Add initial prototype for the GN meta-buildsystem.

tools/gn/location.h

Index: tools/gn/location.h
diff --git a/tools/gn/location.h b/tools/gn/location.h
new file mode 100644
index 0000000000000000000000000000000000000000..20551256e141e723bcd2b345de5f20aa34af8667
--- /dev/null
+++ b/tools/gn/location.h
@@ -0,0 +1,77 @@
+// 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_LOCATION_H_
+#define TOOLS_GN_LOCATION_H_
+
+#include <algorithm>
+
+#include "base/logging.h"
+
+class InputFile;
+
+// Represents a place in a source file. Used for error reporting.
+class Location {
+ public:
+  Location()
+      : file_(NULL),
+        line_number_(-1),
+        char_offset_(-1) {
+  }
+  Location(const InputFile* file, int line_number, int char_offset)
+      : file_(file),
+        line_number_(line_number),
+        char_offset_(char_offset) {
+  }
+
+  const InputFile* file() const { return file_; }
+  int line_number() const { return line_number_; }
+  int char_offset() const { return char_offset_; }
+
+  bool operator==(const Location& other) const {
+    return other.file_ == file_ &&
+           other.line_number_ == line_number_ &&
+           other.char_offset_ == char_offset_;
+  }
+
+  bool operator<(const Location& other) const {
+    DCHECK(file_ == other.file_);
+    if (line_number_ != other.line_number_)
+      return line_number_ < other.line_number_;
+    return char_offset_ < other.char_offset_;
+  }
+
+ private:
+  const InputFile* file_;  // Null when unset.
+  int line_number_;  // -1 when unset.
+  int char_offset_;  // -1 when unset.
+};
+
+// Represents a range in a source file. Used for error reporting.
+// The end is exclusive i.e. [begin, end)
+class LocationRange {
+ public:
+  LocationRange() {}
+  LocationRange(const Location& begin, const Location& end)
+      : begin_(begin),
+        end_(end) {
+    DCHECK(begin_.file() == end_.file());
+  }
+
+  const Location& begin() const { return begin_; }
+  const Location& end() const { return end_; }
+
+  LocationRange Union(const LocationRange& other) const {
+    DCHECK(begin_.file() == other.begin_.file());
+    return LocationRange(
+        begin_ < other.begin_ ? begin_ : other.begin_,
+        end_ < other.end_ ? other.end_ : end_);
+  }
+
+ private:
+  Location begin_;
+  Location end_;
+};
+
+#endif  // TOOLS_GN_LOCATION_H_