From 902f1e6476046d77db84b85c5124537aab7b2178 Mon Sep 17 00:00:00 2001
From: Iampete1 <iampete@hotmail.co.uk>
Date: Fri, 27 Sep 2024 18:29:32 +0100
Subject: [PATCH] AP_Scripting: modules: MAVLink: update to latest version of
 generated code

---
 .../MAVLink/mavlink_msg_COMMAND_LONG.lua      |  1 +
 .../modules/MAVLink/mavlink_msgs.lua          | 94 ++++++++++++++++---
 2 files changed, 81 insertions(+), 14 deletions(-)

diff --git a/libraries/AP_Scripting/modules/MAVLink/mavlink_msg_COMMAND_LONG.lua b/libraries/AP_Scripting/modules/MAVLink/mavlink_msg_COMMAND_LONG.lua
index ba40100f41ae0b..7302529ea4c308 100644
--- a/libraries/AP_Scripting/modules/MAVLink/mavlink_msg_COMMAND_LONG.lua
+++ b/libraries/AP_Scripting/modules/MAVLink/mavlink_msg_COMMAND_LONG.lua
@@ -1,5 +1,6 @@
 local COMMAND_LONG = {}
 COMMAND_LONG.id = 76
+COMMAND_LONG.crc_extra = 152
 COMMAND_LONG.fields = {
              { "param1", "<f" },
              { "param2", "<f" },
diff --git a/libraries/AP_Scripting/modules/MAVLink/mavlink_msgs.lua b/libraries/AP_Scripting/modules/MAVLink/mavlink_msgs.lua
index 34e5a3bd65d3e5..c9b66e1fd3e807 100644
--- a/libraries/AP_Scripting/modules/MAVLink/mavlink_msgs.lua
+++ b/libraries/AP_Scripting/modules/MAVLink/mavlink_msgs.lua
@@ -1,5 +1,9 @@
+-- Auto generated MAVLink parsing script
 local mavlink_msgs = {}
 
+---Lookup the message id for a given message name
+---@param msgname string
+---@return integer -- message id
 function mavlink_msgs.get_msgid(msgname)
   local message_map = require("MAVLink/mavlink_msg_" .. msgname)
   if not message_map then
@@ -8,45 +12,99 @@ function mavlink_msgs.get_msgid(msgname)
   return message_map.id
 end
 
+---Return a object containing everything that is not the payload
+---@param message any -- encoded message
+---@return table
 function mavlink_msgs.decode_header(message)
   -- build up a map of the result
   local result = {}
 
-  local read_marker = 3
+  result.checksum = string.unpack("<H", message, 1)
 
   -- id the MAVLink version
-  result.protocol_version, read_marker = string.unpack("<B", message, read_marker)
-  if (result.protocol_version == 0xFE) then -- mavlink 1
+  local magic = string.unpack("<B", message, 3)
+  if (magic == 0xFE) then -- mavlink 1
     result.protocol_version = 1
-  elseif (result.protocol_version == 0XFD) then --mavlink 2
+  elseif (magic == 0XFD) then --mavlink 2
     result.protocol_version = 2
   else
     error("Invalid magic byte")
   end
 
-  _, read_marker = string.unpack("<B", message, read_marker) -- payload is always the second byte
+  -- fetch payload length
+  result.payload_length = string.unpack("<B", message, 4)
 
-  -- strip the incompat/compat flags
-  result.incompat_flags, result.compat_flags, read_marker = string.unpack("<BB", message, read_marker)
+  -- fetch the incompat/compat flags
+  result.incompat_flags, result.compat_flags = string.unpack("<BB", message, 5)
 
   -- fetch seq/sysid/compid
-  result.seq, result.sysid, result.compid, read_marker = string.unpack("<BBB", message, read_marker)
+  result.seq, result.sysid, result.compid = string.unpack("<BBB", message, 7)
 
   -- fetch the message id
-  result.msgid, read_marker = string.unpack("<I3", message, read_marker)
+  result.msgid = string.unpack("<I3", message, 10)
 
-  return result, read_marker
+  return result
 end
 
+-- generate the x25crc for a given buffer
+---@param buffer string -- buffer to crc
+---@return integer -- resulting crc 0 to 0xFFFF
+function mavlink_msgs.generateCRC(buffer)
+  -- generate the x25crc for a given buffer.
+  local crc = 0xFFFF
+  for i = 1, #buffer do
+      local tmp = string.byte(buffer, i, i) ~ (crc & 0xFF)
+      tmp = (tmp ~ (tmp << 4)) & 0xFF
+      crc = (crc >> 8) ~ (tmp << 8) ~ (tmp << 3) ~ (tmp >> 4)
+      crc = crc & 0xFFFF
+  end
+  return crc
+end
+
+-- Note that this does not parse the serial data, it parses the MAVLink 2 C structure `mavlink_message_t`
+-- This structure is passed in by the ArduPilot bindings as a string
+---@param message any -- encoded message
+---@param msg_map table -- table containing message objects with keys of the message ID
+---@return table|nil -- a table representing the contents of the message, or nill if decode failed
 function mavlink_msgs.decode(message, msg_map)
-  local result, offset = mavlink_msgs.decode_header(message)
+  local result = mavlink_msgs.decode_header(message)
   local message_map = require("MAVLink/mavlink_msg_" .. msg_map[result.msgid])
   if not message_map then
     -- we don't know how to decode this message, bail on it
     return nil
   end
 
+  -- If we have a crc extra for this message then check it
+  -- This ensures compatibility with message definitions generated before the crc check was added
+  if message_map.crc_extra then
+    -- crc of payload and header values
+    local crc_buffer
+    if result.protocol_version == 2 then
+      crc_buffer = string.sub(message, 4, 12 + result.payload_length)
+
+    else
+      -- V1 does not include all fields on the wire
+      crc_buffer = string.char(result.payload_length)
+      crc_buffer = crc_buffer .. string.char(result.seq)
+      crc_buffer = crc_buffer .. string.char(result.sysid)
+      crc_buffer = crc_buffer .. string.char(result.compid)
+      crc_buffer = crc_buffer .. string.char(result.msgid)
+      if result.payload_length > 0 then
+        crc_buffer = crc_buffer .. string.sub(message, 13, 12 + result.payload_length)
+      end
+
+    end
+
+    local crc = mavlink_msgs.generateCRC(crc_buffer .. string.char(message_map.crc_extra))
+
+    if crc ~= result.checksum then
+      -- crc failed
+      return nil
+    end
+  end
+
   -- map all the fields out
+  local offset = 13
   for _,v in ipairs(message_map.fields) do
     if v[3] then
       result[v[1]] = {}
@@ -55,14 +113,22 @@ function mavlink_msgs.decode(message, msg_map)
       end
     else
       result[v[1]], offset = string.unpack(v[2], message, offset)
+      if string.sub(v[2],2,2) == 'c' then
+        -- Got string, unpack includes 0 values to the set length
+        -- this is annoying, so remove them
+        result[v[1]] = string.gsub(result[v[1]], string.char(0), "")
+      end
     end
   end
 
-  -- ignore the idea of a checksum
-
-  return result;
+  return result
 end
 
+---Encode the payload section of a given message
+---@param msgname string -- name of message to encode
+---@param message table -- table containing key value pairs representing the data fields in the message
+---@return integer -- message id
+---@return string -- encoded payload
 function mavlink_msgs.encode(msgname, message)
   local message_map = require("MAVLink/mavlink_msg_" .. msgname)
   if not message_map then