feat(cffi/meta): meta model try out

Author: gynt

tests/test-cffi-lua-meta.lua

@@ -0,0 +1,94 @@
+rps = require("RPS")
+
+StructObjectMetaTable = {
+  -- retrieve all the fields and values of this struct
+  __pairs = function(tt)
+    print("StructObjectMetaTable: __pairs", tt)
+    local itF, itT, itK, itV = ipairs(tt[".meta"].fieldArray)
+    return function(t, k)
+      -- t and k are ignored because we provide pairs return values on an ipairs call
+      itK, itV = itF(itT, itK)
+      return itV, tt[itV]
+    end, tt, nil
+  end,
+  __index = function(tt, k) 
+    print("StructObjectMetaTable: __index", tt, k)
+   
+    local field = tt[".meta"].fields[k]
+    return field:read(tt['.address'])
+  end,
+  __newindex = function(tt, k, v)
+    print("StructObjectMetaTable: __newindex", tt, k,v)
+
+    local field = tt[".meta"].fields[k]
+    field:write(tt['.address'], v)
+  end,
+  __gc = function(tt)
+    if tt['.managed'] == true then
+      print("__gc: deallocating")
+      rps.deallocate(tt['.address'])
+      return
+    end
+    print("__gc: not a managed object")
+  end,
+}
+
+IntField = {
+  read = function(t, address)
+    -- TODO: where to set the offset? Optimize so the number of fields is low and can be reused dynamically?
+    -- metatable this stuff? Should the field know about its embedder, or be agnostic?
+    local addr = address + t.offset
+    print("int:read: at: ", addr)
+    return rps.readInteger(addr)
+  end,
+  write = function(t, address, v)
+    local addr = address + t.offset
+    print("int:write: at: ", addr, v)
+    rps.writeInteger(addr, v)
+  end,
+}
+
+function generateFieldInstance(field, offset)
+  return setmetatable({
+    offset = offset,
+  }, {
+    __index = field,
+  })
+end
+
+ExampleStruct = {
+  size = 4,
+  fields = {
+    field1 = generateFieldInstance(IntField, 0),
+    -- field1 = {
+    --   read = function(f, t, offset)
+    --     -- TODO: where to set the offset? Optimize so the number of fields is low and can be reused dynamically?
+    --     -- metatable this stuff? Should the field know about its embedder, or be agnostic?
+    --     local addr = t['.address'] + offset
+    --     print("int:read: at: ", addr)
+    --     return rps.readInteger(addr)
+    --   end,
+    --   write = function(f, t, offset, v)
+    --     local addr = t['.address'] + offset
+    --     print("int:write: at: ", addr, v)
+    --     rps.writeInteger(addr, v)
+    --   end,
+    -- },
+  },
+  fieldArray = {"field1", }
+}
+
+function generateStruct(t)
+  return setmetatable({
+    ['.meta'] = t, 
+    ['.address'] = rps.allocate(t.size, true),
+    ['.managed'] = true,
+  }, StructObjectMetaTable)
+end
+
+function generateStructExample()
+  return generateStruct(ExampleStruct)
+end
+
+s = generateStructExample()
+