Add initial prototype for the GN meta-buildsystem.

tools/gn/file_template.h

Index: tools/gn/file_template.h
diff --git a/tools/gn/file_template.h b/tools/gn/file_template.h
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+++ b/tools/gn/file_template.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_FILE_TEMPLATE_H_
+#define TOOLS_GN_FILE_TEMPLATE_H_
+
+#include "base/basictypes.h"
+#include "base/containers/stack_container.h"
+#include "tools/gn/err.h"
+#include "tools/gn/value.h"
+
+class ParseNode;
+
+class FileTemplate {
+ public:
+  struct Subrange {
+    enum Type {
+      LITERAL = 0,
+      SOURCE,
+      NAME_PART,
+      NUM_TYPES  // Must be last
+    };
+    Subrange(Type t, const std::string& l = std::string())
+        : type(t),
+          literal(l) {
+    }
+
+    Type type;
+
+    // When type_ == LITERAL, this specifies the literal.
+    std::string literal;
+  };
+
+  // Constructs a template from the given value. On error, the err will be
+  // set. In this case you should not use this object.
+  FileTemplate(const Value& t, Err* err);
+  FileTemplate(const std::vector<std::string>& t);
+  ~FileTemplate();
+
+  // Applies this template to the given list of sources, appending all
+  // results to the given dest list. The sources must be a list for the
+  // one that takes a value as an input, otherwise the given error will be set.
+  void Apply(const Value& sources,
+             const ParseNode* origin,
+             std::vector<Value>* dest,
+             Err* err) const;
+  void ApplyString(const std::string& input,
+                   std::vector<std::string>* output) const;
+
+  // Known template types.
+  static const char kSource[];
+  static const char kSourceNamePart[];
+
+ private:
+  typedef base::StackVector<Subrange, 8> Template;
+  typedef base::StackVector<Template, 8> TemplateVector;
+
+  void ParseInput(const Value& value, Err* err);
+
+  // Parses a template string and adds it to the templates_ list.
+  void ParseOneTemplateString(const std::string& str);
+
+  TemplateVector templates_;
+
+  // The corresponding value is set to true if the given subrange type is
+  // required. This allows us to precompute these types whem applying them
+  // to a given source file.
+  bool types_required_[Subrange::NUM_TYPES];
+
+  DISALLOW_COPY_AND_ASSIGN(FileTemplate);
+};
+
+#endif  // TOOLS_GN_FILE_TEMPLATE_H_