 |
forums.silverfrost.com
Welcome to the Silverfrost forums
|
| View previous topic :: View next topic |
| Author |
Message |
christyleomin
Joined: 08 Apr 2011
Posts: 155
|
 Posted: Fri Sep 23, 2011 9:35 am Post subject: Fixed length binary file (Fortran) |
 |
|
Hi,
I'm reading a fixed length binary file which has several records.I know the length of each record.
I would like to know (for some reson) the number of records that exist in the file which I'm reading.Is there any method, wherein I could detect the number of records existing?
That would make some things easy for me.
Please help
Christy |
|
| Back to top |
|
 |
Wilfried Linder
Joined: 14 Nov 2007
Posts: 314
Location: D�sseldorf, Germany
|
| Posted: Fri Sep 23, 2011 11:32 am Post subject: |
|
|
May be like this?
| Code: | call file_size@(file,size,err_code)
if (err_code .eq. 0) number_of_rec = size/length_of_rec |
Regards - Wilfried |
|
| Back to top |
|
|
christyleomin
Joined: 08 Apr 2011
Posts: 155
|
| Posted: Sat Sep 24, 2011 7:36 pm Post subject: |
|
|
Thanks Wilfred.
Did not get that (sorry)
Do you mean :
| Code: | call file_size(file,size,err_code)
subroutine file_size(file,size,err_code)
character*20 file
integer size,err_code,number_of_records
if(err_code.eq.0)then
no_of_records=size/length_of_record |
Where are we calclating err_code and size?
The length each record is 512. |
|
| Back to top |
|
|
christyleomin
Joined: 08 Apr 2011
Posts: 155
|
| Posted: Sun Sep 25, 2011 1:59 pm Post subject: |
|
|
Hi Wilfred (or) anyone here,
Please can you advise?
Christy |
|
| Back to top |
|
|
Wilfried Linder
Joined: 14 Nov 2007
Posts: 314
Location: D�sseldorf, Germany
|
| Posted: Sun Sep 25, 2011 5:44 pm Post subject: |
|
|
The subroutine file_size@(...) is part of the FTN95 library (see the "@" in the name)! "File" is the name of your input file, "size" and "err_code" are return values. Size is given in bytes, and err_code = 0 means that everything was OK.
Regards - Wilfried |
|
| Back to top |
|
|
christyleomin
Joined: 08 Apr 2011
Posts: 155
|
| Posted: Mon Sep 26, 2011 12:31 am Post subject: |
|
|
| Wilfred, thanks but I will be passing my code to a team who need to have it Fortran 77 -can you advise how to get this in Fortran 77? |
|
| Back to top |
|
|
christyleomin
Joined: 08 Apr 2011
Posts: 155
|
| Posted: Mon Sep 26, 2011 12:38 am Post subject: |
|
|
| Wilfred, thanks but I will be passing my code to a team who need to have it Fortran 77 -can you advise how to get this in Fortran 77? |
|
| Back to top |
|
|
Wilfried Linder
Joined: 14 Nov 2007
Posts: 314
Location: D�sseldorf, Germany
|
| Posted: Mon Sep 26, 2011 9:20 am Post subject: |
|
|
I really don't know if there is a function in standard Fortran 77 to do what you want. Here is a very crude code you may use:
| Code: | program test
implicit none
integer*4 i
character*120 ifile
character*512 string
ifile = 'test.ima'
open(10,file=ifile,access='direct',recl=512,err=900)
i = 10000
100 read(10,rec=i,err=110)string
print*,'number of records: ',i
goto 999
110 i = i-1
goto 100
900 print*,'error opening file'
999 close(10)
end |
Remarks: "ifile" is your input file. You may change the line i = 10000 to a bigger number - it must be the maximum number of records your files can have.
Regards - Wilfried |
|
| Back to top |
|
|
Wilfried Linder
Joined: 14 Nov 2007
Posts: 314
Location: D�sseldorf, Germany
|
| Posted: Mon Sep 26, 2011 9:27 am Post subject: |
|
|
... and here a little bit better with the subroutine you may need:
| Code: | program test
implicit none
integer*4 i
character*120 ifile
ifile = 'test.ima'
call no_of_rec(ifile,i)
if (i .gt. 0) then
print*,'number of records: ',i
else
print*,'error'
end if
end
subroutine no_of_rec(ifile,i)
implicit none
integer*4 i
character*120 ifile
character*512 string
open(10,file=ifile,access='direct',recl=512,err=900)
i = 999999
100 read(10,rec=i,err=110)string
goto 999
110 i = i-1
if (i .gt. 0) goto 100
900 i = -999
999 close(10)
return
end |
Regards - Wilfried
Last edited by Wilfried Linder on Mon Sep 26, 2011 10:33 am; edited 1 time in total |
|
| Back to top |
|
|
JohnCampbell
Joined: 16 Feb 2006
Posts: 2615
Location: Sydney
|
| Posted: Mon Sep 26, 2011 10:11 am Post subject: |
|
|
A binary search might be quicker, depending on the speed of a failed read. I've tested the following changes, assuming 512 byte records.
| Code: | program test
!
character ifile *120
integer*4 file_size_bytes, bytes
external file_size_bytes
!
ifile = 'test.ima'
!
call create_file (ifile, 7213)
!
bytes = file_size_bytes (ifile)
!
write (*,fmt='(a,i0)') 'Number of bytes in file '//trim(ifile)//' = ', bytes
!
end
subroutine create_file (ifile, num)
!
! create a file of "num" records of 2048 bytes to test
! demonstrates record size must only be multiple of 512 bytes
!
character ifile*(*)
integer*4 num, i
!
open (10, file=ifile, access='direct', recl=512*4, iostat=i)
do i = 1,num
write (10, rec=i) i
end do
close (10)
write (*,*) trim (ifile),' created'
end
integer*4 function file_size_bytes (ifile)
!
! determine number of 512 byte records in file
! file record size must be a multiple of 512 bytes
!
character ifile*(*)
!
integer*4 good, bad, i
character string*64
!
open (10, file=ifile, access='direct', recl=512, err=900)
!
good = 0
bad = 0
!
do i = 1,huge(i)
if (bad > 0) then
next = good + (bad-good)/2 ! split the difference
if (next == good) exit
else
next = max (good,512)*2 ! expand the search
end if
read (10,rec=next,err=110) string
print*,i, ' testing', next,' is ok'
good = next
cycle
110 bad = next
print*,i,' testing', next,' is bad'
end do
!
write (*,fmt='(a,i0,a,i0,a)') 'Number of records: ',good,' ( ',i,' tests )'
file_size_bytes = good*512
goto 999
!
900 print*,'error opening file'
file_size_bytes = -1
999 close (10)
end
|
|
|
| Back to top |
|
|
|
|
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, 2005 phpBB Group
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
