Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!feeder4.news.weretis.net!feeder2.ecngs.de!ecngs!feeder.ecngs.de!Xl.tags.giganews.com!border1.nntp.ams.giganews.com!nntp.giganews.com!local2.nntp.ams.giganews.com!nntp.brightview.co.uk!news.brightview.co.uk.POSTED!not-for-mail NNTP-Posting-Date: Mon, 12 Mar 2012 06:56:42 -0500 Date: Mon, 12 Mar 2012 11:56:23 GMT From: Gavin Wraith Newsgroups: comp.sys.acorn.programmer Subject: Re: OS_GBPB 12 in a Wimp task Message-ID: <5fa2466f52.wra1th@wra1th.plus.com> References: <4cf7edf6-12e6-45c9-95b2-700fe371192f@b18g2000vbz.googlegroups.com> <9fa95124-990a-43e2-a561-b4c03bff439c@p7g2000yqk.googlegroups.com> <8299b36e52.Matthew@sinenomine.freeserve.co.uk> Organization: Home User-Agent: Messenger-Pro/1.00c (MsgServe/1.00a) (RISC-OS/5.18) NewsHound/v1.50-32 Lines: 26 X-Usenet-Provider: http://www.giganews.com X-Trace: sv3-3ka2FtSsm8p2T3igTLP9RuPy5fwYZl/LGe3W7GHsyjvapoGHLjagAIhUtXh52bt9zogucZ9SHZABPxN!Ixv7giLHFKflOx/lmdUymB0h1t5d5PC2nobBZ3NXEyWYrphUbo6CDol2bl71SvWEyYyH3XM+7s1P!dfzq X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 X-Original-Bytes: 2538 Xref: csiph.com comp.sys.acorn.programmer:1496 In message Rick Murray wrote: > Your app does a partial OS_GBPB to read an epic list of files (say, > the contents of a well stocked manga scanlation folder). For speed, > it'll do them twenty at a time. > > What happens if: > 1. Something else does an OS_GBPB, especially if within the same > directory structure? > > 2. The list of files *changes* in between polls, like you're counting > and moving the same stuff at the same time? > > While you as an application need to keep track of your own state, the > filesystem hands you a value in R4 of OS_GBPB 12 which may not be > valid at some indeterminate time in the future... I do not think we are in disagreement. I cannot see how any filing operations (or access to any mutable shared resource) can be multitasked unless there is some locking semaphore. I do not know what RISC OS does about this. Can anybody more knowledgeable give a quick answer? -- Gavin Wraith (gavin@wra1th.plus.com) Home page: http://www.wra1th.plus.com/