From cc169d414fdc0ffcf6668455c6bd5ba8944da41e Mon Sep 17 00:00:00 2001
From: David Given <dg@cowlark.com>
Date: Fri, 29 Nov 2024 22:39:34 +0100
Subject: [PATCH] Add experimental support for libdsk 'altback' mode layouts.

---
 lib/config/layout.proto |  5 +++--
 lib/data/layout.cc      | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/lib/config/layout.proto b/lib/config/layout.proto
index 94ec350b..dcb91f41 100644
--- a/lib/config/layout.proto
+++ b/lib/config/layout.proto
@@ -22,8 +22,9 @@ message LayoutProto
     enum Order
     {
         UNDEFINED = 0;
-        CHS = 1;
-        HCS = 2;
+        CHS = 1; // sort by cylinder, then head, then sector -- libdsk 'alt'
+        HCS = 2; // sort by head, then cylinder, then sector -- libdsk 'outout'
+        HCS_RH1 = 3; // as HCS, except the cylinder count for head 1 is reversed -- libdsk 'outback'
     }
 
     message LayoutdataProto
diff --git a/lib/data/layout.cc b/lib/data/layout.cc
index 5d89220c..929ee5c0 100644
--- a/lib/data/layout.cc
+++ b/lib/data/layout.cc
@@ -137,6 +137,20 @@ std::vector<std::pair<int, int>> Layout::getTrackOrdering(
             break;
         }
 
+        case LayoutProto::HCS_RH1:
+        {
+            for (int side = 0; side < sides; side++)
+            {
+                if (side == 0)
+                    for (int track = 0; track < tracks; track++)
+                        trackList.push_back(std::make_pair(track, side));
+                if (side == 1)
+                    for (int track = tracks; track >= 0; track--)
+                        trackList.push_back(std::make_pair(track - 1, side));
+            }
+            break;
+        }
+
         default:
             error("LAYOUT: invalid track trackList");
     }