[Pvfs-users] pvfs_read beyond EOF

[Wei-keng Liao]

What will happen if a read (pvfs_read) reads beyond the current end of 
file (EOF)? According to POSIX, read() should stop at EOF and return the 
number of bytes read to the buffer. The buffer beyond EOF should not be 
touched. (Please correct me if this is wrong.)

But, I found the pvfs_read will set the buffer contents to null for the 
beyond part. Here is the example code I tested: 1) create a new file, 2) 
initialize read buffer, 3) read 10 bytes, 4) print out buffer. (I am using 
PVFS 1.6.3) Is this the way PVFS behaves for reading beyond EOF?

Wei-keng Liao
---------------------------------------------------------------------


#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <pvfs.h>

#define PVFS_FILE_NAME "/pvfs/wkliao/testfile.dat"
#define UNIX_FILE_NAME "testfile.dat"

#define TEST_FILE(filename,ofunc,cfunc,rfunc)    {               \
     fd = ofunc(filename, flag, 0600, 0, 0);                      \
                                                                  \
     readsize = rfunc(fd, buf, 10);                               \
     cfunc(fd);                                                   \
                                                                  \
     printf("readsize for %s = %d bytes\n", filename, readsize);  \
     printf("buf[*]= ");                                          \
     for (i=0; i<10; i++) printf(" '%c'", buf[i]);                \
     printf("\n");                                                \
}

int main(int argc, char **argv) {
     int  i, readsize, flag;
     int  fd;
     char buf[10];

     flag = O_TRUNC | O_CREAT | O_RDWR;

     /* test pvfs file -------------------------------------------*/
     for (i=0; i<10; i++) buf[i] = '1';
     TEST_FILE(PVFS_FILE_NAME, pvfs_open, pvfs_close, pvfs_read);

     /* test unix file -------------------------------------------*/
     for (i=0; i<10; i++) buf[i] = '1';
     TEST_FILE(UNIX_FILE_NAME, open, close, read);

     return 1;
}