#include <jsoncons/json_parser.hpp>
typedef basic_json_parser<char> json_parserjson_parser is an incremental json parser. It can be fed its input
in chunks, and does not require an entire file to be loaded in memory
at one time.
A buffer of text is supplied to the parser with a call to update(buffer).
If a subsequent call to parse_some reaches the end of the buffer in the middle of parsing,
say after digesting the sequence 'f', 'a', 'l', member function stopped() will return false
and source_exhausted() will return true. Additional JSON text can be supplied to the parser,
parse_some called again, and parsing will resume from where it left off.
A typical application will repeatedly call the parse_some function
until stopped() returns true. A stopped state indicates that a content
visitor function returned false, an error occured, or a complete JSON
text has been consumed. If the latter, done() will return true.
As an alternative to repeatedly calling parse_some() until stopped()
returns true, when source_exhausted() is true and there is
no more input, finish_parse may be called.
check_done can be called to check if the input has any unconsumed
non-whitespace characters, which would normally be considered an error.
json_parser is used by the push parser basic_json_reader,
and by the pull parser basic_json_cursor.
json_parser is noncopyable and nonmoveable.
json_parser(); (1)
json_parser(const json_decode_options& options); (2)
json_parser(std::function<bool(json_errc,const ser_context&)> err_handler); (3)
json_parser(const json_decode_options& options,
std::function<bool(json_errc,const ser_context&)> err_handler); (4)
(1) Constructs a json_parser that uses default basic_json_options
and a default parse_error_handler.
(2) Constructs a json_parser that uses the specified basic_json_options
and a default parse_error_handler.
(3) Constructs a json_parser that uses default basic_json_options
and a specified parse_error_handler.
(4) Constructs a json_parser that uses the specified basic_json_options
and a specified parse_error_handler.
Note: It is the programmer's responsibility to ensure that json_reader does not outlive any error visitor passed in the constuctor.
void update(const string_view_type& sv)
void update(const char* data, std::size_t length)
Update the parser with a chunk of JSON
bool done() const
Returns true when the parser has consumed a complete JSON text, false otherwise
bool stopped() const
Returns true if the parser is stopped, false otherwise.
The parser may enter a stopped state as a result of a visitor
function returning false, an error occurred,
or after having consumed a complete JSON text.
bool finished() const
Returns true if the parser is finished parsing, false otherwise.
bool source_exhausted() const
Returns true if the input in the source buffer has been exhausted, false otherwise
void parse_some(json_visitor& visitor)
Parses the source until a complete json text has been consumed or the source has been exhausted.
Parse events are sent to the supplied visitor.
Throws a ser_error if parsing fails.
void parse_some(json_visitor<CharT>& visitor,
std::error_code& ec)
Parses the source until a complete json text has been consumed or the source has been exhausted.
Parse events are sent to the supplied visitor.
Sets ec to a json_errc if parsing fails.
void finish_parse(json_visitor<CharT>& visitor)
Called after source_exhausted() is true and there is no more input.
Repeatedly calls parse_some(visitor) until finished() returns true
Throws a ser_error if parsing fails.
void finish_parse(json_visitor<CharT>& visitor,
std::error_code& ec)
Called after source_exhausted() is true and there is no more input.
Repeatedly calls parse_some(visitor) until finished() returns true
Sets ec to a json_errc if parsing fails.
void skip_bom()
Reads the next JSON text from the stream and reports JSON events to a basic_json_visitor, such as a json_decoder. Throws a ser_error if parsing fails.
void check_done()
Throws if there are any unconsumed non-whitespace characters in the input. Throws a ser_error if parsing fails.
void check_done(std::error_code& ec)
Sets ec to a json_errc if parsing fails.
std::size_t reset() const
Resets the state of the parser to its initial state. In this state
stopped() returns false and done() returns false.
std::size_t restart() const
Resets the stopped state of the parser to false, allowing parsing
to continue.
int main()
{
json_parser parser;
jsoncons::json_decoder<json> decoder;
try
{
parser.update("10");
parser.parse_some(decoder);
std::cout << "(1) done: " << std::boolalpha << parser.done() << ", source_exhausted: " << parser.source_exhausted() << "\n\n";
parser.update(".5");
parser.parse_some(decoder); // This is the end, but the parser can't tell
std::cout << "(2) done: " << std::boolalpha << parser.done() << ", source_exhausted: " << parser.source_exhausted() << "\n\n";
parser.finish_parse(decoder); // Indicates that this is the end
std::cout << "(3) done: " << std::boolalpha << parser.done() << ", source_exhausted: " << parser.source_exhausted() << "\n\n";
parser.check_done(); // Checks if there are any unconsumed
// non-whitespace characters in the input
std::cout << "(4) done: " << std::boolalpha << parser.done() << ", source_exhausted: " << parser.source_exhausted() << "\n\n";
json j = decoder.get_result();
std::cout << "(5) " << j << "\n";
}
catch (const ser_error& e)
{
std::cout << e.what() << std::endl;
}
}Output:
(1) done: false, source_exhausted: true
(2) done: false, source_exhausted: true
(3) done: true, source_exhausted: true
(4) done: true, source_exhausted: true
(5) 10.5
int main()
{
json_parser parser;
jsoncons::json_decoder<json> decoder;
try
{
parser.update("[10");
parser.parse_some(decoder);
std::cout << "(1) done: " << std::boolalpha << parser.done() << ", source_exhausted: " << parser.source_exhausted() << "\n\n";
parser.update(".5]{}");
parser.parse_some(decoder); // The parser reaches the end at ']'
std::cout << "(2) done: " << std::boolalpha << parser.done() << ", source_exhausted: " << parser.source_exhausted() << "\n\n";
parser.finish_parse(decoder); // Indicates that this is the end
std::cout << "(3) done: " << std::boolalpha << parser.done() << ", source_exhausted: " << parser.source_exhausted() << "\n\n";
parser.check_done(); // Checks if there are any unconsumed
// non-whitespace characters in the input
(there are)
}
catch (const ser_error& e)
{
std::cout << "(4) " << e.what() << std::endl;
}
}Output:
(1) done: false, source_exhausted: true
(2) done: true, source_exhausted: false
(3) done: true, source_exhausted: false
(4) Unexpected non-whitespace character after JSON text at line 1 and column 7
int main()
{
std::string s = R"(
{
"A" : "NaN",
"B" : "Infinity",
"C" : "-Infinity"
}
)";
json_options options; // Implements json_decode_options
options.nan_to_str("NaN")
.inf_to_str("Infinity");
json_parser parser(options);
jsoncons::json_decoder<json> decoder;
try
{
parser.update(s);
parser.parse_some(decoder);
parser.finish_parse(decoder);
parser.check_done();
}
catch (const ser_error& e)
{
std::cout << e.what() << std::endl;
}
json j = decoder.get_result(); // performs move
if (j["A"].is<double>())
{
std::cout << "A: " << j["A"].as<double>() << std::endl;
}
if (j["B"].is<double>())
{
std::cout << "B: " << j["B"].as<double>() << std::endl;
}
if (j["C"].is<double>())
{
std::cout << "C: " << j["C"].as<double>() << std::endl;
}
}Output:
A: nan
B: inf
C: -inf