formater: add support for double-quoted fields

Part of #91.

* spot/misc/formater.cc, spot/misc/formater.hh: Here.
* bin/common_output.cc: Adjust automatic output format.
* doc/org/csv.org: Adjust.
* tests/core/lbt.test, tests/core/ltlfilt.test: More tests.
* NEWS: Mention the changes.

spot/misc/formater.cc

@@ -19,8 +19,10 @@
 
 #include "config.h"
 #include <spot/misc/formater.hh>
+#include <spot/misc/escape.hh>
 #include <iostream>
 #include <sstream>
+#include <cstring>
 
 namespace spot
 {
@@ -66,8 +68,22 @@ namespace spot
 
   std::ostream&
   formater::format(const char* fmt)
-    {
-      for (const char* pos = fmt; *pos; ++pos)
+  {
+    for (const char* pos = fmt; *pos; ++pos)
+      {
+        if (*pos == '"')
+          {
+            *output_ << '"';
+            const char* end = strchr(pos + 1, '"');
+            if (!end)
+              continue;
+            std::string tmp(pos + 1, end - (pos + 1));
+            std::ostringstream os;
+            format(os, tmp);
+            escape_rfc4180(*output_, os.str());
+            pos = end;
+            // the end double-quote will be printed below
+          }
         if (*pos != '%')
           {
             *output_ << *pos;
@@ -95,6 +111,7 @@ namespace spot
               break;
             pos = next;
           }
-      return *output_;
-    }
+      }
+    return *output_;
+  }
 }

spot/misc/formater.hh

@@ -173,8 +173,11 @@ namespace spot
     std::ostream&
     format(std::ostream& output, const char* fmt)
     {
+      std::ostream* tmp = output_;
       set_output(output);
-      return format(fmt);
+      format(fmt);
+      set_output(*tmp);
+      return output;
     }
 
     /// Expand the %-sequences in \a fmt, write the result on \a output_.