milestone changed

chris_kohlhoff — Sat, 27 Jun 2009 05:30:10 GMT

milestone Boost 1.40.0 → To Be Determined

cc set

Tue, 11 Aug 2009 09:43:27 GMT

cc trapni@… added

I quite don't think that this has anything to do with HA (::= High Availability) but much more with "High Performance" applications.

However, I'm really very interested in a native boost integration of this, too, but still, i think this can be quite challenging as the input and output descriptors need to match certain criteria on different UNIX-alike operating systems (btw: windows has something similar)

for Linux at least, the requirements are:

input fd must be mmap()-able.
output fd must be a socket.

Although, when it comes to implementing an HTTP server (in my case), you cannot just pass the filename as a string to async_copy(...) as there are moments where you want to send just parts of a file, or even further: multiple different ranges of a file with some memory "chunks" between.

Although, as in HTTP (and I assume this case for most of the file transfer related network protocols) before sending the plain file, you always send some kind of preamble/header, some memory chunk that introduces the range of bytes located in the file. Solaris helps out here with a special syscall, named sendfilev(), which is a combination of writev() and sendfile().

In the end, i think, that a simple "async_copy()" won't be able to cover all this, although, when just implementing a sendfile() wrapper, it won't be long to the next request of sendfilev().

To solve that, I'd like to propose a generalized idea of composed transmit buffers which is an ordered set of chunks of different types (e.g.: mem, file_descriptor, ...) which can be passed to some write(...) and async_write(...) Asio function.

This is basically what I have written for my http server case, i'd be happy to see something like this in Asio anytime soon :)

The following is a list of links where I implemented the composite transmit buffers with sendfile() support:

hope it'll inspire asio development process :)

Boost C++ Libraries: Ticket #3150: boost.asio: async_copy(in, out, ...) for POSIX sendfile() support

milestone changed

cc set