json/tree: reinstate path based parsers

json::tree::node is a fat object, so it's safe to load the source data
from within the parsing function

json/tree.cpp

@@ -247,6 +247,15 @@ MAP(
 #undef INSTANTIATE
 
 
+//-----------------------------------------------------------------------------
+std::unique_ptr<json::tree::node>
+json::tree::parse (const boost::filesystem::path &src)
+{
+    const util::mapped_file data (src.string ().c_str ());
+    return parse (data.as_view<char> ());
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////
 void
 json::tree::write (const json::tree::node &node, std::ostream &os)

json/tree.hpp

@@ -17,16 +17,20 @@
 #ifndef __UTIL_JSON_TREE_HPP
 #define __UTIL_JSON_TREE_HPP
 
+#include "./flat.hpp"
+#include "./fwd.hpp"
+
+#include "../iterator.hpp"
+#include "../view.hpp"
+
 #include <iostream>
 #include <map>
 #include <memory>
 #include <string>
 #include <vector>
 
-#include "../iterator.hpp"
+#include <boost/filesystem/path.hpp>
-#include "../view.hpp"
+
-#include "./flat.hpp"
-#include "./fwd.hpp"
 
 namespace json { namespace tree {
     enum type_t {
@@ -43,6 +47,9 @@ namespace json { namespace tree {
     std::unique_ptr<node>
     parse (util::view<T> data);
 
+    std::unique_ptr<node>
+    parse (const boost::filesystem::path &);
+
     extern void write (const json::tree::node&, std::ostream&);
 
     /// Abstract base for all JSON values