Re: [ECOS] fatfs lseek EOF bug

[Gratian Crisan <nelu at iv dot ro>]

Hi,

please see my answers below:

On Tuesday 10 May 2005 09:48, Savin Zlobec wrote:
> Gratian Crisan wrote:
> >Hi all,
> >
> >I think I've found a bug in the ecos FAT implementation for lseek
> > function. (fatfs_fo_lseek).
> >When calling the function like this 'lseek(fd, 0,  SEEK_CUR)' to get the
> >current file position and the postion is right at the end of the file the
> > fat lseek function returns end of file error EEOF. I've looked at the
> > other filesystems from ecos and did a test in linux and the correct
> > behavior seems to be to return the current position of the end of file if
> > the read/write pointer is at the end of file (equal with the file size).
> >This bug occurs for example when creating a new file, writing some data in
> > it and calling lseek(fd, 0, SEEK_CUR) to get the current file position.
> >
> >Suggestions?
>
> Hi,
>
> I've tryed to reproduce  the bug you described but without success.
> Are you using the latest CVS version of fatfs ?
***
	Yes.

> Can you send me an test case, so I can look into it ?
***
	See the file attached. The test is for an MMC driver but should be pretty 
straight forward to adapt (only the mount command should be changed).
The test creates a file and writes blocks of data into it while printing the 
current file offset. In a new file after writing the first block, for which 
the value returned is 0, the value returned by lseek function is -1. The 
strange thing is that if you overwrite an existing file the lseek function 
correctly returns the current file offset (equal to EOF).

Thanks,
	Nelu

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
#include <string.h>
#include <dirent.h>

#include <cyg/fileio/fileio.h>
#include <cyg/infra/diag.h>

void mmc_write(char fileName[], long nBlocks, long blockSize, unsigned char testChar)
{
	char *buf;
	int i;
	int fd;
	ssize_t wrote;

	if ((buf = (char*)malloc(blockSize)) == NULL) {
		diag_printf("[error] memory allocation failed!\n");
		return;
	}

	memset(buf, testChar, blockSize);

	if ((fd = open(fileName, O_WRONLY|O_CREAT)) < 0){
		diag_printf("[error] opening file %s for write failed!\n", fileName);
		return;
	}

	for(i=0;i<nBlocks;i++) {
		diag_printf("off:%d\n",lseek(fd, 0, SEEK_CUR));

		wrote = write( fd, buf, blockSize );
		if (wrote != blockSize) {
			diag_printf("[warning] incomplete write at block %d\n", i);
		}
	}
	
	close(fd);
}

int main()
{
	int err;
	int i;

	diag_printf("MMC test start ...\n");

	if ((err = mount( "/dev/mmcda0/1", "/", "fatfs" )) < 0) {
		diag_printf("[error] mounting MMC card!\n");
		return 0;
	}
	
	mmc_write("test.txt", 5, 1024, 'x');

	umount( "/" );

	return 1;
}

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