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client code since Linux `inotify` is much like Linux `getdents64`. Expanding on "almost always"..The only time that this `iterator` logic is ***not*** needed on the output of a `read` from inotify fd's is when one passes a length to `read` *guaranteed* to only pass one event struct in the buffer. That unusual circumstance requires (at least!) knowing the length of the delivered filename before an event occurs, and the filename itself is optional for some event types. It is *far* more common to not know lengths in advance which means one passes a buffer big enough for at least one maximum length directory entry (256 bytes) which is then also big enough for *many* "typical" length entries and therefore many events. In such more common scenarios this iterator logic is definitely needed. Further, not using this logic, yet treating the return from read as "the whole answer" can test ok on "thin" event streams (e.g. 1 event per ms), hiding a latent bug of processing only the first event.
98 lines
4.5 KiB
Nim
98 lines
4.5 KiB
Nim
#
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#
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# Nim's Runtime Library
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# (c) Copyright 2012 Dominik Picheta
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#
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# See the file "copying.txt", included in this
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# distribution, for details about the copyright.
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#
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# Get the platform-dependent flags.
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# Structure describing an inotify event.
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type
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InotifyEvent* {.pure, final, importc: "struct inotify_event",
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header: "<sys/inotify.h>".} = object ## An Inotify event.
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wd* {.importc: "wd".}: FileHandle ## Watch descriptor.
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mask* {.importc: "mask".}: uint32 ## Watch mask.
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cookie* {.importc: "cookie".}: uint32 ## Cookie to synchronize two events.
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len* {.importc: "len".}: uint32 ## Length (including NULs) of name.
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name* {.importc: "name".}: char ## Name.
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# Supported events suitable for MASK parameter of INOTIFY_ADD_WATCH.
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const
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IN_ACCESS* = 0x00000001 ## File was accessed.
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IN_MODIFY* = 0x00000002 ## File was modified.
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IN_ATTRIB* = 0x00000004 ## Metadata changed.
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IN_CLOSE_WRITE* = 0x00000008 ## Writtable file was closed.
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IN_CLOSE_NOWRITE* = 0x00000010 ## Unwrittable file closed.
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IN_CLOSE* = (IN_CLOSE_WRITE or IN_CLOSE_NOWRITE) ## Close.
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IN_OPEN* = 0x00000020 ## File was opened.
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IN_MOVED_FROM* = 0x00000040 ## File was moved from X.
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IN_MOVED_TO* = 0x00000080 ## File was moved to Y.
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IN_MOVE* = (IN_MOVED_FROM or IN_MOVED_TO) ## Moves.
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IN_CREATE* = 0x00000100 ## Subfile was created.
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IN_DELETE* = 0x00000200 ## Subfile was deleted.
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IN_DELETE_SELF* = 0x00000400 ## Self was deleted.
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IN_MOVE_SELF* = 0x00000800 ## Self was moved.
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# Events sent by the kernel.
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const
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IN_UNMOUNT* = 0x00002000 ## Backing fs was unmounted.
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IN_Q_OVERFLOW* = 0x00004000 ## Event queued overflowed.
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IN_IGNORED* = 0x00008000 ## File was ignored.
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# Special flags.
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const
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IN_ONLYDIR* = 0x01000000 ## Only watch the path if it is a directory.
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IN_DONT_FOLLOW* = 0x02000000 ## Do not follow a sym link.
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IN_EXCL_UNLINK* = 0x04000000 ## Exclude events on unlinked objects.
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IN_MASK_ADD* = 0x20000000 ## Add to the mask of an already existing watch.
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IN_ISDIR* = 0x40000000 ## Event occurred against dir.
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IN_ONESHOT* = 0x80000000 ## Only send event once.
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# All events which a program can wait on.
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const
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IN_ALL_EVENTS* = (IN_ACCESS or IN_MODIFY or IN_ATTRIB or IN_CLOSE_WRITE or
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IN_CLOSE_NOWRITE or IN_OPEN or IN_MOVED_FROM or IN_MOVED_TO or
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IN_CREATE or IN_DELETE or IN_DELETE_SELF or IN_MOVE_SELF)
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proc inotify_init*(): FileHandle {.cdecl, importc: "inotify_init",
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header: "<sys/inotify.h>".}
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## Create and initialize inotify instance.
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proc inotify_init1*(flags: cint): FileHandle {.cdecl, importc: "inotify_init1",
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header: "<sys/inotify.h>".}
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## Create and initialize inotify instance.
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proc inotify_add_watch*(fd: cint; name: cstring; mask: uint32): cint {.cdecl,
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importc: "inotify_add_watch", header: "<sys/inotify.h>".}
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## Add watch of object NAME to inotify instance FD. Notify about events specified by MASK.
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proc inotify_rm_watch*(fd: cint; wd: cint): cint {.cdecl,
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importc: "inotify_rm_watch", header: "<sys/inotify.h>".}
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## Remove the watch specified by WD from the inotify instance FD.
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iterator inotify_events*(evs: pointer, n: int): ptr InotifyEvent =
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## Abstract the packed buffer interface to yield event object pointers.
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##
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## .. code-block:: Nim
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## var evs = newSeq[byte](8192) # Already did inotify_init+add_watch
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## while (let n = read(fd, evs[0].addr, 8192); n) > 0: # read forever
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## for e in inotify_events(evs[0].addr, n): echo e[].len # echo name lens
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var ev: ptr InotifyEvent = cast[ptr InotifyEvent](evs)
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var n = n
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while n > 0:
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yield ev
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let sz = InotifyEvent.sizeof + int(ev[].len)
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n -= sz
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ev = cast[ptr InotifyEvent](cast[uint](ev) + uint(sz))
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runnableExamples:
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when defined(linux):
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let inoty: FileHandle = inotify_init() ## Create 1 Inotify.
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doAssert inoty >= 0 ## Check for errors (FileHandle is alias to cint).
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let watchdoge: cint = inotify_add_watch(inoty, ".", IN_ALL_EVENTS) ## Add directory to watchdog.
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doAssert watchdoge >= 0 ## Check for errors.
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doAssert inotify_rm_watch(inoty, watchdoge) >= 0 ## Remove directory from the watchdog
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