Re: Setting contents of a large file to a variable.
Re: Setting contents of a large file to a variable.
- Subject: Re: Setting contents of a large file to a variable.
- From: Andrew Oliver <email@hidden>
- Date: Thu, 25 Nov 2004 00:26:03 -0800
On 11/24/04 11:41 PM, "Kumar Shailove" <email@hidden> wrote:
> Hi list,
> I need to manipulate text contained in a very large text file ~ 30-40 MB for
> this I have set the contents of the file to a variable and then manipulate
> that variable and once the variable has been manipulated, I again save the
> file.
> I have written following script for that:
>
> Set x to open for access "myfile.txt"
> Set myText to read x as text
> Close access x
>
> But it gives me the error: Out of Memory.
>
> Any alternative methods to do it?
>
The easiest change to your existing script would be to process the file in
chunks.
The 'read file' accepts optional parameters 'for <double int>' and 'from
<double int>'.
The idea is that you keep a counter as to how much of the file you've read
and iterate through, incrementing the 'from' counter as you go. For example:
set chunkSize to 1024 * 1024 -- 1 megabyte, adjust as necessary.
set done to false
repeat until done
try
set myText to read x as text for chunkSize
doSomethingTo ( myText )
on error
-- close to the end, get the last chunk
set myText to read x as text
doSomethingTo ( myText )
set done to true
end try
end repeat
'read' will keep track of the last position read and automatically start at
that point, so you don¹t need to maintain your own counter.
The only caveats would be if either the data you were manipulating was split
across chunks, or if file size is an exact multiple of chunkSize in which
last the last iteration (in the 'on error' block) may fail, but hopefully
this will get you on the right track.
Andrew
:)
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