Add support for lots of tables (> 200)

Now only a single variable is used (_).

What effect does this have on the file size and runtime? I have no idea.
I don't think it'll be *that* much, though.

bigtest.lua

@@ -0,0 +1,12 @@
+local serialize = require 'ser'
+
+local t = {}
+for i = 1, 15 do
+    t[i] = {}
+    for j = 1, 10 do
+        t[i][j] = {{'woo'}}
+    end
+end
+local s = serialize(t)
+print(s)
+loadstring(s)()

ser.lua

@@ -22,7 +22,7 @@ local function write(t, memo, rev_memo)
 			memo[t] = index
 			rev_memo[index] = t
 		end
-		return '_' .. memo[t]
+		return '_[' .. memo[t] .. ']'
 	else
 		error("Trying to serialize unsupported type " .. ty)
 	end
@@ -53,9 +53,9 @@ end
 
 local function write_table_ex(t, memo, rev_memo, srefs, name)
 	if type(t) == 'function' then
-		return 'local _' .. name .. ' = loadstring ' .. make_safe(dump(t))
+		return '_[' .. name .. '] = loadstring ' .. make_safe(dump(t))
 	end
-	local m = {'local _', name, ' = {'}
+	local m = {'_[', name, '] = {'}
 	local mi = 3
 	for i = 1, #t do -- don't use ipairs here, we need the gaps
 		local v = t[i]
@@ -106,16 +106,17 @@ return function(t)
 	-- phase 3: add all the tricky cyclic stuff
 	for i, v in ipairs(srefs) do
 		n = n + 1
-		result[n] = write_key_value_pair(v[2], v[3], memo, rev_memo, '_' .. v[1])
+		result[n] = write_key_value_pair(v[2], v[3], memo, rev_memo, '_[' .. v[1] .. ']')
 	end
 
 	-- phase 4: add something about returning the main table
-	if result[n]:sub(1, 8) == 'local _0' then
-		result[n] = 'return' .. result[n]:sub(11)
+	if result[n]:sub(1, 5) == '_[0] ' then
+		result[n] = 'return' .. result[n]:sub(7)
 	else
-		result[n + 1] = 'return _0'
+		result[n + 1] = 'return _[0]'
 	end
 
 	-- phase 5: just concatenate everything
-	return concat(result, '\n')
+	result = concat(result, '\n')
+	return n > 1 and 'local _ = {}\n' .. result or result
 end

tests.lua

@@ -36,14 +36,16 @@ case({}, 'return {}', 'empty table')
 case({true}, 'return {true}', 'simple table')
 
 case({{}}, [[
-local _1 = {}
-return {_1}]], 'empty table within a table')
+local _ = {}
+_[1] = {}
+return {_[1]}]], 'empty table within a table')
 
 local _t = {}
 _t.self = _t
-case(_t, [[local _0 = {}
-_0.self = _0
-return _0]], 'simple cycle')
+case(_t, [=[local _ = {}
+_[0] = {}
+_[0].self = _[0]
+return _[0]]=], 'simple cycle')
 
 case_error({coroutine.create(function()end)}, './ser.lua:27: Trying to serialize unsupported type thread', 'unsupported type')
 
@@ -54,12 +56,13 @@ case({'\127\230\255\254\128\12\0128\n\31'}, 'return {"\\127\\230\\255\\254\\128\
 case({['\127\230\255\254\128\12\0128\n\31'] = '\0'}, 'return {["\\127\\230\\255\\254\\128\\12\\0128\\n\\31"] = "\\0"}', 'non-ASCII or control characters in string key')
 
 local x = {}
-case({x, {x}, x}, [[
-local _2 = {}
-local _1 = {}
-local _0 = {_1, _2, _1}
-_2[1] = _1
-return _0]], 'repeated table')
+case({x, {x}, x}, [=[
+local _ = {}
+_[2] = {}
+_[1] = {}
+_[0] = {_[1], _[2], _[1]}
+_[2][1] = _[1]
+return _[0]]=], 'repeated table')
 
 case({['end'] = true, ['false'] = false}, 'return {["false"] = false, ["end"] = true}', 'keywords as table keys')