Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 1483 insertions, 0 deletions

diff --git a/xpcom/reflect/xptinfo/moz.build b/xpcom/reflect/xptinfo/moz.build
new file mode 100644
index 0000000000..9e4ce23258
--- /dev/null
+++ b/xpcom/reflect/xptinfo/moz.build
@@ -0,0 +1,21 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+UNIFIED_SOURCES += [
+    "xptinfo.cpp",
+]
+
+SOURCES += [
+    "!xptdata.cpp",
+]
+
+EXPORTS += [
+    "xptinfo.h",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
diff --git a/xpcom/reflect/xptinfo/xptcodegen.py b/xpcom/reflect/xptinfo/xptcodegen.py
new file mode 100644
index 0000000000..34131f6678
--- /dev/null
+++ b/xpcom/reflect/xptinfo/xptcodegen.py
@@ -0,0 +1,646 @@
+#!/usr/bin/env python
+# jsonlink.py - Merge JSON typelib files into a .cpp file
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import json
+from collections import OrderedDict
+
+import buildconfig
+from perfecthash import PerfectHash
+
+# Pick a nice power-of-two size for our intermediate PHF tables.
+PHFSIZE = 512
+
+
+def indented(s):
+    return s.replace("\n", "\n  ")
+
+
+def cpp(v):
+    if type(v) == bool:
+        return "true" if v else "false"
+    return str(v)
+
+
+def mkstruct(*fields):
+    def mk(comment, **vals):
+        assert len(fields) == len(vals)
+        r = "{ // " + comment
+        r += indented(",".join("\n/* %s */ %s" % (k, cpp(vals[k])) for k in fields))
+        r += "\n}"
+        return r
+
+    return mk
+
+
+##########################################################
+# Ensure these fields are in the same order as xptinfo.h #
+##########################################################
+nsXPTInterfaceInfo = mkstruct(
+    "mIID",
+    "mName",
+    "mParent",
+    "mBuiltinClass",
+    "mMainProcessScriptableOnly",
+    "mMethods",
+    "mConsts",
+    "mFunction",
+    "mNumMethods",
+    "mNumConsts",
+)
+
+##########################################################
+# Ensure these fields are in the same order as xptinfo.h #
+##########################################################
+nsXPTType = mkstruct(
+    "mTag",
+    "mInParam",
+    "mOutParam",
+    "mOptionalParam",
+    "mData1",
+    "mData2",
+)
+
+##########################################################
+# Ensure these fields are in the same order as xptinfo.h #
+##########################################################
+nsXPTParamInfo = mkstruct(
+    "mType",
+)
+
+##########################################################
+# Ensure these fields are in the same order as xptinfo.h #
+##########################################################
+nsXPTMethodInfo = mkstruct(
+    "mName",
+    "mParams",
+    "mNumParams",
+    "mGetter",
+    "mSetter",
+    "mReflectable",
+    "mOptArgc",
+    "mContext",
+    "mHasRetval",
+    "mIsSymbol",
+)
+
+##########################################################
+# Ensure these fields are in the same order as xptinfo.h #
+##########################################################
+nsXPTDOMObjectInfo = mkstruct(
+    "mUnwrap",
+    "mWrap",
+    "mCleanup",
+)
+
+##########################################################
+# Ensure these fields are in the same order as xptinfo.h #
+##########################################################
+nsXPTConstantInfo = mkstruct(
+    "mName",
+    "mSigned",
+    "mValue",
+)
+
+
+# Helper functions for dealing with IIDs.
+#
+# Unfortunately, the way we represent IIDs in memory depends on the endianness
+# of the target architecture. We store an nsIID as a 16-byte, 4-tuple of:
+#
+#   (uint32_t, uint16_t, uint16_t, [uint8_t; 8])
+#
+# Unfortunately, this means that when we hash the bytes of the nsIID on a
+# little-endian target system, we need to hash them in little-endian order.
+# These functions let us split the input hexadecimal string into components,
+# encoding each as a little-endian value, and producing an accurate bytearray.
+#
+# It would be nice to have a consistent representation of IIDs in memory such
+# that we don't have to do these gymnastics to get an accurate hash.
+
+
+def split_at_idxs(s, lengths):
+    idx = 0
+    for length in lengths:
+        yield s[idx : idx + length]
+        idx += length
+    assert idx == len(s)
+
+
+def split_iid(iid):  # Get the individual components out of an IID string.
+    iid = iid.replace("-", "")  # Strip any '-' delimiters
+    return tuple(split_at_idxs(iid, (8, 4, 4, 2, 2, 2, 2, 2, 2, 2, 2)))
+
+
+def iid_bytes(iid):  # Get the byte representation of the IID for hashing.
+    bs = bytearray()
+    for num in split_iid(iid):
+        b = bytearray.fromhex(num)
+        # Match endianness of the target platform for each component
+        if buildconfig.substs["TARGET_ENDIANNESS"] == "little":
+            b.reverse()
+        bs += b
+    return bs
+
+
+# Split a 16-bit integer into its high and low 8 bits
+def splitint(i):
+    assert i < 2 ** 16
+    return (i >> 8, i & 0xFF)
+
+
+# Occasionally in xpconnect, we need to fabricate types to pass into the
+# conversion methods. In some cases, these types need to be arrays, which hold
+# indicies into the extra types array.
+#
+# These are some types which should have known indexes into the extra types
+# array.
+utility_types = [
+    {"tag": "TD_INT8"},
+    {"tag": "TD_UINT8"},
+    {"tag": "TD_INT16"},
+    {"tag": "TD_UINT16"},
+    {"tag": "TD_INT32"},
+    {"tag": "TD_UINT32"},
+    {"tag": "TD_INT64"},
+    {"tag": "TD_UINT64"},
+    {"tag": "TD_FLOAT"},
+    {"tag": "TD_DOUBLE"},
+    {"tag": "TD_BOOL"},
+    {"tag": "TD_CHAR"},
+    {"tag": "TD_WCHAR"},
+    {"tag": "TD_NSIDPTR"},
+    {"tag": "TD_PSTRING"},
+    {"tag": "TD_PWSTRING"},
+    {"tag": "TD_INTERFACE_IS_TYPE", "iid_is": 0},
+]
+
+
+# Core of the code generator. Takes a list of raw JSON XPT interfaces, and
+# writes out a file containing the necessary static declarations into fd.
+def link_to_cpp(interfaces, fd, header_fd):
+    # Perfect Hash from IID to interface.
+    iid_phf = PerfectHash(interfaces, PHFSIZE, key=lambda i: iid_bytes(i["uuid"]))
+    for idx, iface in enumerate(iid_phf.entries):
+        iface["idx"] = idx  # Store the index in iid_phf of the entry.
+
+    # Perfect Hash from name to iid_phf index.
+    name_phf = PerfectHash(interfaces, PHFSIZE, key=lambda i: i["name"].encode("ascii"))
+
+    def interface_idx(name):
+        entry = name and name_phf.get_entry(name.encode("ascii"))
+        if entry:
+            return entry["idx"] + 1  # 1-based, use 0 as a sentinel.
+        return 0
+
+    # NOTE: State used while linking. This is done with closures rather than a
+    # class due to how this file's code evolved.
+    includes = set()
+    types = []
+    type_cache = {}
+    params = []
+    param_cache = {}
+    methods = []
+    max_params = 0
+    method_with_max_params = None
+    consts = []
+    domobjects = []
+    domobject_cache = {}
+    strings = OrderedDict()
+
+    def lower_uuid(uuid):
+        return (
+            "{0x%s, 0x%s, 0x%s, {0x%s, 0x%s, 0x%s, 0x%s, 0x%s, 0x%s, 0x%s, 0x%s}}"
+            % split_iid(uuid)
+        )
+
+    def lower_domobject(do):
+        assert do["tag"] == "TD_DOMOBJECT"
+
+        idx = domobject_cache.get(do["name"])
+        if idx is None:
+            idx = domobject_cache[do["name"]] = len(domobjects)
+
+            includes.add(do["headerFile"])
+            domobjects.append(
+                nsXPTDOMObjectInfo(
+                    "%d = %s" % (idx, do["name"]),
+                    # These methods are defined at the top of the generated file.
+                    mUnwrap="UnwrapDOMObject<mozilla::dom::prototypes::id::%s, %s>"
+                    % (do["name"], do["native"]),
+                    mWrap="WrapDOMObject<%s>" % do["native"],
+                    mCleanup="CleanupDOMObject<%s>" % do["native"],
+                )
+            )
+
+        return idx
+
+    def lower_string(s):
+        if s in strings:
+            # We've already seen this string.
+            return strings[s]
+        elif len(strings):
+            # Get the last string we inserted (should be O(1) on OrderedDict).
+            last_s = next(reversed(strings))
+            strings[s] = strings[last_s] + len(last_s) + 1
+        else:
+            strings[s] = 0
+        return strings[s]
+
+    def lower_symbol(s):
+        return "uint32_t(JS::SymbolCode::%s)" % s
+
+    def lower_extra_type(type):
+        key = describe_type(type)
+        idx = type_cache.get(key)
+        if idx is None:
+            idx = type_cache[key] = len(types)
+            # Make sure `types` is the proper length for any recursive calls
+            # to `lower_extra_type` that might happen from within `lower_type`.
+            types.append(None)
+            realtype = lower_type(type)
+            types[idx] = realtype
+        return idx
+
+    def describe_type(type):  # Create the type's documentation comment.
+        tag = type["tag"][3:].lower()
+        if tag == "legacy_array":
+            return "%s[size_is=%d]" % (describe_type(type["element"]), type["size_is"])
+        elif tag == "array":
+            return "Array<%s>" % describe_type(type["element"])
+        elif tag == "interface_type" or tag == "domobject":
+            return type["name"]
+        elif tag == "interface_is_type":
+            return "iid_is(%d)" % type["iid_is"]
+        elif tag.endswith("_size_is"):
+            return "%s(size_is=%d)" % (tag, type["size_is"])
+        return tag
+
+    def lower_type(type, in_=False, out=False, optional=False):
+        tag = type["tag"]
+        d1 = d2 = 0
+
+        # TD_VOID is used for types that can't be represented in JS, so they
+        # should not be represented in the XPT info.
+        assert tag != "TD_VOID"
+
+        if tag == "TD_LEGACY_ARRAY":
+            d1 = type["size_is"]
+            d2 = lower_extra_type(type["element"])
+
+        elif tag == "TD_ARRAY":
+            # NOTE: TD_ARRAY can hold 16 bits of type index, while
+            # TD_LEGACY_ARRAY can only hold 8.
+            d1, d2 = splitint(lower_extra_type(type["element"]))
+
+        elif tag == "TD_INTERFACE_TYPE":
+            d1, d2 = splitint(interface_idx(type["name"]))
+
+        elif tag == "TD_INTERFACE_IS_TYPE":
+            d1 = type["iid_is"]
+
+        elif tag == "TD_DOMOBJECT":
+            d1, d2 = splitint(lower_domobject(type))
+
+        elif tag.endswith("_SIZE_IS"):
+            d1 = type["size_is"]
+
+        assert d1 < 256 and d2 < 256, "Data values too large"
+        return nsXPTType(
+            describe_type(type),
+            mTag=tag,
+            mData1=d1,
+            mData2=d2,
+            mInParam=in_,
+            mOutParam=out,
+            mOptionalParam=optional,
+        )
+
+    def lower_param(param, paramname):
+        params.append(
+            nsXPTParamInfo(
+                "%d = %s" % (len(params), paramname),
+                mType=lower_type(
+                    param["type"],
+                    in_="in" in param["flags"],
+                    out="out" in param["flags"],
+                    optional="optional" in param["flags"],
+                ),
+            )
+        )
+
+    def is_type_reflectable(type):
+        # All native types end up getting tagged as void*, or as wrapper types around void*
+        if type["tag"] == "TD_VOID":
+            return False
+        if type["tag"] in ("TD_ARRAY", "TD_LEGACY_ARRAY"):
+            return is_type_reflectable(type["element"])
+        return True
+
+    def is_method_reflectable(method):
+        if "hidden" in method["flags"]:
+            return False
+
+        for param in method["params"]:
+            # Reflected methods can't use non-reflectable types.
+            if not is_type_reflectable(param["type"]):
+                return False
+
+        return True
+
+    def lower_method(method, ifacename):
+        methodname = "%s::%s" % (ifacename, method["name"])
+
+        isSymbol = "symbol" in method["flags"]
+        reflectable = is_method_reflectable(method)
+
+        if not reflectable:
+            # Hide the parameters of methods that can't be called from JS to
+            # reduce the size of the file.
+            paramidx = name = numparams = 0
+        else:
+            if isSymbol:
+                name = lower_symbol(method["name"])
+            else:
+                name = lower_string(method["name"])
+
+            numparams = len(method["params"])
+
+            # Check cache for parameters
+            cachekey = json.dumps(method["params"], sort_keys=True)
+            paramidx = param_cache.get(cachekey)
+            if paramidx is None:
+                paramidx = param_cache[cachekey] = len(params)
+                for idx, param in enumerate(method["params"]):
+                    lower_param(param, "%s[%d]" % (methodname, idx))
+
+        nonlocal max_params, method_with_max_params
+        if numparams > max_params:
+            max_params = numparams
+            method_with_max_params = methodname
+        methods.append(
+            nsXPTMethodInfo(
+                "%d = %s" % (len(methods), methodname),
+                mName=name,
+                mParams=paramidx,
+                mNumParams=numparams,
+                # Flags
+                mGetter="getter" in method["flags"],
+                mSetter="setter" in method["flags"],
+                mReflectable=reflectable,
+                mOptArgc="optargc" in method["flags"],
+                mContext="jscontext" in method["flags"],
+                mHasRetval="hasretval" in method["flags"],
+                mIsSymbol=isSymbol,
+            )
+        )
+
+    def lower_const(const, ifacename):
+        assert const["type"]["tag"] in [
+            "TD_INT16",
+            "TD_INT32",
+            "TD_UINT8",
+            "TD_UINT16",
+            "TD_UINT32",
+        ]
+        is_signed = const["type"]["tag"] in ["TD_INT16", "TD_INT32"]
+
+        # Constants are always either signed or unsigned 16 or 32 bit integers,
+        # which we will only need to convert to JS values. To save on space,
+        # don't bother storing the type, and instead just store a 32-bit
+        # unsigned integer, and stash whether to interpret it as signed.
+        consts.append(
+            nsXPTConstantInfo(
+                "%d = %s::%s" % (len(consts), ifacename, const["name"]),
+                mName=lower_string(const["name"]),
+                mSigned=is_signed,
+                mValue="(uint32_t)%d" % const["value"],
+            )
+        )
+
+    def ancestors(iface):
+        yield iface
+        while iface["parent"]:
+            iface = name_phf.get_entry(iface["parent"].encode("ascii"))
+            yield iface
+
+    def lower_iface(iface):
+        method_cnt = sum(len(i["methods"]) for i in ancestors(iface))
+        const_cnt = sum(len(i["consts"]) for i in ancestors(iface))
+
+        # The number of maximum methods is not arbitrary. It is the same value
+        # as in xpcom/reflect/xptcall/genstubs.pl; do not change this value
+        # without changing that one or you WILL see problems.
+        #
+        # In addition, mNumMethods and mNumConsts are stored as a 8-bit ints,
+        # meaning we cannot exceed 255 methods/consts on any interface.
+        assert method_cnt < 250, "%s has too many methods" % iface["name"]
+        assert const_cnt < 256, "%s has too many constants" % iface["name"]
+
+        # Store the lowered interface as 'cxx' on the iface object.
+        iface["cxx"] = nsXPTInterfaceInfo(
+            "%d = %s" % (iface["idx"], iface["name"]),
+            mIID=lower_uuid(iface["uuid"]),
+            mName=lower_string(iface["name"]),
+            mParent=interface_idx(iface["parent"]),
+            mMethods=len(methods),
+            mNumMethods=method_cnt,
+            mConsts=len(consts),
+            mNumConsts=const_cnt,
+            # Flags
+            mBuiltinClass="builtinclass" in iface["flags"],
+            mMainProcessScriptableOnly="main_process_only" in iface["flags"],
+            mFunction="function" in iface["flags"],
+        )
+
+        # Lower methods and constants used by this interface
+        for method in iface["methods"]:
+            lower_method(method, iface["name"])
+        for const in iface["consts"]:
+            lower_const(const, iface["name"])
+
+    # Lower the types which have fixed indexes first, and check that the indexes
+    # seem correct.
+    for expected, ty in enumerate(utility_types):
+        got = lower_extra_type(ty)
+        assert got == expected, "Wrong index when lowering"
+
+    # Lower interfaces in the order of the IID phf's entries lookup.
+    for iface in iid_phf.entries:
+        lower_iface(iface)
+
+    # Write out the final output files
+    fd.write("/* THIS FILE WAS GENERATED BY xptcodegen.py - DO NOT EDIT */\n\n")
+    header_fd.write("/* THIS FILE WAS GENERATED BY xptcodegen.py - DO NOT EDIT */\n\n")
+
+    header_fd.write(
+        """
+#ifndef xptdata_h
+#define xptdata_h
+
+enum class nsXPTInterface : uint16_t {
+"""
+    )
+
+    for entry in iid_phf.entries:
+        header_fd.write("  %s,\n" % entry["name"])
+
+    header_fd.write(
+        """
+};
+
+#endif
+"""
+    )
+
+    # Include any bindings files which we need to include for webidl types
+    for include in sorted(includes):
+        fd.write('#include "%s"\n' % include)
+
+    # Write out our header
+    fd.write(
+        """
+#include "xptinfo.h"
+#include "mozilla/PerfectHash.h"
+#include "mozilla/dom/BindingUtils.h"
+
+// These template methods are specialized to be used in the sDOMObjects table.
+template<mozilla::dom::prototypes::ID PrototypeID, typename T>
+static nsresult UnwrapDOMObject(JS::Handle<JS::Value> aHandle, void** aObj, JSContext* aCx)
+{
+  RefPtr<T> p;
+  nsresult rv = mozilla::dom::UnwrapObject<PrototypeID, T>(aHandle, p, aCx);
+  p.forget(aObj);
+  return rv;
+}
+
+template<typename T>
+static bool WrapDOMObject(JSContext* aCx, void* aObj, JS::MutableHandle<JS::Value> aHandle)
+{
+  return mozilla::dom::GetOrCreateDOMReflector(aCx, reinterpret_cast<T*>(aObj), aHandle);
+}
+
+template<typename T>
+static void CleanupDOMObject(void* aObj)
+{
+  RefPtr<T> p = already_AddRefed<T>(reinterpret_cast<T*>(aObj));
+}
+
+namespace xpt {
+namespace detail {
+
+"""
+    )
+
+    # Static data arrays
+    def array(ty, name, els):
+        fd.write(
+            "const %s %s[] = {%s\n};\n\n"
+            % (ty, name, ",".join(indented("\n" + str(e)) for e in els))
+        )
+
+    array("nsXPTType", "sTypes", types)
+    array("nsXPTParamInfo", "sParams", params)
+    array("nsXPTMethodInfo", "sMethods", methods)
+    # Verify that stack-allocated buffers will do for xptcall implementations.
+    msg = (
+        "Too many method arguments in %s. "
+        "Either reduce the number of arguments "
+        "or increase PARAM_BUFFER_COUNT." % method_with_max_params
+    )
+    fd.write('static_assert(%s <= PARAM_BUFFER_COUNT, "%s");\n\n' % (max_params, msg))
+    array("nsXPTDOMObjectInfo", "sDOMObjects", domobjects)
+    array("nsXPTConstantInfo", "sConsts", consts)
+
+    # The strings array. We write out individual characters to avoid MSVC restrictions.
+    fd.write("const char sStrings[] = {\n")
+    for s, off in strings.items():
+        fd.write("  // %d = %s\n  '%s','\\0',\n" % (off, s, "','".join(s)))
+    fd.write("};\n\n")
+
+    # Build the perfect hash table for InterfaceByIID
+    fd.write(
+        iid_phf.cxx_codegen(
+            name="InterfaceByIID",
+            entry_type="nsXPTInterfaceInfo",
+            entries_name="sInterfaces",
+            lower_entry=lambda iface: iface["cxx"],
+            # Check that the IIDs match to support IID keys not in the map.
+            return_type="const nsXPTInterfaceInfo*",
+            return_entry="return entry.IID().Equals(aKey) ? &entry : nullptr;",
+            key_type="const nsIID&",
+            key_bytes="reinterpret_cast<const char*>(&aKey)",
+            key_length="sizeof(nsIID)",
+        )
+    )
+    fd.write("\n")
+
+    # Build the perfect hash table for InterfaceByName
+    fd.write(
+        name_phf.cxx_codegen(
+            name="InterfaceByName",
+            entry_type="uint16_t",
+            lower_entry=lambda iface: "%-4d /* %s */" % (iface["idx"], iface["name"]),
+            # Get the actual nsXPTInterfaceInfo from sInterfaces, and
+            # double-check that names match.
+            return_type="const nsXPTInterfaceInfo*",
+            return_entry="return strcmp(sInterfaces[entry].Name(), aKey) == 0"
+            " ? &sInterfaces[entry] : nullptr;",
+        )
+    )
+    fd.write("\n")
+
+    # Generate some checks that the indexes for the utility types match the
+    # declared ones in xptinfo.h
+    for idx, ty in enumerate(utility_types):
+        fd.write(
+            'static_assert(%d == (uint8_t)nsXPTType::Idx::%s, "Bad idx");\n'
+            % (idx, ty["tag"][3:])
+        )
+
+    fd.write(
+        """
+const uint16_t sInterfacesSize = mozilla::ArrayLength(sInterfaces);
+
+} // namespace detail
+} // namespace xpt
+"""
+    )
+
+
+def link_and_write(files, outfile, outheader):
+    interfaces = []
+    for file in files:
+        with open(file, "r") as fd:
+            interfaces += json.load(fd)
+
+    iids = set()
+    names = set()
+    for interface in interfaces:
+        assert interface["uuid"] not in iids, "duplicated UUID %s" % interface["uuid"]
+        assert interface["name"] not in names, "duplicated name %s" % interface["name"]
+        iids.add(interface["uuid"])
+        names.add(interface["name"])
+
+    link_to_cpp(interfaces, outfile, outheader)
+
+
+def main():
+    import sys
+    from argparse import ArgumentParser
+
+    parser = ArgumentParser()
+    parser.add_argument("outfile", help="Output C++ file to generate")
+    parser.add_argument("outheader", help="Output C++ header file to generate")
+    parser.add_argument("xpts", nargs="*", help="source xpt files")
+
+    args = parser.parse_args(sys.argv[1:])
+    with open(args.outfile, "w") as fd, open(args.outheader, "w") as header_fd:
+        link_and_write(args.xpts, fd, header_fd)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/xpcom/reflect/xptinfo/xptinfo.cpp b/xpcom/reflect/xptinfo/xptinfo.cpp
new file mode 100644
index 0000000000..c44e97cad4
--- /dev/null
+++ b/xpcom/reflect/xptinfo/xptinfo.cpp
@@ -0,0 +1,105 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#include "xptinfo.h"
+#include "nsISupports.h"
+#include "mozilla/dom/DOMJSClass.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/ArrayUtils.h"
+
+#include "jsfriendapi.h"
+#include "js/Symbol.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace xpt::detail;
+
+////////////////////////////////////
+// Constant Lookup Helper Methods //
+////////////////////////////////////
+
+bool nsXPTInterfaceInfo::HasAncestor(const nsIID& aIID) const {
+  for (const auto* info = this; info; info = info->GetParent()) {
+    if (info->IID() == aIID) {
+      return true;
+    }
+  }
+  return false;
+}
+
+const nsXPTConstantInfo& nsXPTInterfaceInfo::Constant(uint16_t aIndex) const {
+  MOZ_ASSERT(aIndex < ConstantCount());
+
+  if (const nsXPTInterfaceInfo* pi = GetParent()) {
+    if (aIndex < pi->ConstantCount()) {
+      return pi->Constant(aIndex);
+    }
+    aIndex -= pi->ConstantCount();
+  }
+
+  return xpt::detail::GetConstant(mConsts + aIndex);
+}
+
+const nsXPTMethodInfo& nsXPTInterfaceInfo::Method(uint16_t aIndex) const {
+  MOZ_ASSERT(aIndex < MethodCount());
+
+  if (const nsXPTInterfaceInfo* pi = GetParent()) {
+    if (aIndex < pi->MethodCount()) {
+      return pi->Method(aIndex);
+    }
+    aIndex -= pi->MethodCount();
+  }
+
+  return xpt::detail::GetMethod(mMethods + aIndex);
+}
+
+nsresult nsXPTInterfaceInfo::GetMethodInfo(
+    uint16_t aIndex, const nsXPTMethodInfo** aInfo) const {
+  *aInfo = aIndex < MethodCount() ? &Method(aIndex) : nullptr;
+  return *aInfo ? NS_OK : NS_ERROR_FAILURE;
+}
+
+nsresult nsXPTInterfaceInfo::GetConstant(uint16_t aIndex,
+                                         JS::MutableHandle<JS::Value> aConstant,
+                                         char** aName) const {
+  if (aIndex < ConstantCount()) {
+    aConstant.set(Constant(aIndex).JSValue());
+    *aName = moz_xstrdup(Constant(aIndex).Name());
+    return NS_OK;
+  }
+  return NS_ERROR_FAILURE;
+}
+
+////////////////////////////////////
+// nsXPTMethodInfo symbol helpers //
+////////////////////////////////////
+
+const char* nsXPTMethodInfo::SymbolDescription() const {
+  switch (GetSymbolCode()) {
+#define XPC_WELL_KNOWN_SYMBOL_DESCR_CASE(name) \
+  case JS::SymbolCode::name:                   \
+    return #name;
+    JS_FOR_EACH_WELL_KNOWN_SYMBOL(XPC_WELL_KNOWN_SYMBOL_DESCR_CASE)
+#undef XPC_WELL_KNOWN_SYMBOL_DESCR_CASE
+
+    default:
+      return "";
+  }
+}
+
+bool nsXPTMethodInfo::GetId(JSContext* aCx, jsid& aId) const {
+  if (IsSymbol()) {
+    aId = JS::PropertyKey::Symbol(GetSymbol(aCx));
+    return true;
+  }
+
+  JSString* str = JS_AtomizeString(aCx, Name());
+  if (!str) {
+    return false;
+  }
+  aId = JS::PropertyKey::NonIntAtom(str);
+  return true;
+}
diff --git a/xpcom/reflect/xptinfo/xptinfo.h b/xpcom/reflect/xptinfo/xptinfo.h
new file mode 100644
index 0000000000..2456c2c2b5
--- /dev/null
+++ b/xpcom/reflect/xptinfo/xptinfo.h
@@ -0,0 +1,711 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+/**
+ * Structures and methods with information about XPCOM interfaces for use by
+ * XPConnect. The static backing data structures used by this file are generated
+ * from xpidl interfaces by the jsonxpt.py and xptcodegen.py scripts.
+ */
+
+#ifndef xptinfo_h
+#define xptinfo_h
+
+#include <stdint.h>
+#include "nsID.h"
+#include "mozilla/Assertions.h"
+#include "jsapi.h"
+#include "js/Symbol.h"
+#include "js/Value.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+// Forward Declarations
+namespace mozilla {
+namespace dom {
+struct NativePropertyHooks;
+}  // namespace dom
+}  // namespace mozilla
+
+struct nsXPTInterfaceInfo;
+struct nsXPTType;
+struct nsXPTParamInfo;
+struct nsXPTMethodInfo;
+struct nsXPTConstantInfo;
+struct nsXPTDOMObjectInfo;
+
+enum class nsXPTInterface : uint16_t;
+
+// Internal helper methods.
+namespace xpt {
+namespace detail {
+
+inline const nsXPTInterfaceInfo* GetInterface(uint16_t aIndex);
+inline const nsXPTType& GetType(uint16_t aIndex);
+inline const nsXPTParamInfo& GetParam(uint16_t aIndex);
+inline const nsXPTMethodInfo& GetMethod(uint16_t aIndex);
+inline const nsXPTConstantInfo& GetConstant(uint16_t aIndex);
+inline const nsXPTDOMObjectInfo& GetDOMObjectInfo(uint16_t aIndex);
+inline const char* GetString(uint32_t aIndex);
+
+const nsXPTInterfaceInfo* InterfaceByIID(const nsIID& aIID);
+const nsXPTInterfaceInfo* InterfaceByName(const char* aName);
+
+extern const uint16_t sInterfacesSize;
+
+}  // namespace detail
+}  // namespace xpt
+
+/*
+ * An Interface describes a single XPCOM interface, including all of its
+ * methods. We don't record non-scriptable interfaces.
+ */
+struct nsXPTInterfaceInfo {
+  // High efficiency getters for Interfaces based on perfect hashes.
+  static const nsXPTInterfaceInfo* ByIID(const nsIID& aIID) {
+    return xpt::detail::InterfaceByIID(aIID);
+  }
+  static const nsXPTInterfaceInfo* ByName(const char* aName) {
+    return xpt::detail::InterfaceByName(aName);
+  }
+
+  static const nsXPTInterfaceInfo* Get(nsXPTInterface aID) {
+    return ByIndex(uint16_t(aID));
+  }
+
+  // These are only needed for Components_interfaces's enumerator.
+  static const nsXPTInterfaceInfo* ByIndex(uint16_t aIndex) {
+    // NOTE: We add 1 here, as the internal index 0 is reserved for null.
+    return xpt::detail::GetInterface(aIndex + 1);
+  }
+  static uint16_t InterfaceCount() { return xpt::detail::sInterfacesSize; }
+
+  // Interface flag getters
+  bool IsFunction() const { return mFunction; }
+  bool IsBuiltinClass() const { return mBuiltinClass; }
+  bool IsMainProcessScriptableOnly() const {
+    return mMainProcessScriptableOnly;
+  }
+
+  const char* Name() const { return xpt::detail::GetString(mName); }
+  const nsIID& IID() const { return mIID; }
+
+  // Get the parent interface, or null if this interface doesn't have a parent.
+  const nsXPTInterfaceInfo* GetParent() const {
+    return xpt::detail::GetInterface(mParent);
+  }
+
+  // Do we have an ancestor interface with the given IID?
+  bool HasAncestor(const nsIID& aIID) const;
+
+  // Get methods & constants
+  uint16_t ConstantCount() const { return mNumConsts; }
+  const nsXPTConstantInfo& Constant(uint16_t aIndex) const;
+  uint16_t MethodCount() const { return mNumMethods; }
+  const nsXPTMethodInfo& Method(uint16_t aIndex) const;
+
+  nsresult GetMethodInfo(uint16_t aIndex, const nsXPTMethodInfo** aInfo) const;
+  nsresult GetConstant(uint16_t aIndex, JS::MutableHandle<JS::Value> constant,
+                       char** aName) const;
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  nsID mIID;
+  uint32_t mName;  // Index into xpt::detail::sStrings
+
+  uint16_t mParent : 14;
+  uint16_t mBuiltinClass : 1;
+  // XXX(nika): Do we need this if we don't have addons anymore?
+  uint16_t mMainProcessScriptableOnly : 1;
+
+  uint16_t mMethods;  // Index into xpt::detail::sMethods
+
+  uint16_t mConsts : 14;  // Index into xpt::detail::sConsts
+  uint16_t mFunction : 1;
+  // uint16_t unused : 1;
+
+  uint8_t mNumMethods;  // NOTE(24/04/18): largest=nsIDocShell (193)
+  uint8_t mNumConsts;   // NOTE(24/04/18): largest=nsIAccessibleRole (175)
+};
+
+// The fields in nsXPTInterfaceInfo were carefully ordered to minimize size.
+static_assert(sizeof(nsXPTInterfaceInfo) == 28, "wrong size?");
+
+/*
+ * The following enum represents contains the different tag types which
+ * can be found in nsXPTTypeInfo::mTag.
+ *
+ * WARNING: mTag is 5 bits wide, supporting at most 32 tags.
+ */
+enum nsXPTTypeTag : uint8_t {
+  // Arithmetic (POD) Types
+  //  - Do not require cleanup,
+  //  - All bit patterns are valid,
+  //  - Outparams may be uninitialized by caller,
+  //  - Directly supported in xptcall.
+  //
+  // NOTE: The name 'Arithmetic' comes from Harbison/Steele. Despite being a tad
+  // unclear, it is used frequently in xptcall, so is unlikely to be changed.
+  TD_INT8 = 0,
+  TD_INT16 = 1,
+  TD_INT32 = 2,
+  TD_INT64 = 3,
+  TD_UINT8 = 4,
+  TD_UINT16 = 5,
+  TD_UINT32 = 6,
+  TD_UINT64 = 7,
+  TD_FLOAT = 8,
+  TD_DOUBLE = 9,
+  TD_BOOL = 10,
+  TD_CHAR = 11,
+  TD_WCHAR = 12,
+  _TD_LAST_ARITHMETIC = TD_WCHAR,
+
+  // Pointer Types
+  //  - Require cleanup unless NULL,
+  //  - All-zeros (NULL) bit pattern is valid,
+  //  - Outparams may be uninitialized by caller,
+  //  - Supported in xptcall as raw pointer.
+  TD_VOID = 13,
+  TD_NSIDPTR = 14,
+  TD_PSTRING = 15,
+  TD_PWSTRING = 16,
+  TD_INTERFACE_TYPE = 17,
+  TD_INTERFACE_IS_TYPE = 18,
+  TD_LEGACY_ARRAY = 19,
+  TD_PSTRING_SIZE_IS = 20,
+  TD_PWSTRING_SIZE_IS = 21,
+  TD_DOMOBJECT = 22,
+  TD_PROMISE = 23,
+  _TD_LAST_POINTER = TD_PROMISE,
+
+  // Complex Types
+  //  - Require cleanup,
+  //  - Always passed indirectly,
+  //  - Outparams must be initialized by caller,
+  //  - Supported in xptcall due to indirection.
+  TD_UTF8STRING = 24,
+  TD_CSTRING = 25,
+  TD_ASTRING = 26,
+  TD_NSID = 27,
+  TD_JSVAL = 28,
+  TD_ARRAY = 29,
+  _TD_LAST_COMPLEX = TD_ARRAY
+};
+
+static_assert(_TD_LAST_COMPLEX < 32, "nsXPTTypeTag must fit in 5 bits");
+
+/*
+ * A nsXPTType is a union used to identify the type of a method argument or
+ * return value. The internal data is stored as an 5-bit tag, and two 8-bit
+ * integers, to keep alignment requirements low.
+ *
+ * nsXPTType contains 3 extra bits, reserved for use by nsXPTParamInfo.
+ */
+struct nsXPTType {
+  nsXPTTypeTag Tag() const { return static_cast<nsXPTTypeTag>(mTag); }
+
+  // The index in the function argument list which should be used when
+  // determining the iid_is or size_is properties of this dependent type.
+  uint8_t ArgNum() const {
+    MOZ_ASSERT(Tag() == TD_INTERFACE_IS_TYPE || Tag() == TD_PSTRING_SIZE_IS ||
+               Tag() == TD_PWSTRING_SIZE_IS || Tag() == TD_LEGACY_ARRAY);
+    return mData1;
+  }
+
+ private:
+  // Helper for reading 16-bit data values split between mData1 and mData2.
+  uint16_t Data16() const {
+    return static_cast<uint16_t>(mData1 << 8) | mData2;
+  }
+
+ public:
+  // Get the type of the element in the current array or sequence. Arrays only
+  // fit 8 bits of type data, while sequences support up to 16 bits of type data
+  // due to not needing to store an ArgNum.
+  const nsXPTType& ArrayElementType() const {
+    if (Tag() == TD_LEGACY_ARRAY) {
+      return xpt::detail::GetType(mData2);
+    }
+    MOZ_ASSERT(Tag() == TD_ARRAY);
+    return xpt::detail::GetType(Data16());
+  }
+
+  // We store the 16-bit iface value as two 8-bit values in order to
+  // avoid 16-bit alignment requirements for XPTTypeDescriptor, which
+  // reduces its size and also the size of XPTParamDescriptor.
+  const nsXPTInterfaceInfo* GetInterface() const {
+    MOZ_ASSERT(Tag() == TD_INTERFACE_TYPE);
+    return xpt::detail::GetInterface(Data16());
+  }
+
+  const nsXPTDOMObjectInfo& GetDOMObjectInfo() const {
+    MOZ_ASSERT(Tag() == TD_DOMOBJECT);
+    return xpt::detail::GetDOMObjectInfo(Data16());
+  }
+
+  // See the comments in nsXPTTypeTag for an explanation as to what each of
+  // these categories mean.
+  bool IsArithmetic() const { return Tag() <= _TD_LAST_ARITHMETIC; }
+  bool IsPointer() const {
+    return !IsArithmetic() && Tag() <= _TD_LAST_POINTER;
+  }
+  bool IsComplex() const { return Tag() > _TD_LAST_POINTER; }
+
+  bool IsInterfacePointer() const {
+    return Tag() == TD_INTERFACE_TYPE || Tag() == TD_INTERFACE_IS_TYPE;
+  }
+
+  bool IsDependent() const {
+    return (Tag() == TD_ARRAY && InnermostType().IsDependent()) ||
+           Tag() == TD_INTERFACE_IS_TYPE || Tag() == TD_LEGACY_ARRAY ||
+           Tag() == TD_PSTRING_SIZE_IS || Tag() == TD_PWSTRING_SIZE_IS;
+  }
+
+  // Unwrap a nested type to its innermost value (e.g. through arrays).
+  const nsXPTType& InnermostType() const {
+    if (Tag() == TD_LEGACY_ARRAY || Tag() == TD_ARRAY) {
+      return ArrayElementType().InnermostType();
+    }
+    return *this;
+  }
+
+  // In-memory size of native type in bytes.
+  inline size_t Stride() const;
+
+  // Offset the given base pointer to reference the element at the given index.
+  void* ElementPtr(const void* aBase, uint32_t aIndex) const {
+    return (char*)aBase + (aIndex * Stride());
+  }
+
+  // Zero out a native value of the given type. The type must not be 'complex'.
+  void ZeroValue(void* aValue) const {
+    MOZ_RELEASE_ASSERT(!IsComplex(), "Cannot zero a complex value");
+    memset(aValue, 0, Stride());
+  }
+
+  // Indexes into the extra types array of a small set of known types.
+  enum class Idx : uint8_t {
+    INT8 = 0,
+    UINT8,
+    INT16,
+    UINT16,
+    INT32,
+    UINT32,
+    INT64,
+    UINT64,
+    FLOAT,
+    DOUBLE,
+    BOOL,
+    CHAR,
+    WCHAR,
+    NSIDPTR,
+    PSTRING,
+    PWSTRING,
+    INTERFACE_IS_TYPE
+  };
+
+  // Helper methods for fabricating nsXPTType values used by xpconnect.
+  static nsXPTType MkArrayType(Idx aInner) {
+    MOZ_ASSERT(aInner <= Idx::INTERFACE_IS_TYPE);
+    return {TD_LEGACY_ARRAY, false, false, false, 0, (uint8_t)aInner};
+  }
+  static const nsXPTType& Get(Idx aInner) {
+    MOZ_ASSERT(aInner <= Idx::INTERFACE_IS_TYPE);
+    return xpt::detail::GetType((uint8_t)aInner);
+  }
+
+  ///////////////////////////////////////
+  // nsXPTType backwards compatibility //
+  ///////////////////////////////////////
+
+  nsXPTType& operator=(nsXPTTypeTag aPrefix) {
+    mTag = aPrefix;
+    return *this;
+  }
+  operator nsXPTTypeTag() const { return Tag(); }
+
+#define TD_ALIAS_(name_, value_) static constexpr nsXPTTypeTag name_ = value_
+  TD_ALIAS_(T_I8, TD_INT8);
+  TD_ALIAS_(T_I16, TD_INT16);
+  TD_ALIAS_(T_I32, TD_INT32);
+  TD_ALIAS_(T_I64, TD_INT64);
+  TD_ALIAS_(T_U8, TD_UINT8);
+  TD_ALIAS_(T_U16, TD_UINT16);
+  TD_ALIAS_(T_U32, TD_UINT32);
+  TD_ALIAS_(T_U64, TD_UINT64);
+  TD_ALIAS_(T_FLOAT, TD_FLOAT);
+  TD_ALIAS_(T_DOUBLE, TD_DOUBLE);
+  TD_ALIAS_(T_BOOL, TD_BOOL);
+  TD_ALIAS_(T_CHAR, TD_CHAR);
+  TD_ALIAS_(T_WCHAR, TD_WCHAR);
+  TD_ALIAS_(T_VOID, TD_VOID);
+  TD_ALIAS_(T_NSIDPTR, TD_NSIDPTR);
+  TD_ALIAS_(T_CHAR_STR, TD_PSTRING);
+  TD_ALIAS_(T_WCHAR_STR, TD_PWSTRING);
+  TD_ALIAS_(T_INTERFACE, TD_INTERFACE_TYPE);
+  TD_ALIAS_(T_INTERFACE_IS, TD_INTERFACE_IS_TYPE);
+  TD_ALIAS_(T_LEGACY_ARRAY, TD_LEGACY_ARRAY);
+  TD_ALIAS_(T_PSTRING_SIZE_IS, TD_PSTRING_SIZE_IS);
+  TD_ALIAS_(T_PWSTRING_SIZE_IS, TD_PWSTRING_SIZE_IS);
+  TD_ALIAS_(T_UTF8STRING, TD_UTF8STRING);
+  TD_ALIAS_(T_CSTRING, TD_CSTRING);
+  TD_ALIAS_(T_ASTRING, TD_ASTRING);
+  TD_ALIAS_(T_NSID, TD_NSID);
+  TD_ALIAS_(T_JSVAL, TD_JSVAL);
+  TD_ALIAS_(T_DOMOBJECT, TD_DOMOBJECT);
+  TD_ALIAS_(T_PROMISE, TD_PROMISE);
+  TD_ALIAS_(T_ARRAY, TD_ARRAY);
+#undef TD_ALIAS_
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  uint8_t mTag : 5;
+
+  // Parameter bitflags are packed into the XPTTypeDescriptor to save space.
+  // When the TypeDescriptor is not in a parameter, these flags are ignored.
+  uint8_t mInParam : 1;
+  uint8_t mOutParam : 1;
+  uint8_t mOptionalParam : 1;
+
+  // The data for the different variants is stored in these two data fields.
+  // These should only be accessed via the getter methods above, which will
+  // assert if the tag is invalid.
+  uint8_t mData1;
+  uint8_t mData2;
+};
+
+// The fields in nsXPTType were carefully ordered to minimize size.
+static_assert(sizeof(nsXPTType) == 3, "wrong size");
+
+/*
+ * A nsXPTParamInfo is used to describe either a single argument to a method or
+ * a method's result. It stores its flags in the type descriptor to save space.
+ */
+struct nsXPTParamInfo {
+  bool IsIn() const { return mType.mInParam; }
+  bool IsOut() const { return mType.mOutParam; }
+  bool IsOptional() const { return mType.mOptionalParam; }
+  bool IsShared() const { return false; }  // XXX remove (backcompat)
+
+  // Get the type of this parameter.
+  const nsXPTType& Type() const { return mType; }
+  const nsXPTType& GetType() const {
+    return Type();
+  }  // XXX remove (backcompat)
+
+  // Whether this parameter is passed indirectly on the stack. All out/inout
+  // params are passed indirectly, and complex types are always passed
+  // indirectly.
+  bool IsIndirect() const { return IsOut() || Type().IsComplex(); }
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  nsXPTType mType;
+};
+
+// The fields in nsXPTParamInfo were carefully ordered to minimize size.
+static_assert(sizeof(nsXPTParamInfo) == 3, "wrong size");
+
+/*
+ * A nsXPTMethodInfo is used to describe a single interface method.
+ */
+struct nsXPTMethodInfo {
+  bool IsGetter() const { return mGetter; }
+  bool IsSetter() const { return mSetter; }
+  bool IsReflectable() const { return mReflectable; }
+  bool IsSymbol() const { return mIsSymbol; }
+  bool WantsOptArgc() const { return mOptArgc; }
+  bool WantsContext() const { return mContext; }
+  uint8_t ParamCount() const { return mNumParams; }
+
+  const char* Name() const {
+    MOZ_ASSERT(!IsSymbol());
+    return xpt::detail::GetString(mName);
+  }
+  const nsXPTParamInfo& Param(uint8_t aIndex) const {
+    MOZ_ASSERT(aIndex < mNumParams);
+    return xpt::detail::GetParam(mParams + aIndex);
+  }
+
+  bool HasRetval() const { return mHasRetval; }
+  const nsXPTParamInfo* GetRetval() const {
+    return mHasRetval ? &Param(mNumParams - 1) : nullptr;
+  }
+
+  // If this is an [implicit_jscontext] method, returns the index of the
+  // implicit JSContext* argument in the C++ method's argument list.
+  // Otherwise returns UINT8_MAX.
+  uint8_t IndexOfJSContext() const {
+    if (!WantsContext()) {
+      return UINT8_MAX;
+    }
+    if (IsGetter() || IsSetter()) {
+      // Getters/setters always have the context as first argument.
+      return 0;
+    }
+    // The context comes before the return value, if there is one.
+    MOZ_ASSERT_IF(HasRetval(), ParamCount() > 0);
+    return ParamCount() - uint8_t(HasRetval());
+  }
+
+  JS::SymbolCode GetSymbolCode() const {
+    MOZ_ASSERT(IsSymbol());
+    return JS::SymbolCode(mName);
+  }
+
+  JS::Symbol* GetSymbol(JSContext* aCx) const {
+    return JS::GetWellKnownSymbol(aCx, GetSymbolCode());
+  }
+
+  const char* SymbolDescription() const;
+
+  const char* NameOrDescription() const {
+    if (IsSymbol()) {
+      return SymbolDescription();
+    }
+    return Name();
+  }
+
+  bool GetId(JSContext* aCx, jsid& aId) const;
+
+  /////////////////////////////////////////////
+  // nsXPTMethodInfo backwards compatibility //
+  /////////////////////////////////////////////
+
+  const char* GetName() const { return Name(); }
+
+  uint8_t GetParamCount() const { return ParamCount(); }
+  const nsXPTParamInfo& GetParam(uint8_t aIndex) const { return Param(aIndex); }
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  uint32_t mName;    // Index into xpt::detail::sStrings.
+  uint16_t mParams;  // Index into xpt::detail::sParams.
+  uint8_t mNumParams;
+
+  uint8_t mGetter : 1;
+  uint8_t mSetter : 1;
+  uint8_t mReflectable : 1;
+  uint8_t mOptArgc : 1;
+  uint8_t mContext : 1;
+  uint8_t mHasRetval : 1;
+  uint8_t mIsSymbol : 1;
+};
+
+// The fields in nsXPTMethodInfo were carefully ordered to minimize size.
+static_assert(sizeof(nsXPTMethodInfo) == 8, "wrong size");
+
+// This number is chosen to be no larger than the maximum number of parameters
+// any XPIDL-defined function needs; there is a static assert in the generated
+// code from xptcodegen.py to verify that decision.  It is therefore also the
+// maximum number of stack allocated nsXPTCMiniVariant structures for argument
+// passing purposes in PrepareAndDispatch implementations.
+#if defined(MOZ_THUNDERBIRD) || defined(MOZ_SUITE)
+#  define PARAM_BUFFER_COUNT 18
+#else
+#  define PARAM_BUFFER_COUNT 14
+#endif
+
+/**
+ * A nsXPTConstantInfo is used to describe a single interface constant.
+ */
+struct nsXPTConstantInfo {
+  const char* Name() const { return xpt::detail::GetString(mName); }
+
+  JS::Value JSValue() const {
+    if (mSigned || mValue <= uint32_t(INT32_MAX)) {
+      return JS::Int32Value(int32_t(mValue));
+    }
+    return JS::DoubleValue(mValue);
+  }
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  uint32_t mName : 31;  // Index into xpt::detail::mStrings.
+
+  // Whether the value should be interpreted as a int32_t or uint32_t.
+  uint32_t mSigned : 1;
+  uint32_t mValue;  // The value stored as a u32
+};
+
+// The fields in nsXPTConstantInfo were carefully ordered to minimize size.
+static_assert(sizeof(nsXPTConstantInfo) == 8, "wrong size");
+
+/**
+ * Object representing the information required to wrap and unwrap DOMObjects.
+ *
+ * This object will not live in rodata as it contains relocations.
+ */
+struct nsXPTDOMObjectInfo {
+  nsresult Unwrap(JS::Handle<JS::Value> aHandle, void** aObj,
+                  JSContext* aCx) const {
+    return mUnwrap(aHandle, aObj, aCx);
+  }
+
+  bool Wrap(JSContext* aCx, void* aObj,
+            JS::MutableHandle<JS::Value> aHandle) const {
+    return mWrap(aCx, aObj, aHandle);
+  }
+
+  void Cleanup(void* aObj) const { return mCleanup(aObj); }
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  nsresult (*mUnwrap)(JS::Handle<JS::Value> aHandle, void** aObj,
+                      JSContext* aCx);
+  bool (*mWrap)(JSContext* aCx, void* aObj,
+                JS::MutableHandle<JS::Value> aHandle);
+  void (*mCleanup)(void* aObj);
+};
+
+namespace xpt {
+namespace detail {
+
+// The UntypedTArray type allows low-level access from XPConnect to nsTArray
+// internals without static knowledge of the array element type in question.
+class UntypedTArray : public nsTArray_base<nsTArrayFallibleAllocator,
+                                           nsTArray_RelocateUsingMemutils> {
+ public:
+  void* Elements() const { return static_cast<void*>(Hdr() + 1); }
+
+  // Changes the length and capacity to be at least large enough for aTo
+  // elements.
+  bool SetLength(const nsXPTType& aEltTy, uint32_t aTo) {
+    if (!EnsureCapacity<nsTArrayFallibleAllocator>(aTo, aEltTy.Stride())) {
+      return false;
+    }
+
+    if (mHdr != EmptyHdr()) {
+      mHdr->mLength = aTo;
+    }
+
+    return true;
+  }
+
+  // Free backing memory for the nsTArray object.
+  void Clear() {
+    if (mHdr != EmptyHdr() && !UsesAutoArrayBuffer()) {
+      nsTArrayFallibleAllocator::Free(mHdr);
+    }
+    mHdr = EmptyHdr();
+  }
+};
+
+//////////////////////////////////////////////
+// Raw typelib data stored in const statics //
+//////////////////////////////////////////////
+
+// XPIDL information
+extern const nsXPTInterfaceInfo sInterfaces[];
+extern const nsXPTType sTypes[];
+extern const nsXPTParamInfo sParams[];
+extern const nsXPTMethodInfo sMethods[];
+extern const nsXPTConstantInfo sConsts[];
+extern const nsXPTDOMObjectInfo sDOMObjects[];
+
+extern const char sStrings[];
+
+//////////////////////////////////////
+// Helper Methods for fetching data //
+//////////////////////////////////////
+
+inline const nsXPTInterfaceInfo* GetInterface(uint16_t aIndex) {
+  if (aIndex > 0 && aIndex <= sInterfacesSize) {
+    return &sInterfaces[aIndex - 1];  // 1-based as 0 is a marker.
+  }
+  return nullptr;
+}
+
+inline const nsXPTType& GetType(uint16_t aIndex) { return sTypes[aIndex]; }
+
+inline const nsXPTParamInfo& GetParam(uint16_t aIndex) {
+  return sParams[aIndex];
+}
+
+inline const nsXPTMethodInfo& GetMethod(uint16_t aIndex) {
+  return sMethods[aIndex];
+}
+
+inline const nsXPTConstantInfo& GetConstant(uint16_t aIndex) {
+  return sConsts[aIndex];
+}
+
+inline const nsXPTDOMObjectInfo& GetDOMObjectInfo(uint16_t aIndex) {
+  return sDOMObjects[aIndex];
+}
+
+inline const char* GetString(uint32_t aIndex) { return &sStrings[aIndex]; }
+
+}  // namespace detail
+}  // namespace xpt
+
+#define XPT_FOR_EACH_ARITHMETIC_TYPE(MACRO) \
+  MACRO(TD_INT8, int8_t)                    \
+  MACRO(TD_INT16, int16_t)                  \
+  MACRO(TD_INT32, int32_t)                  \
+  MACRO(TD_INT64, int64_t)                  \
+  MACRO(TD_UINT8, uint8_t)                  \
+  MACRO(TD_UINT16, uint16_t)                \
+  MACRO(TD_UINT32, uint32_t)                \
+  MACRO(TD_UINT64, uint64_t)                \
+  MACRO(TD_FLOAT, float)                    \
+  MACRO(TD_DOUBLE, double)                  \
+  MACRO(TD_BOOL, bool)                      \
+  MACRO(TD_CHAR, char)                      \
+  MACRO(TD_WCHAR, char16_t)
+
+#define XPT_FOR_EACH_POINTER_TYPE(MACRO)    \
+  MACRO(TD_VOID, void*)                     \
+  MACRO(TD_NSIDPTR, nsID*)                  \
+  MACRO(TD_PSTRING, char*)                  \
+  MACRO(TD_PWSTRING, wchar_t*)              \
+  MACRO(TD_INTERFACE_TYPE, nsISupports*)    \
+  MACRO(TD_INTERFACE_IS_TYPE, nsISupports*) \
+  MACRO(TD_LEGACY_ARRAY, void*)             \
+  MACRO(TD_PSTRING_SIZE_IS, char*)          \
+  MACRO(TD_PWSTRING_SIZE_IS, wchar_t*)      \
+  MACRO(TD_DOMOBJECT, void*)                \
+  MACRO(TD_PROMISE, mozilla::dom::Promise*)
+
+#define XPT_FOR_EACH_COMPLEX_TYPE(MACRO) \
+  MACRO(TD_UTF8STRING, nsCString)        \
+  MACRO(TD_CSTRING, nsCString)           \
+  MACRO(TD_ASTRING, nsString)            \
+  MACRO(TD_NSID, nsID)                   \
+  MACRO(TD_JSVAL, JS::Value)             \
+  MACRO(TD_ARRAY, xpt::detail::UntypedTArray)
+
+#define XPT_FOR_EACH_TYPE(MACRO)      \
+  XPT_FOR_EACH_ARITHMETIC_TYPE(MACRO) \
+  XPT_FOR_EACH_POINTER_TYPE(MACRO)    \
+  XPT_FOR_EACH_COMPLEX_TYPE(MACRO)
+
+inline size_t nsXPTType::Stride() const {
+  // Compute the stride to use when walking an array of the given type.
+  switch (Tag()) {
+#define XPT_TYPE_STRIDE(tag, type) \
+  case tag:                        \
+    return sizeof(type);
+    XPT_FOR_EACH_TYPE(XPT_TYPE_STRIDE)
+#undef XPT_TYPE_STRIDE
+  }
+
+  MOZ_CRASH("Unknown type");
+}
+
+#endif /* xptinfo_h */