Add initial prototype for the GN meta-buildsystem.

tools/gn/ninja_writer.cc

Index: tools/gn/ninja_writer.cc
diff --git a/tools/gn/ninja_writer.cc b/tools/gn/ninja_writer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8b69a3fc73536a7eaaf258b6d5a1220652bcc9d6
--- /dev/null
+++ b/tools/gn/ninja_writer.cc
@@ -0,0 +1,64 @@
+// Copyright (c) 2013 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.
+
+#include "tools/gn/ninja_writer.h"
+
+#include "tools/gn/location.h"
+#include "tools/gn/ninja_build_writer.h"
+#include "tools/gn/ninja_toolchain_writer.h"
+
+
+NinjaWriter::NinjaWriter(const BuildSettings* build_settings)
+    : build_settings_(build_settings) {
+}
+
+NinjaWriter::~NinjaWriter() {
+}
+
+// static
+bool NinjaWriter::RunAndWriteFiles(const BuildSettings* build_settings) {
+  NinjaWriter writer(build_settings);
+  return writer.WriteRootBuildfiles();
+}
+
+bool NinjaWriter::WriteRootBuildfiles() {
+  // Categorize all targets by toolchain.
+  typedef std::map<Label, std::vector<const Target*> > CategorizedMap;
+  CategorizedMap categorized;
+
+  std::vector<const Target*> all_targets;
+  build_settings_->target_manager().GetAllTargets(&all_targets);
+  for (size_t i = 0; i < all_targets.size(); i++) {
+    categorized[all_targets[i]->label().GetToolchainLabel()].push_back(
+        all_targets[i]);
+  }
+
+  Label default_label =
+      build_settings_->toolchain_manager().GetDefaultToolchainUnlocked();
+
+  // Write out the toolchain buildfiles, and also accumulate the set of
+  // all settings and find the list of targets in the default toolchain.
+  std::vector<const Settings*> all_settings;
+  const std::vector<const Target*>* default_targets = NULL;
+  for (CategorizedMap::const_iterator i = categorized.begin();
+       i != categorized.end(); ++i) {
+    const Settings* settings;
+    {
+      base::AutoLock lock(build_settings_->item_tree().lock());
+      Err ignored;
+      settings =
+          build_settings_->toolchain_manager().GetSettingsForToolchainLocked(
+              LocationRange(), i->first, &ignored);
+    }
+    if (i->first == default_label)
+      default_targets = &i->second;
+    all_settings.push_back(settings);
+    if (!NinjaToolchainWriter::RunAndWriteFile(settings, i->second))
+      return false;
+  }
+
+  // Write the root buildfile.
+  return NinjaBuildWriter::RunAndWriteFile(build_settings_, all_settings,
+                                           *default_targets);
+}