DWORD WINAPI threadFunc(LPVOID data)
{
struct THREAD_PARAMS myParams = *(struct THREAD_PARAMS*) data;
int len;
char bgr[3];
DWORD mutexResult;
int y, x;
for(y=myParams.yMax;y>=myParams.yMin;y--)
{
for(x=0; x<XSIZE ;x++)
{
getColorValuesAt(x * (2.0 / XSIZE) - 1.5, y * (2.0 / YSIZE) - 1.0,&bgr[2],&bgr[1],&bgr[0]);
mutexResult = WaitForSingleObject(mutex, INFINITE);
if(mutexResult == WAIT_OBJECT_0)
{
len=fwrite(bgr,1,3,myParams.file);
if(-1==len || len!=3)
{
perror("write");
exit(4);
}
}else if(mutexResult == WAIT_ABANDONED)
{
return -1;
}
}
}
return 0;
}
// Thread Rountine
DWORD WINAPI run(LPVOID *data) {
// cast void pointer to integer value
int *bins = (int*) data;
int from = bins[0];
int to = bins[1];
int x, y, len;
char bgr[3];
long int bytepos;
printf("Setup thread from %d to %d\n\n", from, to);
for (y = from; y < to; y++) {
for (x = 0; x < XSIZE; x++) {
getColorValuesAt(x * (2.0 / XSIZE) - 1.5, y * (2.0 / YSIZE) - 1.0, &bgr[2], &bgr[1], &bgr[0]);
bytepos = 3*((y * XSIZE) + x) + 54;
// wait until other threads finished writing
// and block others immediately
WaitForSingleObject(sem, INFINITE);
fseek(fd, bytepos, SEEK_SET);
len = fwrite(bgr,1,3,fd);
if (-1 == len || len != 3) {
printf("error while writing\n");
exit(1);
}
// work done, notify semaphore
ReleaseSemaphore(sem, 1, NULL);
}
}
// data was allocated dynamically before thread creation
free(data);
}
void *threadRoutine (void *dataPointer) {
struct ThreadData *td = (struct ThreadData *) dataPointer;
int i, x, y;
char* c;
printf("new thread starting at offset %d, calculating %d values.\n", td->startPos, td->pixelCount);
for (i = 0; i < td->pixelCount; ++i) {
x = (td->startPos + i) % XSIZE;
y = (td->startPos + i) / XSIZE;
c = colorArray[y][x];
getColorValuesAt(x * (2.0 / XSIZE) - 1.5, y * (2.0 / YSIZE) - 1.0,&c[2],&c[1],&c[0]);
}
// we are the only one with a pointer to this - free it
free(td);
td = NULL;
}