Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!van-bc! From: lphillips@lpami.wimsey.bc.ca (Larry Phillips) Newsgroups: comp.sys.amiga.tech Subject: Re: when is a block not a block? Message-ID: <1864@lpami.wimsey.bc.ca> Date: 10 Aug 90 13:34:34 GMT Lines: 48 Return-Path: To: van-bc!rnews In , ked01@ccc.amdahl.com (Kim DeVaughn) writes: >In article <6321@sugar.hackercorp.com> peter@sugar.hackercorp.com (Peter da Silva) writes: >> In article ked01@JUTS.ccc.amdahl.com (Kim DeVaughn) writes: >> > While I understand that other such "oddities" may well arise in the future, >> > what bothers me is not being able to ask the filesystem for the *true* info >> > in a supported way. >> >> *which* filesystem? > >Whichever filesystem is being addressed at the time. > >There *is* a field in the FIB called fib_NumBlocks. What I would like is for >that field to accurately reflect the actual number of blocks allocated (or >some algorithmic variation thereof) by a file, at the time it is interrogated. > >That, and that a filesystem *document* what that field "means" in its own >context. This whole discussion has been a problem for me. I am trying to figure out under what conditions a file system might not know how many blocks (minimum storage units) a given length of data will take up. I can see having some problems with reporting on a file system that supports a variable block length, such as might be found on large IBM disks, where 'block' has no meaning, and data is stored in 'records' with a count being part of the record, but I think there is a way around even that. I do think a file system should have the ability to return: 1. the number of blocks left on a device, if appropriate. 2. the number of blocks that will be used, if appropriate, given the length of a file's data. The 'if appropriate' proviso would allow a file system to return a value to the caller that in effect says 'I have no idea, mate, I just write it out and see if it fits.'. A value of -1 would suffice. All file systems able to determine the number of blocks required, should be able to tell the caller what the requirements are. -larry -- Sex is better than logic, but I can't prove it. +-----------------------------------------------------------------------+ | // Larry Phillips | | \X/ lphillips@lpami.wimsey.bc.ca -or- uunet!van-bc!lpami!lphillips | | COMPUSERVE: 76703,4322 -or- 76703.4322@compuserve.com | +-----------------------------------------------------------------------+