path: root/gcc/json.h

/* JSON trees
   Copyright (C) 2017-2024 Free Software Foundation, Inc.
   Contributed by David Malcolm <dmalcolm@redhat.com>.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC 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 General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#ifndef GCC_JSON_H
#define GCC_JSON_H

/* This header uses std::unique_ptr, but <memory> can't be directly
   included due to issues with macros.  Hence <memory> must be included
   from system.h by defining INCLUDE_MEMORY in any source file using
   json.h.  */

#ifndef INCLUDE_MEMORY
# error "You must define INCLUDE_MEMORY before including system.h to use json.h"
#endif

/* Implementation of JSON, a lightweight data-interchange format.

   See http://www.json.org/
   and http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf
   and https://tools.ietf.org/html/rfc7159

   Supports creating a DOM-like tree of json::value *, and then dumping
   json::value * to text.  */

/* TODO: `libcpp/mkdeps.cc` wants JSON writing support for p1689r5 output;
   extract this code and move to libiberty.  */

namespace json
{

/* Forward decls of json::value and its subclasses (using indentation
   to denote inheritance.  */

class value;
  class object;
  class array;
  class float_number;
  class integer_number;
  class string;
  class literal;

/* An enum for discriminating the subclasses of json::value.  */

enum kind
{
  /* class json::object.  */
  JSON_OBJECT,

  /* class json::array.  */
  JSON_ARRAY,

  /* class json::integer_number.  */
  JSON_INTEGER,

  /* class json::float_number.  */
  JSON_FLOAT,

  /* class json::string.  */
  JSON_STRING,

  /* class json::literal uses these three values to identify the
     particular literal.  */
  JSON_TRUE,
  JSON_FALSE,
  JSON_NULL
};

/* Base class of JSON value.  */

class value
{
 public:
  virtual ~value () {}
  virtual enum kind get_kind () const = 0;
  virtual void print (pretty_printer *pp, bool formatted) const = 0;

  void dump (FILE *, bool formatted) const;
  void DEBUG_FUNCTION dump () const;
};

/* Subclass of value for objects: a collection of key/value pairs
   preserving the ordering in which keys were inserted.

   Preserving the order eliminates non-determinism in the output,
   making it easier for the user to compare repeated invocations.  */

class object : public value
{
 public:
  ~object ();

  enum kind get_kind () const final override { return JSON_OBJECT; }
  void print (pretty_printer *pp, bool formatted) const final override;

  bool is_empty () const { return m_map.is_empty (); }

  void set (const char *key, value *v);

  /* Set the property KEY of this object, requiring V
     to be of a specific json::value subclass.

     This can be used to enforce type-checking, making it easier
     to comply with a schema, e.g.
       obj->set<some_subclass> ("property_name", value)
     leading to a compile-time error if VALUE is not of the
     appropriate subclass.  */
  template <typename JsonType>
  void set (const char *key, std::unique_ptr<JsonType> v)
  {
    set (key, v.release ());
  }

  value *get (const char *key) const;

  void set_string (const char *key, const char *utf8_value);
  void set_integer (const char *key, long v);
  void set_float (const char *key, double v);

  /* Set to literal true/false.  */
  void set_bool (const char *key, bool v);

 private:
  typedef hash_map <char *, value *,
    simple_hashmap_traits<nofree_string_hash, value *> > map_t;
  map_t m_map;

  /* Keep track of order in which keys were inserted.  */
  auto_vec <const char *> m_keys;
};

/* Subclass of value for arrays.  */

class array : public value
{
 public:
  ~array ();

  enum kind get_kind () const final override { return JSON_ARRAY; }
  void print (pretty_printer *pp, bool formatted) const final override;

  void append (value *v);
  void append_string (const char *utf8_value);

  /* Append V to this array, requiring V
     to be a specific json::value subclass.

     This can be used to enforce type-checking, making it easier
     to comply with a schema, e.g.
       arr->append<some_subclass> (value)
     leading to a compile-time error if VALUE is not of the
     appropriate subclass.  */
  template <typename JsonType>
  void append (std::unique_ptr<JsonType> v)
  {
    append (v.release ());
  }

  size_t size () const { return m_elements.length (); }
  value *operator[] (size_t i) const { return m_elements[i]; }

 private:
  auto_vec<value *> m_elements;
};

/* Subclass of value for floating-point numbers.  */

class float_number : public value
{
 public:
  float_number (double value) : m_value (value) {}

  enum kind get_kind () const final override { return JSON_FLOAT; }
  void print (pretty_printer *pp, bool formatted) const final override;

  double get () const { return m_value; }

 private:
  double m_value;
};

/* Subclass of value for integer-valued numbers.  */

class integer_number : public value
{
 public:
  integer_number (long value) : m_value (value) {}

  enum kind get_kind () const final override { return JSON_INTEGER; }
  void print (pretty_printer *pp, bool formatted) const final override;

  long get () const { return m_value; }

 private:
  long m_value;
};


/* Subclass of value for strings.  */

class string : public value
{
 public:
  explicit string (const char *utf8);
  string (const char *utf8, size_t len);
  ~string () { free (m_utf8); }

  enum kind get_kind () const final override { return JSON_STRING; }
  void print (pretty_printer *pp, bool formatted) const final override;

  const char *get_string () const { return m_utf8; }
  size_t get_length () const { return m_len; }

 private:
  char *m_utf8;
  size_t m_len;
};

/* Subclass of value for the three JSON literals "true", "false",
   and "null".  */

class literal : public value
{
 public:
  literal (enum kind kind) : m_kind (kind) {}

  /* Construct literal for a boolean value.  */
  literal (bool value): m_kind (value ? JSON_TRUE : JSON_FALSE) {}

  enum kind get_kind () const final override { return m_kind; }
  void print (pretty_printer *pp, bool formatted) const final override;

 private:
  enum kind m_kind;
};

} // namespace json

#endif  /* GCC_JSON_H  */