Add/Refactor Dir::list() -> DirIter ctor #40
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dir.list() consumes the dir and creates a DirIter. The underlying 'dup()' operation now becomes explicit, one may need to call try_clone() first. the list_self() and list_dir() using this now but are merely convinience wrappers and may (or may not) deprecated in future. Rationale: this simplifies the code a bit (list::open_dir() removed) and is closer to the low level semantics.
* Forgot to forget the Dir handle, thus it would been dropped. * On linux O_PATH was passed when Dir descriptors where opened. This is generally a good thing but broke the refactored list(). This also shown that O_PATH has different enough semantics to be problematic vs. opening handles without (as on other OS'es). Changed this to Dir::open() and Dir::sub_dir() default to opening without O_PATH (but O_DIRECTORY see remarks). * added Dir::open_path() and Dir::sub_dir_path() with O_PATH (urgh, better idea for naming? open_protected() or something like that?) which offer the O_PATH feature on linux.
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There is a bug in the current codebase which blocks progress here: try_clone() calls dup(), but dup()'ed descriptors share the seek offset and internal state, thus these clones can't act independently as iterators. This bug should be already prevalent without the commits fromt this pull request when one clones a Dir multiple times. But the list() introduced here made this apparent. I am searching for a solution to make a 'real' clone of a fd a la: Further note: maybe O_SEARCH will be of help or may be an optional flag. |
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That's interesting. Note also that |
Yes i will investigate this more closely, so far i consider that as experiment. While i had the impression/hopes that handles obtained openat will not shadowed by mount. Will see. |
'Lite' file descriptors are possibly a better naming of what O_PATH does. This introduces then and implements them portable. On systems which do not support O_PATH normal file descriptors are used.
* With FdType/fd_type() one can determine the kind of an underlying file descriptor. Lite descriptors are implemented only in Linux (for now). When O_DIRECTORY is supported it uses fcntl() in favo over stat() * clone_dirfd() tries to do 'the right thing' for duplicating FD's * libc_ok() is a simple wraper for libc calls that return -1 on error, I will refactor the code in the next commits to make use of that more. Please test this! So far it works for me on Linux.
This simplifies the code a bit, in 'release' the same output is generated. debug builds may not inline the libc_ok() and be slightly larger.
This up/downgrade cloning converts into normal/lite handles which was missing before. I hope this fixes tailhook#34 finally.
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Notice: I take back the idea of deprecate list_self() and list_dir() functions. |
dir.list() consumes the dir and creates a DirIter. The underlying 'dup()' operation now
becomes explicit, one may need to call try_clone() first.
the list_self() and list_dir() using this now but are merely convinience wrappers and may (or
may not) deprecated in future.
Rationale: this simplifies the code a bit (list::open_dir() removed) and is closer to the low
level semantics.