Merge branch 'master' into defcleanup

2 files changed, 753 insertions, 4 deletions

diff --git a/tools/amalgamate.py b/tools/amalgamate.py
index d3807c6..4739a94 100755
--- a/tools/amalgamate.py
+++ b/tools/amalgamate.py
@@ -18,14 +18,14 @@ class Amalgamator:
 
     self.output_c.write("// Amalgamated source file\n")
     self.output_c.write('#include "upb.h"\n')
-    self.output_c.write('#include "upb/port_def.inc"\n')
+    self.output_c.write(open("upb/port_def.inc").read())
 
     self.output_h.write("// Amalgamated source file\n")
-    self.output_h.write('#include "upb/port_def.inc"\n')
+    self.output_h.write(open("upb/port_def.inc").read())
 
   def finish(self):
-    self.output_c.write('#include "upb/port_undef.inc"\n')
-    self.output_h.write('#include "upb/port_undef.inc"\n')
+    self.output_c.write(open("upb/port_undef.inc").read())
+    self.output_h.write(open("upb/port_undef.inc").read())
 
   def _process_file(self, infile_name, outfile):
     for line in open(infile_name):
diff --git a/tools/dump_cinit.lua b/tools/dump_cinit.lua
new file mode 100644
index 0000000..93ee12e
--- /dev/null
+++ b/tools/dump_cinit.lua
@@ -0,0 +1,749 @@
+--[[
+
+  Routines for dumping internal data structures into C initializers
+  that can be compiled into a .o file.
+
+--]]
+
+local upbtable = require "upb.table"
+local upb = require "upb"
+local export = {}
+
+-- A tiny little abstraction that decouples the dump_* functions from
+-- what they're writing to (appending to a string, writing to file I/O, etc).
+-- This could possibly matter since naive string building is O(n^2) in the
+-- number of appends.
+function export.str_appender()
+  local str = ""
+  local function append(fmt, ...)
+    str = str .. string.format(fmt, ...)
+  end
+  local function get()
+    return str
+  end
+  return append, get
+end
+
+function export.file_appender(file)
+  local f = file
+  local function append(fmt, ...)
+    f:write(string.format(fmt, ...))
+  end
+  return append
+end
+
+function handler_types(base)
+  local ret = {}
+  for k, _ in pairs(base) do
+    if string.find(k, "^" .. "HANDLER_") then
+      ret[#ret + 1] = k
+    end
+  end
+  return ret
+end
+
+function octchar(num)
+  assert(num < 8)
+  local idx = num + 1  -- 1-based index
+  return string.sub("01234567", idx, idx)
+end
+
+function c_escape(num)
+  assert(num < 256)
+  return string.format("\\%s%s%s",
+                       octchar(math.floor(num / 64)),
+                       octchar(math.floor(num / 8) % 8),
+                       octchar(num % 8));
+end
+
+-- const(f, label) -> UPB_LABEL_REPEATED, where f:label() == upb.LABEL_REPEATED
+function const(obj, name, base)
+  local val = obj[name]
+  base = base or upb
+
+  -- Support both f:label() and f.label.
+  if type(val) == "function" then
+    val = val(obj)
+  end
+
+  for k, v in pairs(base) do
+    if v == val and string.find(k, "^" .. string.upper(name)) then
+      return "UPB_" .. k
+    end
+  end
+  assert(false, "Couldn't find UPB_" .. string.upper(name) ..
+                " constant for value: " .. val)
+end
+
+function sortedkeys(tab)
+  arr = {}
+  for key in pairs(tab) do
+    arr[#arr + 1] = key
+  end
+  table.sort(arr)
+  return arr
+end
+
+function sorted_defs(defs)
+  local sorted = {}
+
+  for def in defs do
+    if def.type == deftype then
+      sorted[#sorted + 1] = def
+    end
+  end
+
+  table.sort(sorted,
+             function(a, b) return a:full_name() < b:full_name() end)
+
+  return sorted
+end
+
+function constlist(pattern)
+  local ret = {}
+  for k, v in pairs(upb) do
+    if string.find(k, "^" .. pattern) then
+      ret[k] = v
+    end
+  end
+  return ret
+end
+
+function boolstr(val)
+  if val == true then
+    return "true"
+  elseif val == false then
+    return "false"
+  else
+    assert(false, "Bad bool value: " .. tostring(val))
+  end
+end
+
+--[[
+
+  LinkTable: an object that tracks all linkable objects and their offsets to
+  facilitate linking.
+
+--]]
+
+local LinkTable = {}
+function LinkTable:new(types)
+  local linktab = {
+    types = types,
+    table = {},  -- ptr -> {type, 0-based offset}
+    obj_arrays = {}  -- Establishes the ordering for each object type
+  }
+  for type, _ in pairs(types) do
+    linktab.obj_arrays[type] = {}
+  end
+  setmetatable(linktab, {__index = LinkTable})  -- Inheritance
+  return linktab
+end
+
+-- Adds a new object to the sequence of objects of this type.
+function LinkTable:add(objtype, ptr, obj)
+  obj = obj or ptr
+  assert(self.table[obj] == nil)
+  assert(self.types[objtype])
+  local arr = self.obj_arrays[objtype]
+  self.table[ptr] = {objtype, #arr}
+  arr[#arr + 1] = obj
+end
+
+-- Returns a C symbol name for the given objtype and offset.
+function LinkTable:csym(objtype, offset)
+  local typestr = assert(self.types[objtype])
+  return string.format("%s[%d]", typestr, offset)
+end
+
+-- Returns the address of the given C object.
+function LinkTable:addr(obj)
+  if obj == upbtable.NULL then
+    return "NULL"
+  else
+    local tabent = assert(self.table[obj], "unknown object: " .. tostring(obj))
+    return "&" .. self:csym(tabent[1], tabent[2])
+  end
+end
+
+-- Returns an array declarator indicating how many objects have been added.
+function LinkTable:cdecl(objtype)
+  return self:csym(objtype, #self.obj_arrays[objtype])
+end
+
+function LinkTable:objs(objtype)
+  -- Return iterator function, allowing use as:
+  --   for obj in linktable:objs(type) do
+  --     -- ...
+  --   done
+  local array = self.obj_arrays[objtype]
+  local i = 0
+  return function()
+    i = i + 1
+    if array[i] then return array[i] end
+  end
+end
+
+function LinkTable:empty(objtype)
+  return #self.obj_arrays[objtype] == 0
+end
+
+--[[
+
+  Dumper: an object that can dump C initializers for several constructs.
+  Uses a LinkTable to resolve references when necessary.
+
+--]]
+
+local Dumper = {}
+function Dumper:new(linktab)
+  local obj = {linktab = linktab}
+  setmetatable(obj, {__index = Dumper})  -- Inheritance
+  return obj
+end
+
+-- Dumps a upb_tabval, eg:
+--   UPB_TABVALUE_INIT(5)
+function Dumper:_value(val, upbtype)
+  if type(val) == "nil" then
+    return "UPB_TABVALUE_EMPTY_INIT"
+  elseif type(val) == "number" then
+    -- Use upbtype to disambiguate what kind of number it is.
+    if upbtype == upbtable.CTYPE_INT32 then
+      return string.format("UPB_TABVALUE_INT_INIT(%d)", val)
+    else
+      -- TODO(haberman): add support for these so we can properly support
+      -- default values.
+      error("Unsupported number type " .. upbtype)
+    end
+  elseif type(val) == "string" then
+    return string.format('UPB_TABVALUE_PTR_INIT("%s")', val)
+  else
+    -- We take this as an object reference that has an entry in the link table.
+    return string.format("UPB_TABVALUE_PTR_INIT(%s)", self.linktab:addr(val))
+  end
+end
+
+-- Dumps a table key.
+function Dumper:tabkey(key)
+  if type(key) == "nil" then
+    return "UPB_TABKEY_NONE"
+  elseif type(key) == "string" then
+    local len = #key
+    local len1 = c_escape(len % 256)
+    local len2 = c_escape(math.floor(len / 256) % 256)
+    local len3 = c_escape(math.floor(len / (256 * 256)) % 256)
+    local len4 = c_escape(math.floor(len / (256 * 256 * 256)) % 256)
+    return string.format('UPB_TABKEY_STR("%s", "%s", "%s", "%s", "%s")',
+                         len1, len2, len3, len4, key)
+  else
+    return string.format("UPB_TABKEY_NUM(%d)", key)
+  end
+end
+
+-- Dumps a table entry.
+function Dumper:tabent(ent)
+  local key = self:tabkey(ent.key)
+  local val = self:_value(ent.value, ent.valtype)
+  local next = self.linktab:addr(ent.next)
+  return string.format('  {%s, %s, %s},\n', key, val, next)
+end
+
+-- Dumps an inttable array entry.  This is almost the same as value() above,
+-- except that nil values have a special value to indicate "empty".
+function Dumper:arrayval(val)
+  if val.val then
+    return string.format("  %s,\n", self:_value(val.val, val.valtype))
+  else
+    return "  UPB_TABVALUE_EMPTY_INIT,\n"
+  end
+end
+
+-- Dumps an initializer for the given strtable/inttable (respectively).  Its
+-- entries must have previously been added to the linktable.
+function Dumper:strtable(t)
+  -- UPB_STRTABLE_INIT(count, mask, type, size_lg2, entries)
+  return string.format(
+      "UPB_STRTABLE_INIT(%d, %d, %s, %d, %s)",
+      t.count, t.mask, const(t, "ctype", upbtable) , t.size_lg2,
+      self.linktab:addr(t.entries[1].ptr))
+end
+
+function Dumper:inttable(t)
+  local lt = assert(self.linktab)
+  -- UPB_INTTABLE_INIT(count, mask, type, size_lg2, ent, a, asize, acount)
+  local entries = "NULL"
+  if #t.entries > 0 then
+    entries = lt:addr(t.entries[1].ptr)
+  end
+  return string.format(
+      "UPB_INTTABLE_INIT(%d, %d, %s, %d, %s, %s, %d, %d)",
+      t.count, t.mask, const(t, "ctype", upbtable), t.size_lg2, entries,
+      lt:addr(t.array[1].ptr), t.array_size, t.array_count)
+end
+
+-- A visitor for visiting all tables of a def.  Used first to count entries
+-- and later to dump them.
+local function gettables(def)
+  if def:def_type() == upb.DEF_MSG then
+    return {int = upbtable.msgdef_itof(def), str = upbtable.msgdef_ntof(def)}
+  elseif def:def_type() == upb.DEF_ENUM then
+    return {int = upbtable.enumdef_iton(def), str = upbtable.enumdef_ntoi(def)}
+  end
+end
+
+local function emit_file_warning(filedef, append)
+  append('/* This file was generated by upbc (the upb compiler) from the input\n')
+  append(' * file:\n')
+  append(' *\n')
+  append(' *     %s\n', filedef:name())
+  append(' *\n')
+  append(' * Do not edit -- your changes will be discarded when the file is\n')
+  append(' * regenerated. */\n\n')
+end
+
+local function join(...)
+  return table.concat({...}, ".")
+end
+
+local function split(str)
+  local ret = {}
+  for word in string.gmatch(str, "%w+") do
+    table.insert(ret, word)
+  end
+  return ret
+end
+
+local function to_cident(...)
+  return string.gsub(join(...), "[%./]", "_")
+end
+
+local function to_preproc(...)
+  return string.upper(to_cident(...))
+end
+
+-- Strips away last path element, ie:
+--   foo.Bar.Baz -> foo.Bar
+local function remove_name(name)
+  local package_end = 0
+  for i=1,string.len(name) do
+    if string.byte(name, i) == string.byte(".", 1) then
+      package_end = i - 1
+    end
+  end
+  return string.sub(name, 1, package_end)
+end
+
+local function start_namespace(package, append)
+  local package_components = split(package)
+  for _, component in ipairs(package_components) do
+    append("namespace %s {\n", component)
+  end
+end
+
+local function end_namespace(package, append)
+  local package_components = split(package)
+  for i=#package_components,1,-1 do
+    append("}  /* namespace %s */\n", package_components[i])
+  end
+end
+
+local function well_known_type(m)
+  local type_map = {}
+  type_map["google.protobuf.Duration"]    = "UPB_WELLKNOWN_DURATION"
+  type_map["google.protobuf.Timestamp"]   = "UPB_WELLKNOWN_TIMESTAMP"
+  type_map["google.protobuf.Value"]       = "UPB_WELLKNOWN_VALUE"
+  type_map["google.protobuf.ListValue"]   = "UPB_WELLKNOWN_LISTVALUE"
+  type_map["google.protobuf.Struct"]      = "UPB_WELLKNOWN_STRUCT"
+  type_map["google.protobuf.DoubleValue"] = "UPB_WELLKNOWN_DOUBLEVALUE"
+  type_map["google.protobuf.FloatValue"]  = "UPB_WELLKNOWN_FLOATVALUE"
+  type_map["google.protobuf.Int64Value"]  = "UPB_WELLKNOWN_INT64VALUE"
+  type_map["google.protobuf.UInt64Value"] = "UPB_WELLKNOWN_UINT64VALUE"
+  type_map["google.protobuf.Int32Value"]  = "UPB_WELLKNOWN_INT32VALUE"
+  type_map["google.protobuf.UInt32Value"] = "UPB_WELLKNOWN_UINT32VALUE"
+  type_map["google.protobuf.BoolValue"]   = "UPB_WELLKNOWN_BOOLVALUE"
+  type_map["google.protobuf.StringValue"] = "UPB_WELLKNOWN_STRINGVALUE"
+  type_map["google.protobuf.BytesValue"]  = "UPB_WELLKNOWN_BYTESVALUE"
+  local t = type_map[m:full_name()]
+  if (t == nil) then
+    t = "UPB_WELLKNOWN_UNSPECIFIED"
+  end
+  return t
+end
+
+--[[
+
+  Top-level, exported dumper functions
+
+--]]
+
+local function dump_defs_c(filedef, append)
+  local defs = {}
+  for def in filedef:defs(upb.DEF_ANY) do
+    defs[#defs + 1] = def
+    if (def:def_type() == upb.DEF_MSG) then
+      for field in def:fields() do
+        defs[#defs + 1] = field
+      end
+    end
+  end
+
+  -- Sort all defs by (type, name).
+  -- This gives us a linear ordering that we can use to create offsets into
+  -- shared arrays like REFTABLES, hash table entries, and arrays.
+  table.sort(defs, function(a, b)
+    if a:def_type() ~= b:def_type() then
+      return a:def_type() < b:def_type()
+    else
+      return a:full_name() < b:full_name() end
+    end
+  )
+
+  -- Perform pre-pass to build the link table.
+  local linktab = LinkTable:new{
+    [upb.DEF_MSG] = "msgs",
+    [upb.DEF_FIELD] = "fields",
+    [upb.DEF_ENUM] = "enums",
+    intentries = "intentries",
+    strentries = "strentries",
+    arrays = "arrays",
+  }
+  local reftable_count = 0
+
+  for _, def in ipairs(defs) do
+    assert(def:is_frozen(), "can only dump frozen defs.")
+    linktab:add(def:def_type(), def)
+    reftable_count = reftable_count + 2
+    local tables = gettables(def)
+    if tables then
+      for _, e in ipairs(tables.str.entries) do
+        linktab:add("strentries", e.ptr, e)
+      end
+      for _, e in ipairs(tables.int.entries) do
+        linktab:add("intentries", e.ptr, e)
+      end
+      for _, e in ipairs(tables.int.array) do
+        linktab:add("arrays", e.ptr, e)
+      end
+    end
+  end
+
+  -- Emit forward declarations.
+  emit_file_warning(filedef, append)
+  append('#include "upb/def.h"\n')
+  append('#include "upb/structdefs.int.h"\n\n')
+  append("static const upb_msgdef %s;\n", linktab:cdecl(upb.DEF_MSG))
+  append("static const upb_fielddef %s;\n", linktab:cdecl(upb.DEF_FIELD))
+  if not linktab:empty(upb.DEF_ENUM) then
+    append("static const upb_enumdef %s;\n", linktab:cdecl(upb.DEF_ENUM))
+  end
+  append("static const upb_tabent %s;\n", linktab:cdecl("strentries"))
+  if not linktab:empty("intentries") then
+    append("static const upb_tabent %s;\n", linktab:cdecl("intentries"))
+  end
+  append("static const upb_tabval %s;\n", linktab:cdecl("arrays"))
+  append("\n")
+  append("#ifdef UPB_DEBUG_REFS\n")
+  append("static upb_inttable reftables[%d];\n", reftable_count)
+  append("#endif\n")
+  append("\n")
+
+  -- Emit defs.
+  local dumper = Dumper:new(linktab)
+
+  local reftable = 0
+
+  append("static const upb_msgdef %s = {\n", linktab:cdecl(upb.DEF_MSG))
+  for m in linktab:objs(upb.DEF_MSG) do
+    local tables = gettables(m)
+    -- UPB_MSGDEF_INIT(name, selector_count, submsg_field_count, itof, ntof,
+    --                 refs, ref2s)
+    append('  UPB_MSGDEF_INIT("%s", %d, %d, %s, %s, %s, %s, %s,' ..
+           ' &reftables[%d], &reftables[%d]),\n',
+           m:full_name(),
+           upbtable.msgdef_selector_count(m),
+           upbtable.msgdef_submsg_field_count(m),
+           dumper:inttable(tables.int),
+           dumper:strtable(tables.str),
+           boolstr(m:_map_entry()),
+           const(m, "syntax"),
+           well_known_type(m),
+           reftable, reftable + 1)
+    reftable = reftable + 2
+  end
+  append("};\n\n")
+
+  append("static const upb_fielddef %s = {\n", linktab:cdecl(upb.DEF_FIELD))
+  for f in linktab:objs(upb.DEF_FIELD) do
+    local subdef = "NULL"
+    if f:has_subdef() then
+      subdef = string.format("(const upb_def*)(%s)", linktab:addr(f:subdef()))
+    end
+    local intfmt
+    if f:type() == upb.TYPE_UINT32 or
+       f:type() == upb.TYPE_INT32 or
+       f:type() == upb.TYPE_UINT64 or
+       f:type() == upb.TYPE_INT64 then
+      intfmt = const(f, "intfmt")
+    else
+      intfmt = "0"
+    end
+    -- UPB_FIELDDEF_INIT(label, type, intfmt, tagdelim, is_extension, lazy,
+    --                   packed, name, num, msgdef, subdef, selector_base,
+    --                   index, --                   default_value)
+    append('  UPB_FIELDDEF_INIT(%s, %s, %s, %s, %s, %s, %s, "%s", %d, %s, ' ..
+           '%s, %d, %d, {0},' .. -- TODO: support default value
+           '&reftables[%d], &reftables[%d]),\n',
+           const(f, "label"), const(f, "type"), intfmt,
+           boolstr(f:istagdelim()), boolstr(f:is_extension()),
+           boolstr(f:lazy()), boolstr(f:packed()), f:name(), f:number(),
+           linktab:addr(f:containing_type()), subdef,
+           upbtable.fielddef_selector_base(f), f:index(),
+           reftable, reftable + 1
+           )
+    reftable = reftable + 2
+  end
+  append("};\n\n")
+
+  if not linktab:empty(upb.DEF_ENUM) then
+    append("static const upb_enumdef %s = {\n", linktab:cdecl(upb.DEF_ENUM))
+    for e in linktab:objs(upb.DEF_ENUM) do
+      local tables = gettables(e)
+      -- UPB_ENUMDEF_INIT(name, ntoi, iton, defaultval)
+      append('  UPB_ENUMDEF_INIT("%s", %s, %s, %d, ' ..
+             '&reftables[%d], &reftables[%d]),\n',
+             e:full_name(),
+             dumper:strtable(tables.str),
+             dumper:inttable(tables.int),
+             --e:default())
+             0,
+             reftable, reftable + 1)
+      reftable = reftable + 2
+    end
+    append("};\n\n")
+  end
+
+  append("static const upb_tabent %s = {\n", linktab:cdecl("strentries"))
+  for ent in linktab:objs("strentries") do
+    append(dumper:tabent(ent))
+  end
+  append("};\n\n");
+
+  if not linktab:empty("intentries") then
+    append("static const upb_tabent %s = {\n", linktab:cdecl("intentries"))
+    for ent in linktab:objs("intentries") do
+      append(dumper:tabent(ent))
+    end
+    append("};\n\n");
+  end
+
+  append("static const upb_tabval %s = {\n", linktab:cdecl("arrays"))
+  for ent in linktab:objs("arrays") do
+    append(dumper:arrayval(ent))
+  end
+  append("};\n\n");
+
+  append("#ifdef UPB_DEBUG_REFS\n")
+  append("static upb_inttable reftables[%d] = {\n", reftable_count)
+  for i = 1,reftable_count do
+    append("  UPB_EMPTY_INTTABLE_INIT(UPB_CTYPE_PTR),\n")
+  end
+  append("};\n")
+  append("#endif\n\n")
+
+  append("static const upb_msgdef *refm(const upb_msgdef *m, const void *owner) {\n")
+  append("  upb_msgdef_ref(m, owner);\n")
+  append("  return m;\n")
+  append("}\n\n")
+  append("static const upb_enumdef *refe(const upb_enumdef *e, const void *owner) {\n")
+  append("  upb_enumdef_ref(e, owner);\n")
+  append("  return e;\n")
+  append("}\n\n")
+
+  append("/* Public API. */\n")
+
+  for m in linktab:objs(upb.DEF_MSG) do
+    append("const upb_msgdef *upbdefs_%s_get(const void *owner)" ..
+           " { return refm(%s, owner); }\n",
+           to_cident(m:full_name()), linktab:addr(m))
+  end
+
+  append("\n")
+
+  for e in linktab:objs(upb.DEF_ENUM) do
+    append("const upb_enumdef *upbdefs_%s_get(const void *owner)" ..
+           " { return refe(%s, owner); }\n",
+           to_cident(e:full_name()), linktab:addr(e))
+  end
+
+  return linktab
+end
+
+local function dump_defs_for_type(format, defs, append)
+  local sorted = sorted_defs(defs)
+  for _, def in ipairs(sorted) do
+    append(format, to_cident(def:full_name()), def:full_name())
+  end
+
+  append("\n")
+end
+
+local function make_children_map(file)
+  -- Maps file:package() or msg:full_name() -> children.
+  local map = {}
+  for def in file:defs(upb.DEF_ANY) do
+    local container = remove_name(def:full_name())
+    if not map[container] then
+      map[container] = {}
+    end
+    table.insert(map[container], def)
+  end
+
+  -- Sort all the lists for a consistent ordering.
+  for name, children in pairs(map) do
+    table.sort(children, function(a, b) return a:name() < b:name() end)
+  end
+
+  return map
+end
+
+local print_classes
+
+local function print_message(def, map, indent, append)
+  append("\n")
+  append("%sclass %s : public ::upb::reffed_ptr<const ::upb::MessageDef> {\n",
+         indent, def:name())
+  append("%s public:\n", indent)
+  append("%s  %s(const ::upb::MessageDef* m, const void *ref_donor = NULL)\n",
+         indent, def:name())
+  append("%s      : reffed_ptr(m, ref_donor) {\n", indent)
+  append("%s    UPB_ASSERT(upbdefs_%s_is(m));\n", indent, to_cident(def:full_name()))
+  append("%s  }\n", indent)
+  append("\n")
+  append("%s  static %s get() {\n", indent, def:name())
+  append("%s    const ::upb::MessageDef* m = upbdefs_%s_get(&m);\n", indent, to_cident(def:full_name()))
+  append("%s    return %s(m, &m);\n", indent, def:name())
+  append("%s  }\n", indent)
+  -- TODO(haberman): add fields
+  print_classes(def:full_name(), map, indent .. "  ", append)
+  append("%s};\n", indent)
+end
+
+local function print_enum(def, indent, append)
+  append("\n")
+  append("%sclass %s : public ::upb::reffed_ptr<const ::upb::EnumDef> {\n",
+         indent, def:name())
+  append("%s public:\n", indent)
+  append("%s  %s(const ::upb::EnumDef* e, const void *ref_donor = NULL)\n",
+         indent, def:name())
+  append("%s      : reffed_ptr(e, ref_donor) {\n", indent)
+  append("%s    UPB_ASSERT(upbdefs_%s_is(e));\n", indent, to_cident(def:full_name()))
+  append("%s  }\n", indent)
+  append("%s  static %s get() {\n", indent, def:name())
+  append("%s    const ::upb::EnumDef* e = upbdefs_%s_get(&e);\n", indent, to_cident(def:full_name()))
+  append("%s    return %s(e, &e);\n", indent, def:name())
+  append("%s  }\n", indent)
+  append("%s};\n", indent)
+end
+
+function print_classes(name, map, indent, append)
+  if not map[name] then
+    return
+  end
+
+  for _, def in ipairs(map[name]) do
+    if def:def_type() == upb.DEF_MSG then
+      print_message(def, map, indent, append)
+    elseif def:def_type() == upb.DEF_ENUM then
+      print_enum(def, indent, append)
+    else
+      error("Unknown def type for " .. def:full_name())
+    end
+  end
+end
+
+local function dump_defs_h(file, append, linktab)
+  local basename_preproc = to_preproc(file:name())
+  append("/* This file contains accessors for a set of compiled-in defs.\n")
+  append(" * Note that unlike Google's protobuf, it does *not* define\n")
+  append(" * generated classes or any other kind of data structure for\n")
+  append(" * actually storing protobufs.  It only contains *defs* which\n")
+  append(" * let you reflect over a protobuf *schema*.\n")
+  append(" */\n")
+  emit_file_warning(file, append)
+  append('#ifndef %s_UPB_H_\n', basename_preproc)
+  append('#define %s_UPB_H_\n\n', basename_preproc)
+  append('#include "upb/def.h"\n\n')
+  append('UPB_BEGIN_EXTERN_C\n\n')
+
+  -- Dump C enums for proto enums.
+
+  append("/* MessageDefs: call these functions to get a ref to a msgdef. */\n")
+  dump_defs_for_type(
+      "const upb_msgdef *upbdefs_%s_get(const void *owner);\n",
+      file:defs(upb.DEF_MSG), append)
+
+  append("/* EnumDefs: call these functions to get a ref to an enumdef. */\n")
+  dump_defs_for_type(
+      "const upb_enumdef *upbdefs_%s_get(const void *owner);\n",
+      file:defs(upb.DEF_ENUM), append)
+
+  append("/* Functions to test whether this message is of a certain type. */\n")
+  dump_defs_for_type(
+      "UPB_INLINE bool upbdefs_%s_is(const upb_msgdef *m) {\n" ..
+      "  return strcmp(upb_msgdef_fullname(m), \"%s\") == 0;\n}\n",
+      file:defs(upb.DEF_MSG), append)
+
+  append("/* Functions to test whether this enum is of a certain type. */\n")
+  dump_defs_for_type(
+      "UPB_INLINE bool upbdefs_%s_is(const upb_enumdef *e) {\n" ..
+      "  return strcmp(upb_enumdef_fullname(e), \"%s\") == 0;\n}\n",
+      file:defs(upb.DEF_ENUM), append)
+
+  append("\n")
+
+  -- fields
+  local fields = {}
+
+  for f in linktab:objs(upb.DEF_FIELD) do
+    local symname = f:containing_type():full_name() .. "." .. f:name()
+    fields[#fields + 1] = {to_cident(symname), f}
+  end
+
+  table.sort(fields, function(a, b) return a[1] < b[1] end)
+
+  append("/* Functions to get a fielddef from a msgdef reference. */\n")
+  for _, field in ipairs(fields) do
+    local f = field[2]
+    local msg_cident = to_cident(f:containing_type():full_name())
+    local field_cident = to_cident(f:name())
+    append("UPB_INLINE const upb_fielddef *upbdefs_%s_f_%s(const upb_msgdef *m) {" ..
+           " UPB_ASSERT(upbdefs_%s_is(m));" ..
+           " return upb_msgdef_itof(m, %d); }\n",
+           msg_cident, field_cident, msg_cident, f:number())
+  end
+
+  append('\nUPB_END_EXTERN_C\n\n')
+
+  -- C++ wrappers.
+  local children_map = make_children_map(file)
+
+  append("#ifdef __cplusplus\n\n")
+  append("namespace upbdefs {\n")
+  start_namespace(file:package(), append)
+  print_classes(file:package(), children_map, "", append)
+  append("\n")
+  end_namespace(file:package(), append)
+  append("}  /* namespace upbdefs */\n\n")
+  append("#endif  /* __cplusplus */\n")
+
+  append("\n")
+  append('#endif  /* %s_UPB_H_ */\n', basename_preproc)
+end
+
+function export.dump_defs(filedef, append_h, append_c)
+  local linktab = dump_defs_c(filedef, append_c)
+  dump_defs_h(filedef, append_h, linktab)
+end
+
+return export