ATL Removal: Part 1 – Removing BEGIN_COM_MAP() and END_COM_MAP()

There are some who feel that ATL is the best thing since sliced bread for COM programming. ATL can abstract a lot of the nitty gritty COM programming away from the COM programmer. My goal today is not to bash ATL. I think it can be a great time saver if used correctly for the right level of code. If you are programming UI, or an IE plugin, go right ahead and use ATL if you like. If you are writing lower level system APIs, please don’t. Also, ATL cannot be used for an excuse for not understanding COM programming or memory management. I have spent the last year fixing lots of bugs because someone didn’t understand what ATL was doing, things like: double frees, double releases, memory leaks, leaked references, and so on. In other words, ATL is not a sliver bullet for API usage ignorance. I don’t like using ATL because: writing straight COM code is not much harder, and ATL makes debugging more annoying. So, in the end for me, ATL does not buy me much, and is somewhat annoying. If you like ATL and know what it is really doing so you use it correctly, go ahead and use it. Independent of my no ATL preference, one API I am maintaining needs to be “low level” and therefore should not depend on ATL, so I am removing ATL from that API.

ATL wants to internally manage the ref counts to your ATL based com object. To do this, it wraps your com object using a template class called CComObject. CComObject basically adds two extra layers to your com object. For debugging, it does make things a little bit more annoying, but it is supposed to manage the lifetime of your object for you.

The first thing to do is to remove the COM_MAP macros needed to set up all of the CComObject hooks. When you have an ATL generated COM object, it creates for you something like this in your header:

BEGIN_COM_MAP(CYourInterface)
  COM_INTERFACE_ENTRY(IYourInterface)
END_COM_MAP()

Basically these macros help write your IUnknown implementation. Not really that big of a time saver as it is not that hard to implement IUnknown. The first step is to remove COM_MAP macro stuff from your header and swap it for the IUnknown definition. Here is one example that you see often:

STDMETHOD(QueryInterface)(IN REFIID riid, OUT void ** ppv);
STDMETHOD_(ULONG, AddRef)(void);
STDMETHOD_(ULONG, Release)(void);

Next, in your cpp file where you implement your com object, you will need to add the implementation of IUnknown. This too is almost boiler plate.

//////////////////////////////////////////////////////////////////////
// Implementation : IUnknown
//////////////////////////////////////////////////////////////////////

ULONG CYourInterface::AddRef()
{
  return InterlockedIncrement(&m_cRef);
}

ULONG CYourInterface::Release()
{
  LONG cRef = InterlockedDecrement(&m_cRef);

  if (0 == cRef)
  {
      delete this;
  }

  return cRef;
}

HRESULT CYourInterface::QueryInterface(REFIID riid, __deref_out_opt void **ppv)
{
  HRESULT hr = S_OK;

  if (ppv)
  {
      *ppv = NULL;
  }
  else
  {
      hr = E_INVALIDARG;
  }

  if (S_OK == hr)
  {
      if ((__uuidof(IUnknown) == riid)  (riid == __uuidof(IYourInterface)))
      {
          AddRef();
          *ppv = (IYourInterface *)this;
      }
      else
      {
          hr = E_NOINTERFACE;
      }
  }

  return hr;
}

Finally make sure that you add a:

LONG m_cRef;

Member in your class, and make sure you initialize it to 1 in your constructor.

m_cRef(1)

GPU Accelerated FDTD Using Cg

Apparently there has been some interested in my old GPU accelerated FDTD code implemented in C and Cg. I also had a CUDA version that had a hard time meeting the performance of the Cg version. I will need to check when I get home to see if I can find the other versions. Here is one version that I found on one of my old sites. It looks like it is version 0.1 and about three years old. I know I have a better versions somewhere out there, but this will give you a "taste" until I can find the other versions. Still, there are some interesting aspects of this code. I used an interesting 3D volume packing scheme for 2D textures that you can read about in GPU Gems 2. Also a lot of the guts of this code initially came from Dom's basic math tutorial for Cg.

cg_fdtd: clean
 gcc test.c -o cg_fdtd -lglut -lGLEW -lCgGL -lpthread

clean:
 rm -f cg_fdtd

test: cg_fdtd
 ./cg_fdtd 256 10

/*
 * test.c
 *
 * author      : Sam Adams
 * date        : 20061027
 * discription : This is my implementation of a basic FDTD using GPU with Cg
 */

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define GLUT_WINDOW_NAME "fdtd window"

typedef enum bool{false, true} bool;
//clock_gettime
// struct for variable parts of GL calls (texture format, float format etc)
struct struct_textureParameters {
 char* name;
 GLenum texTarget;
 GLenum texInternalFormat;
 GLenum texFormat;
 char* shader_source;
};

// struct actually being used (set from command line)
struct struct_textureParameters textureParameters;

int verbose = 1;
int numIterations = 100; //timesteps for fdtd
int texSize = 256;

GLuint glutWindowHandle;
GLuint fb;

enum components{X, Y, Z};

GLuint *exTexID; // these are z slices for fdtd
GLuint *eyTexID; // the +1 is for the output of the calculations
GLuint *ezTexID;
GLuint *hxTexID;
GLuint *hyTexID;
GLuint *hzTexID;
GLuint psTexID, psEmptyTexID;

// Cg vars
CGcontext cgContext;
CGprofile fragmentProfile;
CGprogram fragmentProgram;
//fdtd
////for e fields
CGprogram ex_fp, ey_fp, ez_fp; 
CGparameter ex_ps, ex_e, ex_h1, ex_h2, ex_h3, ex_h4, ex_esctc, ex_eincc, ex_ei, ex_edevcn, ex_dei, ex_ecrl1, ex_ecrl2;
CGparameter ey_e, ey_h1, ey_h2, ey_h3, ey_h4, ey_esctc, ey_eincc, ey_ei, ey_edevcn, ey_dei, ey_ecrl1, ey_ecrl2;
CGparameter ez_e, ez_h1, ez_h2, ez_h3, ez_h4, ez_esctc, ez_eincc, ez_ei, ez_edevcn, ez_dei, ez_ecrl1, ez_ecrl2;
////for h fields
CGprogram hx_fp, hy_fp, hz_fp;
CGparameter hx_h, hx_e1, hx_e2, hx_e3, hx_e4, hx_dt, hx_delta1, hx_delta2;
CGparameter hy_h, hy_e1, hy_e2, hy_e3, hy_e4, hy_dt, hy_delta1, hy_delta2;
CGparameter hz_h, hz_e1, hz_e2, hz_e3, hz_e4, hz_dt, hz_delta1, hz_delta2;

float* tmpData;
//fdtd Cg update sources
char *hx_hUpdate_source = \
"float hUpdate ("\
"in float2 coords : TEXCOORD0, "\
"uniform samplerRECT textureH, "\
"uniform samplerRECT textureE1, "\
"uniform samplerRECT textureE2, "\
"uniform samplerRECT textureE3, "\
"uniform samplerRECT textureE4, "\
"uniform float dt, "\
"uniform float delta1, "\
"uniform float delta2) : COLOR{ "\
"float h = texRECT(textureH, coords); "\
"float e1 = texRECT(textureE1, coords); "\
"float e2 = texRECT(textureE2, coords); "\
"float e3 = texRECT(textureE3, coords+(0.0,1.0)); "\
"float e4 = texRECT(textureE4, coords); "\
"return h + ((dt / 0.0000012566306) *((e1 - e2) / delta1 - (e3 - e4) / delta2)); }";

char *hy_hUpdate_source = \
"float hUpdate ("\
"in float2 coords : TEXCOORD0, "\
"uniform samplerRECT textureH, "\
"uniform samplerRECT textureE1, "\
"uniform samplerRECT textureE2, "\
"uniform samplerRECT textureE3, "\
"uniform samplerRECT textureE4, "\
"uniform float dt, "\
"uniform float delta1, "\
"uniform float delta2) : COLOR{ "\
"float h = texRECT(textureH, coords); "\
"float e1 = texRECT(textureE1, coords+(1.0,0.0)); "\
"float e2 = texRECT(textureE2, coords); "\
"float e3 = texRECT(textureE3, coords); "\
"float e4 = texRECT(textureE4, coords); "\
"return h + ((dt / 0.0000012566306) *((e1 - e2) / delta1 - (e3 - e4) / delta2)); }";

char *hz_hUpdate_source = \
"float hUpdate ("\
"in float2 coords : TEXCOORD0, "\
"uniform samplerRECT textureH, "\
"uniform samplerRECT textureE1, "\
"uniform samplerRECT textureE2, "\
"uniform samplerRECT textureE3, "\
"uniform samplerRECT textureE4, "\
"uniform float dt, "\
"uniform float delta1, "\
"uniform float delta2) : COLOR{ "\
"float h = texRECT(textureH, coords); "\
"float e1 = texRECT(textureE1, coords+(0.0,1.0)); "\
"float e2 = texRECT(textureE2, coords); "\
"float e3 = texRECT(textureE3, coords+(1.0,0.0)); "\
"float e4 = texRECT(textureE4, coords); "\
"return h + ((dt / 0.0000012566306) *((e1 - e2) / delta1 - (e3 - e4) / delta2)); }";

char *ex_eUpdate_source = \
"float eUpdate ("\
"in float2 coords : TEXCOORD0, "\
"uniform samplerRECT texturePS, "\
"uniform samplerRECT textureE, "\
"uniform samplerRECT textureH1, "\
"uniform samplerRECT textureH2, "\
"uniform samplerRECT textureH3, "\
"uniform samplerRECT textureH4, "\
"uniform float esctc, "\
"uniform float eincc, "\
"uniform float ei, "\
"uniform float edevcn, "\
"uniform float dei, "\
"uniform float ecrl1, "\
"uniform float ecrl2 ) : COLOR{ "\
"float ps = texRECT(texturePS, coords); "\
"float e = texRECT(textureE, coords); "\
"float h1 = texRECT(textureH1, coords); "\
"float h2 = texRECT(textureH2, coords+(0.0,1.0)); "\
"float h3 = texRECT(textureH3, coords); "\
"float h4 = texRECT(textureH4, coords); "\
"float tmp = ps;"\
"if(ps != 0.0) tmp = ps;"\
/*"else tmp = e * esctc - eincc * ei - edevcn * dei + (h1 - h2) * ecrl1 - (h3 - h4) * ecrl2;"\*/
"else tmp = e * esctc - eincc * ei - edevcn * dei + ((h1 - h2) * ecrl1) - ((h3 - h4) * ecrl2);"\
"return tmp;}";

//"return e * esctc - eincc * ei - edevcn * dei + (h1 - h2) * ecrl1 - (h3 - h4) * ecrl2;}";
//"return e * esctc - eincc * ei - edevcn * dei + (h1 -h2) * ecrl1;}";

char *ey_eUpdate_source = \
"float eUpdate ("\
"in float2 coords : TEXCOORD0, "\
"uniform samplerRECT textureE, "\
"uniform samplerRECT textureH1, "\
"uniform samplerRECT textureH2, "\
"uniform samplerRECT textureH3, "\
"uniform samplerRECT textureH4, "\
"uniform float esctc, "\
"uniform float eincc, "\
"uniform float ei, "\
"uniform float edevcn, "\
"uniform float dei, "\
"uniform float ecrl1, "\
"uniform float ecrl2 ) : COLOR{ "\
"float e = texRECT(textureE, coords); "\
"float h1 = texRECT(textureH1, coords); "\
"float h2 = texRECT(textureH2, coords); "\
"float h3 = texRECT(textureH3, coords); "\
"float h4 = texRECT(textureH4, coords+(1.0,0.0)); "\
"return e * esctc - eincc * ei - edevcn * dei + (h1 - h2) * ecrl1 - (h3 - h4) * ecrl2; }";

char *ez_eUpdate_source = \
"float eUpdate ("\
"in float2 coords : TEXCOORD0, "\
"uniform samplerRECT textureE, "\
"uniform samplerRECT textureH1, "\
"uniform samplerRECT textureH2, "\
"uniform samplerRECT textureH3, "\
"uniform samplerRECT textureH4, "\
"uniform float esctc, "\
"uniform float eincc, "\
"uniform float ei, "\
"uniform float edevcn, "\
"uniform float dei, "\
"uniform float ecrl1, "\
"uniform float ecrl2 ) : COLOR{ "\
"float e = texRECT(textureE, coords); "\
"float h1 = texRECT(textureH1, coords); "\
"float h2 = texRECT(textureH2, coords+(1.0,0.0)); "\
"float h3 = texRECT(textureH3, coords); "\
"float h4 = texRECT(textureH4, coords+(0.0,1.0)); "\
"return e * esctc - eincc * ei - edevcn * dei + (h1 - h2) * ecrl1 - (h3 - h4) * ecrl2; }";

time_t start, end;

/* prototypes */
void initGLUT(int argc, char **argv);
void initGLEW();
void initFBO();
void createTextures();
void initCG();
void performComputation();
void checkGLErrors (const char *label);
double cpuBench();
void printVector(float *v, int len);
void transferFromTexture(float* data, GLenum fb);
void initMemory();
//void nextSlice(int i);
void transferToTexture(float* data, GLuint texID);

int main(int argc, char **argv){
 int i;
 time_t start, stop;
 float simTime;
 double mflops;
 FILE *f;

 f = fopen("results", "a");

 texSize = atoi(argv[1]);
 numIterations = atoi(argv[2]);

// int start, stop;
// struct timespec res;
// clock_getres(CLOCK_REALTIME, &res);
 textureParameters.name                               = "TEXRECT - float_NV - R - 32";
 textureParameters.texTarget                          = GL_TEXTURE_RECTANGLE_ARB;
 textureParameters.texInternalFormat               = GL_FLOAT_R32_NV;
 textureParameters.texFormat                          = GL_LUMINANCE;
// start =  clock_gettime(CLOCK_REALTIME, &res);
 start = clock();
 initMemory();
 if(verbose) fprintf(stderr,"initalizing GLUT\n");
 initGLUT(argc, argv);
 if(verbose) fprintf(stderr,"initalizing GLEW\n");
 initGLEW();
 if(verbose) fprintf(stderr,"initalizing FBOs\n");
 initFBO();
 if(verbose) fprintf(stderr,"creating textures\n");
 createTextures();
 if(verbose) fprintf(stderr,"initalizing Cg\n");
 initCG();
 if(verbose) fprintf(stderr,"performing calculations\n");
 performComputation();
 stop = clock();
 simTime = (float)(stop-start)/(float)CLOCKS_PER_SEC;
 mflops = (double)(63*texSize*texSize*texSize*numIterations)/1000000.0;
 printf("time was %f\n", simTime);
 fprintf(f,"%i\t%i\t%e\t%e\n",texSize,numIterations,simTime,mflops);
 return 0;
}

void initMemory(){
 tmpData =  (float*)calloc(sizeof(float),texSize*texSize); // to initalize textures to 0.0
 exTexID = (GLuint*)malloc(sizeof(GLuint) * texSize);
 eyTexID = (GLuint*)malloc(sizeof(GLuint) * texSize);
 ezTexID = (GLuint*)malloc(sizeof(GLuint) * texSize);
 hxTexID = (GLuint*)malloc(sizeof(GLuint) * texSize);
 hyTexID = (GLuint*)malloc(sizeof(GLuint) * texSize);
 hzTexID = (GLuint*)malloc(sizeof(GLuint) * texSize);
/*
 exLocation = (int*)malloc(sizeof(int)*texSize);
 eyLocation = (int*)malloc(sizeof(int)*texSize);
 ezLocation = (int*)malloc(sizeof(int)*texSize);
 hxLocation = (int*)malloc(sizeof(int)*texSize);
 hyLocation = (int*)malloc(sizeof(int)*texSize);
 hzLocation = (int*)malloc(sizeof(int)*texSize);

 exLocation_out = eyLocation_out = ezLocation_out = hxLocation_out = hyLocation_out = hzLocation_out = texSize;*/
}

void printVector(float *v, int len){
 int i;

 for(i = 0; i < len; i++) printf("%i)\t%f\n",i,v[i]);
}

/*
 * Checks framebuffer status.
 * Copied directly out of the spec, modified to deliver a return value.
 */
int checkFramebufferStatus() {
 GLenum status;
 status = (GLenum) glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
 switch(status) {
  case GL_FRAMEBUFFER_COMPLETE_EXT:
   printf("Framebuffer complete\n");
   return 1;
  case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT_EXT:
   printf("Framebuffer incomplete, incomplete attachment\n");
   return 0;
  case GL_FRAMEBUFFER_UNSUPPORTED_EXT:
   printf("Unsupported framebuffer format\n");
   return 0;
  case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT_EXT:
   printf("Framebuffer incomplete, missing attachment\n");
   return 0;
  case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS_EXT:
   printf("Framebuffer incomplete, attached images must have same dimensions\n");
   return 0;
  case GL_FRAMEBUFFER_INCOMPLETE_FORMATS_EXT:
   printf("Framebuffer incomplete, attached images must have same format\n");
   return 0;
  case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER_EXT:
   printf("Framebuffer incomplete, missing draw buffer\n");
   return 0;
  case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER_EXT:
   printf("Framebuffer incomplete, missing read buffer\n");
   return 0;
  default:
   printf("Unknown framebuffer status %i\n", (int)status);
 }
 return 0;
}

void checkGLErrors (const char *label) {
 GLenum errCode;
 const GLubyte *errStr;

 if ((errCode = glGetError()) != GL_NO_ERROR) {
  errStr = gluErrorString(errCode);
  printf("OpenGL ERROR: ");
  printf((char*)errStr);
  printf("(Label: ");
  printf(label);
  printf(")\n.");
 }
}

/*
 * Performs the actual calculation.
 */
void performComputation(){
 int i, j;
 int tmp;
 double total;
 double mflops;

 start = clock();
 glEnable(textureParameters.texTarget);
 // attach textures to FBO
 glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, textureParameters.texTarget, exTexID[texSize], 0);
 glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT1_EXT, textureParameters.texTarget, eyTexID[texSize], 0);
 glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT2_EXT, textureParameters.texTarget, ezTexID[texSize], 0);
 // check if that worked
 if(!checkFramebufferStatus()) {
  printf("glFramebufferTexture2DEXT():\t [FAIL]\n");
  exit (-1);
 }// else if (mode == 0) {
 // printf("glFramebufferTexture2DEXT():\t [PASS]\n");
 // }
 // enable fragment profile
 cgGLEnableProfile(fragmentProfile);
 // bind fdtd program
 cgSetParameter1f(ex_esctc, 1.0);
 cgSetParameter1f(ex_eincc, 1.0);
 cgSetParameter1f(ex_ei, 1.0);
 cgSetParameter1f(ex_edevcn, 0.0);
 cgSetParameter1f(ex_dei, 0.0);
 cgSetParameter1f(ex_ecrl1, 217.51);
 cgSetParameter1f(ex_ecrl2, 217.51);

 cgGLBindProgram(ey_fp);
 cgSetParameter1f(ey_esctc, 1.0);
 cgSetParameter1f(ey_eincc, 0.0);
 cgSetParameter1f(ey_ei, 0.0);
 cgSetParameter1f(ey_edevcn, 0.0);
 cgSetParameter1f(ey_dei, 0.0);
 cgSetParameter1f(ey_ecrl1, 217.51);
 cgSetParameter1f(ey_ecrl2, 217.51);

 cgGLBindProgram(ez_fp);
 cgSetParameter1f(ez_esctc, 1.0);
 cgSetParameter1f(ez_eincc, 0.0);
 cgSetParameter1f(ez_ei, 0.0);
 cgSetParameter1f(ez_edevcn, 0.0);
 cgSetParameter1f(ez_dei, 0.0);
 cgSetParameter1f(ez_ecrl1, 217.51);
 cgSetParameter1f(ez_ecrl2, 217.51);

 cgGLBindProgram(hx_fp);
 cgSetParameter1f(hx_dt, 1.0);
 cgSetParameter1f(hx_delta1, 1.0);
 cgSetParameter1f(hx_delta2, 1.0);

 cgGLBindProgram(hy_fp);
 cgSetParameter1f(hy_dt, 1.0);
 cgSetParameter1f(hy_delta1, 1.0);
 cgSetParameter1f(hy_delta2, 1.0);

 cgGLBindProgram(hz_fp);
 cgSetParameter1f(hz_dt, 1.0);
 cgSetParameter1f(hz_delta1, 1.0);
 cgSetParameter1f(hz_delta2, 1.0);

 // sutff that changes should be in the loop...

 for(j = 0; j < numIterations; j++){
  //printf("iteration %i\n",j);
  for(i = 0; i < texSize; i++){
   //update x e field
   cgGLBindProgram(ex_fp);
//   if(i == texSize/2){
//    cgGLSetTextureParameter(ex_ps, psTexID);
//    cgGLEnableTextureParameter(ex_ps);
//   }
//   else{
//    cgGLSetTextureParameter(ex_ps, psEmptyTexID);
//    cgGLEnableTextureParameter(ex_ps);
//   }
   cgGLSetTextureParameter(ex_e, exTexID[i]);
   cgGLEnableTextureParameter(ex_e);
   cgGLSetTextureParameter(ex_h1, hzTexID[i]);
   cgGLEnableTextureParameter(ex_h1);
   cgGLSetTextureParameter(ex_h2, hzTexID[i]);
   cgGLEnableTextureParameter(ex_h2);
   cgGLSetTextureParameter(ex_h3, hyTexID[i]);
   cgGLEnableTextureParameter(ex_h3);
//   fprintf(stdout,"we are doing --i- %i --i-1- %i  %i\n",i, i-1,((i-1 <= 0) ? 0 : i-1)); 
   //if(i) cgGLSetTextureParameter(ex_h4, hyTexID[i-1]);
   if(i > 0) cgGLSetTextureParameter(ex_h4, hyTexID[i]);
   else cgGLSetTextureParameter(ex_h4, hyTexID[0]);
   cgGLEnableTextureParameter(ex_h4);
   glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT);
   glPolygonMode(GL_FRONT,GL_FILL);
   //render/compute 
   glBegin(GL_QUADS);
   glTexCoord2f(0.0, 0.0);
   glVertex2f(0.0, 0.0);
   glTexCoord2f(texSize, 0.0);
   glVertex2f(texSize, 0.0);
   glTexCoord2f(texSize, texSize);
   glVertex2f(texSize, texSize);
   glTexCoord2f(0.0, texSize);
   glVertex2f(0.0, texSize);
   glEnd();
   //get result
//    transferFromTexture(tmpData, hyTexID[i]);
   /*if(i == texSize/2){*/// fprintf(stdout,"h%i) hy ps %e\n",i,tmpData[(texSize*texSize)/2 + 1]);
//    printVector(tmpData, texSize*texSize);
   //}
   transferFromTexture(tmpData, GL_COLOR_ATTACHMENT0_EXT);
   transferToTexture(tmpData, exTexID[i]);
//   if(i == texSize/2){ fprintf(stdout,"e%i) ex ps %e\n",j,tmpData[(texSize*texSize)/2 + 1]);
//    printVector(tmpData, texSize*texSize);
//   }
   //update y e field
   cgGLBindProgram(ey_fp);
   cgGLSetTextureParameter(ey_e, eyTexID[i]);
   cgGLEnableTextureParameter(ey_e);
   cgGLSetTextureParameter(ey_h1, hxTexID[i]);
   cgGLEnableTextureParameter(ey_h1);
   cgGLSetTextureParameter(ey_h2, hxTexID[((i-1 < 0) ? 0 : i-1)]);
   cgGLEnableTextureParameter(ey_h2);
   cgGLSetTextureParameter(ey_h3, hzTexID[i]);
   cgGLEnableTextureParameter(ey_h3);
   cgGLSetTextureParameter(ey_h4, hyTexID[i]);
   cgGLEnableTextureParameter(ey_h4);
   glDrawBuffer(GL_COLOR_ATTACHMENT1_EXT);
   glPolygonMode(GL_FRONT,GL_FILL);
   //render/compute 
   glBegin(GL_QUADS);
   glTexCoord2f(0.0, 0.0);
   glVertex2f(0.0, 0.0);
   glTexCoord2f(texSize, 0.0);
   glVertex2f(texSize, 0.0);
   glTexCoord2f(texSize, texSize);
   glVertex2f(texSize, texSize);
   glTexCoord2f(0.0, texSize);
   glVertex2f(0.0, texSize);
   glEnd();
   //get result
   transferFromTexture(tmpData, GL_COLOR_ATTACHMENT1_EXT);
   transferToTexture(tmpData, eyTexID[i]);

//   if(i == texSize/2){ fprintf(stdout,"e%i) ey ps %e\n",j,tmpData[(texSize*texSize)/2 + 1]);
//    printVector(tmpData, texSize*texSize);
//   }
   //update z e field
   cgGLBindProgram(ez_fp);
   cgGLSetTextureParameter(ez_e, ezTexID[i]);
   cgGLEnableTextureParameter(ez_e);
   cgGLSetTextureParameter(ez_h1, hyTexID[i]);
   cgGLEnableTextureParameter(ez_h1);
   cgGLSetTextureParameter(ez_h2, hyTexID[i]);
   cgGLEnableTextureParameter(ez_h2);
   cgGLSetTextureParameter(ez_h3, hxTexID[i]);
   cgGLEnableTextureParameter(ez_h3);
   cgGLSetTextureParameter(ez_h4, hxTexID[i]);
   cgGLEnableTextureParameter(ez_h4);
   glDrawBuffer(GL_COLOR_ATTACHMENT2_EXT);
   glPolygonMode(GL_FRONT,GL_FILL);
   //render/compute 
   glBegin(GL_QUADS);
   glTexCoord2f(0.0, 0.0);
   glVertex2f(0.0, 0.0);
   glTexCoord2f(texSize, 0.0);
   glVertex2f(texSize, 0.0);
   glTexCoord2f(texSize, texSize);
   glVertex2f(texSize, texSize);
   glTexCoord2f(0.0, texSize);
   glVertex2f(0.0, texSize);
   glEnd();
   //get result
   transferFromTexture(tmpData, GL_COLOR_ATTACHMENT2_EXT);
   transferToTexture(tmpData, ezTexID[i]);

//   if(i == texSize/2){ fprintf(stdout,"e%i) ez ps %e\n",j,tmpData[(texSize*texSize)/2 + 1]);
//    printVector(tmpData, texSize*texSize);
//   }
   //update x h field
   cgGLBindProgram(hx_fp);
   cgGLSetTextureParameter(hx_h, hxTexID[i]);
   cgGLEnableTextureParameter(hx_h);
   cgGLSetTextureParameter(hx_e1, eyTexID[i+1]);
   cgGLEnableTextureParameter(hx_e1);
   cgGLSetTextureParameter(hx_e2, eyTexID[i]);
   cgGLEnableTextureParameter(hx_e2);
   cgGLSetTextureParameter(hx_e3, ezTexID[i]);
   cgGLEnableTextureParameter(hx_e3);
   cgGLSetTextureParameter(hx_e4, ezTexID[i]);
   cgGLEnableTextureParameter(hx_e4);
   glDrawBuffer(GL_COLOR_ATTACHMENT0_EXT);
   glPolygonMode(GL_FRONT,GL_FILL);
   //render/compute 
   glBegin(GL_QUADS);
   glTexCoord2f(0.0, 0.0);
   glVertex2f(0.0, 0.0);
   glTexCoord2f(texSize, 0.0);
   glVertex2f(texSize, 0.0);
   glTexCoord2f(texSize, texSize);
   glVertex2f(texSize, texSize);
   glTexCoord2f(0.0, texSize);
   glVertex2f(0.0, texSize);
   glEnd();
   //get result
   transferFromTexture(tmpData, GL_COLOR_ATTACHMENT0_EXT);
   transferToTexture(tmpData, hxTexID[i]);
//   if(i == texSize/2){ fprintf(stdout,"h%i) hx ps %e\n",j,tmpData[(texSize*texSize)/2 + 1]);
//    printVector(tmpData, texSize*texSize);
//   }
   
   //update y h field
   cgGLBindProgram(hy_fp);
   cgGLSetTextureParameter(hy_h, hyTexID[i]);
   cgGLEnableTextureParameter(hy_h);
   cgGLSetTextureParameter(hy_e1, ezTexID[i]);
   cgGLEnableTextureParameter(hy_e1);
   cgGLSetTextureParameter(hy_e2, ezTexID[i]);
   cgGLEnableTextureParameter(hy_e2);
   cgGLSetTextureParameter(hy_e3, exTexID[i+1]);
   cgGLEnableTextureParameter(hy_e3);
   cgGLSetTextureParameter(hy_e4, exTexID[i]);
   cgGLEnableTextureParameter(hy_e4);
   glDrawBuffer(GL_COLOR_ATTACHMENT1_EXT);
   glPolygonMode(GL_FRONT,GL_FILL);
   //render/compute 
   glBegin(GL_QUADS);
   glTexCoord2f(0.0, 0.0);
   glVertex2f(0.0, 0.0);
   glTexCoord2f(texSize, 0.0);
   glVertex2f(texSize, 0.0);
   glTexCoord2f(texSize, texSize);
   glVertex2f(texSize, texSize);
   glTexCoord2f(0.0, texSize);
   glVertex2f(0.0, texSize);
   glEnd();
   //get result
   transferFromTexture(tmpData, GL_COLOR_ATTACHMENT1_EXT);
   transferToTexture(tmpData, hyTexID[i]);

//   if(i == texSize/2){ fprintf(stdout,"h%i) hy ps %e\n",j,tmpData[(texSize*texSize)/2 + 1]);
//    printVector(tmpData, texSize*texSize);
//   }
   //update z h field
   cgGLBindProgram(hz_fp);
   cgGLSetTextureParameter(hz_h, hzTexID[i]);
   cgGLEnableTextureParameter(hz_h);
   cgGLSetTextureParameter(hz_e1, exTexID[i]);
   cgGLEnableTextureParameter(hz_e1);
   cgGLSetTextureParameter(hz_e2, exTexID[i]);
   cgGLEnableTextureParameter(hz_e2);
   cgGLSetTextureParameter(hz_e3, eyTexID[i]);
   cgGLEnableTextureParameter(hz_e3);
   cgGLSetTextureParameter(hz_e4, eyTexID[i]);
   cgGLEnableTextureParameter(hz_e4);
   glDrawBuffer(GL_COLOR_ATTACHMENT2_EXT);
   glPolygonMode(GL_FRONT,GL_FILL);
   //render/compute 
   glBegin(GL_QUADS);
   glTexCoord2f(0.0, 0.0);
   glVertex2f(0.0, 0.0);
   glTexCoord2f(texSize, 0.0);
   glVertex2f(texSize, 0.0);
   glTexCoord2f(texSize, texSize);
   glVertex2f(texSize, texSize);
   glTexCoord2f(0.0, texSize);
   glVertex2f(0.0, texSize);
   glEnd();
   //get result
   transferFromTexture(tmpData, GL_COLOR_ATTACHMENT2_EXT);
   transferToTexture(tmpData, hzTexID[i]);
//   if(i == texSize/2){ fprintf(stdout,"h%i) hz ps %e\n",j,tmpData[(texSize*texSize)/2 + 1]);
//    printVector(tmpData, texSize*texSize);
//   }
  }
 }
 // done, stop timer, calc MFLOP/s if neccessary
// glFinish();
// end = clock();
// total = (double)(end-start)/(double)CLOCKS_PER_SEC;
// mflops = (double)((3*12 + 3*9)*texSize*texSize*texSize*numIterations) / (total * 1000000.0);
// printf("GPU MFLOP/s for N=%d:\t\t%f\n",texSize, mflops);
 // done, just do some checks if everything went smoothly.
 checkFramebufferStatus();
 checkGLErrors("render()");
 glDisable(textureParameters.texTarget);
// transferFromTexture(tmpData);
// printVector(tmpData, texSize*texSize);
 //printVector(dataX, texSize*texSize);

 // do cpu comarison
// printf("GPU speedup %f\n \n", cpuBench()/total);
}

void transferFromTexture(float* data, GLenum fb){
 // version (a): texture is attached
 // recommended on both NVIDIA and ATI
 glReadBuffer(fb);
 glReadPixels(0, 0, texSize, texSize,textureParameters.texFormat,GL_FLOAT,data);
}

void cgErrorCallback(){
 CGerror lastError = cgGetError();
 if(lastError) {
  printf(cgGetErrorString(lastError));
  printf(cgGetLastListing(cgContext));
  exit(lastError);
 }
}

/*
 * Sets up the Cg runtime and creates shader.
 */
void initCG(void) {
 // set up Cg
 cgSetErrorCallback(cgErrorCallback);
 cgContext = cgCreateContext();
 fragmentProfile = cgGLGetLatestProfile(CG_GL_FRAGMENT);
 cgGLSetOptimalOptions(fragmentProfile);
 // create fragment program
 ex_fp = cgCreateProgram(cgContext, CG_SOURCE, ex_eUpdate_source, fragmentProfile, "eUpdate", NULL);
 ey_fp = cgCreateProgram(cgContext, CG_SOURCE, ey_eUpdate_source, fragmentProfile, "eUpdate", NULL);
 ez_fp = cgCreateProgram(cgContext, CG_SOURCE, ez_eUpdate_source, fragmentProfile, "eUpdate", NULL);

 hx_fp = cgCreateProgram(cgContext, CG_SOURCE, hx_hUpdate_source, fragmentProfile, "hUpdate", NULL);
 hy_fp = cgCreateProgram(cgContext, CG_SOURCE, hy_hUpdate_source, fragmentProfile, "hUpdate", NULL);
 hz_fp = cgCreateProgram(cgContext, CG_SOURCE, hz_hUpdate_source, fragmentProfile, "hUpdate", NULL);
// // load programs
 cgGLLoadProgram(ex_fp);
 cgGLLoadProgram(ey_fp);
 cgGLLoadProgram(ez_fp);
 cgGLLoadProgram(hx_fp);
 cgGLLoadProgram(hy_fp);
 cgGLLoadProgram(hz_fp);
 //and get parameter handles by name
 //ex
 ex_ps = cgGetNamedParameter(ex_fp, "texturePS");
 ex_e = cgGetNamedParameter(ex_fp, "textureE");
 ex_h1 = cgGetNamedParameter(ex_fp, "textureH1");
 ex_h2 = cgGetNamedParameter(ex_fp, "textureH2");
 ex_h3 = cgGetNamedParameter(ex_fp, "textureH3");
 ex_h4 = cgGetNamedParameter(ex_fp, "textureH4");
 ex_esctc = cgGetNamedParameter(ex_fp, "esctc");
 ex_eincc = cgGetNamedParameter(ex_fp, "eincc");
 ex_ei = cgGetNamedParameter(ex_fp, "ei");
 ex_edevcn = cgGetNamedParameter(ex_fp, "edevcn");
 ex_dei = cgGetNamedParameter(ex_fp, "dei");
 ex_ecrl1 = cgGetNamedParameter(ex_fp, "ecrl1");
 ex_ecrl2 = cgGetNamedParameter(ex_fp, "ecrl2");
 //ey
 ey_e = cgGetNamedParameter(ey_fp, "textureE");
 ey_h1 = cgGetNamedParameter(ey_fp, "textureH1");
 ey_h2 = cgGetNamedParameter(ey_fp, "textureH2");
 ey_h3 = cgGetNamedParameter(ey_fp, "textureH3");
 ey_h4 = cgGetNamedParameter(ey_fp, "textureH4");
 ey_esctc = cgGetNamedParameter(ey_fp, "esctc");
 ey_eincc = cgGetNamedParameter(ey_fp, "eincc");
 ey_ei = cgGetNamedParameter(ey_fp, "ei");
 ey_edevcn = cgGetNamedParameter(ey_fp, "edevcn");
 ey_dei = cgGetNamedParameter(ey_fp, "dei");
 ey_ecrl1 = cgGetNamedParameter(ey_fp, "ecrl1");
 ey_ecrl2 = cgGetNamedParameter(ey_fp, "ecrl2");
 //ez
 ez_e = cgGetNamedParameter(ez_fp, "textureE");
 ez_h1 = cgGetNamedParameter(ez_fp, "textureH1");
 ez_h2 = cgGetNamedParameter(ez_fp, "textureH2");
 ez_h3 = cgGetNamedParameter(ez_fp, "textureH3");
 ez_h4 = cgGetNamedParameter(ez_fp, "textureH4");
 ez_esctc = cgGetNamedParameter(ez_fp, "esctc");
 ez_eincc = cgGetNamedParameter(ez_fp, "eincc");
 ez_ei = cgGetNamedParameter(ez_fp, "ei");
 ez_edevcn = cgGetNamedParameter(ez_fp, "edevcn");
 ez_dei = cgGetNamedParameter(ez_fp, "dei");
 ez_ecrl1 = cgGetNamedParameter(ez_fp, "ecrl1");
 ez_ecrl2 = cgGetNamedParameter(ez_fp, "ecrl2");
 //hx
 hx_h = cgGetNamedParameter(hx_fp, "textureH");
 hx_e1 = cgGetNamedParameter(hx_fp, "textureE1");
 hx_e2 = cgGetNamedParameter(hx_fp, "textureE2");
 hx_e3 = cgGetNamedParameter(hx_fp, "textureE3");
 hx_e4 = cgGetNamedParameter(hx_fp, "textureE4");
 hx_dt = cgGetNamedParameter(hx_fp, "dt");
 hx_delta1 = cgGetNamedParameter(hx_fp, "delta1");
 hx_delta2 = cgGetNamedParameter(hx_fp, "delta2");
 //hy
 hy_h = cgGetNamedParameter(hy_fp, "textureH");
 hy_e1 = cgGetNamedParameter(hy_fp, "textureE1");
 hy_e2 = cgGetNamedParameter(hy_fp, "textureE2");
 hy_e3 = cgGetNamedParameter(hy_fp, "textureE3");
 hy_e4 = cgGetNamedParameter(hy_fp, "textureE4");
 hy_dt = cgGetNamedParameter(hy_fp, "dt");
 hy_delta1 = cgGetNamedParameter(hy_fp, "delta1");
 hy_delta2 = cgGetNamedParameter(hy_fp, "delta2");
 //hz
 hz_h = cgGetNamedParameter(hz_fp, "textureH");
 hz_e1 = cgGetNamedParameter(hz_fp, "textureE1");
 hz_e2 = cgGetNamedParameter(hz_fp, "textureE2");
 hz_e3 = cgGetNamedParameter(hz_fp, "textureE3");
 hz_e4 = cgGetNamedParameter(hz_fp, "textureE4");
 hz_dt = cgGetNamedParameter(hz_fp, "dt");
 hz_delta1 = cgGetNamedParameter(hz_fp, "delta1");
 hz_delta2 = cgGetNamedParameter(hz_fp, "delta2");
}

/*
 * Transfers data to texture. 
 * Check web page for detailed explanation on the difference between ATI and NVIDIA.
 */
void transferToTexture (float* data, GLuint texID) {
 // version (a): HW-accelerated on NVIDIA 
 glBindTexture(textureParameters.texTarget, texID);
 glTexSubImage2D(textureParameters.texTarget,0,0,0,texSize,texSize,textureParameters.texFormat,GL_FLOAT,data);
}

/*
 * Sets up a floating point texture with NEAREST filtering.
 * (mipmaps etc. are unsupported for floating point textures)
 */
void setupTexture (const GLuint texID) {
 // make active and bin
 int err;
 glBindTexture(textureParameters.texTarget,texID);
 // turn off filtering and wrap modes
 glTexParameteri(textureParameters.texTarget, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 glTexParameteri(textureParameters.texTarget, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
 glTexParameteri(textureParameters.texTarget, GL_TEXTURE_WRAP_S, GL_CLAMP);
 glTexParameteri(textureParameters.texTarget, GL_TEXTURE_WRAP_T, GL_CLAMP);
 // define texture with floating point format
 glTexImage2D(textureParameters.texTarget,0,textureParameters.texInternalFormat,texSize,texSize,0,textureParameters.texFormat,GL_FLOAT,0);
 // define texture with floating point format
 // check if that worked
 if(err = glGetError() != GL_NO_ERROR){
  printf("glTexImage2D():\t\t\t [FAIL]\n");
  exit(err);
 }
// else if(mode == 0){
  printf("glTexImage2D():\t\t\t [PASS]\n");
// }
 printf("Created a %i by %i floating point texture.\n",texSize,texSize);
}

void createTextures(){
 int i;
 // create textures 
 glGenTextures(texSize+1, exTexID);
 glGenTextures(texSize+1, eyTexID);
 glGenTextures(texSize+1, ezTexID);
 glGenTextures(texSize+1, hxTexID);
 glGenTextures(texSize+1, hyTexID);
 glGenTextures(texSize+1, hzTexID);
 glGenTextures(1, &psTexID);
 glGenTextures(1, &psEmptyTexID);

 tmpData[(texSize*texSize)/2] = 5.0;
 setupTexture(psTexID);
 transferToTexture(tmpData, psTexID);
 tmpData[(texSize*texSize)/2] = 0.0;
 setupTexture(psEmptyTexID);
 transferToTexture(tmpData, psEmptyTexID);

 
 // set up textures
 for(i = 0; i <= texSize; i++){
  setupTexture(exTexID[i]);
  transferToTexture(tmpData, exTexID[i]);
  setupTexture(eyTexID[i]);
  transferToTexture(tmpData, eyTexID[i]);
  setupTexture(ezTexID[i]);
  transferToTexture(tmpData, ezTexID[i]);
  setupTexture(hxTexID[i]);
  transferToTexture(tmpData, hxTexID[i]);
  setupTexture(hyTexID[i]);
  transferToTexture(tmpData, hyTexID[i]);
  setupTexture(hzTexID[i]);
  transferToTexture(tmpData, hzTexID[i]);
 }
 // set texenv mode from modulate (the default) to replace)
 glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
 // check if something went completely wrong
 checkGLErrors ("createFBOandTextures()");
}

/*
 * Creates framebuffer object, binds it to reroute rendering operations 
 * from the traditional framebuffer to the offscreen buffer
 */
void initFBO(){
 // create FBO (off-screen framebuffer)
 glGenFramebuffersEXT(1, &fb);
 // bind offscreen framebuffer (that is, skip the window-specific render target)
 glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fb);
 // viewport for 1:1 pixel=texture mapping
 glMatrixMode(GL_PROJECTION);
 glLoadIdentity();
 gluOrtho2D(0.0, texSize, 0.0, texSize);
 glMatrixMode(GL_MODELVIEW);
 glLoadIdentity();
 glViewport(0, 0, texSize, texSize);
}

void initGLEW (void) {
 int err = glewInit();
 if (GLEW_OK != err) {
  fprintf(stderr,"error: %s\n",(char*)glewGetErrorString(err));
  exit(-1);
 }
}

void initGLUT(int argc, char **argv){
 glutInit(&argc, argv);
 glutWindowHandle = glutCreateWindow(GLUT_WINDOW_NAME);
}

How To Use the String Stream implementation of ISequentialStream

Someone the other day asked how do they use the ISequentialStream string class I implemented.

Here is the original post on the string stream implementation.

This is how you would use it.

HRESULT hr = S_OK;
LPWSTR pszXml = NULL;
ISequentialStream *pStream = NULL;
IXmlReader *pReader = NULL;

hr = GetXmlString(&pszXml);

if (S_OK == hr)
{
   hr = CStringStream::Create(pszXml, &pStream);
}

if (S_OK == hr)
{
   hr = CreateXmlReader(__uuidof(IXmlReader), (void**)&pReader, NULL);
}

if (S_OK == hr)
{
   hr = pReader->SetInput(pStream);
}

//
// rest of your xml parsing here.
//

// cleanup
if (pReader)
{
   pReader->Release();
}

if (pStream)
{
   pStream->Release();
}

if (pszXml)
{
   free(pszXml);
}

Making Your Function Discovery (FD) Provider Run In Proc

I was looking through my basic FD provider sample that I wrote a few months ago and realized that I can't directly publish it on the Internet. I don't want to provide a sample that doesn't do anything real, so I will need to rewrite a new provider sample that publishable and is realistic. In the mean time, if you want to push ahead and try writing your own provider, it is actually not that hard. First, you need to do the standard things for making a new DLL: DLLMain, DLLGetClassObject, implement IClassFactory, et cetera. Then, you need to implement IFunctionDiscoveryProvider. That is it. Well, to get it to work, you will also have to make the proper registrations (hint: use the in box providers registry keys as an example). The second problem will be that your provider will have to implement all of the PnPX stuff to be loaded out of proc because FD will only load known providers inproc by default. If you want to ship a provider, pnpx should be your end game especially if you are doing network type providers. While you are learning the basics, there is a trick to get your FD client to load your non pnpx provider inproc. Note, this is done on the client or provider consumer side. This is how you would do that. I will try to provide a complete sample later if time permits.

hr = pPnpQuery->AddQueryConstraint(
FD_QUERYCONSTRAINT_COMCLSCONTEXT,
FD_CONSTRAINTVALUE_COMCLSCONTEXT_INPROC_SERVER
);

Unit Testing

Since we are between product cycles, they want us to be writing tests and not making changes on the product code until initial planning is done. Testing is like hygiene, not specifically fun, but necessary. Writing unit tests is not my favorite thing to do, but it is need if you want to have quality in your code. So, I went about figuring out how to setup good unit tests in our build environment and how to automate them. I won't go in to those details because they are unique to our environment, but I will provide some slides for a presentation that I gave to my team.

Unit Testing
What Is a Unit Test?
• Unit: smallest testable part of a program: functions, classes, methods
• Validates correct behavior of the unit
• Ideally independent of the other unit tests
• They should cover most code paths
• Generally a white box testing method that is close to the code implementation
• First line of testing
• Should be written in conjunction with the unit of code

What Isn’t Unit Testing?
• A catchall for every bug
• Replacement for other testing
• Functional testing: validates code functions to spec (higher level and more black box than unit tests)
• Integration testing: tests how the units are put together

Why Write Unit Tests?
• Finds bugs early in the development cycle
• Gives confidence that the units you are writing are behaving correctly
• Provides quick feedback if functionality has inadvertently been regressed
• Simplifies refactoring
• Gives confidence when you make late milestone changes
• Documents and defines correct unit behavior

Dev IC Workflow
• Spec & design
• Product code & unit tests
• Check in
• Automation

Unit Test Writing Work Flow
Test Driven Development
TDD Cycle
• Write a test
• Run all unit tests – the new test should fail
• Write some code – write enough code to pass the test
• Run all unit tests – the new test should now pass
• Refactor – clean up the code and tests as needed
• Repeat steps 1-5 until all code units are complete

TDD Benefits
• Promotes better design since you must think about using the API before writing them
• Heavy debugging is rarely needed
• Many of the bugs are found even before it is checked in
• Promotes good unit test coverage
• Discourages code creep
• Unit tests are easier to write before than after

Function Discovery: Callback Objects, Implementing IFunctionDiscoveryNotification

If you missed my introductory post on Function Discovery (FD), you might want to go back there and give it a once over. It will give you a quick primer on what FD is about.

Function Discovery Intro

In my first FD post I provided a sample using the PnP FD provider to enumerate present devices. The FD PnP provider probably the most used provider and is easier to use than SetupDiGetGlassDevs especially if your program is already using COM. Unfortunately my first sample didn’t include a callback object which is required to get notifications from the provider. It gets worse than that; the PnP provider is actually the only provider (except the registry provider) that will provide synchronous results (IFunctionInstanceCollection)when you execute your query. In other words, every other inbox FD provider is asynchronous, and you won’t get any function instance (FI) results unless you provide a callback object and get them asynchronously.

Don’t worry; writing callback objects is easy, and I will show you how with an example. You start off creating a query just like we did in the first example, except we will have to change two parts. First you will need to create your callback object, and then pass it as a parameter to the CreateInstanceCollectionQuery method call. Finally when you execute the query, you will not get a function instance query back unless it is the PnP or registry provider, and the call will return E_PENDING. E_PENDING is not an error if you are using an asynchronous provider; it just means that the provider will give you function instances asynchronously to your call back object. If the provider is async and returns E_PENDING, it should also send FD_EVENTID_SEARCHCOMPLETE to the callback’s OnEvent method.

Here is a simple sample code for a callback object.

class CNotificationCallback : public IFunctionDiscoveryNotification
{
public:

    STDMETHODIMP_(ULONG) AddRef();

    STDMETHODIMP_(ULONG) Release();

    STDMETHODIMP QueryInterface(
        REFIID riid, 
        __deref_out_opt void **ppv);

    STDMETHODIMP OnUpdate(
        QueryUpdateAction enumQueryUpdateAction, 
        FDQUERYCONTEXT fdqcQueryContext, 
        __in IFunctionInstance *pIFunctionInstance);

    STDMETHODIMP OnError(
        HRESULT hr, 
        FDQUERYCONTEXT fdqcQueryContext, 
        PCWSTR pszProvider);

    STDMETHODIMP OnEvent(
        DWORD dwEventID, 
        FDQUERYCONTEXT fdqcQueryContext, 
        PCWSTR pszProvider);

    CNotificationCallback();

protected:
    LONG m_cRef;
};

CNotificationCallback::CNotificationCallback():
    m_cRef(1)
{
}

STDMETHODIMP_(ULONG) CNotificationCallback::AddRef()
{
    return InterlockedIncrement(&m_cRef);
}

STDMETHODIMP_(ULONG) CNotificationCallback::Release()
{
    LONG cRef = InterlockedDecrement(&m_cRef);
    if (0 == cRef)
    {
        delete this;
    }

    return cRef;
}

STDMETHODIMP CNotificationCallback::QueryInterface(
    REFIID riid, 
    __deref_out_opt void **ppv)
{
    HRESULT hr = S_OK;

    if (ppv)
    {
        *ppv = NULL;
    }
    else
    {
        hr = E_INVALIDARG;
    }

    if (S_OK == hr)
    {
        if (__uuidof(IUnknown) == riid )
        {
            AddRef();
            *ppv = (IUnknown*) this;
        }
        else if (__uuidof(IFunctionDiscoveryNotification) == riid)
        {
            AddRef();
            *ppv = (IFunctionDiscoveryNotification*) this;
        }
        else
        {
            hr = E_NOINTERFACE;
        }
    }

    return hr;
}

STDMETHODIMP CNotificationCallback::OnUpdate(
    QueryUpdateAction enumQueryUpdateAction, 
    FDQUERYCONTEXT fdqcQueryContext, 
    __in IFunctionInstance* pIFunctionInstance)
{
    HRESULT hr = S_OK;

    switch (enumQueryUpdateAction)
    {
    case QUA_ADD:
        wprintf(L"QUA_ADD\n");
        break;
    case QUA_REMOVE:
        wprintf(L"QUA_REMOVE\n");
        break;
    case QUA_CHANGE:
        wprintf(L"QUA_CHANGE\n");
        break;
    }

    return S_OK;
}

STDMETHODIMP CNotificationCallback::OnError(
    HRESULT hr, 
    FDQUERYCONTEXT fdqcQueryContext, 
    PCWSTR pszProvider)
{
    wprintf(L"****** ERROR: 0x%08x\n", hr);

    return S_OK;
}

STDMETHODIMP CNotificationCallback::OnEvent(
    DWORD dwEventID, 
    FDQUERYCONTEXT fdqcQueryContext, 
    PCWSTR pszProvider)
{
    wprintf(L"Event: %d\n", dwEventID);

    return S_OK;
}

This is the most basic example of how you might write a callback. Let’s pretend that we wanted to take an async provider like WSD and make it synchronized. One way you could do this is by passing in an empty function instance collection, and a handle that the callback object can signal once it receives FD_EVENTID_SEARCHCOMPLETE from the provider. In the main thread you could just wait on the handle. Often the callback interface is inherited in a bigger fancier class that does a lot more things than implement IFunctionDiscoveryNotification; the sky is the limit on how you want to structure your code here. Just make sure you exercise good tread safety. If you are sharing memory between the main program thread and your callback’s tread, be sure to use a SRW lock.

Now armed with callbacks, you can use two of FD’s main features: enumerating, and receiving notifications. With callbacks you will be able to take advantage of all of the providers on your computer.

Hopefully next time we can see how simple it is to write a FD provider and register it on your computer. Once we can write a simple provider, we can move on to writing full blown PnP-X providers. If you want to skip straight to PnP-X, there is a sample of one in the Windows SDK already, but hopefully I will be able to break it down into more digestible chunks. :)

If you are interested in using FD and want some extra help, email me and I can get you going on writing your provider or whatever you want to get accomplished.

Function Discovery Intro

The other day I wrote a post about using SetupDi to enumerate PnP devices.

SetupDi Post

But SetupDi is not the only API to enumerate devices; Function Discovery can also enumerate PnP devices along with a host of other capabilities.

Function Discovery (FD) came to life as part of Windows Vista. FD’s main goal was to provide a unified API and interfaces for gathering functionality, properties, and notifications from various providers. PnP just happens to be one of the providers. Before FD, different API sets were required for discovering functionality of devices; for example you could use SetupDiGetClassDevs to find physically connected devices, but you had to use other APIs for network devices or printers. Using FD, you can use the same set of interfaces and methods for PnP and any number of devices exposed trough a provider. Vista shipped with in-box-providers for PnP, PnP-X (WSD & SSDP), Registry, NetBIOS, and the capability for third parties to create their own providers, and Windows 7 there are even more providers.

If you have the Windows SDK installed (I assume that you would if you are interested in writing this kind of code), you can do some header spelunking. Check out FunctionDiscoveryCategories.h to get an idea of what providers you can try to use. Also you can dig into the registry to see what other providers are registered on the system at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Function Discovery\Categories.

So if you need to enumerate devices and/or get notifications, FD can help assuming there is a provider for it.

To start out with, I wrote a sample FD code using the PnP provider to enumerate PnP devices just like I did in the SetupDiGetClassDevs example from before. I wrote this a while back now, so I hope there are no bug in this code.

I am having it print out a few properties from each function instance. A good place to go to find what kinds of properties are discoverable through FD is the header files included in the SDK: functiondiscoverykeys.h, and functiondiscoverykeys_devpkey.h. Not all PKEYs are populated by all providers; for example, PKEY_WSD_MetadataVersion will not be populated by the PnP provider, but will be populated by the WSD provider. Generally PKEYs populated by the PnP are prefixed with PKEY_Device_, and the properties you can get with SetupDi are available with the PnP FD provider.

For a more in depth reference to Function Discovery, refer to the official MSDN FD documentation.

/* displays pnp function instances */

#include <stdio.h>
#include <FunctionDiscovery.h>

HRESULT PrintFIs(IFunctionInstanceCollection* FIs);

int __cdecl wmain(
    __in int argc, 
    __in_ecount(argc) PWSTR
)
{
    HRESULT hr = S_OK;
    IFunctionDiscovery *pFD = NULL;
    IFunctionInstanceCollectionQuery *pPnpQuery = NULL;
    IFunctionInstanceCollection *pFICollection = NULL;

    hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);

    // CoCreate FunctionDiscovery
    if (S_OK == hr)
    {
        hr = CoCreateInstance(
                __uuidof(FunctionDiscovery),
                NULL,
                CLSCTX_ALL,
                __uuidof(IFunctionDiscovery),
                (PVOID*)&pFD);
    }

    // Query the pnp provider
    if (S_OK == hr)
    {
        hr = pFD->CreateInstanceCollectionQuery(
                FCTN_CATEGORY_PNP, // pnp category (defined in functiondiscoverycategories.h)
                NULL,              // subcategory
                FALSE,             // include subcategories
                NULL,              // notification callback
                NULL,              // context
                &pPnpQuery);       // FI collection query
    }

    /*
    // * optional *
    // add property constraints
    // generally only works with core FD properties, and not provider specific properties
    if (S_OK == hr)
    {
        PROPVARIANT pv;

        PropVariantClear(&pv);

        pv.vt = VT_UINT;
        pv.uintVal = 0;

        hr = pPnpQuery->AddPropertyConstraint(PKEY_FD_Visibility, &pv, QC_EQUALS);

        PropVariantClear(&pv);
    }
    */

    /*
    // * optional *
    // add query constraints
    // refer to functiondiscoveryconstraints.h
    if (S_OK == hr)
    {
        hr = pPnpQuery->AddQueryConstraint(PNP_CONSTRAINTVALUE_NOTPRESENT, FD_CONSTRAINTVALUE_TRUE);
    }
    */

    if (S_OK == hr)
    {
        hr = pPnpQuery->Execute(&pFICollection);
    }

    if (S_OK == hr)
    {
        hr = PrintFIs(pFICollection);
    }

    // clean up
    if (pFD)
    {
        pFD->Release();
    }

    if (pPnpQuery)
    {
        pPnpQuery->Release();
    }

    if (pFICollection)
    {
        pFICollection->Release();
    }

    CoUninitialize();

    if (S_OK != hr)
    {
        wprintf(L"an error occured (hr == 0x%x)\n", hr);
        return 1;
    }

    return 0;
}

HRESULT PrintFIs(
    IFunctionInstanceCollection* FIs
)
{
    HRESULT hr = S_OK;
    DWORD cFIs = 0;
    IFunctionInstance *pFI = NULL;
    IFunctionInstanceCollection *pDeviceFunctionCollection = NULL;

    if (FIs)
    {
        hr = FIs->GetCount(&cFIs);

        wprintf(L"*******************************************************\n");
        wprintf(L"* %i Function Instances\n", cFIs);
        wprintf(L"*******************************************************\n\n");

        // go through each function instance
        for (DWORD i = 0; S_OK == hr && i < cFIs; i++)
        {
            hr = FIs->Item(i, &pFI);

            if (S_OK == hr)
            {
                IPropertyStore *pPropertyStore = NULL;

                pFI->OpenPropertyStore(STGM_READ, &pPropertyStore);

                if (pPropertyStore)
                {
                    PROPVARIANT pv;

                    PropVariantClear(&pv);

                    // PKEYs can be found in these headers in the SDK:
                    // functiondiscoverykeys.h functiondiscoverykeys_devpkey.h
                    // Providers do not populate all PKEYs.
                    hr = pPropertyStore->GetValue(PKEY_Device_FriendlyName, &pv);

                    if (S_OK == hr)
                    {
                        wprintf(L"Device Friendly Name : \"%s\"\n", (pv.vt == VT_LPWSTR) ? pv.pwszVal : L"");
                    }

                    PropVariantClear(&pv);


                    hr = pPropertyStore->GetValue(PKEY_Device_InstanceId, &pv);

                    if (S_OK == hr && VT_LPWSTR == pv.vt)
                    {
                        wprintf(L"\tDevice Instance ID : \"%s\"\n", pv.pwszVal);
                    }

                    PropVariantClear(&pv);

                    hr = pPropertyStore->GetValue(PKEY_Device_Class, &pv);

                    if (S_OK == hr && VT_LPWSTR == pv.vt)
                    {
                        wprintf(L"\tClass : %s",pv.pwszVal);
                    }

                    PropVariantClear(&pv);

                    hr = pPropertyStore->GetValue(PKEY_Device_ClassGuid, &pv);

                    if (S_OK == hr && VT_CLSID == pv.vt)
                    {
                        wprintf(L"\t(GUID : %x-%x-%x-%x%x-%x%x%x%x%x%x)\n",
                                pv.puuid->Data1, 
                                pv.puuid->Data2, 
                                pv.puuid->Data3, 
                                pv.puuid->Data4[0],
                                pv.puuid->Data4[1],
                                pv.puuid->Data4[2],
                                pv.puuid->Data4[3],
                                pv.puuid->Data4[4],
                                pv.puuid->Data4[5],
                                pv.puuid->Data4[6],
                                pv.puuid->Data4[7]
                                );
                    }

                    PropVariantClear(&pv);

                    pPropertyStore->Release();
                }
            }

            if (pFI)
            {
                pFI->Release();
                pFI = NULL;
            }

            if (pDeviceFunctionCollection)
            {
                pDeviceFunctionCollection->Release();
                pDeviceFunctionCollection = NULL;
            }
        }
    }

    return hr;
}