CODEWITHSUNDEEP
javafileinputstream
DMo
DMo

Reputation: 621

Why am I getting an index out of bounds when I try to read certain bytes from a file?

Can anyone figure out why I'm getting an index out of bounds exception here? I can read in the first lot of data but when I try and loop this again it errors. Im also getting an 'assigned value is never used' error on the is.read(readBytes, offset, length); part of this too.

InetAddress address = packet.getAddress();

int port = packet.getPort();

RRQ RRQ = new RRQ();

int offset = 0;
int length = 512;
int block = 0;

byte[] readBytes = new byte[512];

File file = new File(filename);
FileInputStream is = new FileInputStream(file);

int fileBytes = is.read(readBytes, offset, length);

DatagramPacket outPacket = RRQ.doRRQ(readBytes, block, address, port);
socket.send(outPacket);

block++;

if (fileBytes != -1)
{                   
    socket.receive(packet);

    offset = offset + fileBytes;

    System.out.println(offset);

    Exceptions here:fileBytes = is.read(readBytes, offset, length);

    outPacket = RRQ.doRRQ(readBytes, block, address, port);
    socket.send(outPacket);
    block++;
}

Upvotes: 0

Views: 4343

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1500615

Look at this call:

fileBytes = is.read(readBytes, offset, length);

That's fine when offset is 0 - but when it's not 0, you're asking to read 512 bytes into an array which is only 512 bytes long, but not starting at the beginning of the array - therefore there's not enough room for all 512 bytes that you've asked for.

I suspect you want:

fileBytes = is.read(readBytes, offset, length - offset);

... or alternatively, just leave offset as 0. It's not clear what RRQ.doRRQ does, but it's suspicious that you don't pass in offset...

Upvotes: 11

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