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eLua components
================================================================================

Besides the Lua core, the platform modules (docs/platform_modules.txt) and the
Newlib 'glue code', eLua uses a number of other code modules (components) for
extended functionality. This is a great thing if you actually need the whole
functionality in your code, but otherwise it becomes a waste of memory space. 
Since eLua was designed to be as flexible as possible, it includes a mechanism 
that allows the user to select exactly what components he needs. Only the 
selected components will be part of the eLua image. Please note that this is 
_not_ a replacement of the platform modules mechanism, the two are complementary
to each other, since the components are not connected with the platform 
interface (docs/platform_interface.txt) in any way.
To use this feature, every platform (src/platform/[name]) must include a file
named "platform_conf.h" that specifies (among other things) what components 
should be built for that platform. For example, the LM3S "platform_conf.h" file 
might look like this:

(BEGIN src/platform/lm3s/platform_conf.h)
// Define here what components you want for this platform

#ifndef __PLATFORM_CONF_H__
#define __PLATFORM_CONF_H__

#define BUILD_XMODEM
#define BUILD_SHELL
#define BUILD_ROMFS
#define BUILD_TERM
........................................
(END src/platform/lm3s/platform_conf.h)

In this case, the XMODEM, SHELL, ROMFS and TERM components will be built. On the
other hand, the i386 "platform_conf.h" will probably have less components:

(BEGIN src/platform/i386/platform_conf.h)
// Define here what components you want for this platform

#ifndef __PLATFORM_CONF_H__
#define __PLATFORM_CONF_H__

#define BUILD_ROMFS
#define BUILD_SHELL
........................................
(END src/platform/i386/platform_conf.h)

You don't need to modify any other part of your code, just rebuild your image
after you made changes to this file (docs/building.txt)
Below you can find a list of eLua components and their functionality.

XMODEM
================================================================================
The XMODEM component enables eLua to receive Lua source files via its shell and 
execute them (docs/the_elua_shell.txt). If you don't need to use "recv" from the
shell you can skip this component.
To enable: 
  #define BUILD_XMODEM

Also, XMODEM is configured with a number of constants also defined in
platform_conf.h. They are:

XMODEM_UART_ID : the id of the UART on which XMODEM runs
XMODEM_TIMER_ID : the id of the timer used by the XMODEM implementation


SHELL
================================================================================
This enables the build of the eLua shell (docs/the_elua_shell.txt). If you don't
need the shell, don't enable this component. eLua will execute the "lua" command
at startup if the eLua shell is not built. The shell comes in two flavours: over
a serial line or over TCP/IP (currently you can't have both at the same time).
To enable shell over a serial line:
  #define BUILD_SHELL
  #define BUILD_CON_GENERIC
To enable shell over TCP/IP:
  #define BUILD_SHELL
  #define BUILD_CON_TCP

ROMFS
================================================================================
If you need to use the ROM file system (docs/the_rom_file_system.txt) enable
this component, otherwise you can skip it.
To enable: 
  #define BUILD_ROMFS

TERM
================================================================================
The TERM module adds support for ANSI terminals. See docs/terminal_support.txt
for details. If you don't need it, and if you're willing to miss the opportunity
of playing hangman in eLua (examples/hangman.lua) you can skip this component :)
To enable: 
  #define BUILD_TERM

Also, TERM is configured with a number of constants also defined in 
platform_conf.h. THey are:

TERM_UART_ID - the id of the UART on which TERM runs
TERM_TIMER_ID - the id of the timer used by the TERM implementation
TERM_LINES - number of lines in the terminal emulator
TERM_COLS - number of columns in the terminal emulator
TERM_TIMEOUT - inter-key timeout (used to detect keys that send multiple codes,
  such as up/down/left/right keys).

IMPORTANT NOTE: TERM doesn't currently work over TCP/IP. 

uIP
================================================================================
uIP is the TCP/IP stack used curently by eLua to provide networking support
(docs/tcpip_in_elua.txt). You can enable the TCP/IP stack and two of its services 
(the DHCP client and the DNS resolver).
To enable uIP (thus TCP/IP support): 
  #define BUILD_UIP
To enable the DHCP client:
  #define BUILD_DHCPC
To enable the DNS resolver:
  #define BUILD_DNS