diff --git a/md5.lua b/md5.lua
index 5f75fef..9a6381d 100644
--- a/md5.lua
+++ b/md5.lua
@@ -35,177 +35,181 @@ local char, byte, format, rep, sub =
 local bit_or, bit_and, bit_not, bit_xor, bit_rshift, bit_lshift
 
 local ok, bit = pcall(require, 'bit')
-if not ok then ok, bit = pcall(require, 'bit32') end
-
 if ok then
-
-  bit_not = bit.bnot
-
-  local tobit = function(n)
-    return n <= 0x7fffffff and n or -(bit_not(n) + 1)
-  end
-
-  local normalize = function(f)
-    return function(a,b) return tobit(f(tobit(a), tobit(b))) end
-  end
-
-  bit_or, bit_and, bit_xor = normalize(bit.bor), normalize(bit.band), normalize(bit.bxor)
-  bit_rshift, bit_lshift = normalize(bit.rshift), normalize(bit.lshift)
-
+  bit_or, bit_and, bit_not, bit_xor, bit_rshift, bit_lshift = bit.bor, bit.band, bit.bnot, bit.xor, bit.rshift, bit.lshift
 else
+  ok, bit = pcall(require, 'bit32')
 
-  local function tbl2number(tbl)
-    local result = 0
-    local power = 1
-    for i = 1, #tbl do
-      result = result + tbl[i] * power
-      power = power * 2
+  if ok then
+
+    bit_not = bit.bnot
+
+    local tobit = function(n)
+      return n <= 0x7fffffff and n or -(bit_not(n) + 1)
     end
-    return result
-  end
 
-  local function expand(t1, t2)
-    local big, small = t1, t2
-    if(#big < #small) then
-      big, small = small, big
+    local normalize = function(f)
+      return function(a,b) return tobit(f(tobit(a), tobit(b))) end
     end
-    -- expand small
-    for i = #small + 1, #big do
-      small[i] = 0
-    end
-  end
 
-  local to_bits -- needs to be declared before bit_not
+    bit_or, bit_and, bit_xor = normalize(bit.bor), normalize(bit.band), normalize(bit.bxor)
+    bit_rshift, bit_lshift = normalize(bit.rshift), normalize(bit.lshift)
 
-  bit_not = function(n)
-    local tbl = to_bits(n)
-    local size = math.max(#tbl, 32)
-    for i = 1, size do
-      if(tbl[i] == 1) then
-        tbl[i] = 0
-      else
-        tbl[i] = 1
+  else
+
+    local function tbl2number(tbl)
+      local result = 0
+      local power = 1
+      for i = 1, #tbl do
+        result = result + tbl[i] * power
+        power = power * 2
       end
-    end
-    return tbl2number(tbl)
-  end
-
-  -- defined as local above
-  to_bits = function (n)
-    if(n < 0) then
-      -- negative
-      return to_bits(bit_not(math.abs(n)) + 1)
-    end
-    -- to bits table
-    local tbl = {}
-    local cnt = 1
-    local last
-    while n > 0 do
-      last      = n % 2
-      tbl[cnt]  = last
-      n         = (n-last)/2
-      cnt       = cnt + 1
+      return result
     end
 
-    return tbl
-  end
-
-  bit_or = function(m, n)
-    local tbl_m = to_bits(m)
-    local tbl_n = to_bits(n)
-    expand(tbl_m, tbl_n)
-
-    local tbl = {}
-    for i = 1, #tbl_m do
-      if(tbl_m[i]== 0 and tbl_n[i] == 0) then
-        tbl[i] = 0
-      else
-        tbl[i] = 1
+    local function expand(t1, t2)
+      local big, small = t1, t2
+      if(#big < #small) then
+        big, small = small, big
+      end
+      -- expand small
+      for i = #small + 1, #big do
+        small[i] = 0
       end
     end
 
-    return tbl2number(tbl)
-  end
+    local to_bits -- needs to be declared before bit_not
 
-  bit_and = function(m, n)
-    local tbl_m = to_bits(m)
-    local tbl_n = to_bits(n)
-    expand(tbl_m, tbl_n)
-
-    local tbl = {}
-    for i = 1, #tbl_m do
-      if(tbl_m[i]== 0 or tbl_n[i] == 0) then
-        tbl[i] = 0
-      else
-        tbl[i] = 1
+    bit_not = function(n)
+      local tbl = to_bits(n)
+      local size = math.max(#tbl, 32)
+      for i = 1, size do
+        if(tbl[i] == 1) then
+          tbl[i] = 0
+        else
+          tbl[i] = 1
+        end
       end
+      return tbl2number(tbl)
     end
 
-    return tbl2number(tbl)
-  end
-
-  bit_xor = function(m, n)
-    local tbl_m = to_bits(m)
-    local tbl_n = to_bits(n)
-    expand(tbl_m, tbl_n)
-
-    local tbl = {}
-    for i = 1, #tbl_m do
-      if(tbl_m[i] ~= tbl_n[i]) then
-        tbl[i] = 1
-      else
-        tbl[i] = 0
+    -- defined as local above
+    to_bits = function (n)
+      if(n < 0) then
+        -- negative
+        return to_bits(bit_not(math.abs(n)) + 1)
       end
+      -- to bits table
+      local tbl = {}
+      local cnt = 1
+      local last
+      while n > 0 do
+        last      = n % 2
+        tbl[cnt]  = last
+        n         = (n-last)/2
+        cnt       = cnt + 1
+      end
+
+      return tbl
     end
 
-    return tbl2number(tbl)
+    bit_or = function(m, n)
+      local tbl_m = to_bits(m)
+      local tbl_n = to_bits(n)
+      expand(tbl_m, tbl_n)
+
+      local tbl = {}
+      for i = 1, #tbl_m do
+        if(tbl_m[i]== 0 and tbl_n[i] == 0) then
+          tbl[i] = 0
+        else
+          tbl[i] = 1
+        end
+      end
+
+      return tbl2number(tbl)
+    end
+
+    bit_and = function(m, n)
+      local tbl_m = to_bits(m)
+      local tbl_n = to_bits(n)
+      expand(tbl_m, tbl_n)
+
+      local tbl = {}
+      for i = 1, #tbl_m do
+        if(tbl_m[i]== 0 or tbl_n[i] == 0) then
+          tbl[i] = 0
+        else
+          tbl[i] = 1
+        end
+      end
+
+      return tbl2number(tbl)
+    end
+
+    bit_xor = function(m, n)
+      local tbl_m = to_bits(m)
+      local tbl_n = to_bits(n)
+      expand(tbl_m, tbl_n)
+
+      local tbl = {}
+      for i = 1, #tbl_m do
+        if(tbl_m[i] ~= tbl_n[i]) then
+          tbl[i] = 1
+        else
+          tbl[i] = 0
+        end
+      end
+
+      return tbl2number(tbl)
+    end
+
+    bit_rshift = function(n, bits)
+      local high_bit = 0
+      if(n < 0) then
+        -- negative
+        n = bit_not(math.abs(n)) + 1
+        high_bit = 0x80000000
+      end
+
+      local floor = math.floor
+
+      for i=1, bits do
+        n = n/2
+        n = bit_or(floor(n), high_bit)
+      end
+      return floor(n)
+    end
+
+    bit_lshift = function(n, bits)
+      if(n < 0) then
+        -- negative
+        n = bit_not(math.abs(n)) + 1
+      end
+
+      for i=1, bits do
+        n = n*2
+      end
+      return bit_and(n, 0xFFFFFFFF)
+    end
   end
 
-  bit_rshift = function(n, bits)
-    local high_bit = 0
-    if(n < 0) then
-      -- negative
-      n = bit_not(math.abs(n)) + 1
-      high_bit = 0x80000000
-    end
-
-    local floor = math.floor
-
-    for i=1, bits do
-      n = n/2
-      n = bit_or(floor(n), high_bit)
-    end
-    return floor(n)
+  -- convert little-endian 32-bit int to a 4-char string
+  local function lei2str(i)
+    local f=function (s) return char( bit_and( bit_rshift(i, s), 255)) end
+    return f(0)..f(8)..f(16)..f(24)
   end
 
-  bit_lshift = function(n, bits)
-    if(n < 0) then
-      -- negative
-      n = bit_not(math.abs(n)) + 1
+  -- convert raw string to big-endian int
+  local function str2bei(s)
+    local v=0
+    for i=1, #s do
+      v = v * 256 + byte(s, i)
     end
-
-    for i=1, bits do
-      n = n*2
-    end
-    return bit_and(n, 0xFFFFFFFF)
+    return v
   end
 end
 
--- convert little-endian 32-bit int to a 4-char string
-local function lei2str(i)
-  local f=function (s) return char( bit_and( bit_rshift(i, s), 255)) end
-  return f(0)..f(8)..f(16)..f(24)
-end
-
--- convert raw string to big-endian int
-local function str2bei(s)
-  local v=0
-  for i=1, #s do
-    v = v * 256 + byte(s, i)
-  end
-  return v
-end
-
 -- convert raw string to little-endian int
 local function str2lei(s)
   local v=0