Guru: Decoding Base64 ASCII

August 18, 2025 Chris Ringer

A co-worker of mine recently asked me how to decode a base64 ASCII string in RPG, received from an HTTP response. My response was “that’s easy”, simply use the relevant SQL function BASE64_DECODE. I promptly wrote some sample code and after some debugging I realized this function threw me a curveball.

Let me demonstrate the issue and offer a simple solution.

01 **Free
02 ctl-opt DftActGrp(*No) Copyright('(C) Chris Ringer');

03 dcl-s string_UTF8   varchar(1000) ccsid(*UTF8);
04 dcl-s base64_UTF8   varchar(1350) ccsid(*UTF8);
05 dcl-s decoded_UTF8  varchar(1000) ccsid(*UTF8);
06 dcl-s decoded_Hex   varchar(1000) ccsid(*HEX);

07 Exec SQL Set Option Commit=*NONE, Naming=*SYS;
08 string_UTF8 =