Nmap Development: Re: [NSE][PATCH] string_ext library

[Sven Klemm <sven () c3d2 de>]

> > Currently there is already a tohex() function in stdnse.lua which only
> > works for numbers. It's probably best to rename my function to tohex()
> > since this is more in line with the lua function names.
> >
> > Do you think we should put this function into its own module or do you
> > think it should be added to stdnse?
> I would actually recommend extending the tohex() function to handle
> strings or numbers. Perhaps the other functions could be extended in
> the same way as well.
I've attached a patch which extends stdnse.tohex() to support strings 
and numbers and the new formatting options and adjusts the 
documentation accordingly.
Cheers,
Sven

--
Sven Klemm
http://cthulhu.c3d2.de/~sven/

Index: docs/scripting.xml
===================================================================
--- docs/scripting.xml  (revision 10448)
+++ docs/scripting.xml  (working copy)
@@ -2127,12 +2127,17 @@
           </listitem>
         </varlistentry>
         <varlistentry>
-          <term><option>string = stdnse.tohex(n)</option>
+          <term><option>string = stdnse.tohex(s, options)</option>
           </term>
           <listitem>
             <para>
-              Converts the given number, <literal>n</literal>, to a string
-              in a hexadecimal number format (e.g. 10 becomes "a").
+              Converts the given number or string, <literal>s</literal>, to a
+              string in a hexadecimal number format (e.g. 10 becomes "a"). 
+              <literal>options</literal> is a table containing parameters to
+              control the formatting. You may specify <literal>options.separator</literal>
+              which will be used as separator for groups of consecutive bytes.
+              With <literal>options.group</literal> you can control the group
+              length to be used with <literal>options.separator</literal>.
             </para>
           </listitem>
         </varlistentry>
Index: nselib/stdnse.lua
===================================================================
--- nselib/stdnse.lua   (revision 10448)
+++ nselib/stdnse.lua   (working copy)
@@ -143,10 +143,43 @@
   return ("%o"):format(n)
 end
 
---- Converts the given number, n, to a string in a hexidecimal number format.
--- () param n Number to convert.
--- () return String in hexidecimal format.
-function tohex(n)
-  assert(tonumber(n), "number expected");
-  return ("%x"):format(n);
+--- encode string or number to hexadecimal
+-- example: stdnse.tohex("abc") => "616263"
+--          stdnse.tohex("abc",{separator=":"}) => "61:62:63"
+--          stdnse.tohex("abc",{separator=":",group=2}) => "6162:63"
+--          stdnse.tohex(123456) => "1e240"
+--          stdnse.tohex(123456,{separator=":"}) => "1:e2:40"
+--          stdnse.tohex(123456,{separator=":",group=2}) => "1:e240"
+-- () param s string or number to be encoded
+-- () param options table specifiying formatting options
+-- () return hexadecimal encoded string
+tohex = function( s, options ) 
+  options = options or {}
+  local group = options.group or 1
+  local separator = options.separator or ""
+
+  if type( s ) == 'number' then
+    local hex = ("%x"):format(s)
+    local fmt_table = {}
+    local index
+    group = group * 2 
+    for i=#hex,1,-group do
+      -- index must be consecutive otherwise table.concat won't work
+      index = math.ceil(i/group)
+      fmt_table[index] = hex:sub(math.max(i-group+1,1),i)
+    end
+
+    return table.concat( fmt_table, separator )
+  elseif type( s ) == 'string' then
+    local fmt_table = {}
+    for i=1,#s,group do
+      table.insert( fmt_table, string.rep("%02x", math.min(#s-i+1,group)))
+    end
+
+    separator = separator:gsub("%%","%%%%")
+    return table.concat( fmt_table, separator ):format(s:byte(1, #s))
+  else
+    error( "Type not supported in tohex(): " .. type(s), 2 )
+  end
 end
+

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