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Colin B Maharaj
Guest
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 Posted: Fri May 11, 2007 2:53 pm Post subject: 32 bit File O and 64 Bit File IO |
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Hi all,
just wondering, I have this application that does a lot
of file processing and the size requirements of one
of my installations may pass the 2 gig limit soon!
I am using the BCB stock file routines
like FileOpen, FileCreate, FileRead, FileWrite.
I had realize some time back that there are
both 64 and 32 bit routines in the same name
now my questions:
1. Does the FileWrite routine writes pass 2 or 4 GIGs nowhere do I see
that FileWrite is 64 bit based?
2. Similarly does the FileRead routine work pass the 2 or 4 GIGs point?
.. It is clear that FileSeek is both 64 and 32 bit based. So
doe it mean that most of my recoding will be based on
using a 64 bit file pointer for seek operations and thats it!! (?)
I am using BCB6 on XP
BTW: Should I switch to Vista Ultimate (got it as a gift!)
Thanks
Colin B Maharaj
Programmer
I-CNS Limited
Trinidad WI. |
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Bob Gonder
Guest
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| Posted: Fri May 11, 2007 7:12 pm Post subject: Re: 32 bit File O and 64 Bit File IO |
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Colin B Maharaj wrote:
| Quote: | 1. Does the FileWrite routine writes pass 2 or 4 GIGs nowhere do I see
that FileWrite is 64 bit based?
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Should not matter unless you are trying to write more than 4 GB in one
call. (Notice that there is _no_ position argument, which would be the
limiting file-size factor.) The limiting factor is the OS. You can use
files as large as the underlying OS allows.
| Quote: | 2. Similarly does the FileRead routine work pass the 2 or 4 GIGs point?
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Again, there is no positioning argument, so the size of the file does
not matter. Only the size of your read matters.
| Quote: | It is clear that FileSeek is both 64 and 32 bit based. So
doe it mean that most of my recoding will be based on
using a 64 bit file pointer for seek operations and thats it!! (?)
|
If it does use 64bit integers, then yes.
(The 32/64 overload is seen on the Delphi, but not C++ help)
Otherwise, you might look to the WinApi
CreateFile()
ReadFile()
WriteFile()
SetFilePointer() uses 2-32bit integers for a 64bit offset.
SetFilePointerEx() uses 1-64bit integer. |
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Remy Lebeau (TeamB)
Guest
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| Posted: Fri May 11, 2007 9:59 pm Post subject: Re: 32 bit File O and 64 Bit File IO |
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"Colin B Maharaj" <noreply (AT) myhost (DOT) com> wrote in message
news:46443D35.2050709 (AT) myhost (DOT) com...
| Quote: | Does the FileWrite routine writes pass 2 or 4 GIGs
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Yes.
| Quote: | nowhere do I see that FileWrite is 64 bit based?
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It doesn't need to be, because it doesn't deal with file offsets
directly, so it doesn't care whether the current offset is past 2GB or
not.
| Quote: | Similarly does the FileRead routine work pass the 2 or 4 GIGs point?
|
Yes.
| Quote: | It is clear that FileSeek is both 64 and 32 bit based. So
doe it mean that most of my recoding will be based on
using a 64 bit file pointer for seek operations and thats it!! (?)
|
File pointers have always been 64-bit at the OS level.
SetFilePointer() has supported 64-bit file sizes for many years now.
FileSeek(), however, did not utilize the higher 32 bits until BCB6.
Gambit |
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Remy Lebeau (TeamB)
Guest
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| Posted: Fri May 11, 2007 10:00 pm Post subject: Re: 32 bit File O and 64 Bit File IO |
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"Bob Gonder" <notbg (AT) notmindspring (DOT) invalid> wrote in message
news:a1t8439ecms6dam3jiasc4nm3j4tbps17d (AT) 4ax (DOT) com...
| Quote: | If it does use 64bit integers, then yes.
(The 32/64 overload is seen on the Delphi, but not C++ help)
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The 64-bit overload of FileSeek() is in BCB6's help file.
Gambit |
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Bob Gonder
Guest
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| Posted: Sat May 12, 2007 12:06 am Post subject: Re: 32 bit File O and 64 Bit File IO |
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Remy Lebeau (TeamB) wrote:
| Quote: | "Bob Gonder" wrote in message
(The 32/64 overload is seen on the Delphi, but not C++ help)
The 64-bit overload of FileSeek() is in BCB6's help file.
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Ah yes, so it is.
Wonder why it's not in the BDS version? |
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Colin B Maharaj
Guest
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| Posted: Sat May 12, 2007 3:42 pm Post subject: Re: 32 bit File O and 64 Bit File IO |
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It was really simpler than
I thought. Now my application can read/write to a
160GB file now (at least)!
I did a lot of coding doing my own file io routines on an
application I wrote many years ago before I know a hint
about SQL (my/ms/oracle).
The reporting is based on flat files.
And folks still use it today.
Just have to move everything to a RDBMS now
or at least have this as an option for
the SQL savvy user.
Thanks for all the responses.
Colin B Maharaj
Full time developer
php/xhtml/c++/javascript/css/cshell
Trinidad, West Indies
[ I Liberated myself from the ]
[ Telecoms company I once worked ]
Remy Lebeau (TeamB) wrote:
| Quote: | "Colin B Maharaj" <noreply (AT) myhost (DOT) com> wrote in message
news:46443D35.2050709 (AT) myhost (DOT) com...
Does the FileWrite routine writes pass 2 or 4 GIGs
Yes.
nowhere do I see that FileWrite is 64 bit based?
It doesn't need to be, because it doesn't deal with file offsets
directly, so it doesn't care whether the current offset is past 2GB or
not.
Similarly does the FileRead routine work pass the 2 or 4 GIGs point?
Yes.
It is clear that FileSeek is both 64 and 32 bit based. So
doe it mean that most of my recoding will be based on
using a 64 bit file pointer for seek operations and thats it!! (?)
File pointers have always been 64-bit at the OS level.
SetFilePointer() has supported 64-bit file sizes for many years now.
FileSeek(), however, did not utilize the higher 32 bits until BCB6.
Gambit
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