Re: Execution of pre compiled lua code from memory mapped files
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- Subject: Re: Execution of pre compiled lua code from memory mapped files
- From: Michael Welsh Duggan <mwd@...>
- Date: 2015年5月29日 10:13:05 -0400
Tim Hill <drtimhill@gmail.com> writes:
>> On May 28, 2015, at 2:42 AM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
>>
>> 2015年05月28日 11:21 GMT+02:00 Hans Riekehof <Riekehof@schoeps.de>:
>>
>>> My idea is to have this for pre compiled lua code because I want to
>>> write a lot of code in Lua and not in C/C++.
>>
>> Lua compiles to bytecode for a virtual machine. That VM is different
>> for every major Lua release: 5.1, 5.2, 5.3 etc, but the same within minor
>> releases 5.2.1, 5.2.2 etc. However, it is not supposed to portable across
>> different architectures.
>>
>> I'm not entirely sure I understand what you want. Can you show us
>> what the Lua code would look like in a postulated Lua dialect that has
>> this feature?
>
> The poster wants to execute directly from a bytecode file via
> memory-mapping to save on RAM footprint by avoiding the need to
> copy/load the bytecode into memory before execution. The issue of
> portability isn't a problem here since (presumably) the bytecode and
> Lua interpreter are all embedded in the flash/ROM image at the same
> time.
>
> Given that Lua is designed for embedded systems it’s a bit surprising
> that this isn’t part of the core API.
I'm confused. Although not part of the core library, luaL_loadbufferx()
exists, and is implemented in a very small amount of code:
typedef struct LoadS {
const char *s;
size_t size;
} LoadS;
static const char *getS (lua_State *L, void *ud, size_t *size) {
LoadS *ls = (LoadS *)ud;
(void)L; /* not used */
if (ls->size == 0) return NULL;
*size = ls->size;
ls->size = 0;
return ls->s;
}
LUALIB_API int luaL_loadbufferx (lua_State *L, const char *buff, size_t size,
const char *name, const char *mode) {
LoadS ls;
ls.s = buff;
ls.size = size;
return lua_load(L, getS, &ls, name, mode);
}
I use luaL_loadbufferx() to compile compiled lua into my binaries (along
with a small script that converts the binary compiled lua file into a C
array). I feel that I must be missing something about the original
question.
--
Michael Welsh Duggan
(mwd@cert.org)