New outlib library for output-related functions

nselib/outlib.lua

@@ -0,0 +1,49 @@
+--- Helper functions for NSE script output
+--
+-- These functions are useful for ensuring output is consistently ordered
+-- between scans and following conventions for output formatting.
+--
+-- @author Daniel Miller
+-- @copyright Same as Nmap--See https://nmap.org/book/man-legal.html
+-- @class module
+-- @name outlib
+
+local tableaux = require "tableaux"
+local keys = tableaux.keys
+
+local coroutine = require "coroutine"
+local wrap = coroutine.wrap
+local yield = coroutine.yield
+
+local table = require "table"
+local sort = table.sort
+
+local setmetatable = setmetatable
+local ipairs = ipairs
+
+local _ENV = {}
+
+--- Create a table that yields elements sorted by key when iterated over with pairs()
+--
+-- The returned table is like a sorted view of the original table; it should be
+-- treated as read-only, and any new data should be added to the original table
+-- instead.
+--@param  t    The table whose data should be used
+--@return out  A table that can be passed to pairs() to get sorted results
+function sorted_by_key(t)
+  local out = {}
+  setmetatable(out, {
+    __pairs = function(_)
+      local order = keys(t)
+      sort(order)
+      return wrap(function()
+        for i,k in ipairs(order) do
+          yield(k, t[k])
+        end
+      end)
+    end
+  })
+  return out
+end
+
+return _ENV