How to split file into chunks while still writing into it?

Question

Hi,

I tried to create byte array blocks from file whil the process was still using the file for writing. Actually I am storing video into file and I would like to create chunks from the same file while recording.

The following method was supposed to read blocks of bytes from file:

private byte[] getBytesFromFile(File file) throws IOException{
    InputStream is = new FileInputStream(file);
    long length = file.length();

    int numRead = 0;

    byte[] bytes = new byte[(int)length - mReadOffset];
    numRead = is.read(bytes, mReadOffset, bytes.length - mReadOffset);
    if(numRead != (bytes.length - mReadOffset)){
        throw new IOException("Could not completely read file " + file.getName());
    }

    mReadOffset += numRead;
    is.close();
    return bytes;
}

But the problem is that all array elements are set to 0 and I guess it is because the writing process locks the file.

I would bevery thankful if anyone of you could show any other way to create file chunks while writing into file.

Answer 1

If it were me, I would have it chunked by the process/thread writing to the file. This is how Log4j seems to do it, at any rate. It should be possible to make an OutputStream which automatically starts writing to a new file every N bytes.

Answer 2

Solved the problem:

private void getBytesFromFile(File file) throws IOException {
    FileInputStream is = new FileInputStream(file); //videorecorder stores video to file

    java.nio.channels.FileChannel fc = is.getChannel();
    java.nio.ByteBuffer bb = java.nio.ByteBuffer.allocate(10000);

    int chunkCount = 0;

    byte[] bytes;

    while(fc.read(bb) >= 0){
        bb.flip();
        //save the part of the file into a chunk
        bytes = bb.array();
        storeByteArrayToFile(bytes, mRecordingFile + "." + chunkCount);//mRecordingFile is the (String)path to file
        chunkCount++;
        bb.clear();
    }
}

private void storeByteArrayToFile(byte[] bytesToSave, String path) throws IOException {
    FileOutputStream fOut = new FileOutputStream(path);
    try {
        fOut.write(bytesToSave);
    }
    catch (Exception ex) {
        Log.e("ERROR", ex.getMessage());
    }
    finally {
        fOut.close();
    }
}