JsonParser.h

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// # JsonParser.h: Class for parsing Json-style key:value lines
// # Copyright (C) 2016
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library is distributed in the hope that it will be useful, but WITHOUT
// # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
// #                        520 Edgemont Road
// #                        Charlottesville, VA 22903-2475 USA
 
#ifndef CASA_JSONPARSER_H
#define CASA_JSONPARSER_H
 
// # Includes
#include <casacore/casa/BasicSL/String.h>
#include <casacore/casa/Exceptions/Error.h>
 
extern "C" {
int JsonGramwrap();  // yywrap
}
 
namespace casacore {
 
// # Forward Declarations
class JsonValue;
class JSonKVMap;
 
// <summary>
// Class for parsing Json-style key:value lines.
// </summary>
 
// <use visibility=export>
// <reviewed reviewer="" date="" tests="tJsonKVMap">
// </reviewed>
 
// # <prerequisite>
// # </prerequisite>
 
// <synopsis>
// JsonParser is a class for parsing JSON files. Its function 'parse'
// is the main function to do so.
// It can handle any JSON file (not only those generated by JsonOut).
// It supports (i.e., strips) possible comments in C, C++ and Python style.
// It also supports complex numbers (structs with fields "r" and "i").
// Escaped characters in a string value are translated into their ASCII counterparts.
//
// The result of the parser is a JsonKVMap object containing all fields
// and values (scalars, arrays and structs, possibly nested in any way).
// The values in the map are stored as JsonValue objects, which have functions to
// get the value with the proper type.
// </synopsis>
 
// <example>
// The following example is the opposite of the one given for class JsonOut.
// <srcblock>
// // Parse the given JSON file.
// JsonKVMap jmap = JsonParser::parseFile (fileName);
// // Check if the version is correct.
// AlwaysAssert (jmap.getInt("Version", 1) == 1, AipsError);
// uInt axis = jmap.get("Axis").getInt();
// // Get the vector of names from the map and JsonValue.
// Vector<String> names(jmap.get("Images").getArrayString());
// </srcblock>
// </example>
 
// <motivation>
// JSON is a commonly used interchange format.
// However, commonly available parsers do not support data type Complex. Also, comments
// are often not supported (alas standard Json does not allow comments).
// </motivation>
 
// # <todo asof="1996/03/10">
// #   <li>
// # </todo>
 
class JsonParser {
 public:
  // Parse the command in the given string and return the resulting map.
  static JsonKVMap parse(const String& command);
 
  // Parse the given file and return the resulting map.
  // Comments are ignored; they can be indicated by // or # till eol
  // or be enclosed in / * and * /.
  static JsonKVMap parseFile(const String& fileName);
 
  // Give the next chunk of input for the scanner.
  static int input(char* buf, int max_size);
 
  // Give the current position (for read or update).
  static int& position() { return theirPosition; }
 
  // Remove all possible escape characters and convert as needed (including <src>\uxxxx</src>).
  static String removeEscapes(const String& in);
 
  // Let the parser set the final KeyValueMap.
  static void setMap(JsonKVMap* map) { theirJsonMap = map; }
 
 private:
  static int theirPosition;
  static const char* theirCommand;
  static JsonKVMap* theirJsonMap;
};
 
// The global yyerror function for the parser.
// It throws an exception with the current token.
void JsonGramerror(const char*);
 
// </group>
 
}  // namespace casacore
 
#endif