Added StyledStreamWriter, which has no reason to derive from Writer, since its write() method does cannot return a string and must take a stream.

include/json/writer.h

@@ -30,6 +30,7 @@ namespace Json {
    {
    public:
       FastWriter();
+      virtual ~FastWriter(){}
 
       void enableYAMLCompatibility();
 
@@ -61,7 +62,7 @@ namespace Json {
     *
     * \sa Reader, Value, Value::setComment()
     */
-   class JSON_API StyledWriter
+   class JSON_API StyledWriter: public Writer
    {
    public:
       StyledWriter();
@@ -98,13 +99,71 @@ namespace Json {
       bool addChildValues_;
    };
 
+   /** \brief Writes a Value in <a HREF="http://www.json.org">JSON</a> format in a human friendly way,
+        to a stream rather than to a string.
+    *
+    * The rules for line break and indent are as follow:
+    * - Object value:
+    *     - if empty then print {} without indent and line break
+    *     - if not empty the print '{', line break & indent, print one value per line
+    *       and then unindent and line break and print '}'.
+    * - Array value:
+    *     - if empty then print [] without indent and line break
+    *     - if the array contains no object value, empty array or some other value types,
+    *       and all the values fit on one lines, then print the array on a single line.
+    *     - otherwise, it the values do not fit on one line, or the array contains
+    *       object or non empty array, then print one value per line.
+    *
+    * If the Value have comments then they are outputed according to their #CommentPlacement.
+    *
+    * \param indentation Each level will be indented by this amount extra.
+    * \sa Reader, Value, Value::setComment()
+    */
+   class JSON_API StyledStreamWriter
+   {
+   public:
+      StyledStreamWriter( std::string indentation="\t" );
+      ~StyledStreamWriter(){}
+
+   public:
+      /** \brief Serialize a Value in <a HREF="http://www.json.org">JSON</a> format.
+       * \param out Stream to write to. (Can be ostringstream, e.g.)
+       * \param root Value to serialize.
+       * \note There is no point in deriving from Writer, since write() should not return a value.
+       */
+      void write( std::ostream &out, const Value &root );
+
+   private:
+      void writeValue( const Value &value );
+      void writeArrayValue( const Value &value );
+      bool isMultineArray( const Value &value );
+      void pushValue( const std::string &value );
+      void writeIndent();
+      void writeWithIndent( const std::string &value );
+      void indent();
+      void unindent();
+      void writeCommentBeforeValue( const Value &root );
+      void writeCommentAfterValueOnSameLine( const Value &root );
+      bool hasCommentForValue( const Value &value );
+      static std::string normalizeEOL( const std::string &text );
+
+      typedef std::vector<std::string> ChildValues;
+
+      ChildValues childValues_;
+      std::ostream* document_;
+      std::string indentString_;
+      int rightMargin_;
+      std::string indentation_;
+      bool addChildValues_;
+   };
+
    std::string JSON_API valueToString( Value::Int value );
    std::string JSON_API valueToString( Value::UInt value );
    std::string JSON_API valueToString( double value );
    std::string JSON_API valueToString( bool value );
    std::string JSON_API valueToQuotedString( const char *value );
 
-   /// \brief Output using the StyledWriter.
+   /// \brief Output using the StyledStreamWriter.
    /// \see Json::operator>>()
    std::ostream& operator<<( std::ostream&, const Value &root );
 

src/lib_json/json_writer.cpp

@@ -476,10 +476,291 @@ StyledWriter::normalizeEOL( const std::string &text )
    return normalized;
 }
 
+
+// Class StyledStreamWriter
+// //////////////////////////////////////////////////////////////////
+
+StyledStreamWriter::StyledStreamWriter( std::string indentation )
+   : document_(NULL)
+   , rightMargin_( 74 )
+   , indentation_( indentation )
+{
+}
+
+
+void
+StyledStreamWriter::write( std::ostream &out, const Value &root )
+{
+   document_ = &out;
+   addChildValues_ = false;
+   indentString_ = "";
+   writeCommentBeforeValue( root );
+   writeValue( root );
+   writeCommentAfterValueOnSameLine( root );
+   *document_ << "\n";
+   document_ = NULL; // Forget the stream, for safety.
+}
+
+
+void 
+StyledStreamWriter::writeValue( const Value &value )
+{
+   switch ( value.type() )
+   {
+   case nullValue:
+      pushValue( "null" );
+      break;
+   case intValue:
+      pushValue( valueToString( value.asInt() ) );
+      break;
+   case uintValue:
+      pushValue( valueToString( value.asUInt() ) );
+      break;
+   case realValue:
+      pushValue( valueToString( value.asDouble() ) );
+      break;
+   case stringValue:
+      pushValue( valueToQuotedString( value.asCString() ) );
+      break;
+   case booleanValue:
+      pushValue( valueToString( value.asBool() ) );
+      break;
+   case arrayValue:
+      writeArrayValue( value);
+      break;
+   case objectValue:
+      {
+         Value::Members members( value.getMemberNames() );
+         if ( members.empty() )
+            pushValue( "{}" );
+         else
+         {
+            writeWithIndent( "{" );
+            indent();
+            Value::Members::iterator it = members.begin();
+            while ( true )
+            {
+               const std::string &name = *it;
+               const Value &childValue = value[name];
+               writeCommentBeforeValue( childValue );
+               writeWithIndent( valueToQuotedString( name.c_str() ) );
+               *document_ << " : ";
+               writeValue( childValue );
+               if ( ++it == members.end() )
+               {
+                  writeCommentAfterValueOnSameLine( childValue );
+                  break;
+               }
+               *document_ << ",";
+               writeCommentAfterValueOnSameLine( childValue );
+            }
+            unindent();
+            writeWithIndent( "}" );
+         }
+      }
+      break;
+   }
+}
+
+
+void 
+StyledStreamWriter::writeArrayValue( const Value &value )
+{
+   unsigned size = value.size();
+   if ( size == 0 )
+      pushValue( "[]" );
+   else
+   {
+      bool isArrayMultiLine = isMultineArray( value );
+      if ( isArrayMultiLine )
+      {
+         writeWithIndent( "[" );
+         indent();
+         bool hasChildValue = !childValues_.empty();
+         unsigned index =0;
+         while ( true )
+         {
+            const Value &childValue = value[index];
+            writeCommentBeforeValue( childValue );
+            if ( hasChildValue )
+               writeWithIndent( childValues_[index] );
+            else
+            {
+	       writeIndent();
+               writeValue( childValue );
+            }
+            if ( ++index == size )
+            {
+               writeCommentAfterValueOnSameLine( childValue );
+               break;
+            }
+            *document_ << ",";
+            writeCommentAfterValueOnSameLine( childValue );
+         }
+         unindent();
+         writeWithIndent( "]" );
+      }
+      else // output on a single line
+      {
+         assert( childValues_.size() == size );
+         *document_ << "[ ";
+         for ( unsigned index =0; index < size; ++index )
+         {
+            if ( index > 0 )
+               *document_ << ", ";
+            *document_ << childValues_[index];
+         }
+         *document_ << " ]";
+      }
+   }
+}
+
+
+bool 
+StyledStreamWriter::isMultineArray( const Value &value )
+{
+   int size = value.size();
+   bool isMultiLine = size*3 >= rightMargin_ ;
+   childValues_.clear();
+   for ( int index =0; index < size  &&  !isMultiLine; ++index )
+   {
+      const Value &childValue = value[index];
+      isMultiLine = isMultiLine  ||
+                     ( (childValue.isArray()  ||  childValue.isObject())  &&  
+                        childValue.size() > 0 );
+   }
+   if ( !isMultiLine ) // check if line length > max line length
+   {
+      childValues_.reserve( size );
+      addChildValues_ = true;
+      int lineLength = 4 + (size-1)*2; // '[ ' + ', '*n + ' ]'
+      for ( int index =0; index < size  &&  !isMultiLine; ++index )
+      {
+         writeValue( value[index] );
+         lineLength += int( childValues_[index].length() );
+         isMultiLine = isMultiLine  &&  hasCommentForValue( value[index] );
+      }
+      addChildValues_ = false;
+      isMultiLine = isMultiLine  ||  lineLength >= rightMargin_;
+   }
+   return isMultiLine;
+}
+
+
+void 
+StyledStreamWriter::pushValue( const std::string &value )
+{
+   if ( addChildValues_ )
+      childValues_.push_back( value );
+   else
+      *document_ << value;
+}
+
+
+void 
+StyledStreamWriter::writeIndent()
+{
+  /*
+    Some comments in this method would have been nice. ;-)
+
+   if ( !document_.empty() )
+   {
+      char last = document_[document_.length()-1];
+      if ( last == ' ' )     // already indented
+         return;
+      if ( last != '\n' )    // Comments may add new-line
+         *document_ << '\n';
+   }
+  */
+   *document_ << indentString_;
+}
+
+
+void 
+StyledStreamWriter::writeWithIndent( const std::string &value )
+{
+   writeIndent();
+   *document_ << value;
+}
+
+
+void 
+StyledStreamWriter::indent()
+{
+   indentString_ += indentation_;
+}
+
+
+void 
+StyledStreamWriter::unindent()
+{
+   assert( indentString_.size() >= indentation_.size() );
+   indentString_.resize( indentString_.size() - indentation_.size() );
+}
+
+
+void 
+StyledStreamWriter::writeCommentBeforeValue( const Value &root )
+{
+   if ( !root.hasComment( commentBefore ) )
+      return;
+   *document_ << normalizeEOL( root.getComment( commentBefore ) );
+   *document_ << "\n";
+}
+
+
+void 
+StyledStreamWriter::writeCommentAfterValueOnSameLine( const Value &root )
+{
+   if ( root.hasComment( commentAfterOnSameLine ) )
+      *document_ << " " + normalizeEOL( root.getComment( commentAfterOnSameLine ) );
+
+   if ( root.hasComment( commentAfter ) )
+   {
+      *document_ << "\n";
+      *document_ << normalizeEOL( root.getComment( commentAfter ) );
+      *document_ << "\n";
+   }
+}
+
+
+bool 
+StyledStreamWriter::hasCommentForValue( const Value &value )
+{
+   return value.hasComment( commentBefore )
+          ||  value.hasComment( commentAfterOnSameLine )
+          ||  value.hasComment( commentAfter );
+}
+
+
+std::string 
+StyledStreamWriter::normalizeEOL( const std::string &text )
+{
+   std::string normalized;
+   normalized.reserve( text.length() );
+   const char *begin = text.c_str();
+   const char *end = begin + text.length();
+   const char *current = begin;
+   while ( current != end )
+   {
+      char c = *current++;
+      if ( c == '\r' ) // mac or dos EOL
+      {
+         if ( *current == '\n' ) // convert dos EOL
+            ++current;
+         normalized += '\n';
+      }
+      else // handle unix EOL & other char
+         normalized += c;
+   }
+   return normalized;
+}
+
+
 std::ostream& operator<<( std::ostream &sout, const Value &root )
 {
-   Json::StyledWriter writer;
+   Json::StyledStreamWriter writer;
-   sout << writer.write(root);
+   writer.write(sout, root);
    return sout;
 }