Add initial prototype for the GN meta-buildsystem.

tools/gn/source_dir.h

Index: tools/gn/source_dir.h
diff --git a/tools/gn/source_dir.h b/tools/gn/source_dir.h
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+// 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.
+
+#ifndef TOOLS_GN_SOURCE_DIR_H_
+#define TOOLS_GN_SOURCE_DIR_H_
+
+#include <string>
+
+#include "base/containers/hash_tables.h"
+#include "base/files/file_path.h"
+#include "base/logging.h"
+#include "base/strings/string_piece.h"
+
+class SourceFile;
+
+// Represents a directory within the source tree. Source dirs begin and end in
+// slashes.
+//
+// If there is one slash at the beginning, it will mean a system-absolute file
+// path. On Windows, absolute system paths will be of the form "/C:/foo/bar".
+//
+// Two slashes at the beginning indicate a path relative to the source root.
+class SourceDir {
+ public:
+  SourceDir();
+  explicit SourceDir(const base::StringPiece& p);
+  ~SourceDir();
+
+  // Resolves a file or dir name relative to this source directory. Will return
+  // an empty SourceDir/File on error. Empty input is always an error (it's
+  // possible we should say ResolveRelativeDir vs. an empty string should be
+  // the source dir, but we require "." instead).
+  SourceFile ResolveRelativeFile(const base::StringPiece& p) const;
+  SourceDir ResolveRelativeDir(const base::StringPiece& p) const;
+
+  // Resolves this source file relative to some given source root. Returns
+  // an empty file path on error.
+  base::FilePath Resolve(const base::FilePath& source_root) const;
+
+  bool is_null() const { return value_.empty(); }
+  const std::string& value() const { return value_; }
+
+  // Returns true if this path starts with a "//" which indicates a path
+  // from the source root.
+  bool is_source_absolute() const {
+    return value_.size() >= 2 && value_[0] == '/' && value_[1] == '/';
+  }
+
+  // Returns true if this path starts with a single slash which indicates a
+  // system-absolute path.
+  bool is_system_absolute() const {
+    return !is_source_absolute();
+  }
+
+  // Returns a source-absolute path starting with only one slash at the
+  // beginning (normally source-absolute paths start with two slashes to mark
+  // them as such). This is normally used when concatenating directories
+  // together.
+  //
+  // This function asserts that the directory is actually source-absolute. The
+  // return value points into our buffer.
+  base::StringPiece SourceAbsoluteWithOneSlash() const {
+    CHECK(is_source_absolute());
+    return base::StringPiece(&value_[1], value_.size() - 1);
+  }
+
+  void SwapInValue(std::string* v);
+
+  bool operator==(const SourceDir& other) const {
+    return value_ == other.value_;
+  }
+  bool operator!=(const SourceDir& other) const {
+    return !operator==(other);
+  }
+  bool operator<(const SourceDir& other) const {
+    return value_ < other.value_;
+  }
+
+ private:
+  friend class SourceFile;
+  std::string value_;
+
+  // Copy & assign supported.
+};
+
+namespace BASE_HASH_NAMESPACE {
+
+#if defined(COMPILER_GCC)
+template<> struct hash<SourceDir> {
+  std::size_t operator()(const SourceDir& v) const {
+    hash<std::string> h;
+    return h(v.value());
+  }
+};
+#elif defined(COMPILER_MSVC)
+inline size_t hash_value(const SourceDir& v) {
+  return hash_value(v.value());
+}
+#endif  // COMPILER...
+
+}  // namespace BASE_HASH_NAMESPACE
+
+#endif  // TOOLS_GN_SOURCE_DIR_H_