[patch] Lua data library

[Lourival Vieira Neto]

Hi Folks,

I've implemented the core features of the Lua data library; the patch
is attached. Luadata provides C and Lua APIs to handle binary data
using Lua scripts. Here is a briefly description of those:

1. Lua API:

1.1 creation

- data.new(table)

Returns a new data object initialized with the given byte array. For example:

d1 = data.new{0xFF, 0xFE, 0x00} --> returns a data object with 3 bytes.

1.2 layout

- data.layout(table)

Returns a new layout table based on table argument, which should have
the following formats for its fields:

(i) field = {<offset>, <length> [, <endian>]} or
(ii) field = {offset = <offset>, length = <length> [endian = <endian>]}

Where, field is the name of the field, <offset> is the offset in bits
(MSB 0), <length> is the length in bits, endian is a string that
indicates the field endianness ('host', 'net', 'little', 'big'). The
default value for endian is 'big'.

Here are a couple examples:

(i) l1 = data.layout{msb = {0, 1}, uint32 = {0, 32}, uint64le = {0,
64, 'little'}}

(ii) l2 = data.layout{msb = {offset = 0, length = 1},
net_unaligned_uint16 = {offset = 1, length = 16, endian = 'net'}}

- d:layout(layout | table)

Applies a layout table on a given data object. If a regular table is
passed, it calls data.layout(table) first. For example:

d1:layout(l1) -- applies l1 layout into d1 data object
d2:layout{byte = {0, 8}} -- creates and applies a new layout into d2 data object

2. API C

2.1 creation

- int ldata_newref(lua_State *L, void *ptr, size_t size);

Creates a new data object pointing to ptr (without copying it), leaves
the data object on the top of the Lua stack and returns a reference
for it. The data object will not be garbage-collected until it is
unreferred.

2.2 deletion

- void ldata_unref(lua_State *L, int ref);

Removes the ptr from the data object and releases the data-object
reference, allowing it to be garbage-collected. After that, it is safe
to free the ptr pointer.

Regards,
--
Lourival Vieira Neto