Add initial prototype for the GN meta-buildsystem.

tools/gn/source_dir.cc

Index: tools/gn/source_dir.cc
diff --git a/tools/gn/source_dir.cc b/tools/gn/source_dir.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5739b527f5620703dc98d6d3d9a1dae52ddc4511
--- /dev/null
+++ b/tools/gn/source_dir.cc
@@ -0,0 +1,98 @@
+// 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/source_dir.h"
+
+#include "base/logging.h"
+#include "tools/gn/filesystem_utils.h"
+#include "tools/gn/source_file.h"
+
+namespace {
+
+void AssertValueSourceDirString(const std::string& s) {
+  DCHECK(!s.empty());
+  DCHECK(s[0] == '/');
+  DCHECK(EndsWithSlash(s));
+}
+
+}  // namespace
+
+SourceDir::SourceDir() {
+}
+
+SourceDir::SourceDir(const base::StringPiece& p)
+    : value_(p.data(), p.size()) {
+  if (!EndsWithSlash(value_))
+    value_.push_back('/');
+  AssertValueSourceDirString(value_);
+}
+
+SourceDir::~SourceDir() {
+}
+
+SourceFile SourceDir::ResolveRelativeFile(const base::StringPiece& p) const {
+  SourceFile ret;
+
+  // It's an error to resolve an empty string or one that is a directory
+  // (indicated by a trailing slash) because this is the function that expects
+  // to return a file.
+  if (p.empty() || (p.size() > 0 && p[p.size() - 1] == '/'))
+    return SourceFile();
+  if (p[0] == '/') {
+    // Absolute path.
+    ret.value_.assign(p.data(), p.size());
+    return ret;
+  }
+
+  ret.value_.reserve(value_.size() + p.size());
+  ret.value_.assign(value_);
+  ret.value_.append(p.data(), p.size());
+
+  NormalizePath(&ret.value_);
+  return ret;
+}
+
+SourceDir SourceDir::ResolveRelativeDir(const base::StringPiece& p) const {
+  SourceDir ret;
+
+  if (p.empty())
+    return ret;
+  if (p[0] == '/') {
+    // Absolute path.
+    return SourceDir(p);
+  }
+
+  ret.value_.reserve(value_.size() + p.size());
+  ret.value_.assign(value_);
+  ret.value_.append(p.data(), p.size());
+
+  NormalizePath(&ret.value_);
+  if (!EndsWithSlash(ret.value_))
+    ret.value_.push_back('/');
+  AssertValueSourceDirString(ret.value_);
+
+  return ret;
+}
+
+base::FilePath SourceDir::Resolve(const base::FilePath& source_root) const {
+  if (is_null())
+    return base::FilePath();
+
+  std::string converted;
+  if (is_system_absolute()) {
+    converted = value_;
+    ConvertPathToSystem(&converted);
+    return base::FilePath(UTF8ToFilePath(converted));
+  }
+
+  // String the double-leading slash for source-relative paths.
+  converted.assign(&value_[2], value_.size() - 2);
+  ConvertPathToSystem(&converted);
+  return source_root.Append(UTF8ToFilePath(converted));
+}
+
+void SourceDir::SwapInValue(std::string* v) {
+  value_.swap(*v);
+  AssertValueSourceDirString(value_);
+}