protobuf/upb/bindings/lua/upb.lua

--
-- upb - a minimalist implementation of protocol buffers.
--
-- Copyright (c) 2009 Google Inc.  See LICENSE for details.
-- Author: Josh Haberman <jhaberman@gmail.com>
--
-- Pure-Lua support functions that are part of the "upb" module.
-- This file is embedded and packaged into the "upb" C module binary -- it
-- should not be installed or used directly!

return function(upb)
  -- A convenience function for building/linking/freezing defs
  -- while maintaining their original order.
  --
  -- Sample usage:
  --   local m1, m2 = upb.build_defs{
  --     upb.MessageDef{full_name = "M1", fields = {
  --         upb.FieldDef{
  --           name = "m2",
  --           number = 1,
  --           type = upb.TYPE_MESSAGE,
  --           subdef_name = ".M2"
  --         },
  --       }
  --     },
  --     upb.MessageDef{full_name = "M2"}
  --   }
  upb.build_defs = function(defs)
    upb.SymbolTable(defs)
    -- Lua 5.2 puts unpack in the table library.
    return (unpack or table.unpack)(defs)
  end

  local ipairs_iter = function(array, last_index)
    local next_index = last_index + 1
    if next_index > #array then
      return nil
    end
    return next_index, array[next_index]
  end

  -- For iterating over the indexes and values of a upb.Array.
  --
  -- for i, val in upb.ipairs(array) do
  --   -- ...
  -- end
  upb.ipairs = function(array)
    return ipairs_iter, array, 0
  end

  local set_named = function(obj, init)
    for k, v in pairs(init) do
      local func = obj["set_" .. k]
      if not func then
        error("Cannot set member: " .. k)
      end
      func(obj, v)
    end
  end

  -- Capture references to the functions we're wrapping.
  local RealFieldDef = upb.FieldDef
  local RealEnumDef = upb.EnumDef
  local RealMessageDef = upb.MessageDef
  local RealSymbolTable = upb.SymbolTable

  -- FieldDef constructor; a wrapper around the real constructor that can
  -- set initial properties.
  --
  -- User can specify initialization values like so:
  --   upb.FieldDef{label=upb.LABEL_REQUIRED, name="my_field", number=5,
  --                type=upb.TYPE_INT32, default_value=12, type_name="Foo"}
  upb.FieldDef = function(init)
    local f = RealFieldDef()

    if init then
      -- Other members are often dependent on type, so set that first.
      if init.type then
        f:set_type(init.type)
        init.type = nil
      end

      set_named(f, init)
    end

    return f
  end


  -- MessageDef constructor; a wrapper around the real constructor that can
  -- set initial properties.
  --
  -- User can specify initialization values like so:
  --   upb.MessageDef{full_name="MyMessage", extstart=8000, fields={...}}
  upb.MessageDef = function(init)
    local m = RealMessageDef()

    if init then
      for _, f in pairs(init.fields or {}) do
        m:add(f)
      end
      init.fields = nil

      set_named(m, init)
    end

    return m
  end

  -- EnumDef constructor; a wrapper around the real constructor that can
  -- set initial properties.
  --
  -- User can specify initialization values like so:
  --   upb.EnumDef{full_name="MyEnum",
  --     values={
  --       {"FOO_VALUE_1", 1},
  --       {"FOO_VALUE_2", 2}
  --     }
  --   }
  upb.EnumDef = function(init)
    local e = RealEnumDef()

    if init then
      for _, val in pairs(init.values or {}) do
        e:add(val[1], val[2])
      end
      init.values = nil

      set_named(e, init)
    end

    return e
  end

  -- SymbolTable constructor; a wrapper around the real constructor that can
  -- add an initial set of defs.
  upb.SymbolTable = function(defs)
    local s = RealSymbolTable()

    if defs then
      s:add(defs)
    end

    return s
  end
end