Method Stdio.sendfile()

Method sendfile: object Stdio.sendfile(array(string) headers, object(File) from, int offset, int len, array(string) trailers, object(File) to)
object Stdio.sendfile(array(string) headers, object(File) from, int offset, int len, array(string) trailers, object(File) to, function(int:void) callback, mixed ... args)
Description
: Sends headers followed by len bytes starting at offset from the file from followed by trailers to the file to. When completed callback will be called with the total number of bytes sent as the first argument, followed by args.

Any of headers, from and trailers may be left out by setting them to 0.

Setting offset to -1 means send from the current position in from.

Setting len to -1 means send until from's end of file is reached.
Note: The sending is performed asynchronously, and may complete before the function returns.

For callback to be called, the backend must be active (ie main() must have returned -1).

In some cases, the backend must also be active for any sending to be performed at all.
Bugs: FIXME: Support for timeouts?
See also: Stdio.File.set_nonblocking