From f369cc23a9d3664dabecf280e2d1d0b980d19ad4 Mon Sep 17 00:00:00 2001
From: Seth Hillbrand <seth@kipro-pcb.com>
Date: Thu, 6 Oct 2022 15:03:58 -0700
Subject: [PATCH] Handle arbitrary unit counts

---
 eeschema/lib_symbol.cpp                 |  16 +--
 qa/unittests/eeschema/test_lib_part.cpp | 145 ++++++++++++++++++++++++
 2 files changed, 153 insertions(+), 8 deletions(-)

diff --git a/eeschema/lib_symbol.cpp b/eeschema/lib_symbol.cpp
index 93686e340a..07a1a84786 100644
--- a/eeschema/lib_symbol.cpp
+++ b/eeschema/lib_symbol.cpp
@@ -589,6 +589,9 @@ wxString LIB_SYMBOL::SubReference( int aUnit, bool aAddSeparator )
 {
     wxString subRef;
 
+    if( aUnit < 1 )
+        return subRef;
+
     if( m_subpartIdSeparator != 0 && aAddSeparator )
         subRef << wxChar( m_subpartIdSeparator );
 
@@ -602,17 +605,14 @@ wxString LIB_SYMBOL::SubReference( int aUnit, bool aAddSeparator )
         // use one letter if letter = A .. Z or a ... z, and 2 letters otherwise
         // first letter is expected to be 'A' or 'a' (i.e. 26 letters are available)
         int u;
-        aUnit -= 1;     // Unit number starts to 1. now to 0.
 
-        while( aUnit >= 26 )    // more than one letter are needed
+        do
         {
-            u = aUnit / 26;
-            subRef << wxChar( m_subpartFirstId + u -1 );
-            aUnit %= 26;
-        }
+            u = ( aUnit - 1 ) % 26;
+            subRef = wxChar( m_subpartFirstId + u ) + subRef;
+            aUnit = ( aUnit - u ) / 26;
+        } while( aUnit > 0 );
 
-        u = m_subpartFirstId + aUnit;
-        subRef << wxChar( u );
     }
 
     return subRef;
diff --git a/qa/unittests/eeschema/test_lib_part.cpp b/qa/unittests/eeschema/test_lib_part.cpp
index c82008af99..7819946fbd 100644
--- a/qa/unittests/eeschema/test_lib_part.cpp
+++ b/qa/unittests/eeschema/test_lib_part.cpp
@@ -197,6 +197,151 @@ BOOST_AUTO_TEST_CASE( SubReference )
             false,
             "AA",
         },
+        {
+            28,
+            false,
+            "AB",
+        },
+        {
+            53,
+            false,
+            "BA",
+        },
+        {
+            79,
+            false,
+            "CA",
+        },
+        {
+            105,
+            false,
+            "DA",
+        },
+        {
+            131,
+            false,
+            "EA",
+        },
+        {
+            157,
+            false,
+            "FA",
+        },
+        {
+            183,
+            false,
+            "GA",
+        },
+        {
+            209,
+            false,
+            "HA",
+        },
+        {
+            235,
+            false,
+            "IA",
+        },
+        {
+            261,
+            false,
+            "JA",
+        },
+        {
+            287,
+            false,
+            "KA",
+        },
+        {
+            313,
+            false,
+            "LA",
+        },
+        {
+            339,
+            false,
+            "MA",
+        },
+        {
+            365,
+            false,
+            "NA",
+        },
+        {
+            391,
+            false,
+            "OA",
+        },
+        {
+            417,
+            false,
+            "PA",
+        },
+        {
+            443,
+            false,
+            "QA",
+        },
+        {
+            469,
+            false,
+            "RA",
+        },
+        {
+            495,
+            false,
+            "SA",
+        },
+        {
+            521,
+            false,
+            "TA",
+        },
+        {
+            547,
+            false,
+            "UA",
+        },
+        {
+            573,
+            false,
+            "VA",
+        },
+        {
+            599,
+            false,
+            "WA",
+        },
+        {
+            625,
+            false,
+            "XA",
+        },
+        {
+            651,
+            false,
+            "YA",
+        },
+        {
+            677,
+            false,
+            "ZA",
+        },
+        {
+            702,
+            false,
+            "ZZ",
+        },
+        {
+            703,
+            false,
+            "AAA",
+        },
+        {
+            728,
+            false,
+            "AAZ",
+        },
         { // haven't configured a separator, so should be nothing
             1,
             true,