Bootstrapping LuaJIT on Android

android_main.c

#include <android/log.h>
#include "android_native_app_glue.h"

#include "lua.h"
#include "lualib.h"
#include "lauxlib.h"

#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "beamer", __VA_ARGS__))
#define LOGF(...) ((void)__android_log_print(ANDROID_LOG_FATAL, "beamer", __VA_ARGS__))

static struct android_app* state = NULL;

const char *reader(lua_State *L, void *data, size_t *size)
{
    static char buffer[1024];
    *size = AAsset_read(data, buffer, 1024);
    if(*size < 0)
        *size = 0;
    return buffer;
}

static int loader_lua_asset (lua_State *L)
{
    const char *filename;
    const char *name = luaL_checkstring(L, 1);
    luaL_gsub(L, name, ".", LUA_DIRSEP);
    lua_pushstring(L, ".lua");
    lua_concat(L, 2);
    name = lua_tostring(L, -1);

    AAsset* asset = AAssetManager_open(state->activity->assetManager,
        name, AASSET_MODE_BUFFER);
    
    if(asset == NULL)
    {
        lua_pushfstring(L, "\n\tno asset '%s'", name);
        return 1;
    }

    if (lua_load(L, reader, asset, name) != 0)
        luaL_error(L, "error loading module '%s' from asset '%s':\n\t%s",
            lua_tostring(L, 1), name, lua_tostring(L, -1));

    AAsset_close(asset);

    return 1;
}

void android_main(struct android_app* _state)
{
    // Make sure glue isn't stripped.
    app_dummy();
    state = _state;

    LOGI("opening lua");
    lua_State *L = lua_open();
    luaL_openlibs(L);

    // register the lua loader
    LOGI("registering loader_lua_asset in package.loaders");
    lua_getglobal(L, "package");
    lua_getfield(L, -1, "loaders");
    lua_pushcfunction(L, loader_lua_asset);
    lua_rawseti(L, -2, 2);
    lua_pop(L, 2);

    // now we're going to load init_android.lua, printing a backtrace on errors
    LOGI("running init_android.lua");
    lua_getglobal(L, "debug");
    lua_getfield(L, -1, "traceback");

    {
        // load init_android module
        lua_pushcfunction(L, loader_lua_asset);
        lua_pushstring(L, "init_android");
        lua_call(L, 1, 1);
    }

    // call it with our android_app* as a parameter
    lua_pushlightuserdata(L, state);
    if(lua_pcall(L, 1, 0, -3) != 0)
    {
        LOGF("%s", lua_tostring(L, -1));
    }

    LOGI("closing lua");
    lua_close(L);
    LOGI("application done");
}