From 0667130fc45ac85992e27e40b8167ac8cdd5b9ef Mon Sep 17 00:00:00 2001
From: Mikael Pettersson <mikpelinux@gmail.com>
Date: Thu, 14 Aug 2025 16:04:45 +0200
Subject: [PATCH] elf2boot: move uint36_to_c36 conversion to extint

---
 erlang/apps/elf2boot/src/elf2boot.erl |  8 +-------
 erlang/apps/lib/src/extint.erl        | 10 ++++++++++
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/erlang/apps/elf2boot/src/elf2boot.erl b/erlang/apps/elf2boot/src/elf2boot.erl
index 4e9fe48..815763a 100644
--- a/erlang/apps/elf2boot/src/elf2boot.erl
+++ b/erlang/apps/elf2boot/src/elf2boot.erl
@@ -288,13 +288,7 @@ outfp_fseekw({h36, OutFP}, WordOffset) ->
   stdio9:fseek(OutFP, {bof, WordOffset*4}).
 
 outfp_fputw(Word, {c36, IoDev}) ->
-  B4 =  Word         band 15,
-  B3 = (Word bsr 4)  band 255,
-  B2 = (Word bsr 12) band 255,
-  B1 = (Word bsr 20) band 255,
-  B0 = (Word bsr 28) band 255,
-  Bytes = [B0, B1, B2, B3, B4],
-  stdio8:fputs(Bytes, IoDev);
+  stdio8:fputs(extint:uint36_to_c36(Word), IoDev);
 outfp_fputw(Word, {h36, OutFP}) ->
   stdio9:fputs(extint:uint36_to_ext(Word), OutFP).
 
diff --git a/erlang/apps/lib/src/extint.erl b/erlang/apps/lib/src/extint.erl
index e885cdf..4f49d3a 100644
--- a/erlang/apps/lib/src/extint.erl
+++ b/erlang/apps/lib/src/extint.erl
@@ -32,6 +32,7 @@
         , uint32_from_ext/1
         , uint32_to_ext/1
         , uint36_from_ext/1
+        , uint36_to_c36/1
         , uint36_to_ext/1
         , uint64_from_ext/1
         , uint64_to_ext/1
@@ -83,6 +84,15 @@ uint36_to_ext(U36) ->
    _B2 = (U36 bsr  9) band ?UINT9_MAX,
    _B3 =  U36         band ?UINT9_MAX].
 
+%% This converts a 36-bit word to 5 octets in KLH10's C36 format.
+-spec uint36_to_c36(uint36_t()) -> [uint8_t()].
+uint36_to_c36(U36) ->
+  [_B0 = (U36 bsr 28) band 255,
+   _B1 = (U36 bsr 20) band 255,
+   _B2 = (U36 bsr 12) band 255,
+   _B3 = (U36 bsr  4) band 255,
+   _B4 =  U36         band  15].
+
 -spec uint64_from_ext([uint8_t()]) -> uint64_t().
 uint64_from_ext([B0, B1, B2, B3, B4, B5, B6, B7]) ->
   ((B0 band ?UINT8_MAX) bsl 56) bor