Script to inline shader into C header file

OpenGL compiles shader code as text at runtime. It is inconvienent to
edit shader code as const char[] inside the C++ source code.

This CL contains script that reads file contents, turns them into const
char[], and combine them into a header file.

BUG=385924

Review-Url: https://codereview.chromium.org/2036023003
Cr-Commit-Position: refs/heads/master@{#398142}

remoting/client/opengl/BUILD.gn

+shaders = [
+  "tex_coord_to_view.vert",
+  "draw_tex.frag",
+]
+
+action("inline_shaders") {
+  script = "../../tools/build/shader_to_header.py"
+  out_path = "${root_gen_dir}/remoting/client/opengl/shaders.h"
+  inputs = shaders
+  outputs = [
+    out_path,
+  ]
+  args = [ rebase_path(out_path) ] + rebase_path(shaders)
+}

remoting/tools/build/shader_to_header.py

+#!/usr/bin/python
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Helper script to inline files as const char[] into a C header file.
+
+Example:
+
+Input file in_a.vert:
+1"
+2
+3\
+
+Input file in_b.frag:
+4
+5
+6
+
+shader_to_header.py "output.h" "in_a.vert" "in_b.frag" will generate this:
+
+#ifndef OUTPUT_H_BSGN3bbEMBDD0ucC
+#define OUTPUT_H_BSGN3bbEMBDD0ucC
+
+const char kInAVert[] = "1\"\n2\n3\\\n";
+
+const char kInBFrag[] = "4\n5\n6\n";
+
+#endif  // OUTPUT_H_BSGN3bbEMBDD0ucC
+
+
+"""
+
+import os.path
+import random
+import string
+import sys
+
+RANDOM_STRING_LENGTH = 16
+STRING_CHARACTERS = (string.ascii_uppercase +
+                    string.ascii_lowercase +
+                    string.digits)
+
+def random_str():
+  return ''.join(random.choice(STRING_CHARACTERS)
+          for _ in range(RANDOM_STRING_LENGTH))
+
+
+def escape_text(line):
+  # encode('string-escape') doesn't escape double quote so you need to manually
+  # escape it.
+  return line.encode('string-escape').replace('"', '\\"')
+
+
+def main():
+  if len(sys.argv) < 3:
+    print 'Usage: shader_to_header.py <output-file> <input-files...>'
+    return 1
+
+  output_path = sys.argv[1]
+  include_guard = (os.path.basename(output_path).upper().replace('.', '_') +
+                  '_' + random_str())
+
+  with open(output_path, 'w') as output_file:
+    output_file.write('#ifndef ' + include_guard + '\n' +
+                      '#define ' + include_guard + '\n\n')
+
+    existing_names = set()
+    argc = len(sys.argv)
+    for i in xrange(2, argc):
+      input_path = sys.argv[i]
+
+      with open(input_path, 'r') as input_file:
+        # hello_world.vert -> kHelloWorldVert
+        const_name = ('k' + os.path.basename(input_path).title()
+                     .replace('_', '').replace('.', ''))
+        if const_name in existing_names:
+          print >> sys.stderr, ('Error: Constant name ' + const_name +
+                ' is already used by a previous file. Files with the same' +
+                ' name can\'t be inlined into the same header.')
+          return 1
+
+        existing_names.add(const_name)
+        text = input_file.read()
+
+        inlined = ('const char ' + const_name + '[] = "' + escape_text(text) +
+                  '";\n\n');
+        output_file.write(inlined)
+
+    output_file.write('#endif  // ' + include_guard + '\n')
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())