On Thu, Jan 30, 2025 at 08:54:03PM +0100, Thomas Weißschuh wrote: > From: Thomas Weißschuh <[email protected]> > > Add an allocation-free implementation of readdir() and related > functions. The implementation is modelled after the one for FILE.
I think you'd need to mention/remind the two important points that come out of that choice, one being that DIR is a fake pointer that instead stores ~fd so that it can be turned back to a valid FD, and that subsequent readdir() calls will only work from the same file unit since it relies on a local static storage. Better have this visible in the commit message so that in the event someone faces a difficulty due to this, they can easily find that it's an on-purpose design choice. > Signed-off-by: Thomas Weißschuh <[email protected]> > Signed-off-by: Thomas Weißschuh <[email protected]> > > --- > I'm not entirely sure where to put it. It doesn't really belong into > stdio.h, but that's where the FILE stuff is. > sys.h wants alphabetical ordering, but IMO these functions should stick > together. My man pages suggest that userland code will include <dirent.h>, thus I think it could be the moment to create it with that new code. > diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h > index > 3892034198dd566d21a5cc0a9f67cf097d428393..1f275a0a7b6b2c6f1c15405d027c282bb77aa618 > 100644 > --- a/tools/include/nolibc/stdio.h > +++ b/tools/include/nolibc/stdio.h (...) > +static __attribute__((unused)) > +struct dirent *readdir(DIR *dirp) > +{ > + static struct dirent dirent; > + > + char buf[sizeof(struct linux_dirent64) + NAME_MAX]; I'm uncertain where NAME_MAX is defined, I haven't found it in the nolibc sources, just double-checking that it's not just in your build environment by accident. > + struct linux_dirent64 *ldir = (void *)buf; > + intptr_t i = (intptr_t)dirp; > + int fd, ret; > + > + if (i >= 0) { > + SET_ERRNO(EBADF); > + return NULL; > + } > + > + fd = ~i; > + > + ret = getdents64(fd, ldir, sizeof(buf)); > + if (ret == -1 || ret == 0) > + return NULL; > + > + /* > + * getdents64() returns as many entries as fit the buffer. > + * readdir() can only return one entry at a time. > + * Make sure the non-returned ones are not skipped. > + */ > + ret = lseek(fd, ldir->d_off, SEEK_SET); > + if (ret == -1) > + return NULL; > + > + dirent = (struct dirent) { > + .d_ino = ldir->d_ino, > + }; > + strlcpy(dirent.d_name, ldir->d_name, sizeof(dirent.d_name)); Just out of curiosity, could this copy fail, and if so, should we handle it (e.g. NAME_MAX != 255) ? My guess here is that if it could almost never fail and checking it would needlessly complicate the function, let's just handle it with a comment for now. And if it cannot at all, let's mention why on top of it as well. Thanks, Willy
