Add Custom Functions (Rapid Edition)#

Do you have such trouble?

  • There is an algorithm implemented by C, how to get it into LuatOS

  • I just want to add a function, LuatOS code a lot of what’s wrong?

This article takes air101/air103 as an example to introduce how to add functions for lua code to call.

preparatory knowledge#

  • A little vscode experience, basic C language programming ability

  • Can compile existing code, such as air101/air103. If not, first look at Compile Tutorial

  • It is better to understand the basic operation of git.

Expected effect#

local ok, msg = sayhi("wendal", 18)
log.info("custom", ok, msg) -- Print true/false and a paragraph

Create a new c file and store the sample code.#

  1. Using vscode, open the source directory of air101/air103

  2. Navigate to the app/custom directory to create a new file myapi.c

  3. Paste the following

//-------------------
//    LuatOS The header file for, located in the LuatOS library's luat/include
#include "luat_base.h"   // basic function
#include "luat_malloc.h" // memory allocation function

#define LUAT_LOG_TAG "custom"

#include "luat_log.h"    // log function, supporting LUAT_LOG_TAG

// -------------------
// Need to use the header file, import it yourself
//#include "xxx.h"
// -------------------

// function prototype int $name(lua_State *L)
// int The number of return values, which refers to the number of values popped from lua's stack as return values.
// C The function prototype has only one parameter, and the corresponding lua parameter is in the virtual stack of lua.
static int luat_custom_sayhi(lua_State *L) { // static Not necessary, but recommend added.
    size_t len;
    const char* name = luaL_checklstring(L, 1, &len); // corresponds to the first parameter of the lua call,  "wendal"
    int age = luaL_checkinteger(L, 2);                // corresponding to the second parameter of lua call, the value 123

    // age If it's less than 19, it's "the right age.""
    if (age < 19) {
        // Push 2 return values into lua stack
        lua_pushboolean(L, 1); // Pressing in true
        lua_pushfstring(L, "%s's age is %d", name, age); // age is correct!!!
    }
    // Otherwise, the current is the "wrong age"."
    else {
        // Push 2 return values into lua stack
        lua_pushboolean(L, 1); // Pressing in false
        lua_pushfstring(L, "%s's age is 18, always!!", name); // No, wendal is only 18
    }
    return 2; // Here is the number of return values, not the correct/error return code such as 0/1.
}

void luat_custom_init(lua_State *L) { // Function declaration in luat_base.h
    LLOGD("custom init begin ...");

    // Add a global function, the function name is sayhi
    lua_pushcfunction(L, luat_custom_sayhi); // Push stack first
    lua_setglobal(L, "sayhi");               // Pressing in _G.sayhi = XXX

    LLOGD("custom init done");
    return; // No return value required.
}

Enable custom function construction#

  1. Open app/include/luat_conf_bsp.h

  2. In the middle, add the following macro definition

#define LUAT_HAS_CUSTOM_LIB_INIT 1

test happily#

  1. Execute xmake and compile it regular

  2. Brush machine, under the script, see the effect

You fill in ^_^

  • Compilation failed? Fix syntax errors according to prompts

  • After brushing the machine, the prompt cannot find the sayhi-make sure the compilation is correct, make sure the correct underlying firmware file is selected, and make sure the new underlying layer is brushed in.

Can’t do it? Ask for help? To the QQ group for help or gitee post.#

  1. QQ Group: 1061642968

  2. gitee: https://gitee.com/openLuat/LuatOS By the way, order a star, thank you

Expansion 1-there are many functions, can I make a library?#

It must be possible. It is also a quick way to change it directly with a ready-made copy of lib_xx.c.

  • First, give the library a cool name.

  • Imitate the existing luat_lib_xxx.c to write a library

  • At first, it was suggested to write only one function and declare the “rotable_Reg” and “luaopen_xxx” methods.

  • Call the luaopen_xxx method in the custom_init.

  • If you do not use custom_init, luat_base_xxx.c also declares

Expansion 2-Add static libraries for linking#

  • Need a little xmake knowledge, but the search string can also be added

  • Put the file into the lib directory, assuming the name is libcool.a

  • Modify xmake.lua to look ./lib/libgt.a

  • Before or after it, add ./lib/libcool. a, noting the space before and after

  • happily compiled