Handling little-endian numbers in RPG

Chaps,
 
I am writing some code to import data from a stream file. The numeric data
is held in little-endian byte order. Is there an easy way to handle/convert
this data to big-endian byte order?
 
I tried a simple conversion as follows:
 
*****************************************************************
p convertEndian   b                                              
*****************************************************************
d convertEndian   pi            10i 0                            
d integerIn                     10i 0 value                      
                                                                 
d                 ds                  static                     
d integerOut                    10i 0                            
d integerOut_1                   3u 0 overlay(integerOut:1)      
d integerOut_2                   3u 0 overlay(integerOut:2)
d integerOut_3                   3u 0 overlay(integerOut:3)
d integerOut_4                   3u 0 overlay(integerOut:4)
*****************************************************************
 /free                                                           
                                                                 
  // Convert byte order...                                       
  integerOut = integerIn;                                        
  return (integerOut_1) + (integerOut_2 * (2**8)) +              
         (integerOut_3 * (2**16)) + (integerOut_4 * (2**24));    
                                                                 
 /end-free                                                       
*****************************************************************
p convertEndian   e                                              
***************************************************************** 
 
I know this isn't totally correct, and I'm not sure if it would handle
negative numbers. Will simply swapping the byte order do the job? I'm not
sure where the sign bit is in both cases. I assume that it will work for
unsigned ints/shorts (obviously replacing the i with a u).
 
OR - is there a way of defining a numeric field (int, short) as
little-endian in RPG???
 
Your help would be appreciated.
 
Cheers
 
Larry Ducie