#!/usr/bin/luajit
local ffi = require('ffi')

local length     = 1000000
local iterations = 1000

ffi.cdef[[
struct tm { uint64_t tv_sec; uint32_t tv_nsec; };
int clock_gettime(int clockid, struct tm *r);
int RAND_bytes(unsigned char *buf, int num);
]]

local libopenssl = ffi.load('libcrypto')

local CLOCK_PROCESS_CPUTIME_ID = 2
local times = ffi.new('struct tm[2]')

local function randomstr(len)
    local buffer = ffi.new('uint8_t[?]', len)
    libopenssl.RAND_bytes(buffer, len)
    return buffer
end

local srcstr = randomstr(length)

local function searchmax(src, len)
   local counters = ffi.new('int32_t[256]')
   for i = 0, len - 1 do
      counters[src[i]] = counters[src[i]] + 1
   end
   for i = 255, 1, -1 do
     if counters[i] ~= 0 then
       return i
     end
   end
   return 0
end

local lmx  = 0
local rslt = {}

ffi.C.clock_gettime(CLOCK_PROCESS_CPUTIME_ID, times[0]);
for i = 1, iterations do
   rslt[i] = searchmax(srcstr, length)
end
ffi.C.clock_gettime(CLOCK_PROCESS_CPUTIME_ID, times[1]);

print(string.format(
   "%d %f",
    rslt[1],
    tonumber(times[1].tv_sec - times[0].tv_sec)
    + (times[1].tv_nsec - times[0].tv_nsec) * 0.000000001))