Visual Studio generators for GN

tools/gn/xml_element_writer.h

+// Copyright 2016 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_XML_ELEMENT_WRITER_H_
+#define TOOLS_GN_XML_ELEMENT_WRITER_H_
+
+#include <iosfwd>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/strings/string_piece.h"
+
+// Vector of XML attribute key-value pairs.
+class XmlAttributes
+    : public std::vector<std::pair<base::StringPiece, base::StringPiece>> {
+ public:
+  XmlAttributes();
+  XmlAttributes(const base::StringPiece& attr_key,
+                const base::StringPiece& attr_value);
+
+  XmlAttributes& add(const base::StringPiece& attr_key,
+                     const base::StringPiece& attr_value);
+};
+
+// Helper class for writing XML elements. New XML element is started in
+// XmlElementWriter constructor and ended in its destructor. XmlElementWriter
+// handles XML file formatting in order to produce human-readable document.
+class XmlElementWriter {

[tfarina, 2016/01/29 16:32:18]

Hum, XmlWriter [1] had no good use for you case?
[1] -
https://chromium.googlesource.com/chromium/src/+/master/third_party/libxml/ch...

[Tomasz Moniuszko, 2016/02/01 14:13:24]

Well, XmlWriter could be used for sure but its API isn't as convenient as
XmlElementWriter's. For instance to write two nested elements with attributes
and text it's enough to write:

scoped_ptr<XmlElementWriter> locals =
    project.SubElement("PropertyGroup", XmlAttributes("Label", "Locals"));
locals->SubElement("PlatformToolset")->Text(kToolsetVersion);

It also allows to write directly to underlying output stream either by using
StartContent() method or by providing attribute value writer. Accessing stream
directly should be faster than copying values several times.

I wrote XmlElementWriter as a simple specialized utility at the beginning.
Intended to be used internally by VisualStudioWriter only. Then I was asked to
move it to separate file to make it possible to reuse it for other IDE files
writers.

+ public:
+  // Starts new XML element. This constructor adds no indentation and is
+  // designed for XML root element.
+  XmlElementWriter(std::ostream& out,
+                   const std::string& tag,
+                   const XmlAttributes& attributes);
+  // Starts new XML element with specified indentation.
+  XmlElementWriter(std::ostream& out,
+                   const std::string& tag,
+                   const XmlAttributes& attributes,
+                   int indent);
+  // Starts new XML element with specified indentation. Specialized constructor
+  // that allows writting XML element with single attribute without copying
+  // attribute value.
+  template <class Writer>
+  XmlElementWriter(std::ostream& out,
+                   const std::string& tag,
+                   const std::string& attribute_name,
+                   const Writer& attribute_value_writer,
+                   int indent);
+  // Ends XML element. All sub-elements should be ended at this point.
+  ~XmlElementWriter();
+
+  // Writes arbitrary XML element text.
+  void Text(const base::StringPiece& content);
+
+  // Starts new XML sub-element. Caller must ensure that parent element outlives
+  // its children.
+  scoped_ptr<XmlElementWriter> SubElement(const std::string& tag);
+  scoped_ptr<XmlElementWriter> SubElement(const std::string& tag,
+                                          const XmlAttributes& attributes);
+  template <class Writer>
+  scoped_ptr<XmlElementWriter> SubElement(const std::string& tag,
+                                          const std::string& attribute_name,
+                                          const Writer& attribute_value_writer);
+
+  // Finishes opening tag if it isn't finished yet and optionally starts new
+  // document line. Returns the stream where XML element content can be written.
+  // This is an alternative to Text() and SubElement() methods.
+  std::ostream& StartContent(bool start_new_line);
+
+ private:
+  // Output stream. XmlElementWriter objects for XML element and its
+  // sub-elements share the same output stream.
+  std::ostream& out_;
+
+  // XML element tag name.
+  std::string tag_;
+
+  // XML element indentation in the document.
+  int indent_;
+
+  // Flag indicating if opening tag is finished with '>' character already.
+  bool opening_tag_finished_;
+
+  // Flag indicating if XML element should be written in one document line.
+  bool one_line_;
+
+  DISALLOW_COPY_AND_ASSIGN(XmlElementWriter);
+};
+
+template <class Writer>
+XmlElementWriter::XmlElementWriter(std::ostream& out,
+                                   const std::string& tag,
+                                   const std::string& attribute_name,
+                                   const Writer& attribute_value_writer,
+                                   int indent)
+    : out_(out),
+      tag_(tag),
+      indent_(indent),
+      opening_tag_finished_(false),
+      one_line_(true) {
+  out << std::string(indent, ' ') << '<' << tag;
+  out << ' ' << attribute_name << "=\"";
+  attribute_value_writer(out);
+  out << '\"';
+}
+
+template <class Writer>
+scoped_ptr<XmlElementWriter> XmlElementWriter::SubElement(
+    const std::string& tag,
+    const std::string& attribute_name,
+    const Writer& attribute_value_writer) {
+  StartContent(true);
+  return make_scoped_ptr(new XmlElementWriter(
+      out_, tag, attribute_name, attribute_value_writer, indent_ + 2));
+}
+
+#endif  // TOOLS_GN_XML_ELEMENT_WRITER_H_