From 6c99d1b3c6440a025de75f9a78ad674292510682 Mon Sep 17 00:00:00 2001
From: Izaya Orihara <redtailedairways@gmail.com>
Date: Wed, 25 Jan 2017 12:13:14 +1100
Subject: [PATCH] Added an emulator and eventual separate library for emulating
 the T400

---
 test3d_t400/emut400.lua | 51 +++++++++++++++++++++++++
 test3d_t400/t400.lua    | 85 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 136 insertions(+)
 create mode 100644 test3d_t400/emut400.lua
 create mode 100644 test3d_t400/t400.lua

diff --git a/test3d_t400/emut400.lua b/test3d_t400/emut400.lua
new file mode 100644
index 0000000..20c27ac
--- /dev/null
+++ b/test3d_t400/emut400.lua
@@ -0,0 +1,51 @@
+stab = {}
+stab.stack = {}
+stab.pc = 1
+stab.cins = 0
+mem = {}
+t400 = require "t400"
+
+while true do
+ io.write("*> ")
+ i=io.read()
+ it = {}
+ for s in i:gmatch("%S+") do it[#it+1] = s end
+ if it[1] == "peek" then
+  print(mem[tonumber(it[2])])
+ elseif it[1] == "poke" then
+  mem[tonumber(it[2])] = tonumber(it[3])
+ elseif it[1] == "push" then
+  stab.stack[#stab.stack+1] = tonumber(it[2])
+ elseif it[1] == "dumpstack" then
+  for k,v in ipairs(stab.stack) do print(k,v) end
+ elseif it[1] == "ppc" then
+  print(stab.pc)
+ elseif it[1] == "spc" then
+  stab.pc=tonumber(it[2])
+ elseif it[1] == "step" then
+  local scount = tonumber(it[2]) or 1
+  for i = 1, scount do
+   stab.cins = mem[stab.pc]
+   stab,rw,addr,val=t400.run(stab)
+   if rw == "halt" then break end
+   if rw == "read" then
+    stab.stack[#stab.stack+1] = mem[addr]
+   elseif rw == "write" then
+    mem[addr] = dat
+   end
+  end
+ elseif it[1] == "load" then
+  local f,e = io.open(it[2])
+  if f == nil then
+   print("Error: "..e)
+  else
+   local n = tonumber(it[3]) or 0
+   local c = f:read("*a")
+   f:close()
+   for v in c:gmatch("%S+") do
+    mem[n] = tonumber(v) or 0
+    n = n + 1
+   end
+  end
+ end
+end
diff --git a/test3d_t400/t400.lua b/test3d_t400/t400.lua
new file mode 100644
index 0000000..136f030
--- /dev/null
+++ b/test3d_t400/t400.lua
@@ -0,0 +1,85 @@
+local t = {}
+-- internal state
+--- program counter (pc)
+--- current instruction (ci) -- only passed from the environment to the emulator
+--- stack (stack)
+local function pop(s)
+ return table.remove(s,#s) or 0
+end
+local function push(s,v)
+ v=v or 0
+ s[#s+1] = v%4096
+ if #s > 16 then
+  table.remove(s,1)
+ end
+end
+
+function t.run(stab)
+ -- variables
+ local pc = stab.pc or 1
+ local ci = stab.cins or 0
+ local stack = stab.stack or {}
+ local rstack = stab.rstack or {}
+ local pci = 1
+ local rw = nil
+ local addr = 0
+ local dat = 0
+ -- instruction processing
+ if ci == 4095 then -- ppc
+  push(stack,pc)
+ elseif ci == 4094 then -- swp
+  a=pop(stack)
+  b=pop(stack)
+  push(stack,a)
+  pusk(stack,b)
+ elseif ci == 4093 then -- read
+  rw = "read" -- terrible IPC
+  addr = pop(stack)
+ elseif ci == 4092 then -- write
+  rw = "write"
+  addr = pop(stack)
+  dat = pop(stack)
+ elseif ci == 4091 then -- add
+  push(stack,pop(stack)+pop(stack))
+ elseif ci == 4090 then -- sub
+  push(stack,pop(stack)+pop(stack))
+ elseif ci == 4089 then -- jmp
+  pc = pop(stack)
+  pci = 0
+ elseif ci == 4088 then -- sez
+  if pop(stack) == 0 then
+   pci = pci + 1
+  end
+ elseif ci == 4087 then -- jez
+  local a = pop(stack)
+  if pop(stack) == 0 then
+   pc = a
+   pci = 0
+  end
+ elseif ci == 4086 then -- jsr
+  push(rstack,pc)
+  pc = pop(stack)
+  pci = 0
+ elseif ci == 4085 then -- ret
+  pc = pop(rstack)
+ elseif ci == 4084 then -- dup
+  local v = pop(stack)
+  push(stack,v)
+  push(stack,v)
+ elseif ci == 4083 then -- drop
+  pop(stack)
+ elseif ci == 4082 then -- hlt
+  rw = "halt"
+ else
+  push(stack,ci)
+ end
+ -- return stuff
+ stab = {}
+ stab.pc = pc + pci -- increment pc
+ stab.cins = 0
+ stab.stack = stack
+ stab.rstack = rstack
+ return stab, rw, addr, dat
+end
+
+return t