add stride

slice.lua

@@ -24,7 +24,7 @@ local function make(ct, len, cap)
   local atype = ffi.typeof("$ [?]", ct)
   local array = atype(cap)
 
-  return setmetatable({len = len, cap = cap, s = array, array = array, type = ct}, mt)
+  return setmetatable({len = len, cap = cap, s = array, array = array, type = ct, stride = ffi.sizeof(ct)}, mt)
 end
 
 local function sametype(a, b) -- not sure how to test if same - should we try casting src to dest?
@@ -38,7 +38,7 @@ mt = {
         if not i then i = 0 end
         if not j then j = s.len end
         local len = j - i
-        return setmetatable({len = len, cap = s.cap, s = s.s + i, array = s.array, type = s.type}, mt)
+        return setmetatable({len = len, cap = s.cap, s = s.s + i, array = s.array, type = s.type, stride = ffi.sizeof(s.type)}, mt)
       end
     end
     if i == 'table' then return totable(s) end

test.lua

@@ -3,6 +3,7 @@ local ffi = require "ffi"
 local slice = require "slice"
 
 local int_t = ffi.typeof("int")
+local byte_t = ffi.typeof("uint8_t")
 
 local a, b
 
@@ -45,5 +46,7 @@ a = slice.make(int_t, {1, 2, 3})
 b = slice.make(int_t, {4, 5, 6})
 assert(tostring(a..b) == "[1,2,3,4,5,6]")
 
+a = slice.make(byte_t, {1, 2, 3})
+assert(a.stride == 1)