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jsoncons::cbor::basic_cbor_encoder

#include <jsoncons_ext/cbor/cbor_encoder.hpp>

template<
    class Sink>
> class basic_cbor_encoder final : public json_visitor

basic_cbor_encoder is noncopyable

basic_cbor_encoder

Four specializations for common sink types are defined:

Type Definition
cbor_stream_encoder basic_cbor_encoderjsoncons::binary_stream_sink
cbor_bytes_encoder basic_cbor_encoder<jsoncons::bytes_sink<std::vector<uint8_t>>>

Member types

Type Definition
char_type char
sink_type Sink
string_view_type

Constructors

explicit basic_cbor_encoder(Sink&& sink)

Constructs a new encoder that writes to the specified destination.

Destructor

virtual ~basic_cbor_encoder() noexcept

Member functions

void reset();

Reset encoder to write another value to the same sink

void reset(Sink&& sink)

Reset encoder to write a new value to a new sink

void begin_object_with_tag(uint64_t raw_tag);                          // (since 1.2.0)

void begin_object_with_tag(std::size_t length, uint64_t raw_tag);      // (since 1.2.0)

void begin_array_with_tag(uint64_t raw_tag);                           // (since 1.2.0)

void begin_array_with_tag(std::size_t length, uint64_t raw_tag);       // (since 1.2.0)

void null_value_with_tag(uint64_t raw_tag);                            // (since 1.2.0)

void bool_value_with_tag(bool value, uint64_t raw_tag);                // (since 1.2.0)

void string_value_with_tag(const string_view_type& value, 
    uint64_t raw_tag);                                                 // (since 1.2.0) 

template <typename ByteStringLike>
void byte_string_value_with_tag(const ByteStringLike& value, 
    uint64_t raw_tag);                                                 // (since 1.2.0) 

void double_value_with_tag(double value, uint64_t raw_tag);            // (since 1.2.0) 

void uint64_value_with_tag(uint64_t value, uint64_t raw_tag);          // (since 1.2.0) 

void int64_value_with_tag(int64_t value, uint64_t raw_tag);            // (since 1.2.0)

Inherited from jsoncons::basic_json_visitor

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

template <typename ByteStringLike>
bool byte_string_value(const ByteStringLike & 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 <typename 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 <typename 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 <typename 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 <typename 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.

Examples

Encode to CBOR buffer
Encode to CBOR stream
Encode with raw CBOR tags (since 1.2.0)
Encode Typed Array tags - array of half precision floating-point
Encode Typed Array tags - multi-dimensional column major tag

Encode to CBOR buffer

#include <jsoncons/json.hpp>
#include <jsoncons_ext/cbor/cbor.hpp>
#include <iomanip>

int main()
{
    std::vector<uint8_t> buffer;
    cbor::cbor_bytes_encoder encoder(buffer);

    encoder.begin_array(); // Indefinite length array
    encoder.string_value("cat");
    std::vector<uint8_t> purr = {'p','u','r','r'};
    encoder.byte_string_value(purr);
    std::vector<uint8_t> hiss = {'h','i','s','s'};
    encoder.byte_string_value(hiss, semantic_tag::base64); // suggested conversion to base64
    encoder.int64_value(1431027667, semantic_tag::epoch_second);
    encoder.end_array();
    encoder.flush();

    std::cout << byte_string_view(buffer) << "\n\n";

/* 
    9f -- Start indefinte length array
      63 -- String value of length 3
        636174 -- "cat"
      44 -- Byte string value of length 4
        70757272 -- 'p''u''r''r'
      d6 - Expected conversion to base64
      44
        68697373 -- 'h''i''s''s'
      c1 -- Tag value 1 (seconds relative to 1970-01-01T00:00Z in UTC time)
        1a -- 32 bit unsigned integer
          554bbfd3 -- 1431027667
      ff -- "break" 
*/ 
}

Output:

9f,63,63,61,74,44,70,75,72,72,d6,44,68,69,73,73,c1,1a,55,4b,bf,d3,ff

Encode to CBOR stream

#include <jsoncons/json.hpp>
#include <jsoncons_ext/cbor/cbor.hpp>
#include <iomanip>

int main()
{
    std::ostringstream os;
    cbor::cbor_stream_encoder encoder(os);

    encoder.begin_array(3); // array of length 3
    encoder.string_value("-18446744073709551617", semantic_tag::bigint);
    encoder.string_value("184467440737095516.16", semantic_tag::bigdec);
    encoder.int64_value(1431027667, semantic_tag::epoch_second);
    encoder.end_array();
    encoder.flush();

    std::cout << byte_string_view(os.str()) << "\n\n";

/*
    83 -- array of length 3
      c3 -- Tag 3 (negative bignum)
      49 -- Byte string value of length 9
        010000000000000000 -- Bytes content
      c4 -- Tag 4 (decimal fraction)
        82 -- Array of length 2
          21 -- -2 (exponent)
          c2 Tag 2 (positive bignum)
          49 -- Byte string value of length 9
            010000000000000000
      c1 -- Tag 1 (seconds relative to 1970-01-01T00:00Z in UTC time)
        1a -- 32 bit unsigned integer
          554bbfd3 -- 1431027667
*/
}

Output:

83,c3,49,01,00,00,00,00,00,00,00,00,c4,82,21,c2,49,01,00,00,00,00,00,00,00,00,c1,1a,55,4b,bf,d3

Encode with raw CBOR tags (since 1.2.0)

#include <cassert>
#include <iostream>
#include <jsoncons_ext/cbor/cbor.hpp>

namespace cbor = jsoncons::cbor;

int main()
{
    std::vector<uint8_t> data;
    cbor::cbor_bytes_encoder encoder(data);
    encoder.begin_array(1);
    encoder.uint64_value_with_tag(10, 0xC1);
    encoder.end_array();
    encoder.flush();

    cbor::cbor_bytes_cursor cursor(data);
    assert(cursor.current().event_type() == jsoncons::staj_event_type::begin_array);
    cursor.next();
    assert(cursor.raw_tag() == 0xC1);
    assert(cursor.current().get<uint64_t>() == 10);
}

Encode Typed Array tags - array of half precision floating-point

#include <jsoncons/json.hpp>
#include <jsoncons_ext/cbor/cbor.hpp>
#include <iomanip>

int main()
{
    std::vector<uint8_t> buffer;

    auto options = cbor::cbor_options{}
        .use_typed_arrays(true);
    cbor::cbor_bytes_encoder encoder(buffer, options);

    std::vector<uint16_t> values = {0x3bff,0x3c00,0x3c01,0x3555};
    encoder.typed_array(half_arg, values);

    // buffer contains a half precision floating-point, native endian, Typed Array 
    std::cout << "(1)\n" << byte_string_view(buffer) << "\n\n";

    auto j = cbor::decode_cbor<json>(buffer);

    std::cout << "(2)\n";
    for (auto item : j.array_range())
    {
        std::cout << std::boolalpha << item.is_half() 
                  << " " << std::hex << (int)item.as<uint16_t>() 
                  << " " << std::defaultfloat << item.as<double>() << "\n";
    }
    std::cout << "\n";

    std::cout << "(3)\n" << pretty_print(j) << "\n\n";
}

Output

(1)
d8 54 48 ff 3b 00 3c 01 3c 55 35

(2)
true 3bff 0.999512
true 3c00 1
true 3c01 1.00098
true 3555 0.333252

(3)
[
    0.99951171875,
    1.0,
    1.0009765625,
    0.333251953125
]

Encode Typed Array tags - multi-dimensional column major tag

#include <jsoncons/json.hpp>
#include <jsoncons_ext/cbor/cbor.hpp>

int main()
{
    std::vector<uint8_t> v;

    cbor::cbor_bytes_encoder encoder(v);
    std::vector<std::size_t> shape = { 2,3 };
    encoder.begin_multi_dim(shape, semantic_tag::multi_dim_column_major);
    encoder.begin_array(6);
    encoder.uint64_value(2);
    encoder.uint64_value(4);
    encoder.uint64_value(8);
    encoder.uint64_value(4);
    encoder.uint64_value(16);
    encoder.uint64_value(256);
    encoder.end_array();
    encoder.end_multi_dim();

    std::cout << "(1)\n" << byte_string_view(v) << "\n\n";

    auto j = cbor::decode_cbor<json>(v);
    std::cout << "(2) " << j.tag() << "\n";
    std::cout << pretty_print(j) << "\n\n";
}

Output:

(1)
d9 04 10 82 82 02 03 86 02 04 08 04 10 19 01 00

(2) multi-dim-column-major
[
    [2, 3],
    [2, 4, 8, 4, 16, 256]
]

See also

byte_string_view