1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
|
[](https://travis-ci.org/fengari-lua/fengari)
[](https://opensource.org/licenses/MIT)
[](https://webchat.freenode.net/?channels=fengari)
<p align="center">
<img src="https://github.com/fengari-lua/fengari/raw/master/logo.png" alt="Fengari" width="304" height="304">
</p>
# Fengari
🐺 φεγγάρι - The Lua VM written in JS ES6 for Node and the browser
This repository contains the core fengari code (which is a port of the Lua C library) which includes parser, virtual machine and base libraries.
However it is rare to use this repository directly.
- To use fengari in a web browser as easily as you might use JavaScript, see [fengari-web](https://github.com/fengari-lua/fengari-web)
- [fengari-interop](https://github.com/fengari-lua/fengari-interop) is a lua library that makes interoperating with JavaScript objects simple, it is already included in fengari-web.
- For a clone of the `lua` command line tool, but running under node.js, see [fengari-node-cli](https://github.com/fengari-lua/fengari-node-cli)
### The JS API
Once you've loaded fengari, you can use the JS API:
```js
const luaconf = fengari.luaconf;
const lua = fengari.lua;
const lauxlib = fengari.lauxlib;
const lualib = fengari.lualib;
const L = lauxlib.luaL_newstate();
lualib.luaL_openlibs(L);
lua.lua_pushliteral(L, "hello world!");
```
The JS API is exactly the same as the C API so `fengari.lua` exposes the same constants and functions as `lua.h`, `fengari.lauxlib` the same as `lauxlib.h` and `fengari.lualib` the same as `lualib.h`. If you're unfamiliar with the C API, you can take a look at [the manual](http://www.lua.org/manual/5.3/manual.html#4).
## Semantics
Fengari implements Lua 5.3 semantics and will hopefully follow future Lua releases. If you find any noticeable difference between Fengari and Lua's behaviours, please [report it](https://github.com/fengari-lua/fengari/issues).
### Strings
Lua strings are 8-bits clean and can embed `\0`. Which means that invalid UTF-8/16 strings are valid Lua strings. Lua functions like `string.dump` even use strings as a way of storing binary data.
To address that issue, Fengari uses [`Uint8Array`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array) objects containing the raw bytes to implement lua strings. To push a JS string on the stack you can use `lua_pushliteral` which will convert it to an array of bytes before pushing it. To get a Lua string on the stack as a JS string you can use `lua_tojsstring` which will attempt to convert it to a UTF-16 JS string. The latter won't give you what you expect if the Lua string is not a valid UTF-16 sequence. You can also convert strings with `luastring_of`, `to_luastring`, `to_jsstring` and `to_uristring`.
### Integers
The JS number type is always a double, and hence cannot accurately represent integers with more than 53 bits. As such, we've taken the route of a rarely used define (`LUA_INT_TYPE=LUA_INT_LONG`) in the PUC-Rio sources, where floats are doubles, but integers are 32 bits.
### `require` and `package.loadlib`
In the browser `require` and `package.loadlib` try to find a file by making synchronous XHR requests.
`require` has been extended to allow searchers to yield.
### _Missing_ features
- `lua_gc`/`collectgarbage`: Fengari relies on the JS garbage collector and does not implement its own.
- The following functions are only available in Node:
- The entire `io` lib
- `os.remove`
- `os.rename`
- `os.tmpname`
- `os.execute`
- `debug.debug()` doesn't work from web workers due to lack of a method to get synchronous user input
- [Weak tables](http://www.lua.org/manual/5.3/manual.html#2.5.2)
- `__gc` metamethods
### _Differences_
- `package.jspath` instead of `package.cpath`
- `LUA_JSPATH_DEFAULT` instead of `LUA_CPATH_DEFAULT` (and contains .js extensions rather than .so or .dll extensions)
- `lua_tointegerx` and `lua_tonumberx` do not have out-parameters indicating conversion success. Instead, ``false`` is returned when conversion fails.
- `luaL_execresult` takes an extra argument: an error object. The error object should have a fields `status`, `signal` and `errno`.
- `luaL_fileresult` takes an extra argument: an error object. The error object should have a field `errno`.
### Configuring
Some luaconf options can be chosen at library load time. Fengari looks for `process.env.FENGARICONF` and if it exists, parses it as a JSON string.
## Extensions
### `dv = lua_todataview(L, idx)`
Equivalent to `lua_tolstring` but returns a [`DataView`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView) instead of a string.
### `lua_pushjsfunction(L, func)`
Alias for `lua_pushcfunction`.
### `lua_pushjsclosure(L, func, n)`
Alias for `lua_pushcclosure`.
### `lua_atnativeerror(L, func)`
Sets a function to be called if a native JavaScript error is thrown across a lua pcall.
The function will be run as if it were a message handler (see https://www.lua.org/manual/5.3/manual.html#2.3).
The current message handler will be run after the native error handler returns.
### `b = lua_isproxy(p, L)`
Returns a boolean `b` indicating whether `p` is a proxy (See `lua_toproxy`).
If `L` is non-null, only returns `true` if `p` belongs to the same global state.
### `p = lua_toproxy(L, idx)`
Returns a JavaScript object `p` that holds a reference to the lua value at the stack index `idx`.
This object can be called with a lua_State to push the value onto that state's stack.
This example would be an inefficient way to write `lua_pushvalue(L, 1)`:
```js
var p = lua_toproxy(L, 1);
p(L);
````
### `fengari` library
A library containing metadata about the fengari release.
- `AUTHORS`
- `COPYRIGHT`
- `RELEASE`
- `VERSION`
- `VERSION_MAJOR`
- `VERSION_MINOR`
- `VERSION_NUM`
- `VERSION_RELEASE`
This library is automatically loaded by `luaL_openlibs` into the global `"fengari"`.
## NYI
- `io.input()`: partially implemented
- `io.lines()`
- `io.open()`
- `io.output()`: partially implemented
- `io.popen()`
- `io.read()`
- `io.tmpfile()`
- `file:lines()`
- `file:read()`
- `file:setvbuf()`
- `file:__gc()`
## References
- [Source code for Lua 5.3](lua.org/source/5.3/)
- [Lua 5.2 Bytecode and Virtual Machine](http://files.catwell.info/misc/mirror/lua-5.2-bytecode-vm-dirk-laurie/lua52vm.html)
- [Lua 5.3 Bytecode Reference](http://the-ravi-programming-language.readthedocs.io/en/latest/lua_bytecode_reference.html)
- [A No-Frills Introduction to Lua 5.1 VM Instructions](http://luaforge.net/docman/83/98/ANoFrillsIntroToLua51VMInstructions.pdf)
|
