basic_json_visitor.md

jsoncons::basic_json_visitor

#include <jsoncons/json_visitor.hpp>

template <
    class CharT
> class basic_json_visitor

Defines an interface for producing and consuming JSON events.

Aliases for common character types are provided:

Type	Definition
json_visitor	basic_json_visitor<char>
wjson_visitor	basic_json_visitor<wchar_t>

Member types

Member type	Definition
char_type	CharT
string_view_type	A non-owning view of a string, holds a pointer to character data and length. Supports conversion to and from strings. Will be typedefed to the C++ 17 std::string view if C++ 17 is detected or if JSONCONS_HAS_STD_STRING_VIEW is defined, otherwise proxied.

Public event producer interface

void flush(); (1)

bool begin_object(semantic_tag tag=semantic_tag::none,
                  const ser_context& context=ser_context()); (2)

bool begin_object(std::size_t length, 
                  semantic_tag tag=semantic_tag::none, 
                  const ser_context& context = ser_context()); (3)

bool end_object(const ser_context& context = ser_context()); (4)

bool begin_array(semantic_tag tag=semantic_tag::none,
                 const ser_context& context=ser_context()); (5)

bool begin_array(std::size_t length, 
                 semantic_tag tag=semantic_tag::none,
                 const ser_context& context=ser_context()); (6)

bool end_array(const ser_context& context=ser_context()); (7)

bool key(const string_view_type& name, 
          const ser_context& context=ser_context()); (8)

bool null_value(semantic_tag tag = semantic_tag::none,
                const ser_context& context=ser_context()); (9) 

bool bool_value(bool value, 
                semantic_tag tag = semantic_tag::none,
                const ser_context& context=ser_context()); (10) 

bool string_value(const string_view_type& value, 
                  semantic_tag tag = semantic_tag::none, 
                  const ser_context& context=ser_context()); (11) 

bool byte_string_value(const byte_string_view& source, 
                       semantic_tag tag=semantic_tag::none, 
                       const ser_context& context=ser_context()); (12) (until 0.152.0)

template <class Source>
bool byte_string_value(const Source& souce, 
                       semantic_tag tag=semantic_tag::none, 
                       const ser_context& context=ser_context()); (12) (since 0.152.0)

template <class Source>
bool byte_string_value(const Source& souce, 
                       uint64_t ext_tag, 
                       const ser_context& context=ser_context()); (13) (since 0.152.0)

bool uint64_value(uint64_t value, 
                  semantic_tag tag = semantic_tag::none, 
                  const ser_context& context=ser_context()); (14)

bool int64_value(int64_t value, 
                 semantic_tag tag = semantic_tag::none, 
                 const ser_context& context=ser_context()); (15)

bool half_value(uint16_t value, 
                semantic_tag tag = semantic_tag::none, 
                const ser_context& context=ser_context()); (16)

bool double_value(double value, 
                  semantic_tag tag = semantic_tag::none, 
                  const ser_context& context=ser_context()); (17)

bool begin_object(semantic_tag tag,
                  const ser_context& context,
                  std::error_code& ec); (18)

bool begin_object(std::size_t length, 
                  semantic_tag tag, 
                  const ser_context& context,
                  std::error_code& ec); (19)

bool end_object(const ser_context& context, 
                std::error_code& ec); (20)

bool begin_array(semantic_tag tag, 
                 const ser_context& context, 
                 std::error_code& ec); (21)

bool begin_array(std::size_t length, 
                 semantic_tag tag, 
                 const ser_context& context, 
                 std::error_code& ec); (22)

bool end_array(const ser_context& context, 
               std::error_code& ec); (23)

bool key(const string_view_type& name, 
          const ser_context& context, 
          std::error_code& ec); (24)

bool null_value(semantic_tag tag,
                const ser_context& context,
                std::error_code& ec); (25) 

bool bool_value(bool value, 
                semantic_tag tag,
                const ser_context& context,
                std::error_code& ec); (26) 

bool string_value(const string_view_type& value, 
                  semantic_tag tag, 
                  const ser_context& context,
                  std::error_code& ec); (27) 

bool byte_string_value(const byte_string_view& source, 
                       semantic_tag tag, 
                       const ser_context& context,
                       std::error_code& ec); (28) (until 0.152.0)

template <class Source>   
bool byte_string_value(const Source& source, 
                       semantic_tag tag, 
                       const ser_context& context,
                       std::error_code& ec); (28) (since 0.152.0)

template <class Source>   
bool byte_string_value(const Source& source, 
                       uint64_t ext_tag, 
                       const ser_context& context,
                       std::error_code& ec); (29) (since 0.152.0)

bool uint64_value(uint64_t value, 
                  semantic_tag tag, 
                  const ser_context& context,
                  std::error_code& ec); (30)

bool int64_value(int64_t value, 
                 semantic_tag tag, 
                 const ser_context& context,
                 std::error_code& ec); (31)

bool half_value(uint16_t value, 
                semantic_tag tag, 
                const ser_context& context,
                std::error_code& ec); (32)

bool double_value(double value, 
                  semantic_tag tag, 
                  const ser_context& context,
                  std::error_code& ec); (33)

template <class T>
bool typed_array(const span<T>& data, 
                 semantic_tag tag=semantic_tag::none,
                 const ser_context& context=ser_context()); (34)

bool typed_array(half_arg_t, const span<const uint16_t>& s,
    semantic_tag tag = semantic_tag::none,
    const ser_context& context = ser_context()); (35)

bool begin_multi_dim(const span<const size_t>& shape,
                     semantic_tag tag,
                     const ser_context& context); (36) 

bool end_multi_dim(const ser_context& context=ser_context()); (37) 

template <class T>
bool typed_array(const span<T>& data, 
                 semantic_tag tag,
                 const ser_context& context,
                 std::error_code& ec); (38)

bool typed_array(half_arg_t, const span<const uint16_t>& s,
                 semantic_tag tag,
                 const ser_context& context,
                 std::error_code& ec); (39)

bool begin_multi_dim(const span<const size_t>& shape,
                     semantic_tag tag,
                     const ser_context& context, 
                     std::error_code& ec); (40)

bool end_multi_dim(const ser_context& context,
                   std::error_code& ec); (41) 

(1) Flushes whatever is buffered to the destination.

(2) Indicates the begining of an object of indefinite length. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(3) Indicates the begining of an object of known length. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(4) Indicates the end of an object. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(5) Indicates the beginning of an indefinite length array. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(6) Indicates the beginning of an array of known length. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(7) Indicates the end of an array. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(8) Writes the name part of an object name-value pair. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(9) Writes a null value. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(10) Writes a boolean value. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(11) Writes a text string value. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(12) Writes a byte string value source with a generic tag. Type Source must be a container that has member functions data() and size(), and member type value_type with size exactly 8 bits (since 0.152.0.) Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(13) Writes a byte string value source with a format specific tag, ext_tag. Type Source must be a container that has member functions data() and size(), and member type value_type with size exactly 8 bits (since 0.152.0.) Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(14) Writes a non-negative integer value. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(15) Writes a signed integer value. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(16) Writes a half precision floating point value. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(17) Writes a double precision floating point value. Returns true if the consumer wishes to receive more events, false otherwise. Throws a ser_error on parse errors.

(18)-(33) Same as (2)-(17), except sets ec and returns false on parse errors.

Private event consumer interface

virtual void visit_flush() = 0; (1)

virtual bool visit_begin_object(semantic_tag tag, 
                                const ser_context& context, 
                                std::error_code& ec) = 0; (2)

virtual bool visit_begin_object(std::size_t length, 
                                semantic_tag tag, 
                                const ser_context& context, 
                                std::error_code& ec); (3)

virtual bool visit_end_object(const ser_context& context, 
                              std::error_code& ec) = 0; (4)

virtual bool visit_begin_array(semantic_tag tag, 
                               const ser_context& context, 
                               std::error_code& ec) = 0; (5)

virtual bool visit_begin_array(std::size_t length, 
                               semantic_tag tag, 
                               const ser_context& context, 
                               std::error_code& ec); (6)

virtual bool visit_end_array(const ser_context& context, 
                             std::error_code& ec) = 0; (7)

virtual bool visit_key(const string_view_type& name, 
                       const ser_context& context, 
                       std::error_code&) = 0; (8)

virtual bool visit_null(semantic_tag tag, 
                        const ser_context& context, 
                        std::error_code& ec) = 0; (9)

virtual bool visit_bool(bool value, 
                        semantic_tag tag, 
                        const ser_context& context, 
                        std::error_code&) = 0; (10)

virtual bool visit_string(const string_view_type& value, 
                          semantic_tag tag, 
                          const ser_context& context, 
                          std::error_code& ec) = 0; (11)

virtual bool visit_byte_string(const byte_string_view& value, 
                               semantic_tag tag, 
                               const ser_context& context,
                               std::error_code& ec) = 0; (12)

virtual bool visit_byte_string(const byte_string_view& value, 
                               uint64_t ext_tag, 
                               const ser_context& context,
                               std::error_code& ec); (13)

virtual bool visit_uint64(uint64_t value, 
                          semantic_tag tag, 
                          const ser_context& context,
                          std::error_code& ec) = 0; (14)

virtual bool visit_int64(int64_t value, 
                         semantic_tag tag,
                         const ser_context& context,
                         std::error_code& ec) = 0; (15)

virtual bool visit_half(uint16_t value, 
                        semantic_tag tag,
                        const ser_context& context,
                        std::error_code& ec); (16)

virtual bool visit_double(double value, 
                          semantic_tag tag,
                          const ser_context& context,
                          std::error_code& ec) = 0; (17)

virtual bool visit_typed_array(const span<const uint8_t>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (18)

virtual bool visit_typed_array(const span<const uint16_t>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (19)

virtual bool visit_typed_array(const span<const uint32_t>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (20)

virtual bool visit_typed_array(const span<const uint64_t>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (21)

virtual bool visit_typed_array(const span<const int8_t>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (22)

virtual bool visit_typed_array(const span<const int16_t>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (23)

virtual bool visit_typed_array(const span<const int32_t>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (24)

virtual bool visit_typed_array(const span<const int64_t>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (25)

virtual bool visit_typed_array(half_arg_t, 
                               const span<const uint16_t>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (26)

virtual bool visit_typed_array(const span<const float>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (27)

virtual bool visit_typed_array(const span<const double>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (28)

virtual bool visit_typed_array(const span<const float128_type>& data, 
                               semantic_tag tag,
                               const ser_context& context, 
                               std::error_code& ec); (29)

virtual bool visit_begin_multi_dim(const span<const size_t>& shape,
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (30)

virtual bool visit_end_multi_dim(const ser_context& context,
                                 std::error_code& ec); (31)

(1) Allows producers of json events to flush any buffered data.

(2) Handles the beginning of an object of indefinite length. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(3) Handles the beginning of an object of known length. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(4) Handles the end of an object. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(5) Handles the beginning of an array of indefinite length. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(6) Handles the beginning of an array of known length. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(7) Handles the end of an array. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(8) Handles the name part of an object name-value pair. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(9) Handles a null value. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(10) Handles a boolean value. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(11) Handles a string value. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(12) Handles a byte string value associated with a generic tag. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(13) Handles a byte string value associated with a format specific tag. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(14) Handles a non-negative integer value. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(15) Handles a signed integer value. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(16) Handles a half precision floating point value. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

(17) Handles a double precision floating point value. Returns true if the producer should generate more events, false otherwise. Sets ec and returns false on parse errors.

Parameters

tag - a jsoncons semantic tag context - parse context information including line and column number ec - a parse error code

Exceptions

The overloads that do not take a std::error_code& parameter throw a ser_error on parse errors, constructed with the error code as the error code argument and line and column from the context.

The overloads that take a std::error_code& parameter set it to the error code and return false on parse errors.

See also

semantic_tag

basic_default_json_visitor

basic_json_filter

byte_string_view