Add hardware_threads() function (#111)

* Add hardware_threads() function

README.md

@@ -37,6 +37,7 @@ Requires C++14 compiler compliance. Tested with GCC 4.9+, clang 3.8 and Visual S
       * [effil.thread_id()](#id--effilthread_id)
       * [effil.yield()](#effilyield)
       * [effil.sleep()](#effilsleeptime-metric)
+      * [effil.hardware_threads()](#id--effilhardware_threads)
     * [Table](#table)
       * [effil.table()](#table--effiltabletbl)
       * [__newindex: table[key] = value](#tablekey--value)
@@ -306,6 +307,11 @@ Suspend current thread.
 
 **input**: [time metrics](#time-metrics) arguments.
 
+### `effil.hardware_threads()`
+Returns the number of concurrent threads supported by implementation.
+Basically forwards value from [std::thread::hardware_concurrency](https://en.cppreference.com/w/cpp/thread/thread/hardware_concurrency).
+**output**: number of concurrent hardware threads.
+
 ## Table
 `effil.table` is a way to exchange data between effil threads. It behaves almost like standard lua tables.
 All operations with shared table are thread safe. **Shared table stores** primitive types (number, boolean, string), function, table, light userdata and effil based userdata. **Shared table doesn't store** lua threads (coroutines) or arbitrary userdata. See examples of shared table usage [here](#examples)

src/cpp/lua-module.cpp

@@ -108,6 +108,7 @@ int luaopen_effil(lua_State* L) {
             "ipairs",       SharedTable::globalLuaIPairs,
             "size",         luaSize,
             "allow_table_upvalues",    luaAllowTableUpvalues,
+            "hardware_threads",        std::thread::hardware_concurrency,
             sol::meta_function::index, luaIndex
     );
 

tests/lua/thread.lua

@@ -4,6 +4,10 @@ local effil = effil
 
 test.thread.tear_down = default_tear_down
 
+test.thread.hardware_threads = function()
+    test.is_true(effil.hardware_threads() >= 0)
+end
+
 test.thread.wait = function ()
     local thread = effil.thread(function()
         print 'Effil is not that tower'