[Positioning] TextFileWriter: '-' for stdout

The user can now use '-' as file name to write results or logs to
stdout.

owlps-positioning/src/textfilewriter.cc

@@ -2,6 +2,8 @@
 #include "configuration.hh"
 #include "posexcept.hh"
 
+#include <iostream>
+
 using namespace std ;
 
 
@@ -10,21 +12,33 @@ using namespace std ;
 
 
 /**
- * @param _file_name The name of the file to open.
+ * @param _file_name The name of the file to open ('-' for the standard
+ * output).
  * @throw error_opening_input_file if the file cannot be opened.
  */
 TextFileWriter::TextFileWriter(const string &_file_name):
   file_name(_file_name)
 {
-  file.open(file_name.c_str()) ;
-  if (! file)
-    throw error_opening_output_file(file_name) ;
+  if (file_name == "-")
+    {
+      file_buf = file.rdbuf() ;
+      file.std::ios::rdbuf(std::cout.rdbuf()) ;
+    }
+  else
+    {
+      file.open(file_name.c_str()) ;
+      if (! file)
+        throw error_opening_output_file(file_name) ;
+    }
 }
 
 
 TextFileWriter::~TextFileWriter()
 {
-  file.close() ;
+  if (file_name == "-")
+    file.std::ios::rdbuf(file_buf) ;
+  else
+    file.close() ;
 }
 
 

owlps-positioning/src/textfilewriter.hh

@@ -4,12 +4,19 @@
 #include <string>
 #include <fstream>
 
-/// Write text to a file
+/// Writes text to a file
+/**
+ * If the file name is a dash ('-'), the standard output is used.
+ */
 class TextFileWriter
 {
 private:
+  /// Name of the output file
   std::string file_name ;
+  /// Stream associated with the file
   std::ofstream file ;
+  /// Original rdbuf of the stream
+  std::streambuf *file_buf ;
 
 public:
   TextFileWriter(const std::string &_file_name) ;