Writing in a file from multiple threads

Question

I\'m writing a download manager in Objective-C which downloads file from multiple segments at the same times in order to improve the speed. Each segement of the file is download

Answer 1

Queue up the segment-objects as they are received to a writer-thread. The writer-thread should keep a list of out-of-order objects so that the actual disk-writing is sequential. If a segment download fails, it can be pushed back onto the downloading thread pool for another try, (perhaps an internal retry-count should be kept). I suggest a pool of segment-objects to prevent one or more failed download of one segment resulting in runaway memory use as later segments are downloaded and added to the list.