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engram.lua
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engram.lua
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require "pack"
local getfenv, getinfo = debug.getfenv, debug.getinfo
local bpack = string.pack
local _OP = 2^0
local _A = 2^6
local _B = 2^(6 + 8 + 9)
local _C = 2^(6 + 8)
local _Bx = 2^(6 + 8)
local OP_MOVE = 0
local OP_LOADK = 1
local OP_GETGLOBAL = 5
local OP_GETTABLE = 6
local OP_SETTABLE = 9
local OP_NEWTABLE = 10
local OP_CALL = 28
local OP_TAILCALL = 29
local OP_RETURN = 30
local OP_CLOSURE = 36
local OP_iABC = 0
local OP_iABx = 1
local OP_MODES = {
[OP_MOVE ] = 0,
[OP_LOADK ] = 1,
[OP_GETGLOBAL] = 1,
[OP_GETTABLE ] = 0,
[OP_SETTABLE ] = 0,
[OP_NEWTABLE ] = 0,
[OP_CALL ] = 0,
[OP_TAILCALL ] = 0,
[OP_RETURN ] = 0,
[OP_CLOSURE ] = 1,
}
-- const types
local TNIL = 0
local TBIT = 1
local TNUM = 3
local TSTR = 4
local VNIL = { }
local strdump,strsub,tostring,type = string.dump,string.sub,tostring,type
local Common = { } do
local class = Common
class.__index = class
local samp = strdump(function() end)
local header = strsub(samp, 1, 12)
function class.new(class, name)
local self = setmetatable({
opcode = { };
kcache = { };
consts = { };
protos = { };
locals = { };
vstack = 2;
vcount = 0;
source = name;
}, class)
local seen = self:alloc()
self:emit(OP_NEWTABLE, seen, 16, 0)
self.seenreg = seen
self.seenidx = 0
self.seentbl = { }
return self
end
function class.alloc(self)
local index = self.vstack
self.vstack = index + 1
if self.vstack > self.vcount then
self.vcount = self.vstack
end
return index
end
function class.emit(self, o, a, b, c)
a = a or 0
b = b or 0
local m = OP_MODES[o]
local opcode = self.opcode
if m == OP_iABC then
c = c or 0
opcode[#opcode + 1] = o*_OP + a*_A + b*_B + c*_C
elseif m == OP_iABx then
opcode[#opcode + 1] = o*_OP + a*_A + b*_Bx
else
error("unknown op mode "..tostring(m).." for: "..OP[o])
end
end
function class.bake(self)
-- bake prologue
local source
if self.source then
source = bpack("a", self.source.."\0")
else
source = bpack("a", "")
end
-- mandatory final return
self:emit(OP_RETURN, 0, 1, 0)
local lndefn = bpack('=I', 0)
local lnlast = bpack('=I', 0)
local nupval = bpack('b', 0)
local nparam = bpack('b', 0)
local vararg = bpack('b', 2)
local vcount = bpack('b', self.vcount)
local buffer = {source, lndefn, lnlast, nupval, nparam, vararg, vcount}
-- bake opcode
buffer[#buffer + 1] = bpack("=I", #self.opcode)
for i,op in ipairs(self.opcode) do
buffer[#buffer + 1] = bpack("=I", op)
end
-- bake consts
buffer[#buffer + 1] = bpack("=I", #self.consts)
for index,value in ipairs(self.consts) do
local vtype = type(value)
local ctype, const
if value == VNIL then
const = bpack('b', TNIL)
elseif vtype == "boolean" then
const = bpack('bb', TBIT, value and 1 or 0)
elseif vtype == "number" then
const = bpack('bn', TNUM, value)
elseif vtype == "string" then
const = bpack('ba', TSTR, value.."\0")
end
buffer[#buffer + 1] = const
end
-- bake protos
buffer[#buffer + 1] = bpack("=I", #self.protos)
for i,dump in ipairs(self.protos) do
buffer[#buffer + 1] = dump
end
-- bake debug stuff, lninfo, locals, upvals
buffer[#buffer + 1] = bpack("=I", 0)
buffer[#buffer + 1] = bpack("=I", 0)
buffer[#buffer + 1] = bpack("=I", 0)
return header..table.concat(buffer, '')
end
function class.const(self, value)
if value == nil then value = VNIL end
if self.kcache[value] then
return self.kcache[value]
end
local index = #self.consts
self.kcache[value] = index
self.consts[index + 1] = value
return index
end
function class.save_item(self, obj)
if self.locals[obj] then
return self.locals[obj]
end
local reg = self:alloc()
if self.seentbl[obj] then
local key = self.seentbl[obj]
self:emit(OP_GETTABLE, reg, self.seenreg, self:const(key) + 256)
return reg
end
local t = type(obj)
if t == "number" then
return self:save_const(obj, reg)
elseif t == "boolean" then
return self:save_const(obj, reg)
elseif t == "string" then
return self:save_const(obj, reg)
end
self.locals[obj] = reg
if t == "table" then
self:save_table(obj, reg)
elseif t == "function" then
self:save_function(obj, reg)
elseif t == "userdata" then
self:save_userdata(obj, reg)
elseif t == "thread" then
-- in the unlikely event that this is ever implemented,
self:save_thread(obj, reg)
end
local idx = self.seenidx + 1
self.seenidx = idx
self.seentbl[obj] = idx
local key = self:save_item(idx)
self.vstack = key
self:emit(OP_SETTABLE, self.seenreg, key, reg)
self.locals[obj] = nil
return reg
end
function class.save_const(self, obj, reg)
self:emit(OP_LOADK, reg, self:const(obj))
return reg
end
function class.save_table(self, obj, reg)
self:emit(OP_NEWTABLE, reg, 0, 0)
local free = self.vstack
for k,v in next, obj, nil do
local kreg = self:save_item(k)
local vreg = self:save_item(v)
self:emit(OP_SETTABLE, reg, kreg, vreg)
self.vstack = free
end
return reg
end
function class.save_function(self, obj, reg)
local dump = strdump(obj)
local body = strsub(dump, 13)
self.protos[#self.protos + 1] = body
self:emit(OP_CLOSURE, reg, #self.protos - 1)
return reg
end
function class.save_thread(self, obj, reg)
return self:save_const(nil, reg)
end
function class.save_userdata(self, obj, reg)
local meta = debug.getmetatable(obj)
if meta and meta.__persist then
local func = meta.__persist(obj)
return self:save_function(func, reg)
else
return self:save_const(nil, reg)
end
end
end
local LightContext = setmetatable({ }, { __index = Common }) do
local class = LightContext
local super = Common
class.__index = class
function class.new(class)
local self = super.new(class)
return self
end
function class.save(self, data, func)
local dreg = self:save_item(data)
if func then
local freg = self:save_function(func, self:alloc())
local arg1 = self:alloc()
self:emit(OP_MOVE, arg1, dreg)
self:emit(OP_TAILCALL, freg, 2, 0)
self:emit(OP_RETURN, freg, 0, 0)
else
self:emit(OP_RETURN, dreg, 2, 0)
end
return self:bake()
end
function class.save_thread(self, obj, reg)
return self:save_const(nil, reg)
end
function class.save_userdata(self, obj, reg)
return self:save_const(nil, reg)
end
end
local HeavyContext = setmetatable({ }, { __index = Common }) do
local class = HeavyContext
local super = Common
class.__index = class
function class.new(class, env)
local self = super.new(class)
self.global = { }
for k,v in next, env, nil do
self.global[v] = k
end
local dbug = self:alloc()
self.locals[debug] = dbug
self:emit(OP_GETGLOBAL, dbug, self:const("debug"))
local dest = self:alloc()
self.locals[debug.setmetatable] = dest
self:emit(OP_GETTABLE, dest, dbug, self:const("setmetatable") + 256)
self.setmeta = dest
local dest = self:alloc()
self.locals[debug.setupvalue] = dest
self:emit(OP_GETTABLE, dest, dbug, self:const("setupvalue") + 256)
self.setuval = dest
return self
end
function class.save(self, obj)
local base = self:save_item(obj)
self:emit(OP_RETURN, base, 2, 0)
return self:bake()
end
function class.save_item(self, obj)
if self.global[obj] ~= nil then
local reg = self:alloc()
local key = self.global[obj]
self:emit(OP_GETGLOBAL, reg, self:const(key))
return reg
end
return super.save_item(self, obj)
end
local getupval, getinfo = debug.getupvalue, debug.getinfo
function class.save_function(self, obj, reg)
super.save_function(self, obj, reg)
if getupval(obj, 1) then
local base = self.vstack
local arg1 = base + 1
local arg2 = base + 2
local arg3 = base + 3
self:emit(OP_MOVE, base, self.setuval)
self:emit(OP_MOVE, arg1, reg)
local idx, got, val = 0
while true do
idx = idx + 1
got,val = getupval(obj, idx)
if not got then break end
self.vstack = arg2
self:save_item(idx)
self:save_item(val)
self:emit(OP_CALL, base, 3, 1)
end
self.vstack = base
end
return reg
end
function class.save_table(self, obj, reg)
super.save_table(self, obj, reg)
local meta = debug.getmetatable(obj)
if meta ~= nil then
local mreg = self:save_item(meta)
local base = self:alloc()
local arg1 = self:alloc()
local arg2 = self:alloc()
self:emit(OP_MOVE, base, self.setmeta)
self:emit(OP_MOVE, arg1, reg)
self:emit(OP_MOVE, arg2, mreg)
self:emit(OP_CALL, base, 3, 1)
self.vstack = mreg
end
return reg
end
end
local function engram(obj, env)
local ctx = env and HeavyContext:new(env) or LightContext:new()
return loadstring(ctx:save(obj))
end
return {
engram = engram;
}