Getting Started with QNX Neutrino - QNX Software Systems

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© 2009, QNX Software Systems GmbH & Co. KG.
// create the output string
string = ocb -> attr -> inode - 1 + ’A’;
// return it to the client
MsgReply (ctp -> rcvid, nbytes,
&string + ocb -> offset,
nbytes);
// update flags and offset
ocb -> attr -> flags |= IOFUNC_ATTR_ATIME
| IOFUNC_ATTR_DIRTY_TIME;
ocb -> offset += nbytes;
} else {
// nothing to return, indicate End Of File
MsgReply (ctp -> rcvid, EOK, NULL, 0);
}
}
// already done the reply ourselves
return (_RESMGR_NOREPLY);
dirent_size()
The helper routine dirent_size() simply calculates the number of bytes required for the
struct dirent, given the alignment constraints. Again, this is slight overkill for our
simple resource manager, because we know how big each directory entry is going to
be — all filenames are exactly one byte in length. However, it’s a useful utility routine.
int
dirent_size (char *fname)
{
return (ALIGN (sizeof (struct dirent) - 4 + strlen (fname)));
}
dirent_fill()
Finally, the helper routine dirent_fill() is used to stuff the values passed to it (namely,
the inode, offset and fname fields) into the directory entry also passed. As an added
bonus, it returns a pointer to where the next directory entry should begin, taking into
account alignment.
struct dirent *
dirent_fill (struct dirent *dp, int inode, int offset,
char *fname)
{
dp -> d_ino = inode;
dp -> d_offset = offset;
strcpy (dp -> d_name, fname);
dp -> d_namelen = strlen (dp -> d_name);
dp -> d_reclen = ALIGN (sizeof (struct dirent) - 4
+ dp -> d_namelen);
return ((struct dirent *) ((char *) dp +
dp -> d_reclen));
}
282 Chapter 5 • Resource Managers April 30, 2009