| Re: reading portions of a large binary file [message #74268] |
Sat, 08 January 2011 07:41 |
oxfordenergyservices
Messages: 56
Registered: January 2009
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Member |
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On Jan 8, 3:38 pm, geoff <oxfordenergyservi...@googlemail.com> wrote:
> On Jan 8, 3:00 pm, David Fanning <n...@dfanning.com> wrote:
>
>> geoff writes:
>>> if the answer I am looking for is read_binary, then I've found it!
>
>> The answer could well be Read_Binary, but the method
>> underlying that would be the associated variable method
>> of reading the data. See the ASSOC command in IDL.
>
> thanks. i used
>
> strip=read_binary('bin',data_start=na*4,data_type=4,data_dim s=[n2-
> n1+1])
>
> which seems to work fine except when na gets too big (my offset is 3
> billion or so)
>
> I assume I'll have the same problem in assoc because long ints don't
> go that high?
>
> i'm assuming this is not possible then for an offset greater than max
> of long?
ahh! long64. all working! thanks David
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| Re: reading portions of a large binary file [message #74269 is a reply to message #74268] |
Sat, 08 January 2011 07:38  |
oxfordenergyservices
Messages: 56
Registered: January 2009
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Member |
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On Jan 8, 3:00 pm, David Fanning <n...@dfanning.com> wrote:
> geoff writes:
>> if the answer I am looking for is read_binary, then I've found it!
>
> The answer could well be Read_Binary, but the method
> underlying that would be the associated variable method
> of reading the data. See the ASSOC command in IDL.
>
thanks. i used
strip=read_binary('bin',data_start=na*4,data_type=4,data_dim s=[n2-
n1+1])
which seems to work fine except when na gets too big (my offset is 3
billion or so)
I assume I'll have the same problem in assoc because long ints don't
go that high?
i'm assuming this is not possible then for an offset greater than max
of long?
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| Re: reading portions of a large binary file [message #74270 is a reply to message #74269] |
Sat, 08 January 2011 07:00 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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geoff writes:
> if the answer I am looking for is read_binary, then I've found it!
The answer could well be Read_Binary, but the method
underlying that would be the associated variable method
of reading the data. See the ASSOC command in IDL.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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| Re: reading portions of a large binary file [message #74271 is a reply to message #74270] |
Sat, 08 January 2011 05:17 |
oxfordenergyservices
Messages: 56
Registered: January 2009
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Member |
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On Jan 8, 12:59 pm, geoff <oxfordenergyservi...@googlemail.com> wrote:
> Hi
>
> I have a large (4GB file) which is basically a large 2-D matrix of
> elevations. I want to read just some portion of this file
> (representing a lat/long box). I could read in the whole file line by
> line (because it is too big for RAM) and just take out the relevant
> bits, or preferably I want it to only read off the disc the relevant
> bits of the file. Is this possible in IDL? I vaguely remember this
> being possible in fortran but can't find it by googling.
>
> Thanks
if the answer I am looking for is read_binary, then I've found it!
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