BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Integral value > unsigned _int64?          BorlandTalk.com Forum Index -> C++ Builder (Language C++) View previous topic :: View next topic   Author Message Andrue Cope [TeamB] Guest Posted: Mon Dec 12, 2005 11:37 am    Post subject: Integral value > unsigned _int64? I have a potential need for an integral value with more than 64 bits. Has anything been mentioned in the standard yet or am I looking at rolling my own/using a 3rd party library? For the time being it won't be an issue but one or two of my calculations that risked 32-bit overflow now risk 64-bit overflow. At present it's not very likely a file would grow to that size but I like to plan advance :) -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Alan Bellingham Guest Posted: Mon Dec 12, 2005 2:02 pm    Post subject: Re: Integral value > unsigned _int64? "Andrue Cope [TeamB]" <no.spam (AT) not (DOT) a.valid.address> wrote: Quote: I have a potential need for an integral value with more than 64 bits. Has anything been mentioned in the standard yet or am I looking at rolling my own/using a 3rd party library? Sounds like a job for a BigInt class. At least until you're on a platform with support for ... 128-bit integers. Quote: For the time being it won't be an issue but one or two of my calculations that risked 32-bit overflow now risk 64-bit overflow. At present it's not very likely a file would grow to that size but I like to plan advance I expect most file systems to start having problems if file sizes exceed 64 bits. Or even 63 bits (allowing seek from end). That's millions of terabytes. Allowing 1TB as a sensible maximum right now, then you have 23 doublings of capacity to worry about first. Moore's law will give you an approximate time before you can expect that to occur, but frankly, it's probably easier to check your currently supported file systems and see if any of them support greater than 64-bit addressing yet. Alan Bellingham -- ACCU Conference 2006 - 19-22 April, Randolph Hotel, Oxford, UK Back to top Andrue Cope [TeamB] Guest Posted: Mon Dec 12, 2005 3:02 pm    Post subject: Re: Integral value > unsigned _int64? Alan Bellingham wrote: Quote: it's probably easier to check your currently supported file systems and see if any of them support greater than 64-bit addressing yet. Not at the moment. In fact those that could often don't. Even Microsoft are leary about NTFS: http://www.microsoft.com/whdc/device/storage/LUN_SP1.mspx But this is why I'm not too desperate and was little more than curious. "However, NTFS reduces this, because it supports a 32-bit cluster number " ...that intrigues me because cluster numbers in NTFS are 64-bit. I can only assume this is a coding limitation rather than a file system limitation. It's just that when you are multiplying a number of clusters (QWORD) by the cluster size in bytes (DWORD) a wise programmer ponders the issue of 64-bit overflow. You could argue that it'll be at least a decade before it becomes a problem but then I've been working on this code base for 13 years already :) -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Bob Gonder Guest Posted: Mon Dec 12, 2005 4:40 pm    Post subject: Re: Integral value > unsigned _int64? Andrue Cope [TeamB] wrote: Quote: It's just that when you are multiplying a number of clusters (QWORD) by the cluster size in bytes (DWORD) a wise programmer ponders the issue of 64-bit overflow. You could argue that it'll be at least a decade before it becomes a problem but then I've been working on this code base for 13 years already I think the more usual solution is to first divide by K, M G or T so you get a reasonable number of digits when you multiply.. ie. scale first, then multiply. That works for displays, but if you need it internal, then don't multiply in the first place. Just use the two values for looping. Back to top Andrue Cope [TeamB] Guest Posted: Mon Dec 12, 2005 4:46 pm    Post subject: Re: Integral value > unsigned _int64? Bob Gonder wrote: Quote: That works for displays, but if you need it internal, then don't multiply in the first place. Just use the two values for looping. Generally we do but this is when our code needs to calculate the size of a file. BytesInCluster*NumberOfClustersInChain. For now I've put guards in. It was easy enough, just upgrade the existing guards. So far the widening has gone quite well but I haven't produced a compiling library yet. I think that'll be sometime later this week, lol. -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Bob Gonder Guest Posted: Mon Dec 12, 2005 5:08 pm    Post subject: Re: Integral value > unsigned _int64? Andrue Cope [TeamB] wrote: Quote: That works for displays, but if you need it internal, then don't multiply in the first place. Just use the two values for looping. Generally we do but this is when our code needs to calculate the size of a file. BytesInCluster*NumberOfClustersInChain. Well, yes, but to what purpose? What are you going to do with that size? I can only think of 3 things. 1) Display it (20 digit file size is unintelligable) 2) Allocate memory buffer for it (yeah, right) 3) Process the file (can be broken down into cluster ops) OTOH, if you are dead set on having really big numbers, then as Alan mentioned, BigInt library would be the way to go. I would think that if all your code used such a library, then as larger ALUs come on market, the library would refactor the now intrinsic sized functions to native code, and also expand the size of Big Int to the next doubling. This presupposes that the CPU size will need to keep up with the disk addressing sizes. Back to top Andrue Cope [TeamB] Guest Posted: Mon Dec 12, 2005 5:28 pm    Post subject: Re: Integral value > unsigned _int64? Bob Gonder wrote: Quote: Well, yes, but to what purpose? What are you going to do with that size? I can only think of 3 things. To copy it out. The code I'm writing is our runtime library and it's providing low level I/O access exactly as the Win32 API does for everyone else. If a file has that many bytes allocated to it I have to address the issue somehow. Simply denying it or hiding it is not an option any more than it would be for an operating system. At present the guards are in place to catch this if/when it ever happens but that still leaves a logical hole that I don't like. Past experience has shown that to be a time bomb waiting to go off. Quote: OTOH, if you are dead set on having really big numbers At this moment in time it's not a pressing issue but I'll point out that since this code is interpreting file systems created by operating systems it's not us who are demanding anything. Quite a few modern file systems have this potential dilemma. -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Bob Gonder Guest Posted: Tue Dec 13, 2005 7:07 am    Post subject: Re: Integral value > unsigned _int64? Andrue Cope [TeamB] wrote: Quote: To copy it out. The code I'm writing is our runtime library and it's providing low level I/O access exactly as the Win32 API does for So you're thinking seek() ? I've seen Win handle it a few ways: LowPart, HighPart LowPart, *HighPart These days you could probably get away with int64 for LowPart, and stick with *HighPart. At some future time, *HighPart might point to 3 int64's to complete an int256. But that might have endian issues? On a side note, just how big is 2^128, and how many atoms comprise the Earth? IOW unless we manage to pack many megs into a single disk atom, 128 bit addressing should suffice. Back to top Andrue Cope [TeamB] Guest Posted: Tue Dec 13, 2005 9:14 am    Post subject: Re: Integral value > unsigned _int64? Bob Gonder wrote: Quote: On a side note, just how big is 2^128, and how many atoms comprise the Earth? IOW unless we manage to pack many megs into a single disk atom, 128 bit addressing should suffice. I would hope so but I like to have these things covered. It's amazing some of the things we encounter especially if the file system has got corrupted. -- Andrue Cope [TeamB] [Bicester, Uk] http://info.borland.com/newsgroups/guide.html Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> C++ Builder (Language C++) All times are GMT Page 1 of 1   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.