2009/12/5 Bakul Shah <bakul+pl...@bitblocks.com>: > int newfd = fdfork(oldfd);
i'm not sure that there needs to be a new syscall to enable this. a driver would be adequate. here's one possibility: the driver implements "buffered streams" - i.e. reads are lazy, but previous reads can be re-read. bind '#β4.8192' /mnt/bufstream to get a buffered, read-only stream of fd 4, with an 8K buffer. open /mnt/bufstream/data to get a new window on the stream. if you read at an offset beyond anything previously read, it triggers a read on the underlying fd, which may block. if the offset isn't within the buffer size, then the read returns -1; otherwise the read is satisfied from the buffered data. the underlying assumption is that the fd is stream-, not message-oriented - as with tcp; message boundaries are not preserved. if you wanted it, an "fd join" driver could be simply implemented in a similar way: bind '#j4.5' /mnt/joined open /mnt/joined/data to get a (read-only) fd that satisfies reads from fd 4 until eof, then fd 5. both of these might make a fun exercise for a rainy day.
