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Sorting a binary File

Posted on 2004-10-02
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Along the same lines of my other question, I also want to have it do this: I have a program that writes error information to a binary file. Each error code has an ID and alot of other information with it. Since the legacy app shows the error code but not the info, I want to write a command line program that will sort all of the of the information on the ID code and display the contents of the whole file to me sorted.
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Question by:microcoop
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by:Jaime Olivares
ID: 12211435
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by:microcoop
ID: 12211804
I posted both questions, this isn't duplicate the other one is searching but this one is sorting.
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by:CmdrRickHunter
ID: 12212834
You dont "sort a file," you read in the data from a file, sort it, and display it.

pseudo code:

open the file
read in all the "records" into an array (or other container)
close the file
sort the records by whatever criteria you want
output all the information you want
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Jaime Olivares earned 250 total points
ID: 12212851
What you need is an memory index, either if records are fixed- or variable lenght, the index will provide you a fast access to your file, and allow you to sort fastly.
You have 2 alternatives of indexes in mi opinion:
Offset only.- The index array will contain the file position of the init of every record. Every time you want to access a record randomly, go to de index, retrieve offset, and jump into the file, read record data, reading key first.
Offset and key.- The index array will contain also the key or ID of every record, so you don't have to read the file to locate or even sort the file. Once you have located the record by index in the index, then load rest of data into memory, it is more efficient but comsumes more memory, if file is not so bigger, then it is a good alternative.

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