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◆ sax_parse() [1/2]
template<template< typename U, typename V, typename... Args > class ObjectType = std::map, template< typename U, typename... Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer>
template<typename SAX >
The SAX event lister must follow the interface of json_sax.
This function reads from a compatible input. Examples are:
- an array of 1-byte values
- strings with character/literal type with size of 1 byte
- input streams
- container with contiguous storage of 1-byte values. Compatible container types include
std::vector , std::string , std::array , std::valarray , and std::initializer_list . Furthermore, C-style arrays can be used with std::begin() /std::end() . User-defined containers can be used as long as they implement random-access iterators and a contiguous storage.
- Precondition
- Each element of the container has a size of 1 byte. Violating this precondition yields undefined behavior. This precondition is enforced with a static assertion.
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The container storage is contiguous. Violating this precondition yields undefined behavior. This precondition is enforced with an assertion.
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Each element of the container has a size of 1 byte. Violating this precondition yields undefined behavior. This precondition is enforced with a static assertion.
- Warning
- There is no way to enforce all preconditions at compile-time. If the function is called with a noncompliant container and with assertions switched off, the behavior is undefined and will most likely yield segmentation violation.
- Parameters
-
[in] | i | input to read from |
[in,out] | sax | SAX event listener |
[in] | format | the format to parse (JSON, CBOR, MessagePack, or UBJSON) |
[in] | strict | whether the input has to be consumed completely |
- Returns
- return value of the last processed SAX event
- Exceptions
-
parse_error.101 | if a parse error occurs; example: ""unexpected end of input; expected string literal"" |
parse_error.102 | if to_unicode fails or surrogate error |
parse_error.103 | if to_unicode fails |
- Complexity^^ Linear in the length of the input. The parser is a predictive
- LL(1) parser. The complexity can be higher if the SAX consumer sax has a super-linear complexity.
- Note
- A UTF-8 byte order mark is silently ignored.
- Example^^ The example below demonstrates the sax_parse() function
- reading from string and processing the events with a user-defined SAX event consumer. ^^
4 #include <nlohmann/json.hpp> 14 std::vector<std::string> events; 18 events.push_back( "value: null"); 22 bool boolean( bool val) override 24 events.push_back( "value: " + std::string(val ? "true" : "false")); 30 events.push_back( "value: " + std::to_string(val)); 36 events.push_back( "value: " + std::to_string(val)); 42 events.push_back( "value: " + s); 48 events.push_back( "value: " + val); 52 bool start_object(std::size_t elements) override 54 events.push_back( "start: object"); 58 bool end_object() override 60 events.push_back( "end: object"); 64 bool start_array(std::size_t elements) override 66 events.push_back( "start: array"); 70 bool end_array() override 72 events.push_back( "end: array"); 78 events.push_back( "key: " + val); 84 events.push_back( "error: " + std::string(ex.what())); 97 "Title": "View from 15th Floor", 99 "Url": "http://www.example.com/image/481989943", 104 "IDs": [116, 943, 234, 38793], 105 "Distance": 12.723374634 111 sax_event_consumer sec; 117 for ( auto& event : sec.events) 119 std::cout << "(" << event << ") "; 123 std::cout << "\nresult: " << std::boolalpha << result << std::endl; NumberFloatType number_float_t a type for a number (floating-point)
basic_json<> json default JSON class
static bool sax_parse(detail::input_adapter &&i, SAX *sax, input_format_t format=input_format_t::json, const bool strict=true) generate SAX events
NumberIntegerType number_integer_t a type for a number (integer)
NumberUnsignedType number_unsigned_t a type for a number (unsigned)
detail::parse_error parse_error exception indicating a parse error
StringType string_t a type for a string
json_sax< basic_json > json_sax_t SAX interface type, see nlohmann::json_sax.
detail::exception exception general exception of the basic_json class
Output (play with this example online):^^ (start: object) (key: Image) (start: object) (key: Width) (value: 800) (key: Height) (value: 600) (key: Title) (value: View from 15th Floor) (key: Thumbnail) (start: object) (key: Url) (value: http://www.example.com/image/481989943) (key: Height) (value: 125) (key: Width) (value: 100) (end: object) (key: Animated) (value: false) (key: IDs) (start: array) (value: 116) (value: 943) (value: 234) (value: 38793) (end: array) (key: Distance) (value: 12.723374634) (end: object) (end: object)
result: true
^^ The example code above can be translated withg++ -std=c++11 -Isingle_include doc/examples/sax_parse.cpp -o sax_parse
- Since
- version 3.2.0
Definition at line 18518 of file json.hpp.
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