Overlapped calls (esp. texture loading) via plugin

local overlapper=require("overlapper")
 
 function wait(ms)
    local start = os.timer()
    local finish = start+ms
    while (finish > os.timer()) do
    end
 end
 
-- First try function containing simple assignment expression to local
local answer
overlapper.overlapCall(function() wait(3) answer=3+4 end)
 
-- Print answer. First print should be nil since funtion delays for 3s
-- Second print should be corect since waits for completion
print("answer=", answer)
overlapper.overlapWait()
print("answer(wait)=", answer)

//
//  overlapper.mm
//  GiderosiPadPlayer plugin
//
 
#include "gideros.h"
#include "lua.h"
#include "lauxlib.h"
 
#import <Foundation/Foundation.h>
 
<a href="http://forum.gideros.rocks/profile/interface" rel="nofollow">@interface</a> OverlapThread : NSObject
+(void)start: (id) Lid;
<a href="http://forum.gideros.rocks/profile/end" rel="nofollow">@end</a>
 
<a href="http://forum.gideros.rocks/profile/implementation" rel="nofollow">@implementation</a> OverlapThread
 
NSLock* lock=NULL;
 
+(void)start: (id) Lid 
{
    lua_State* L= (lua_State*)[Lid pointerValue];
    if (lock==NULL)
    {
        lock=[[NSLock alloc] init];
    }
    [lock lock];
 
    assert(lua_isfunction(L, -1)==1);
    if (lua_isnil(L, -1)==0)
    {
        usleep(1000);
        lua_call(L, 0, 0);
    }
    [lock unlock];
}
<a href="http://forum.gideros.rocks/profile/end" rel="nofollow">@end</a>
 
static int overlapCall(lua_State *L)
{
    assert(lua_isfunction(L, -1)==1);
    lua_State *threadL=lua_newthread(L);
    lua_xmove(L, threadL, 2);
    lua_xmove(threadL, L, 1);
    assert(lua_isfunction(threadL, -1)==1);
    assert(lua_isthread(L, -1)==1);
    [NSThread detachNewThreadSelector:<a href="http://forum.gideros.rocks/profile/selector%28start" rel="nofollow">@selector(start</a><img class="emoji" src="http://forum.gideros.rocks/resources/emoji/smile.png" title=":)" alt=":)" height="20" /> toTarget:[OverlapThread class] withObject: [NSValue valueWithPointer: threadL]];
    return 1;
}
 
static int overlapWait(lua_State *L)
{
    [lock lock];
    [lock unlock];
    return 0;
}
 
static int loader(lua_State *L)
{
    //This is a list of functions that can be called from Lua
    const luaL_Reg functionlist[] = {
        {"overlapCall", overlapCall },
        {"overlapWait", overlapWait },
        {NULL, NULL},
    };
    luaL_register(L, "overlapper", functionlist);
 
    //return the pointer to the plugin
    return 1;
}
 
static void g_initializePlugin(lua_State* L)
{
    lua_getglobal(L, "package");
    lua_getfield(L, -1, "preload");
 
    lua_pushcfunction(L, loader);
    lua_setfield(L, -2, "overlapper");
 
    lua_pop(L, 2);    
}
 
static void g_deinitializePlugin(lua_State *L)
{   }
 
REGISTER_PLUGIN("overlapper", "1.0")