microSecond elapsed time library

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microSecond elapsed time library

AllanPfalzgraf

This was written for Windows and may be portable (possibly with minor changes).  It had to be C++ to eliminate compile errors.

The table returned by read() is saved as a time reference.

The reference table when passed to elapsed() will return the microSeconds since the reference time.  Elapsed time is 32 bits.

 

// Query Performance Counter Library Module for Lua

// qpc.cpp

 

#include <windows.h>

 

#define qpc_cpp

#define LUA_LIB

 

#include "lua.hpp"

 

LARGE_INTEGER Frequency;

 

/*

* get_frequency -

* Returns the frequency of the Performance Counter

*

* Inputs:

*            none

* Outputs:

*            Frequency

*/

static LARGE_INTEGER get_frequency()

{

    LARGE_INTEGER    Frequency;

 

       QueryPerformanceFrequency(&Frequency);

 

       return Frequency;

}

 

/*

* Query_Counter -

* Reads the performance counter returns a table containing low and high 32 bit parts.

*

* Inputs:

*            none

* Outputs:

*            table of 64 bit count in two 32 bit parts

*

*            returns 1.

*/

static int Query_Counter( lua_State *L )

{

    LARGE_INTEGER    Count;

 

       QueryPerformanceCounter(&Count);

 

       lua_newtable( L );

 

       lua_pushnumber( L, 1 );

       lua_pushinteger( L, Count.u.LowPart );

       lua_settable( L, -3 );

 

       lua_pushnumber( L, 2 );

       lua_pushinteger( L, Count.u.HighPart );

       lua_settable( L, -3 );

 

       return 1;

}

 

 

static int Elapsed_Time( lua_State *L )

{

#define TABLE              1

    LARGE_INTEGER    Old_Count;

    LARGE_INTEGER    uSeconds;

 

       QueryPerformanceCounter(&uSeconds);

 

       luaL_checktype( L, TABLE, LUA_TTABLE );

 

       lua_rawgeti(L, TABLE, 1);

       Old_Count.u.LowPart = (luaL_checkint(L, lua_gettop(L)));

       lua_pop(L, 1);

       lua_rawgeti(L, TABLE, 2);

       Old_Count.u.HighPart = (luaL_checkint(L, lua_gettop(L)));

       lua_pop(L, 1);

 

       if (uSeconds.QuadPart > Old_Count.QuadPart)

              uSeconds.QuadPart -= Old_Count.QuadPart;

       else

       {

              Old_Count.u.LowPart ^= 0xffffffff;

              Old_Count.u.HighPart ^= 0xffffffff;

              Old_Count.QuadPart += 1;

              uSeconds.QuadPart += Old_Count.QuadPart;

       }

             

       uSeconds.QuadPart *= 1000000;

       uSeconds.QuadPart /= Frequency.QuadPart;

 

       lua_pushinteger(L, uSeconds.u.LowPart);

 

       return 1;

 

#undef TABLE

}

 

 

/*

* qpclib[]

*

* This array provides the relation between the function names and the names used in the Lua script to reference the functions.

*

* The format of this array is defined in the Lua C API.

*

*/

static const luaL_Reg qpc[] = {

  {"read", Query_Counter},

  {"elapsed", Elapsed_Time},

  {NULL, NULL}

};

 

/*

* luaopen_qpc

*

* This function opens the performance counter library and makes its references known to Lua for scripts.

*

*/

LUALIB_API int luaopen_qpc (lua_State *L) {

  luaL_newlib(L, qpc);

  Frequency = get_frequency();

  return 1;

}

 

 

 

 

Allan Pfalzgraf
EATON

W126N7250 Flint Drive

Menomonee Falls, WI   53051

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fax: 414 449-6616
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