CreateFile & ReadFile Questions

[azntekkan]

Hi, i'm currently using the CreateFile and ReadFile functions in my program. I need to read in large chunks of data really fast. But i'm having some trouble with the functions.

videoYUV=CreateFile("C:\\Documents and Settings\\mliu\\Desktop\\YUVPLAYER\\pond.yuv", GENERIC_READ, FILE_SHARE_READ,NULL, OPEN_EXISTING,  FILE_ATTRIBUTE_NORMAL|FILE_FLAG_NO_BUFFERING ,NULL);  


	for(int k=0;k<5;k++)
	{
		ReadFile(videoYUV,YP[k],518400*2,&bytesread,&gOverLapped);
		
		gOverLapped.Offset+=518400*2;
	}

I'm currently using the FILE_FLAG_NO_BUFFERING, because i need the speed.

The problem is that the readFile only works if i read in exactly 518400*2 bytes, any less the function fails.

I need this value to be dynamic, i.e i'm reading in frames, each frame is width*height*1.5 bytes.

If anyone who is fimilar with these functions could help me out or suggest another function of would be greatly appreciated.

 

[tchouch]

for(int k=0;k<5;k++)
{
ReadFile(videoYUV,YP[k],518400*2,&bytesread,NULL);

gOverLapped.Offset+=518400*2;
}

 

[palbano]

>> readFile only works if i read in exactly 518400*2
>> bytes, any less the function fails.

There is no such limitation of ReadFile(), please clarify the function fails, that does not tell us anything.


-pete

 

[azntekkan]

Hey, Sorry if I was unclear, but i have fixed my error. It turns out if i set the no buffer flag i can only use increments of 512(harddrive sector size). Thanks for all the help.