From 2a7078d6d349f345b17addbec845609b1c29ac90 Mon Sep 17 00:00:00 2001
From: XeonSquared <redtailedairways@gmail.com>
Date: Thu, 3 Aug 2023 10:21:32 +1000
Subject: [PATCH] add bootloader compatible with mtpt

---
 partition/README.md     |  2 +-
 partition/driveboot.lua | 68 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 1 deletion(-)
 create mode 100644 partition/driveboot.lua

diff --git a/partition/README.md b/partition/README.md
index ec8d769..18a594e 100644
--- a/partition/README.md
+++ b/partition/README.md
@@ -1,4 +1,4 @@
-# Simple partition table format
+# Minitel Partition Table (MTPT)
 
 This document specifies a general partition table format suitable for both unmanaged disks, and tapes.
 
diff --git a/partition/driveboot.lua b/partition/driveboot.lua
new file mode 100644
index 0000000..390fc69
--- /dev/null
+++ b/partition/driveboot.lua
@@ -0,0 +1,68 @@
+function computer.getBootAddress()
+ return component.invoke(component.list("eeprom")(),"getData")
+end
+function computer.setBootAddress(a)
+ return component.invoke(component.list("eeprom")(),"setData",a)
+end
+return (function()
+local rv
+local function getProxy(addr)
+ if type(addr) == "string" then
+  return component.proxy(addr)
+ end
+ return addr
+end
+
+local eformat = "c20c4>I4>I4"
+function parsePartitions(s)
+ local rt = {}
+ for i = 1, s:len(), 32 do
+  local n, t, start, length = string.unpack(eformat, s, i)
+  n = n:gsub("\0", "")
+  if n ~= "" then
+   rt[#rt+1] = {n,t,start,length}
+  end
+ end
+ return rt
+end
+
+function getPartitions(drive)
+ return parsePartitions(drive.readSector(drive.getCapacity() / drive.getSectorSize()))
+end
+
+local function offsetSector(part,sector)
+ if sector < 1 or sector > part[4] then error("invalid offset, not in a usable sector") end
+ return (part[3] - 1) + sector
+end
+local function readSector(drive,part,sector)
+ return drive.readSector(offsetSector(part,sector)):gsub("\0+$","")
+end
+local function readPart(drive,part)
+ local rv = ""
+ for i = 1, part[4] do
+  rv=rv .. readSector(drive,part,i)
+ end
+ return rv
+end
+
+local candidates={computer.getBootAddress()}
+for a,_ in component.list("drive") do
+ candidates[#candidates+1] = a
+end
+for i,a in ipairs(candidates) do
+ computer.beep(("."):rep(i))
+ local d = getProxy(a)
+ if type(d) == "table" then
+  for k,v in ipairs(getPartitions(d)) do
+   if v[2] == "boot" then
+    local rv = load(readPart(d,v))
+    if rv then
+     computer.beep("-")
+     computer.setBootAddress(a)
+     return rv
+    end
+   end
+  end
+ end
+end
+end)()()