Reading file chunk by chunk

Question

I want to read a file piece by piece. The file is split up into several pieces which are stored on different types of media. What I currently do is call each seperate piece of the file and then merge it back to the original file.

The issue is that I need to wait until all the chunks arrive before I can play/open the file. Is it possible to read the chunks as they are arriving as opposed to waiting for them to all arrive.

I am working on media file (movie file).

Where are you reading this data from? Why do you need to wait? — cklab, Jun 19 '12 at 23:23

cklab · Answer 1 · 2012-06-19T22:11:02.267

13

See InputSteram.read(byte[]) for reading bytes at a time.

Example code:

try {
    File file = new File("myFile");
    FileInputStream is = new FileInputStream(file);
    byte[] chunk = new byte[1024];
    int chunkLen = 0;
    while ((chunkLen = is.read(chunk)) != -1) {
        // your code..
    }
} catch (FileNotFoundException fnfE) {
    // file not found, handle case
} catch (IOException ioE) {
    // problem reading, handle case
}

edited Jun 19 '12 at 22:11

answered Jun 19 '12 at 22:05

cklab

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yes, but in that case I still need to wait until I got all the chunks. my problem is that I have several chunks 1 to n... while I waiting the second chunk arrived, I would like to be able open the file. @cklab – david Jun 19 '12 at 22:57

Frank Visaggio · Accepted Answer · 2012-06-22T16:21:26.047

2

what you want is source data line. This is perfect for when your data is too large to hold it in memory at once, so you can start playing it before you receive the entire file. Or if the file never ends.

look at the tutorial for source data line here

http://docs.oracle.com/javase/6/docs/api/java/io/FileInputStream.html#read

I would use this FileInputSteam

edited Jun 22 '12 at 16:21

answered Jun 19 '12 at 22:10

Frank Visaggio

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dave what kind of file are you dealing with? XML text, mp3 , ect...I think a little bit more information would help your question. – Frank Visaggio Jun 20 '12 at 14:03
hey david check out my revised answer. I let me know if that solves your question – Frank Visaggio Jun 22 '12 at 16:21

score 1 · Answer 3 · 2019-03-01T06:07:03.263

Instead of older io you can try nio for reading file chunk by chunk in memory not full file . You can use Channel to get datas from multiple source

RandomAccessFile aFile = new RandomAccessFile(
                        "test.txt","r");
        FileChannel inChannel = aFile.getChannel();
        long fileSize = inChannel.size();
        ByteBuffer buffer = ByteBuffer.allocate((int) fileSize);
        inChannel.read(buffer);
        //buffer.rewind();
        buffer.flip();
        for (int i = 0; i < fileSize; i++)
        {
            System.out.print((char) buffer.get());
        }
        inChannel.close();
        aFile.close();

Reading file chunk by chunk

3 Answers3

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