Question

I’m trying to write a very large file to another very large file. I’m receiving this error on the filechannel writing line and I’m unsure why. I thought it was because I was going out of the limits of the data type long but long can go up to 9,223,372,036,854,775,807 and I’m only going up to 5,372,896,745 at the most. Any ideas why this is occurring? Is there some limit that MappedByteBuffer has? This doesn’t occur for smaller files and I haven’t run into any issues using the same code in a java desktop application. (Only happens on Android)

File f1 = new File(filename1); 

FileChannel fic, foc;
long fsize;
MappedByteBuffer mBUf;

FileOutputStream out = new FileOutputStream(f1,true); 
foc = out.getChannel();

File f2 = new File(filename2);
FileInputStream in = new FileInputStream(f2); 

fic = in.getChannel();
fsize = fic.size();

for (long b = 0; b < fsize; b += 65536)
{
    if (fsize - b < Resource.MEMORY_ALLOC_SIZE)
        mBUf = fic.map(FileChannel.MapMode.READ_ONLY, b, fsize - b);
    else
        mBUf = fic.map(FileChannel.MapMode.READ_ONLY, b, Resource.MEMORY_ALLOC_SIZE);
    foc.write(mBUf); //ERROR HERE!
}               

fic.close();
in.close();
foc.close();
out.close();

Any ideas/feedback is appreciated!

Answer 1

Is there some limit that MappedByteBuffer has?

Of course there is. It is limited by the available virtual memory for a start, and after that by the virtual address space.

You should be using transferTo() for this task rather than MappedByteBuffers,, as there is no agreed means of disposing of the virtual address space occupied by the latter.