From 5d1ba0388af2f66d1d83db755361d3b2eb5f68ad Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 10 Aug 2015 18:30:25 +0200
Subject: Add streaming API to serializer

Show what can be done with it in the xhtml example.
---
 xml/serializer     | 16 ++++++++++++++++
 xml/serializer.ixx | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

(limited to 'xml')

diff --git a/xml/serializer b/xml/serializer
index 316a501..eb592df 100644
--- a/xml/serializer
+++ b/xml/serializer
@@ -185,6 +185,8 @@ namespace xml
     // namespace is declared. If both prefix and namespace are empty,
     // then the default namespace declaration is cleared (xmlns="").
     //
+    // This function should be called after start_element().
+    //
     void
     namespace_decl (const std::string& ns, const std::string& prefix);
 
@@ -251,6 +253,20 @@ namespace xml
     genxSender sender_;
     std::size_t depth_;
   };
+
+  // Stream-like interface for serializer. If the passed argument
+  // is a function with the void f(serializer&) signature or is a
+  // function object with the void operator() (serializer&) const
+  // operator, then this function (object) is called with the passed
+  // serializer. Otherwise, the argument is passed to the serializer's
+  // characters() function.
+  //
+  serializer&
+  operator<< (serializer&, void (*func) (serializer&));
+
+  template <typename T>
+  serializer&
+  operator<< (serializer&, const T& value);
 }
 
 #include <xml/serializer.ixx>
diff --git a/xml/serializer.ixx b/xml/serializer.ixx
index ea3dcf0..5cff976 100644
--- a/xml/serializer.ixx
+++ b/xml/serializer.ixx
@@ -118,4 +118,59 @@ namespace xml
   {
     characters (value_traits<T>::serialize (value, *this));
   }
+
+  // operator<<
+  //
+
+  inline serializer&
+  operator<< (serializer& s, void (*func) (serializer&))
+  {
+    func (s);
+    return s;
+  }
+
+  namespace details
+  {
+    // Detect whether T defines void operator(A) const.
+    //
+    template <typename T, typename A>
+    struct is_functor
+    {
+      typedef char no[1];
+      typedef char yes[2];
+
+      template <typename X, X> struct check;
+
+      template <typename>
+      static no& test (...);
+
+      template <typename X>
+      static yes& test (check<void (X::*) (A) const, &X::operator ()>*);
+
+      static const bool value = sizeof (test<T> (0)) == sizeof (yes);
+    };
+
+    template <typename T, bool = is_functor<T, serializer&>::value>
+    struct inserter;
+
+    template <typename T>
+    struct inserter<T, true>
+    {
+      static void insert (serializer& s, const T& f) {f (s);}
+    };
+
+    template <typename T>
+    struct inserter<T, false>
+    {
+      static void insert (serializer& s, const T& v) {s.characters (v);}
+    };
+  }
+
+  template <typename T>
+  inline serializer&
+  operator<< (serializer& s, const T& value)
+  {
+    details::inserter<T>::insert (s, value);
+    return s;
+  }
 }
-- 
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