jsoncpp/include/json/writer.h

// Copyright 2007-2010 Baptiste Lepilleur and The JsonCpp Authors
// Distributed under MIT license, or public domain if desired and
// recognized in your jurisdiction.
// See file LICENSE for detail or copy at http://jsoncpp.sourceforge.net/LICENSE

#ifndef JSON_WRITER_H_INCLUDED
#define JSON_WRITER_H_INCLUDED

#if !defined(JSON_IS_AMALGAMATION)
#include "value.h"
#endif // if !defined(JSON_IS_AMALGAMATION)
#include <ostream>
#include <string>
#include <vector>

// Disable warning C4251: <data member>: <type> needs to have dll-interface to
// be used by...
#if defined(JSONCPP_DISABLE_DLL_INTERFACE_WARNING) && defined(_MSC_VER)
#pragma warning(push)
#pragma warning(disable : 4251)
#endif // if defined(JSONCPP_DISABLE_DLL_INTERFACE_WARNING)

#pragma pack(push, 8)

namespace Json {

class Value;

/**
 *
 * Usage:
 *  \code
 *  using namespace Json;
 *  void writeToStdout(StreamWriter::Factory const& factory, Value const& value)
 * { std::unique_ptr<StreamWriter> const writer( factory.newStreamWriter());
 *    writer->write(value, &std::cout);
 *    std::cout << std::endl;  // add lf and flush
 *  }
 *  \endcode
 */
class JSON_API StreamWriter {
protected:
  OStream* sout_; // not owned; will not delete
public:
  StreamWriter();
  virtual ~StreamWriter();
  /** Write Value into document as configured in sub-class.
   *   Do not take ownership of sout, but maintain a reference during function.
   *   \pre sout != NULL
   *   \return zero on success (For now, we always return zero, so check the
   *   stream instead.) \throw std::exception possibly, depending on
   * configuration
   */
  virtual int write(Value const& root, OStream* sout) = 0;

  /** \brief A simple abstract factory.
   */
  class JSON_API Factory {
  public:
    virtual ~Factory();
    /** \brief Allocate a CharReader via operator new().
     * \throw std::exception if something goes wrong (e.g. invalid settings)
     */
    virtual StreamWriter* newStreamWriter() const = 0;
  }; // Factory
};   // StreamWriter

/** \brief Write into stringstream, then return string, for convenience.
 * A StreamWriter will be created from the factory, used, and then deleted.
 */
String JSON_API writeString(StreamWriter::Factory const& factory,
                            Value const& root);

/** \brief Build a StreamWriter implementation.

* Usage:
*   \code
*   using namespace Json;
*   Value value = ...;
*   StreamWriterBuilder builder;
*   builder["commentStyle"] = "None";
*   builder["indentation"] = "   ";  // or whatever you like
*   std::unique_ptr<Json::StreamWriter> writer(
*      builder.newStreamWriter());
*   writer->write(value, &std::cout);
*   std::cout << std::endl;  // add lf and flush
*   \endcode
*/
class JSON_API StreamWriterBuilder : public StreamWriter::Factory {
public:
  // Note: We use a Json::Value so that we can add data-members to this class
  // without a major version bump.
  /** Configuration of this builder.
   *  Available settings (case-sensitive):
   *  - "commentStyle": "None" or "All"
   *  - "indentation":  "<anything>".
   *  - Setting this to an empty string also omits newline characters.
   *  - "enableYAMLCompatibility": false or true
   *  - slightly change the whitespace around colons
   *  - "dropNullPlaceholders": false or true
   *  - Drop the "null" string from the writer's output for nullValues.
   *    Strictly speaking, this is not valid JSON. But when the output is being
   *    fed to a browser's JavaScript, it makes for smaller output and the
   *    browser can handle the output just fine.
   *  - "useSpecialFloats": false or true
   *  - If true, outputs non-finite floating point values in the following way:
   *    NaN values as "NaN", positive infinity as "Infinity", and negative
   *  infinity as "-Infinity".
   *  - "precision": int
   *  - Number of precision digits for formatting of real values.
   *  - "precisionType": "significant"(default) or "decimal"
   *  - Type of precision for formatting of real values.
   *  - "emitUTF8": false or true
   *  - If true, outputs raw UTF8 strings instead of escaping them.

   *  You can examine 'settings_` yourself
   *  to see the defaults. You can also write and read them just like any
   *  JSON Value.
   *  \sa setDefaults()
   */
  Json::Value settings_;

  StreamWriterBuilder();
  ~StreamWriterBuilder() override;

  /**
   * \throw std::exception if something goes wrong (e.g. invalid settings)
   */
  StreamWriter* newStreamWriter() const override;

  /** \return true if 'settings' are legal and consistent;
   *   otherwise, indicate bad settings via 'invalid'.
   */
  bool validate(Json::Value* invalid) const;
  /** A simple way to update a specific setting.
   */
  Value& operator[](const String& key);

  /** Called by ctor, but you can use this to reset settings_.
   * \pre 'settings' != NULL (but Json::null is fine)
   * \remark Defaults:
   * \snippet src/lib_json/json_writer.cpp StreamWriterBuilderDefaults
   */
  static void setDefaults(Json::Value* settings);
};

/** \brief Abstract class for writers.
 * \deprecated Use StreamWriter. (And really, this is an implementation detail.)
 */
class JSON_API Writer {
public:
  virtual ~Writer();

  virtual String write(const Value& root) = 0;
};

/** \brief Outputs a Value in <a HREF="http://www.json.org">JSON</a> format
 *without formatting (not human friendly).
 *
 * The JSON document is written in a single line. It is not intended for 'human'
 *consumption,
 * but may be useful to support feature such as RPC where bandwidth is limited.
 * \sa Reader, Value
 * \deprecated Use StreamWriterBuilder.
 */
#if defined(_MSC_VER)
#pragma warning(push)
#pragma warning(disable : 4996) // Deriving from deprecated class
#endif
class JSON_API FastWriter
    : public Writer {
public:
  FastWriter();
  ~FastWriter() override = default;

  void enableYAMLCompatibility();

  /** \brief Drop the "null" string from the writer's output for nullValues.
   * Strictly speaking, this is not valid JSON. But when the output is being
   * fed to a browser's JavaScript, it makes for smaller output and the
   * browser can handle the output just fine.
   */
  void dropNullPlaceholders();

  void omitEndingLineFeed();

public: // overridden from Writer
  String write(const Value& root) override;

private:
  void writeValue(const Value& value);

  String document_;
  bool yamlCompatibilityEnabled_{false};
  bool dropNullPlaceholders_{false};
  bool omitEndingLineFeed_{false};
};
#if defined(_MSC_VER)
#pragma warning(pop)
#endif

/** \brief Writes a Value in <a HREF="http://www.json.org">JSON</a> format in a
 *human friendly way.
 *
 * 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.
 *
 * \sa Reader, Value, Value::setComment()
 * \deprecated Use StreamWriterBuilder.
 */
#if defined(_MSC_VER)
#pragma warning(push)
#pragma warning(disable : 4996) // Deriving from deprecated class
#endif
class JSON_API
    StyledWriter : public Writer {
public:
  StyledWriter();
  ~StyledWriter() override = default;

public: // overridden from Writer
  /** \brief Serialize a Value in <a HREF="http://www.json.org">JSON</a> format.
   * \param root Value to serialize.
   * \return String containing the JSON document that represents the root value.
   */
  String write(const Value& root) override;

private:
  void writeValue(const Value& value);
  void writeArrayValue(const Value& value);
  bool isMultilineArray(const Value& value);
  void pushValue(const String& value);
  void writeIndent();
  void writeWithIndent(const String& value);
  void indent();
  void unindent();
  void writeCommentBeforeValue(const Value& root);
  void writeCommentAfterValueOnSameLine(const Value& root);
  static bool hasCommentForValue(const Value& value);
  static String normalizeEOL(const String& text);

  using ChildValues = std::vector<String>;

  ChildValues childValues_;
  String document_;
  String indentString_;
  unsigned int rightMargin_{74};
  unsigned int indentSize_{3};
  bool addChildValues_{false};
};
#if defined(_MSC_VER)
#pragma warning(pop)
#endif

/** \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.
 *
 * \sa Reader, Value, Value::setComment()
 * \deprecated Use StreamWriterBuilder.
 */
#if defined(_MSC_VER)
#pragma warning(push)
#pragma warning(disable : 4996) // Deriving from deprecated class
#endif
class JSON_API
    StyledStreamWriter {
public:
  /**
   * \param indentation Each level will be indented by this amount extra.
   */
  StyledStreamWriter(String indentation = "\t");
  ~StyledStreamWriter() = default;

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(OStream& out, const Value& root);

private:
  void writeValue(const Value& value);
  void writeArrayValue(const Value& value);
  bool isMultilineArray(const Value& value);
  void pushValue(const String& value);
  void writeIndent();
  void writeWithIndent(const String& value);
  void indent();
  void unindent();
  void writeCommentBeforeValue(const Value& root);
  void writeCommentAfterValueOnSameLine(const Value& root);
  static bool hasCommentForValue(const Value& value);
  static String normalizeEOL(const String& text);

  using ChildValues = std::vector<String>;

  ChildValues childValues_;
  OStream* document_;
  String indentString_;
  unsigned int rightMargin_{74};
  String indentation_;
  bool addChildValues_ : 1;
  bool indented_ : 1;
};
#if defined(_MSC_VER)
#pragma warning(pop)
#endif

#if defined(JSON_HAS_INT64)
String JSON_API valueToString(Int value);
String JSON_API valueToString(UInt value);
#endif // if defined(JSON_HAS_INT64)
String JSON_API valueToString(LargestInt value);
String JSON_API valueToString(LargestUInt value);
String JSON_API valueToString(
    double value, unsigned int precision = Value::defaultRealPrecision,
    PrecisionType precisionType = PrecisionType::significantDigits);
String JSON_API valueToString(bool value);
String JSON_API valueToQuotedString(const char* value);

/// \brief Output using the StyledStreamWriter.
/// \see Json::operator>>()
JSON_API OStream& operator<<(OStream&, const Value& root);

} // namespace Json

#pragma pack(pop)

#if defined(JSONCPP_DISABLE_DLL_INTERFACE_WARNING)
#pragma warning(pop)
#endif // if defined(JSONCPP_DISABLE_DLL_INTERFACE_WARNING)

#endif // JSON_WRITER_H_INCLUDED