Lua (5.3) Language addition (#4804)

* starting Lua port of python implmention. Syncing commit

* Bulk of Lua module port from Python done. Not tested, only static analysis. Need to work on binary strings. Started work on flatc lua code generation

* Fixed all the basic errors to produced a binary output from the builder, don't know if it is generated correctly, but it contains data, so that must be good

* fixed binary set command that was extending the array improperly

* continued improvement

* Moved lua submodules down a directory so their names don't clash with potential other modules. Added compat module to provide Lua versioning logic

* Successful sample port from Python

* working on testing Lua code with formal tests

* continued to work on tests and fixes to code to make tests pass

* Added reading buffer test

* Changed binaryarray implmentation to use a temporary table for storing data, and then serialize it to a string when requested. This double the rate of building flatbuffers compared to the string approach.

* Didn't need encode module as it just added another layer of indirection that isn't need

* profiled reading buffers, optimizations to increase read performance of monster data to ~7 monster / millisecond

* Writing profiler improvments. Get about
~2 monsters/millisecond building rate

* removed Numpy generation from Lua (came from the Python port)

* math.pow is deprecated in Lua 5.3, so changed to ^ notation. Also added .bat script for starting Lua tests

* adding results of generate_code.bat

* simple edits for code review in PR.

* There was a buffer overflow in inserting the keywords into the unorder set for both the Lua and Python code gens. Changed insertion to use iterators.

* fixed spacing issue

* basic documenation/tutorial updates. Updated sample_binary.lua to reflect the tutorial better

* removed windows-specific build step in Lua tests

samples/sample_binary.lua

@@ -0,0 +1,107 @@
+-- need to update the Lua path to point to the local flatbuffers implementation
+package.path = string.format("../lua/?.lua;%s",package.path)
+package.path = string.format("./lua/?.lua;%s",package.path)
+
+-- require the library
+local flatbuffers = require("flatbuffers")
+
+local binaryArray = flatbuffers.binaryArray-- for hex dump utility
+
+-- require the files generated from the schema
+local weapon = require("MyGame.Sample.Weapon")
+local monster = require("MyGame.Sample.Monster")
+local vec3 = require("MyGame.Sample.Vec3")
+local color = require("MyGame.Sample.Color")
+local equipment = require("MyGame.Sample.Equipment")
+
+-- get access to the builder, providing an array of size 1024
+local builder = flatbuffers.Builder(1024)
+
+local weaponOne = builder:CreateString("Sword")
+local weaponTwo = builder:CreateString("Axe")
+
+-- Create the first 'Weapon'
+weapon.Start(builder)
+weapon.AddName(builder, weaponOne)
+weapon.AddDamage(builder, 3)
+local sword = weapon.End(builder)
+
+-- Create the second 'Weapon'
+weapon.Start(builder)
+weapon.AddName(builder, weaponTwo)
+weapon.AddDamage(builder, 5)
+local axe = weapon.End(builder)
+
+-- Serialize a name for our mosnter, called 'orc'
+local name = builder:CreateString("Orc")
+
+-- Create a `vector` representing the inventory of the Orc. Each number
+-- could correspond to an item that can be claimed after he is slain.
+-- Note: Since we prepend the bytes, this loop iterates in reverse.
+monster.StartInventoryVector(builder, 10)
+for i=10,1,-1 do
+    builder:PrependByte(i)
+end
+local inv = builder:EndVector(10)
+
+-- Create a FlatBuffer vector and prepend the weapons.
+-- Note: Since we prepend the data, prepend them in reverse order.
+monster.StartWeaponsVector(builder, 2)
+builder:PrependUOffsetTRelative(axe)
+builder:PrependUOffsetTRelative(sword)
+local weapons = builder:EndVector(2)
+
+-- Create our monster by using Start() andEnd()
+monster.Start(builder)
+monster.AddPos(builder, vec3.CreateVec3(builder, 1.0, 2.0, 3.0))
+monster.AddHp(builder, 300)
+monster.AddName(builder, name)
+monster.AddInventory(builder, inv)
+monster.AddColor(builder, color.Red)
+monster.AddWeapons(builder, weapons)
+monster.AddEquippedType(builder, equipment.Weapon)
+monster.AddEquipped(builder, axe)
+local orc = monster.End(builder)
+
+-- Call 'Finish()' to instruct the builder that this monster is complete.
+builder:Finish(orc)
+
+-- Get the flatbuffer as a string containing the binary data
+local bufAsString = builder:Output()
+
+-- Convert the string representation into binary array Lua structure
+local buf = flatbuffers.binaryArray.New(bufAsString)
+
+-- Get an accessor to the root object insert the buffer
+local mon = monster.GetRootAsMonster(buf, 0)
+
+assert(mon:Mana() == 150)
+assert(mon:Hp() == 300)
+assert(mon:Name() == "Orc")
+assert(mon:Color() == color.Red)
+assert(mon:Pos():X() == 1.0)
+assert(mon:Pos():Y() == 2.0)
+assert(mon:Pos():Z() == 3.0)
+
+for i=1,mon:InventoryLength() do
+    assert(mon:Inventory(i) == i)
+end
+
+local expected = { 
+    {w = 'Sword', d = 3}, 
+    {w = 'Axe', d = 5}
+}
+
+for i=1,mon:WeaponsLength() do
+   assert(mon:Weapons(i):Name() == expected[i].w)
+   assert(mon:Weapons(i):Damage() == expected[i].d)
+end
+
+assert(mon:EquippedType() == equipment.Weapon)
+
+local unionWeapon = weapon.New()
+unionWeapon:Init(mon:Equipped().bytes,mon:Equipped().pos)
+assert(unionWeapon:Name() == "Axe")
+assert(unionWeapon:Damage() == 5)
+
+print("The Lua FlatBuffer example was successfully created and verified!")