On 24/08/2010 17:11, Dean Michael Berris wrote:
Good day everyone,
I am currently taking some time to implement some functionality into cpp-netlib [0] (shameless plug) and somehow I've stumbled into a sort of conundrum.
First, some background: I'm trying to abstract away the string building routines of the network library to come up with the most efficient way of doing the following:
1. Efficiently allocate space to contain a string being built from literals and variable length strings. 2. Be able to build/traverse the string lazily (i.e., it doesn't matter that the string is contiguous in memory as in the case of C-strings, or whether they are built/backed by a stream as in Haskell ByteString).
It seems to be what you're looking for is a range (or a slight refinement). I.e. an entity that can be iterated. Arrays, tuples, strings, vectors, lists, a pair of istream_iterator, a pair of pointers, a concatenation of ranges, a transformed range, etc. are all ranges.
3. As much as possible be "automagically" network-safe (i.e. can be dealt with by Boost.Asio without having to do much acrobatics with it).
I suppose you'd have to linearize it. Sending it in multiple chunks would have different behaviour on different types of sockets.
What I wanted to be able to do (and am reproducing at the moment) is a means of doing the following:
string_handle f = /* some means of building a string */; string_handle s = str("Literal:") ^ f ^ str("\r\n\r\n"); std::string some_string = string_handle; // convert to string and build lazily
How about: boost::lazy_range<char> f = /* some means of building a string */ boost::lazy_range<char> s = boost::adaptors::join( boost::as_literal("Literal"), f, boost::as_literal("\r\n\r\n") ); std::string some_string; boost::copy(s, std::back_inserter(some_string)); boost::lazy_range is not actually in boost, but that would be a type erased range, and I've got an implementation somewhere. Of course, not using type erasure at all (i.e. replacing lazy_range by auto or the actual type of the expression) would allow it to be quite faster.