JsonValue.h

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// # JsonValue.h: Class to hold any JSON value
// # 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_JSONVALUE_H
#define CASA_JSONVALUE_H
 
// # Includes
#include <casacore/casa/Arrays/ArrayFwd.h>
#include <casacore/casa/BasicSL/String.h>
#include <casacore/casa/BasicSL/Complex.h>
#include <casacore/casa/Utilities/DataType.h>
#include <casacore/casa/Utilities/Assert.h>
#include <casacore/casa/Exceptions/Error.h>
#include <vector>
#include <iosfwd>
 
namespace casacore {
 
// # Forward Declarations
class JsonKVMap;
class ValueHolder;
class IPosition;
 
// <summary>
// Class to hold any JSON value
// </summary>
 
// <use visibility=export>
// <reviewed reviewer="" date="" tests="tJsonValue">
// </reviewed>
 
// # <prerequisite>
// # </prerequisite>
 
// <synopsis>
// Class JsonValue can hold an arbitrary JSON value which can be a scalar,
// a JsonKVMap object, or a vector of JsonValue objects. In this way
// JSON values can be nested in any way.
//
// Internally scalar values are kept as Bool, Int64, Double, DComplex or
// String values. The functions to obtain the value convert if possible.
// Note that conversion from Int64 to Bool is supported.
// The value can also be obtained as a ValueHolder object making it easier
// to use in other Casacore code.
// Null is also a valid JsonValue. A null value can be obtained as a
// floating point value resulting in a NaN. It can also be obtained as a
// null ValueHolder. Getting it for other types results in an exception.
//
// It is possible to obtain the value as a multi-dimensional Array object
// if the values are regular, thus if nested vectors have the same sizes.
// The data type of an Array is the 'highest' data type of a value in it.
//
// Normally a JsonValue object is created by JsonParser and is the
// interface to obtain a value of a field in a parsed JSON file.
// However, users can create JsonValue objects as well.
// </synopsis>
 
// <motivation>
// JSON is a commonly used interchange format.
// </motivation>
 
// # <todo asof="1996/03/10">
// #   <li>
// # </todo>
 
class JsonValue {
 public:
  // The default constructor results in a null value.
  JsonValue();
 
  // Construct value with given type.
  // <group>
  JsonValue(Bool);
  JsonValue(int);
  JsonValue(Int64);
  JsonValue(double);
  JsonValue(const DComplex&);
  JsonValue(const char*);
  JsonValue(const String&);
  JsonValue(const std::vector<JsonValue>&);
  JsonValue(const JsonKVMap&);
  // </group>
 
  // Copy constructor (copy semantics).
  JsonValue(const JsonValue&);
 
  // Assignment (copy semantics).
  JsonValue& operator=(const JsonValue&);
 
  ~JsonValue();
 
  // Is the value a null value?
  Bool isNull() const { return itsValuePtr == 0; }
 
  // Is the value a vector?
  Bool isVector() const { return itsDataType == TpOther; }
 
  // Is the value a value map?
  Bool isValueMap() const { return itsDataType == TpRecord; }
 
  // Return the size of a value vector or map (1 is returned for a scalar).
  size_t size() const;
 
  // Get the data type of the value.
  // A ValueMap is returned as TpRecord, a vector as TpOther.
  DataType dataType() const { return itsDataType; }
 
  // Get the most common data type of the value inside a possibly
  // nested vector.
  // <br>- If the value is a single value, that type is returned.
  // <br>- If any vector value is a ValueMap, TpRecord is returned.
  // <br>- If any vector contains non-matching data types, TpOther is
  //       returned.
  // <br>- Otherwise the 'highest' data type is returned.
  // <group>
  DataType arrayDataType() const;
  DataType vectorDataType(const std::vector<JsonValue>& vec) const;
  // </group>
 
  // Get the shape of an array (possibly nested vector).
  // An exception is thrown if a vector contains a ValueMap or if
  // the array shape is irregular (nested vectors have different sizes).
  IPosition shape() const;
  IPosition vectorShape(const std::vector<JsonValue>& vec) const;
 
  // Get the value as a ValueHolder.
  // A null value results in a null (empty) ValueHolder.
  // An exception is thrown if the value cannot be represented as such,
  // because it is a vector of differently typed values or nested vectors.
  ValueHolder getValueHolder() const;
 
  // Get the value in the given data type.
  // Numeric data type promotion can be done as well as conversion of
  // integer to bool (0=False, other=True). An exception is thrown if
  // a mismatching data type is used.
  // Note that a null value can only be obtained as double (giving NaN).
  // <group>
  Bool getBool() const;
  Int64 getInt() const;
  double getDouble() const;
  DComplex getDComplex() const;
  const String& getString() const;
  // </group>
 
  // As above, but get the value as a vector.
  // If the value is a scalar, a vector with length 1 is returned.
  // <group>
  std::vector<Bool> getVecBool() const;
  std::vector<Int64> getVecInt() const;
  std::vector<double> getVecDouble() const;
  std::vector<DComplex> getVecDComplex() const;
  std::vector<String> getVecString() const;
  const std::vector<JsonValue>& getVector() const;
  // </group>
 
  // Get the value as a JsonKVMap (no conversion is possible).
  const JsonKVMap& getValueMap() const;
 
  // Get the value as an Array. The value must be a scalar or a
  // regularly nested vector.
  // <group>
  Array<Bool> getArrayBool() const;
  Array<Int64> getArrayInt() const;
  Array<double> getArrayDouble() const;
  Array<DComplex> getArrayDComplex() const;
  Array<String> getArrayString() const;
  // </group>
 
  // Get functions for templated purposes
  // <group>
  void get(Bool& value) const { value = getBool(); }
  void get(Int64& value) const { value = getInt(); }
  void get(double& value) const { value = getDouble(); }
  void get(DComplex& value) const { value = getDComplex(); }
  void get(String& value) const { value = getString(); }
  void get(std::vector<Bool>& value) const { value = getVecBool(); }
  void get(std::vector<Int64>& value) const { value = getVecInt(); }
  void get(std::vector<double>& value) const { value = getVecDouble(); }
  void get(std::vector<DComplex>& value) const { value = getVecDComplex(); }
  void get(std::vector<String>& value) const { value = getVecString(); }
  void get(std::vector<JsonValue>& value) const { value = getVector(); }
  void get(JsonKVMap& value) const;
  // </group>
 
  // Show value on given ostream.
  friend ostream& operator<<(ostream&, const JsonValue&);
 
 private:
  // Remove the value.
  void clear();
 
  // Copy the value from another one.
  void copyValue(const JsonValue& that);
 
  // Fill an array from nested vector in a recursive way.
  template <typename T>
  T* fillArray(T* data, const T* dataEnd, const std::vector<JsonValue>& vec) const {
    for (std::vector<JsonValue>::const_iterator iter = vec.begin(); iter != vec.end(); ++iter) {
      if (iter->dataType() == TpOther) {
        data = fillArray(data, dataEnd, iter->getVector());
      } else {
        AlwaysAssert(data < dataEnd, AipsError);
        iter->get(*data);
        data++;
      }
    }
    return data;
  }
 
  DataType itsDataType;
  void* itsValuePtr;
};
 
}  // namespace casacore
 
#endif