常用lua的功能函数

util.lua

local ffi=require('ffi')
ffi.cdef [[
  struct hostent {
    char  *h_name;            /* official name of host */
    char **h_aliases;         /* alias list */
    int    h_addrtype;        /* host address type */
    int    h_length;          /* length of address */
    char **h_addr_list;       /* list of addresses */
  };
  struct hostent *gethostbyname(const char *name);
  int gethostname(char *name, size_t len);
  struct myaddr { uint8_t b1, b2, b3, b4; }; 
]]
local _M = {}
function _M.get_hostname()
    local result
    local C = ffi.C
    local SIZE = 128

    local buf = ffi.new("unsigned char[?]", SIZE)
    local res = C.gethostname(buf, SIZE)

    if res == 0 then
       local hostname =  ffi.string(buf, SIZE)
       result = string.gsub(hostname, "%z+$", "")
    else
       local f = io.popen ("/bin/hostname")
       local hostname = f:read("*a") or ""
       f:close()
       result = string.gsub(hostname, "\n$", "")
    end

    return result
end

function  _M.gethostbyname(hostname)
   local hostent = ffi.C.gethostbyname(tostring(hostname))
   if hostent == nil then
      return 'Not Found'
   else
      local result = '"' .. ffi.string(hostent.h_name) .. '" : [ '
      local i = 0
      while i < (hostent.h_length / 4) do
         local myaddr = ffi.cast('struct myaddr*', hostent.h_addr_list[i])
         result = result .. string.format('%d.%d.%d.%d ',myaddr.b1, myaddr.b2, myaddr.b3, myaddr.b4)
         i = i + 1
      end
      result = result .. ']'
      return result
   end
end

return _M