Find render_map offset for twbt

find_twbt.lua

local ms=require('memscan')
local cs=ms.get_code_segment()

function get_ptr_size(  )
	local v=df.new('uintptr_t')
	local ret=df.sizeof(v)
	df.delete(v)
	return ret
end

function print_off(name, off )
	print(string.format("%s : %x %x",name,off,off-dfhack.internal.getRebaseDelta()))
end

local ptr_size=get_ptr_size()

local vtoff=dfhack.internal.getVTable('viewscreen_dwarfmodest')
--print_off("Vtable:",vtoff)

local vtable=ms.CheckedArray.new('uintptr_t',vtoff,vtoff+3*ptr_size)

local render_method=vtable[2] --third method aka render
--print_off("render",render_method)

function list_all_possible_calls(start,len )
	local func=ms.CheckedArray.new('uint8_t',start,start+len) --should be near
	local possible_calls={}

	for i=0,#func-1 do
		if func[i]==0xe8 then
			table.insert(possible_calls,i)
		end
	end
	return possible_calls
end
function get_call_target( offset )
	local call_offset=df.reinterpret_cast('int32_t',offset+1)
	local ret=call_offset.value+offset+5
	if cs:contains_range(ret,1) then
		return ret
	else
		return nil
	end
end
function list_all_valid_calls( start,len )
	local all_calls=list_all_possible_calls(start,len)
	local ret={}
	for i,v in ipairs(all_calls) do
		local ct=get_call_target(start+v)
		if ct then
			table.insert(ret,ct)
		end
	end
	return ret
end
--TODO(warmist): this is probably stupid, but without disassembler ( sad face ) i can't say for sure 
--if it's part of instruction or an arg, so we just hope to find only one?

local possible_calls=list_all_valid_calls(render_method,50)

if #possible_calls==0 then
	qerror("Failed to find call instruction in render vmethod")
elseif #possible_calls>1 then
	qerror("Found multiple 0xe8 (call) in render vmethod start")
end

local dwarfmode_render_main=possible_calls[1]
print_off("twbt_render_map",dwarfmode_render_main)

--[[ other not used offset(s)
local dfrender=list_all_valid_calls(dwarfmode_render_main,200)[2] --this could be further
print_off("A_RENDER_MAP",dfrender)
]]