] Factor in constant fields when computing block length. Issue #528.

Author: mjpt777

sbe-tool/src/main/java/uk/co/real_logic/sbe/xml/EnumType.java

@@ -168,6 +168,11 @@ public PrimitiveType encodingType()
      */
     public int encodedLength()
     {
+        if (presence() == Presence.CONSTANT)
+        {
+            return 0;
+        }
+
         return encodingType.size();
     }
 

sbe-tool/src/main/java/uk/co/real_logic/sbe/xml/Message.java

@@ -425,7 +425,14 @@ else if (field.type() != null)
                     return blockLength;
                 }
 
-                blockLength = field.computedOffset() + fieldLength;
+                if (field.presence() == Presence.CONSTANT)
+                {
+                    blockLength = field.computedOffset();
+                }
+                else
+                {
+                    blockLength = field.computedOffset() + fieldLength;
+                }
             }
         }
 
@@ -440,7 +447,7 @@ private static void validateBlockLength(
             handleError(
                 node,
                 "specified blockLength provides insufficient space " +
-                computedBlockLength + " > " + specifiedBlockLength);
+                    computedBlockLength + " > " + specifiedBlockLength);
         }
     }
 }