Add initial prototype for the GN meta-buildsystem.

tools/gn/source_file.h

Index: tools/gn/source_file.h
diff --git a/tools/gn/source_file.h b/tools/gn/source_file.h
new file mode 100644
index 0000000000000000000000000000000000000000..d883bc061f6106e0a0826db6732f84023cf5cc78
--- /dev/null
+++ b/tools/gn/source_file.h
@@ -0,0 +1,97 @@
+// 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_FILE_H_
+#define TOOLS_GN_SOURCE_FILE_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 SourceDir;
+
+// Represents a file within the source tree. Always begins in a slash, never
+// ends in one.
+class SourceFile {
+ public:
+  SourceFile();
+
+  // Takes a known absolute source file. Always begins in a slash.
+  explicit SourceFile(const base::StringPiece& p);
+
+  ~SourceFile();
+
+  bool is_null() const { return value_.empty(); }
+  const std::string& value() const { return value_; }
+
+  // Returns everythign after the last slash.
+  std::string GetName() const;
+  SourceDir GetDir() 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;
+
+  // Returns true if this file 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 file 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 names together.
+  //
+  // This function asserts that the file 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);
+  }
+
+  bool operator==(const SourceFile& other) const {
+    return value_ == other.value_;
+  }
+  bool operator!=(const SourceFile& other) const {
+    return !operator==(other);
+  }
+  bool operator<(const SourceFile& other) const {
+    return value_ < other.value_;
+  }
+
+ private:
+  friend class SourceDir;
+
+  std::string value_;
+
+  // Copy & assign supported.
+};
+
+namespace BASE_HASH_NAMESPACE {
+
+#if defined(COMPILER_GCC)
+template<> struct hash<SourceFile> {
+  std::size_t operator()(const SourceFile& v) const {
+    hash<std::string> h;
+    return h(v.value());
+  }
+};
+#elif defined(COMPILER_MSVC)
+inline size_t hash_value(const SourceFile& v) {
+  return hash_value(v.value());
+}
+#endif  // COMPILER...
+
+}  // namespace BASE_HASH_NAMESPACE
+
+#endif  // TOOLS_GN_SOURCE_FILE_H_