Question

I’m trying to seek 1,000 bytes into a file handle and write it to an instance of NSData (or NSMutableData).

What am I doing wrong here?

    int offset = 1000;
    NSFileHandle *fHandle;
    NSMutableData *data;
    fHandle = [NSFileHandle fileHandleForReadingAtPath:@"bigtextfile.txt"];
    [fHandle seekToFileOffset:offset];

    data = [NSMutableData data];
    [fHandle writeData:data];
    [fHandle closeFile];
    [data length]; // this comes out to 0 bytes?

Answer 1

I am not sure you trying to read data after seeking or want to write some thing there? — you are opening file for reading then you are trying to write empty data.

If you want to read then using following line or similar API’s not write

data = [fHandle availableData];

If you want to write then open the file for writing — then have some content in NSData object and write it to the file.