Tag Archives: c++

offsetof macro in C

I just discovered this macro available in C: offsetof. Here is an simple example:

struct
{
  char a;
  int b;
  char c;
} example;
 
struct example s1;
 
unsigned int offset;
offset = (unsigned int)(&(((example *)(0))->b));

Thanks to offsetof (in the header stddef.h), the last line can be rewritten in:

unsigned int offset;
offset = offsetof(example, b);

[via]


Small Log System

Here is a small piece of code that can be useful if you need to quickly generate traces (or log) in your apps:

class cLog
{
public:
  cLog(char *logfile){};
  static void trace(const char *s)
  { if(s) log <<  s << std::endl; };
  static std::ofstream log;
};
std::ofstream cLog::log("c:\\app_log.txt");

Just use it as follows:

cLog::trace("this is a log");
cLog::trace("this is a second trace");

Embedded Your Shader Souce Code In Your C/C++ Apps

The NVIDIA developer blog shows a way to include shaders codes to your
windows exe: blogs.nvidia.com/developers/2007/03/inlining_shader.html.

But this example is not fully operational. I slightly modified the code to make it totally operational (I compiled it on vc++ 6.0):

1) Add a define to your resource.h file:
#define IDF_SHADEFILE 1000

2) Add an entry in your resource.rc file:
IDF_SHADERFILE RCDATA DISCARDABLE "myShader.glsl"

3) Use the resource in your code:
HMODULE hModule = GetModuleHandle(NULL);
HRSRC hResource = FindResource(hModule, (LPCTSTR)IDF_SHADERFILE, RT_RCDATA);
if(hResource) 
{
  DWORD dwSize = SizeofResource(hModule, hResource);
  HGLOBAL hGlobal = LoadResource(hModule, hResource);
  if(hGlobal) 
  {
    LPVOID pData = LockResource(hGlobal);
    if(pData) 
    {
	// Cast pData to a char * and you have your shader
	char *shader_code = (char *)pData;
	
        // Now do whatever you want with shader_code pointer. 
	// Do not forget that shader_code is not a zero-terminated string!
	// Use dwSize to handle that.
			
    }
  }
}