#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 err_handler.
(2) Constructs a json_parser that uses the specified basic_json_options
and a default err_handler.
(3) Constructs a json_parser that uses default basic_json_options
and a specified err_handler.
(4) Constructs a json_parser that uses the specified basic_json_options
and a specified err_handler.
Note: It is the programmer's responsibility to ensure that a basic_json_parser does not outlive any string 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.
void reset() const
Resets the state of the parser to its initial state. In this state
stopped() returns false and done() returns false.
void 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