--- Buffered network I/O helper functions.
--
-- The functions in this module can be used for delimiting data received by the
-- <code>nmap.receive_buf</code> function in the Network I/O API (which see).
-- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html

module(... or "match",  package.seeall)
require "pcre"

--various functions for use with nse's nsock:receive_buf - function

-- e.g. 
-- sock:receive_buf(regex("myregexpattern")) - does a match using pcre- regular-
--                                           - expressions
-- sock:receive_buf(numbytes(80)) - is the buffered version of 
--                                  sock:receive_bytes(80) - i.e. it returns
--                                  exactly 80 bytes and no more 

--- Return a function that allows delimiting with a regular expression.
--
-- This function is a wrapper around <code>pcre.exec</code>. Its purpose is to
-- give script developers the ability to use regular expressions for delimiting
-- instead of Lua's string patterns.
-- @param pattern The regex.
-- @usage sock:receive_buf(match.regex("myregexpattern"))
-- @see nmap.receive_buf
-- @see pcre.exec
regex = function(pattern)
	local r = pcre.new(pattern, 0,"C")

	return function(buf)
		local s,e = r:exec(buf, 0,0);
		return s,e
	end
end

--- Return a function that allows delimiting at a certain number of bytes.
--
-- This function can be used to get a buffered version of
-- <code>sock:receive_bytes(n)</code> in case a script requires more than one
-- fixed-size chunk, as the unbuffered version may return more bytes than
-- requested and thus would require you to do the parsing on your own. 
-- @param num Number of bytes.
-- @usage sock:receive_buf(match.numbytes(80))
-- @see nmap.receive_buf
numbytes = function(num)
	local n = num
	return function(buf)
		if(string.len(buf) >=n) then
			return n, n
		end
		return nil
	end
end