C functions with shared state

[Tim Hunter <TimHunter@...>]

In Lua I can define two functions that share state through a closure:

function newf(state)
   local function a()
      -- do something with state
  end
  local function b()
     -- do something with state
  end
   return a, b
end

a, b = newf(state)

Can I do this in C? How?

The reason I ask is that, in my environment I don't have access to the 
normal srand and rand functions in the C library. What I have is a 
random-number generator function (only callable from C) that takes its 
seed as an argument and updates the seed for the next call, like this:

long seed, r;

r = myrand(&seed);

I'd like to use this function to generate random numbers, but define two 
functions, callable from Lua, to maintain the seed. The first function 
would act like srand and set the seed, the second function would act 
like rand, calling the random number generator and, upon its return, 
updating the seed for the next call.