On Dec 18 18:47, Martin Wege via Cygwin wrote: > On Fri, Dec 1, 2023 at 10:52 AM Corinna Vinschen via Cygwin > <cygwin@cygwin.com> wrote: > > > > On Nov 30 04:55, Martin Wege via Cygwin wrote: > > > Hello, > > > > > > Does Cygwin have tools (modified /usr/bin/dd ?) to read/write NTFS > > > alternate data streams? > > > > No. As you know, the colon is translated to a normal filename > > character, and there's no POSIX-like API to expose ADS raw to user > > space. > > > > There is, however, an old function we still expose to user space > > for backward compat: > > > > #include <sys/cygwin.h> > > > > int cygwin_attach_handle_to_fd (char *name, > > int fd, > > HANDLE handle, > > mode_t bin, > > DWORD myaccess); > > > > This allows to sneak in a HANDLE into a Cygwin file descriptor > > representation, kind of like this: > > > > HANDLE h; > > int fd; > > > > h = CreateFile ("foo:bar", GENERIC_READ, FILE_SHARE_VALID_FLAGS, > > NULL, OPEN_EXISTING, 0, NULL); > > if (h != INVALID_HANDLE_VALUE) > > { > > fd = cygwin_attach_handle_to_fd ("foo", -1, h, 0, GENERIC_READ); > > if (fd < 0) > > bail_out; > > } > > > > For the bin parameter, only 0, O_BINARY or O_TEXT are acceptable, > > for myaccess, only GENERIC_READ and/or GENERIC_WRITE are acceptable. > > Could this be abstracted into O_XATTR support, i.e. openat() file with > O_XATTR, and then have access to the alternate data streams in a > (virtual) subdir?
I'm not too hot on adding more open(2) flags, the reason being, that we have room left for only 7 more flags in the 32 bit mode. Nobody knows what comes along officially in future. Apart from that, this sounds like a nice idea for Cygwin 3.6, provided somebody implements it, https://cygwin.com/acronyms/#SHTDI Assuming we can live without actually having a subdir and just allowing to open and create a file with the O_XATTR flag, it might be pretty simple to implement. The path handling code would just have to drop the colon from the list of characters converted to the private-use Unicode area. Implementing the subdir is a bit more complicated, especially when taking opendir/readdir of that virtual subdir into account, but it would certainly be doable. Corinna -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple