scripts: Port master codegen script from VVL
diff --git a/scripts/common_codegen.py b/scripts/common_codegen.py
index 8954532..d56ebac 100644
--- a/scripts/common_codegen.py
+++ b/scripts/common_codegen.py
@@ -18,10 +18,7 @@
 #
 # Author: Mark Lobodzinski <mark@lunarg.com>
 
-import os,re,sys,string
-import xml.etree.ElementTree as etree
-from generator import *
-from collections import namedtuple
+import os
 
 # Copyright text prefixing all headers (list of strings).
 prefixStrings = [
@@ -71,3 +68,7 @@
     if platform is not None:
         protect = platform_dict[platform]
     return protect
+
+# helper to define paths relative to the repo root
+def repo_relative(path):
+    return os.path.abspath(os.path.join(os.path.dirname(__file__), '..', path))
diff --git a/scripts/generate_source.py b/scripts/generate_source.py
new file mode 100755
index 0000000..fb1d150
--- /dev/null
+++ b/scripts/generate_source.py
@@ -0,0 +1,118 @@
+#!/usr/bin/env python3
+# Copyright (c) 2019 The Khronos Group Inc.
+# Copyright (c) 2019 Valve Corporation
+# Copyright (c) 2019 LunarG, Inc.
+# Copyright (c) 2019 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# Author: Mike Schuchardt <mikes@lunarg.com>
+
+import argparse
+import common_codegen
+import filecmp
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+
+# files to exclude from --verify check
+verify_exclude = ['.clang-format']
+
+def main(argv):
+    parser = argparse.ArgumentParser(description='Generate source code for this repository')
+    parser.add_argument('registry', metavar='REGISTRY_PATH', help='path to the Vulkan-Headers registry directory')
+    group = parser.add_mutually_exclusive_group()
+    group.add_argument('-i', '--incremental', action='store_true', help='only update repo files that change')
+    group.add_argument('-v', '--verify', action='store_true', help='verify repo files match generator output')
+    args = parser.parse_args(argv)
+
+    gen_cmds = [[common_codegen.repo_relative('scripts/loader_genvk.py'),
+                 '-registry', os.path.abspath(os.path.join(args.registry,  'vk.xml')),
+                 '-quiet',
+                 filename] for filename in ['vk_dispatch_table_helper.h',
+                                            'vk_layer_dispatch_table.h',
+                                            'vk_loader_extensions.h',
+                                            'vk_loader_extensions.c',
+                                            'vk_enum_string_helper.h',
+                                            'vk_safe_struct.h',
+                                            'vk_safe_struct.cpp',
+                                            'vk_object_types.h',
+                                            'vk_extension_helper.h',
+                                            'vk_typemap_helper.h']]
+
+    repo_dir = common_codegen.repo_relative('loader/generated')
+
+    # get directory where generators will run
+    if args.verify or args.incremental:
+        # generate in temp directory so we can compare or copy later
+        temp_obj = tempfile.TemporaryDirectory(prefix='VulkanLoader_generated_source_')
+        temp_dir = temp_obj.name
+        gen_dir = temp_dir
+    else:
+        # generate directly in the repo
+        gen_dir = repo_dir
+
+    # run each code generator
+    for cmd in gen_cmds:
+        print(' '.join(cmd))
+        try:
+            subprocess.check_call([sys.executable] + cmd,
+                                  # ignore generator output, vk_validation_stats.py is especially noisy
+                                  stdout=subprocess.DEVNULL,
+                                  cwd=gen_dir)
+        except Exception as e:
+            print('ERROR:', str(e))
+            return 1
+
+    # optional post-generation steps
+    if args.verify:
+        # compare contents of temp dir and repo
+        temp_files = set(os.listdir(temp_dir))
+        repo_files = set(os.listdir(repo_dir))
+        files_match = True
+        for filename in sorted((temp_files | repo_files) - set(verify_exclude)):
+            if filename not in repo_files:
+                print('ERROR: Missing repo file', filename)
+                files_match = False
+            elif filename not in temp_files:
+                print('ERROR: Missing generator for', filename)
+                files_match = False
+            elif not filecmp.cmp(os.path.join(temp_dir, filename),
+                               os.path.join(repo_dir, filename),
+                               shallow=False):
+                print('ERROR: Repo files do not match generator output for', filename)
+                files_match = False
+
+        # return code for test scripts
+        if files_match:
+            print('SUCCESS: Repo files match generator output')
+            return 0
+        return 1
+
+    elif args.incremental:
+        # copy missing or differing files from temp directory to repo
+        for filename in os.listdir(temp_dir):
+            temp_filename = os.path.join(temp_dir, filename)
+            repo_filename = os.path.join(repo_dir, filename)
+            if not os.path.exists(repo_filename) or \
+               not filecmp.cmp(temp_filename, repo_filename, shallow=False):
+                print('update', repo_filename)
+                shutil.copyfile(temp_filename, repo_filename)
+
+    return 0
+
+if __name__ == '__main__':
+    sys.exit(main(sys.argv[1:]))
+
diff --git a/scripts/loader_genvk.py b/scripts/loader_genvk.py
index 273c929..bcf0f7a 100644
--- a/scripts/loader_genvk.py
+++ b/scripts/loader_genvk.py
@@ -453,6 +453,11 @@
 
     args = parser.parse_args()
 
+    # default scripts path to be same as registry
+    if not args.scripts:
+        args.scripts = os.path.dirname(args.registry)
+        print(args.scripts)
+
     scripts_dir = os.path.dirname(os.path.abspath(__file__))
     registry_dir = os.path.join(scripts_dir, args.scripts)
     sys.path.insert(0, registry_dir)