CODEWITHSUNDEEP
c#
aleczandru
aleczandru

Reputation: 5449

Open a file without loading it into memory at once

Hi I have a problem to solve for college and I have a hard time understanding the sentence of the problem.

This is the problem I have :

Reverse the order of bytes from a file without loading the entire file into memory at once.You have to solve this problem in C# , Java , PHP and Python.

Now there are two things that I do not understand here.

First I am not sure if bytes refer to the actual characters of the file , or to something else.The problem does not state if it is a text file or not.

Second I am not sure how to open a file without actualy loading into memory.

This is how I would normaly approach this problem , but I think if I do it this way the file gets loaded into memory:

     string fileName = 'file.txt';
     reader = new StreamReader(fileName);

     string line;
     while ((line = reader.ReadLine()) != null)
     {
          Console.WriteLine(line + "\n");
     }

Also I am not sure how I would actualy reverse all the characters if I am reading it one line at the time.

EDIT Sorry for posting in multiple languages I do not want the solution for the problem I only want to clarify it so I can solve it myself.I assumed that because I have to solve it in four different languages the concept would apply to all 4 and it did not matter who answer

Upvotes: 0

Views: 1351

Answers (1)

Julián Urbano
Julián Urbano

Reputation: 8488

Open a FileStream and use the Seek method to go to the end of the file. From there, go backwards, reading one byte at a time. This will read in reverse order. So, until you reach the beginning of the file, loop:

read 1 byte
// do whatever you want with that byte...write to another file?
seek back 2 bytes

As to efficiency, you can read a buffer of, say, 1024 bytes in memory. That way, you don't issue Read operations for each byte of the file. Once you have the buffer filled, reverse it and you're good to go.

Upvotes: 1

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