Complete documentation for 3.11.0 (#3464)

* 👥 update contributor and sponsor list

* 🚧 document BJData format

* 🚧 document BJData format

* 📝 clarified documentation of [json.exception.parse_error.112]

* ✏️ adjust titles

* 📝 add more examples

* 🚨 adjust warnings for index.md files

* 📝 add more examples

* 🔥 remove example for deprecated code

* 📝 add missing enum entry

* 📝 overwork table for binary formats

*  add test to create table for binary formats

* 📝 fix wording in example

* 📝 add more examples

* Update iterators.md (#3481)

*  add check for overloads to linter #3455

* 👥 update contributor list

* 📝 add more examples

* 📝 fix documentation

* 📝 add more examples

* 🎨 fix indentation

* 🔥 remove example for destructor

* 📝 overwork documentation

* Updated BJData documentation, #3464 (#3493)

* update bjdata.md for #3464

* Minor edit

* Fix URL typo

* Add info on demoting ND array to a 1-D optimized array when singleton dimension

Co-authored-by: Chaoqi Zhang <prncoprs@163.com>
Co-authored-by: Qianqian Fang <fangqq@gmail.com>
pull/3502/head
Niels Lohmann 2022-05-17 13:08:56 +02:00 committed by GitHub
parent a8a547d7a2
commit 6a7392058e
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
102 changed files with 1990 additions and 247 deletions

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@ -54,7 +54,7 @@ There are myriads of [JSON](https://json.org) libraries out there, and each may
- **Trivial integration**. Our whole code consists of a single header file [`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp). That's it. No library, no subproject, no dependencies, no complex build system. The class is written in vanilla C++11. All in all, everything should require no adjustment of your compiler flags or project settings.
- **Serious testing**. Our class is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](https://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [Core Infrastructure Initiative (CII) best practices](https://bestpractices.coreinfrastructure.org/projects/289).
- **Serious testing**. Our code is heavily [unit-tested](https://github.com/nlohmann/json/tree/develop/tests/src) and covers [100%](https://coveralls.io/r/nlohmann/json) of the code, including all exceptional behavior. Furthermore, we checked with [Valgrind](https://valgrind.org) and the [Clang Sanitizers](https://clang.llvm.org/docs/index.html) that there are no memory leaks. [Google OSS-Fuzz](https://github.com/google/oss-fuzz/tree/master/projects/json) additionally runs fuzz tests against all parsers 24/7, effectively executing billions of tests so far. To maintain high quality, the project is following the [Core Infrastructure Initiative (CII) best practices](https://bestpractices.coreinfrastructure.org/projects/289).
Other aspects were not so important to us:
@ -69,6 +69,10 @@ See the [contribution guidelines](https://github.com/nlohmann/json/blob/master/.
You can sponsor this library at [GitHub Sponsors](https://github.com/sponsors/nlohmann).
### :office: Corporate Sponsor
[![](https://upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Codacy-logo-black.svg/320px-Codacy-logo-black.svg.png)](https://github.com/codacy)
### :label: Named Sponsors
- [Michael Hartmann](https://github.com/reFX-Mike)
@ -1599,6 +1603,20 @@ I deeply appreciate the help of the following people.
- [Dirk Stolle](https://github.com/striezel) fixed typos in documentation.
- [Daniel Albuschat](https://github.com/daniel-kun) corrected the parameter name in the `parse` documentation.
- [Prince Mendiratta](https://github.com/Prince-Mendiratta) fixed a link to the FAQ.
- [Florian Albrechtskirchinger](https://github.com/falbrechtskirchinger) implemented `std::string_view` support for object keys and made dozens of other improvements.
- [Qianqian Fang](https://github.com/fangq) implemented the Binary JData (BJData) format.
- [pketelsen](https://github.com/pketelsen) added macros `NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT` and `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT`.
- [DarkZeros](https://github.com/DarkZeros) adjusted to code to not clash with Arduino defines.
- [flagarde](https://github.com/flagarde) fixed the output of `meta()` for MSVC.
- [Giovanni Cerretani](https://github.com/gcerretani) fixed a check for `std::filesystem`.
- [Dimitris Apostolou](https://github.com/rex4539) fixed a typo.
- [Ferry Huberts](https://github.com/fhuberts) fixed a typo.
- [Michael Nosthoff](https://github.com/heinemml) fixed a typo.
- [JungHoon Lee](https://github.com/jhnlee) fixed a typo.
- [Faruk D.](https://github.com/fdiblen) fixed the CITATION.CFF file.
- [Andrea Cocito](https://github.com/puffetto) added a clarification on macro usage to the documentation.
- [Krzysiek Karbowiak](https://github.com/kkarbowiak) refactored the tests to use `CHECK_THROWS_WITH_AS`.
- [Chaoqi Zhang](https://github.com/prncoprs) fixed a typo.
Thanks a lot for helping out! Please [let me know](mailto:mail@nlohmann.me) if I forgot someone.
@ -1613,7 +1631,7 @@ The library itself consists of a single header file licensed under the MIT licen
- [**Artistic Style**](http://astyle.sourceforge.net) for automatic source code indentation
- [**Clang**](https://clang.llvm.org) for compilation with code sanitizers
- [**CMake**](https://cmake.org) for build automation
- [**Codacity**](https://www.codacy.com) for further [code analysis](https://www.codacy.com/app/nlohmann/json)
- [**Codacy**](https://www.codacy.com) for further [code analysis](https://www.codacy.com/app/nlohmann/json)
- [**Coveralls**](https://coveralls.io) to measure [code coverage](https://coveralls.io/github/nlohmann/json)
- [**Coverity Scan**](https://scan.coverity.com) for [static analysis](https://scan.coverity.com/projects/nlohmann-json)
- [**cppcheck**](http://cppcheck.sourceforge.net) for static analysis

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@ -0,0 +1,23 @@
#include <iostream>
#include <nlohmann/json.hpp>
// define a byte container based on std::vector
using byte_container_with_subtype = nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>;
using json = nlohmann::json;
int main()
{
// (1) create empty container
auto c1 = byte_container_with_subtype();
std::vector<std::uint8_t> bytes = {{0xca, 0xfe, 0xba, 0xbe}};
// (2) create container
auto c2 = byte_container_with_subtype(bytes);
// (3) create container with subtype
auto c3 = byte_container_with_subtype(bytes, 42);
std::cout << json(c1) << "\n" << json(c2) << "\n" << json(c3) << std::endl;
}

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@ -0,0 +1,3 @@
{"bytes":[],"subtype":null}
{"bytes":[202,254,186,190],"subtype":null}
{"bytes":[202,254,186,190],"subtype":42}

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@ -0,0 +1,21 @@
#include <iostream>
#include <nlohmann/json.hpp>
// define a byte container based on std::vector
using byte_container_with_subtype = nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>;
using json = nlohmann::json;
int main()
{
std::vector<std::uint8_t> bytes = {{0xca, 0xfe, 0xba, 0xbe}};
// create container with subtype
auto c1 = byte_container_with_subtype(bytes, 42);
std::cout << "before calling clear_subtype(): " << json(c1) << '\n';
c1.clear_subtype();
std::cout << "after calling clear_subtype(): " << json(c1) << '\n';
}

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@ -0,0 +1,2 @@
before calling clear_subtype(): {"bytes":[202,254,186,190],"subtype":42}
after calling clear_subtype(): {"bytes":[202,254,186,190],"subtype":null}

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@ -0,0 +1,19 @@
#include <iostream>
#include <nlohmann/json.hpp>
// define a byte container based on std::vector
using byte_container_with_subtype = nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>;
int main()
{
std::vector<std::uint8_t> bytes = {{0xca, 0xfe, 0xba, 0xbe}};
// create container
auto c1 = byte_container_with_subtype(bytes);
// create container with subtype
auto c2 = byte_container_with_subtype(bytes, 42);
std::cout << std::boolalpha << "c1.has_subtype() = " << c1.has_subtype()
<< "\nc2.has_subtype() = " << c2.has_subtype() << std::endl;
}

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@ -0,0 +1,2 @@
c1.has_subtype() = false
c2.has_subtype() = true

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@ -0,0 +1,22 @@
#include <iostream>
#include <nlohmann/json.hpp>
// define a byte container based on std::vector
using byte_container_with_subtype = nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>;
using json = nlohmann::json;
int main()
{
std::vector<std::uint8_t> bytes = {{0xca, 0xfe, 0xba, 0xbe}};
// create container without subtype
auto c = byte_container_with_subtype(bytes);
std::cout << "before calling set_subtype(42): " << json(c) << '\n';
// set the subtype
c.set_subtype(42);
std::cout << "after calling set_subtype(42): " << json(c) << '\n';
}

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@ -0,0 +1,2 @@
before calling set_subtype(42): {"bytes":[202,254,186,190],"subtype":null}
after calling set_subtype(42): {"bytes":[202,254,186,190],"subtype":42}

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@ -0,0 +1,22 @@
#include <iostream>
#include <nlohmann/json.hpp>
// define a byte container based on std::vector
using byte_container_with_subtype = nlohmann::byte_container_with_subtype<std::vector<std::uint8_t>>;
int main()
{
std::vector<std::uint8_t> bytes = {{0xca, 0xfe, 0xba, 0xbe}};
// create container
auto c1 = byte_container_with_subtype(bytes);
// create container with subtype
auto c2 = byte_container_with_subtype(bytes, 42);
std::cout << "c1.subtype() = " << c1.subtype()
<< "\nc2.subtype() = " << c2.subtype() << std::endl;
// in case no subtype is set, return special value
assert(c1.subtype() == static_cast<byte_container_with_subtype::subtype_type>(-1));
}

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@ -0,0 +1,2 @@
c1.subtype() = 18446744073709551615
c2.subtype() = 42

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@ -0,0 +1,28 @@
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// tagged byte string
std::vector<std::uint8_t> vec = {{0xd8, 0x42, 0x44, 0xcA, 0xfe, 0xba, 0xbe}};
// cbor_tag_handler_t::error throws
try
{
auto b_throw_on_tag = json::from_cbor(vec, true, true, json::cbor_tag_handler_t::error);
}
catch (json::parse_error& e)
{
std::cout << e.what() << std::endl;
}
// cbor_tag_handler_t::ignore ignores the tag
auto b_ignore_tag = json::from_cbor(vec, true, true, json::cbor_tag_handler_t::ignore);
std::cout << b_ignore_tag << std::endl;
// cbor_tag_handler_t::store stores the tag as binary subtype
auto b_store_tag = json::from_cbor(vec, true, true, json::cbor_tag_handler_t::store);
std::cout << b_store_tag << std::endl;
}

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@ -0,0 +1,3 @@
[json.exception.parse_error.112] parse error at byte 1: syntax error while parsing CBOR value: invalid byte: 0xD8
{"bytes":[202,254,186,190],"subtype":null}
{"bytes":[202,254,186,190],"subtype":66}

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@ -0,0 +1,11 @@
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
std::cout << std::boolalpha
<< "one < two : " << json::default_object_comparator_t{}("one", "two") << "\n"
<< "three < four : " << json::default_object_comparator_t{}("three", "four") << std::endl;
}

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@ -0,0 +1,2 @@
one < two : true
three < four : false

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@ -0,0 +1,24 @@
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// create JSON value with invalid UTF-8 byte sequence
json j_invalid = "ä\xA9ü";
try
{
std::cout << j_invalid.dump() << std::endl;
}
catch (json::type_error& e)
{
std::cout << e.what() << std::endl;
}
std::cout << "string with replaced invalid characters: "
<< j_invalid.dump(-1, ' ', false, json::error_handler_t::replace)
<< "\nstring with ignored invalid characters: "
<< j_invalid.dump(-1, ' ', false, json::error_handler_t::ignore)
<< '\n';
}

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@ -0,0 +1,3 @@
[json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9
string with replaced invalid characters: "ä<>ü"
string with ignored invalid characters: "äü"

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@ -0,0 +1,20 @@
#include <iostream>
#include <iomanip>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// create byte vector
std::vector<std::uint8_t> v = {0x7B, 0x69, 0x07, 0x63, 0x6F, 0x6D, 0x70, 0x61,
0x63, 0x74, 0x54, 0x69, 0x06, 0x73, 0x63, 0x68,
0x65, 0x6D, 0x61, 0x69, 0x00, 0x7D
};
// deserialize it with BJData
json j = json::from_bjdata(v);
// print the deserialized JSON value
std::cout << std::setw(2) << j << std::endl;
}

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@ -0,0 +1,4 @@
{
"compact": true,
"schema": 0
}

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@ -0,0 +1,18 @@
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
auto alloc = json::get_allocator();
using traits_t = std::allocator_traits<decltype(alloc)>;
json* j = traits_t::allocate(alloc, 1);
traits_t::construct(alloc, j, "Hello, world!");
std::cout << *j << std::endl;
traits_t::destroy(alloc, j);
traits_t::deallocate(alloc, j, 1);
}

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@ -0,0 +1 @@
"Hello, world!"

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@ -1,29 +0,0 @@
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// create JSON values
json j_object = {{"one", 1}, {"two", 2}};
json j_array = {1, 2, 4, 8, 16};
//////////////////////////////////////////////////////////////////////////
// The static function iterator_wrapper was deprecated in version 3.1.0
// and will be removed in version 4.0.0. Please replace all occurrences
// of iterator_wrapper(j) with j.items().
//////////////////////////////////////////////////////////////////////////
// example for an object
for (auto& x : json::iterator_wrapper(j_object))
{
std::cout << "key: " << x.key() << ", value: " << x.value() << '\n';
}
// example for an array
for (auto& x : json::iterator_wrapper(j_array))
{
std::cout << "key: " << x.key() << ", value: " << x.value() << '\n';
}
}

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@ -1,7 +0,0 @@
key: one, value: 1
key: two, value: 2
key: 0, value: 1
key: 1, value: 2
key: 2, value: 4
key: 3, value: 8
key: 4, value: 16

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@ -0,0 +1,19 @@
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
// different JSON Pointers
json::json_pointer ptr1("/foo/0");
json::json_pointer ptr2("/a~1b");
// implicit conversion to string
std::string s;
s += ptr1;
s += "\n";
s += ptr2;
std::cout << s << std::endl;
}

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@ -0,0 +1,2 @@
/foo/0
/a~1b

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@ -0,0 +1,13 @@
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
json::json_pointer::string_t s = "This is a string.";
std::cout << s << std::endl;
std::cout << std::boolalpha << std::is_same<json::json_pointer::string_t, json::string_t>::value << std::endl;
}

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@ -0,0 +1,2 @@
This is a string.
true

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@ -19,7 +19,6 @@ int main()
json::json_pointer ptr11("/ ");
json::json_pointer ptr12("/m~0n");
std::cout << ptr1.to_string() << '\n'
<< ptr2.to_string() << '\n'
<< ptr3.to_string() << '\n'

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@ -0,0 +1,12 @@
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
std::cout << "JSON for Modern C++ version "
<< NLOHMANN_JSON_VERSION_MAJOR << "."
<< NLOHMANN_JSON_VERSION_MINOR << "."
<< NLOHMANN_JSON_VERSION_PATCH << std::endl;
}

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@ -0,0 +1 @@
JSON for Modern C++ version 3.10.5

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@ -0,0 +1,11 @@
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
std::cout << std::boolalpha
<< "json::object_comparator_t(\"one\", \"two\") = " << json::object_comparator_t{}("one", "two") << "\n"
<< "json::object_comparator_t(\"three\", \"four\") = " << json::object_comparator_t{}("three", "four") << std::endl;
}

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@ -0,0 +1,2 @@
json::object_comparator_t("one", "two") = true
json::object_comparator_t("three", "four") = false

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@ -0,0 +1,14 @@
#include <iostream>
#include <nlohmann/json.hpp>
using ordered_json = nlohmann::ordered_json;
int main()
{
ordered_json j;
j["one"] = 1;
j["two"] = 2;
j["three"] = 3;
std::cout << j.dump(2) << '\n';
}

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@ -0,0 +1,5 @@
{
"one": 1,
"two": 2,
"three": 3
}

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@ -6,7 +6,7 @@
using json = nlohmann::json;
// a simple event consumer that collects string representations of the passed
// values; not inheriting from json::json_sax_t is not required, but can
// values; note inheriting from json::json_sax_t is not required, but can
// help not to forget a required function
class sax_event_consumer : public json::json_sax_t
{
@ -15,79 +15,79 @@ class sax_event_consumer : public json::json_sax_t
bool null() override
{
events.push_back("value: null");
events.push_back("null()");
return true;
}
bool boolean(bool val) override
{
events.push_back("value: " + std::string(val ? "true" : "false"));
events.push_back("boolean(val=" + std::string(val ? "true" : "false") + ")");
return true;
}
bool number_integer(number_integer_t val) override
{
events.push_back("value: " + std::to_string(val));
events.push_back("number_integer(val=" + std::to_string(val) + ")");
return true;
}
bool number_unsigned(number_unsigned_t val) override
{
events.push_back("value: " + std::to_string(val));
events.push_back("number_unsigned(val=" + std::to_string(val) + ")");
return true;
}
bool number_float(number_float_t val, const string_t& s) override
{
events.push_back("value: " + s);
events.push_back("number_float(val=" + std::to_string(val) + ", s=" + s + ")");
return true;
}
bool string(string_t& val) override
{
events.push_back("value: " + val);
events.push_back("string(val=" + val + ")");
return true;
}
bool start_object(std::size_t elements) override
{
events.push_back("start: object");
events.push_back("start_object(elements=" + std::to_string(elements) + ")");
return true;
}
bool end_object() override
{
events.push_back("end: object");
events.push_back("end_object()");
return true;
}
bool start_array(std::size_t elements) override
{
events.push_back("start: array");
events.push_back("start_array(elements=" + std::to_string(elements) + ")");
return true;
}
bool end_array() override
{
events.push_back("end: array");
events.push_back("end_array()");
return true;
}
bool key(string_t& val) override
{
events.push_back("key: " + val);
events.push_back("key(val=" + val + ")");
return true;
}
bool binary(json::binary_t& val) override
{
events.push_back("binary");
events.push_back("binary(val=[...])");
return true;
}
bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex) override
{
events.push_back("error: " + std::string(ex.what()));
events.push_back("parse_error(position=" + std::to_string(position) + ", last_token=" + last_token + ",\n ex=" + std::string(ex.what()) + ")");
return false;
}
};
@ -107,22 +107,23 @@ int main()
"Width": 100
},
"Animated" : false,
"IDs": [116, 943, 234, 38793],
"IDs": [116, 943, 234, -38793],
"DeletionDate": null,
"Distance": 12.723374634
}
}
}]
)";
// create a SAX event consumer object
sax_event_consumer sec;
// parse and serialize JSON
// parse JSON
bool result = json::sax_parse(text, &sec);
// output the recorded events
for (auto& event : sec.events)
{
std::cout << "(" << event << ") ";
std::cout << event << "\n";
}
// output the result of sax_parse

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@ -1,2 +1,37 @@
(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
start_object(elements=18446744073709551615)
key(val=Image)
start_object(elements=18446744073709551615)
key(val=Width)
number_unsigned(val=800)
key(val=Height)
number_unsigned(val=600)
key(val=Title)
string(val=View from 15th Floor)
key(val=Thumbnail)
start_object(elements=18446744073709551615)
key(val=Url)
string(val=http://www.example.com/image/481989943)
key(val=Height)
number_unsigned(val=125)
key(val=Width)
number_unsigned(val=100)
end_object()
key(val=Animated)
boolean(val=false)
key(val=IDs)
start_array(elements=18446744073709551615)
number_unsigned(val=116)
number_unsigned(val=943)
number_unsigned(val=234)
number_integer(val=-38793)
end_array()
key(val=DeletionDate)
null()
key(val=Distance)
number_float(val=12.723375, s=12.723374634)
end_object()
end_object()
parse_error(position=460, last_token=12.723374634<U+000A> }<U+000A> }],
ex=[json.exception.parse_error.101] parse error at line 17, column 6: syntax error while parsing value - unexpected ']'; expected end of input)
result: false

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@ -0,0 +1,114 @@
#include <iostream>
#include <iomanip>
#include <sstream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
// a simple event consumer that collects string representations of the passed
// values; note inheriting from json::json_sax_t is not required, but can
// help not to forget a required function
class sax_event_consumer : public json::json_sax_t
{
public:
std::vector<std::string> events;
bool null() override
{
events.push_back("null()");
return true;
}
bool boolean(bool val) override
{
events.push_back("boolean(val=" + std::string(val ? "true" : "false") + ")");
return true;
}
bool number_integer(number_integer_t val) override
{
events.push_back("number_integer(val=" + std::to_string(val) + ")");
return true;
}
bool number_unsigned(number_unsigned_t val) override
{
events.push_back("number_unsigned(val=" + std::to_string(val) + ")");
return true;
}
bool number_float(number_float_t val, const string_t& s) override
{
events.push_back("number_float(val=" + std::to_string(val) + ", s=" + s + ")");
return true;
}
bool string(string_t& val) override
{
events.push_back("string(val=" + val + ")");
return true;
}
bool start_object(std::size_t elements) override
{
events.push_back("start_object(elements=" + std::to_string(elements) + ")");
return true;
}
bool end_object() override
{
events.push_back("end_object()");
return true;
}
bool start_array(std::size_t elements) override
{
events.push_back("start_array(elements=" + std::to_string(elements) + ")");
return true;
}
bool end_array() override
{
events.push_back("end_array()");
return true;
}
bool key(string_t& val) override
{
events.push_back("key(val=" + val + ")");
return true;
}
bool binary(json::binary_t& val) override
{
events.push_back("binary(val=[...])");
return true;
}
bool parse_error(std::size_t position, const std::string& last_token, const json::exception& ex) override
{
events.push_back("parse_error(position=" + std::to_string(position) + ", last_token=" + last_token + ",\n ex=" + std::string(ex.what()) + ")");
return false;
}
};
int main()
{
// CBOR byte string
std::vector<std::uint8_t> vec = {{0x44, 0xcA, 0xfe, 0xba, 0xbe}};
// create a SAX event consumer object
sax_event_consumer sec;
// parse CBOR
bool result = json::sax_parse(vec, &sec, json::input_format_t::cbor);
// output the recorded events
for (auto& event : sec.events)
{
std::cout << event << "\n";
}
// output the result of sax_parse
std::cout << "\nresult: " << std::boolalpha << result << std::endl;
}

View File

@ -0,0 +1,3 @@
binary(val=[...])
result: true

View File

@ -0,0 +1,63 @@
#include <iostream>
#include <iomanip>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
// function to print BJData's diagnostic format
void print_byte(uint8_t byte)
{
if (32 < byte and byte < 128)
{
std::cout << (char)byte;
}
else
{
std::cout << (int)byte;
}
}
int main()
{
// create a JSON value
json j = R"({"compact": true, "schema": false})"_json;
// serialize it to BJData
std::vector<std::uint8_t> v = json::to_bjdata(j);
// print the vector content
for (auto& byte : v)
{
print_byte(byte);
}
std::cout << std::endl;
// create an array of numbers
json array = {1, 2, 3, 4, 5, 6, 7, 8};
// serialize it to BJData using default representation
std::vector<std::uint8_t> v_array = json::to_bjdata(array);
// serialize it to BJData using size optimization
std::vector<std::uint8_t> v_array_size = json::to_bjdata(array, true);
// serialize it to BJData using type optimization
std::vector<std::uint8_t> v_array_size_and_type = json::to_bjdata(array, true, true);
// print the vector contents
for (auto& byte : v_array)
{
print_byte(byte);
}
std::cout << std::endl;
for (auto& byte : v_array_size)
{
print_byte(byte);
}
std::cout << std::endl;
for (auto& byte : v_array_size_and_type)
{
print_byte(byte);
}
std::cout << std::endl;
}

View File

@ -0,0 +1,4 @@
{i7compactTi6schemaF}
[i1i2i3i4i5i6i7i8]
[#i8i1i2i3i4i5i6i7i8
[$i#i812345678

View File

@ -184,6 +184,7 @@ Strong exception safety: if an exception occurs, the original value stays intact
## See also
- documentation on [checked access](../../features/element_access/checked_access.md)
- see [`operator[]`](operator%5B%5D.md) for unchecked access by reference
- see [`value`](value.md) for access with default value

View File

@ -241,7 +241,7 @@ basic_json(basic_json&& other) noexcept;
- Overload 5:
!!! note
!!! note "Empty initializer list"
When used without parentheses around an empty initializer list, `basic_json()` is called instead of this
function, yielding the JSON `#!json null` value.

View File

@ -20,6 +20,23 @@ ignore
store
: store tagged values as binary container with subtype (for bytes 0xd8..0xdb)
## Examples
??? example
The example below shows how the different values of the `cbor_tag_handler_t` influence the behavior of
[`from_cbor`](from_cbor.md) when reading a tagged byte string.
```cpp
--8<-- "examples/cbor_tag_handler_t.cpp"
```
Output:
```json
--8<-- "examples/cbor_tag_handler_t.output"
```
## Version history
- Added in version 3.9.0. Added value `store` in 3.10.0.

View File

@ -60,8 +60,8 @@ Logarithmic in the size of the JSON object.
## Notes
1. This method always returns `#!cpp false` when executed on a JSON type that is not an object.
2. This method can be executed on any JSON value type.
- This method always returns `#!cpp false` when executed on a JSON type that is not an object.
- This method can be executed on any JSON value type.
!!! info "Postconditions"

View File

@ -14,6 +14,22 @@ when looking up a key in an object.
The actual comparator used depends on [`object_t`](object_t.md) and can be obtained via
[`object_comparator_t`](object_comparator_t.md).
## Examples
??? example
The example below demonstrates the default comparator.
```cpp
--8<-- "examples/default_object_comparator_t.cpp"
```
Output:
```json
--8<-- "examples/default_object_comparator_t.output"
```
## Version history
- Added in version 3.11.0.

View File

@ -20,6 +20,23 @@ replace
ignore
: ignore invalid UTF-8 sequences; all bytes are copied to the output unchanged
## Examples
??? example
The example below shows how the different values of the `error_handler_t` influence the behavior of
[`dump`](dump.md) when reading serializing an invalid UTF-8 sequence.
```cpp
--8<-- "examples/error_handler_t.cpp"
```
Output:
```json
--8<-- "examples/error_handler_t.output"
```
## Version history
- Added in version 3.4.0.

View File

@ -0,0 +1,93 @@
# <small>nlohmann::basic_json::</small>from_bjdata
```cpp
// (1)
template<typename InputType>
static basic_json from_bjdata(InputType&& i,
const bool strict = true,
const bool allow_exceptions = true);
// (2)
template<typename IteratorType>
static basic_json from_bjdata(IteratorType first, IteratorType last,
const bool strict = true,
const bool allow_exceptions = true);
```
Deserializes a given input to a JSON value using the BJData (Binary JData) serialization format.
1. Reads from a compatible input.
2. Reads from an iterator range.
The exact mapping and its limitations is described on a [dedicated page](../../features/binary_formats/bjdata.md).
## Template parameters
`InputType`
: A compatible input, for instance:
- an `std::istream` object
- a `FILE` pointer
- a C-style array of characters
- a pointer to a null-terminated string of single byte characters
- an object `obj` for which `begin(obj)` and `end(obj)` produces a valid pair of iterators.
`IteratorType`
: a compatible iterator type
## Parameters
`i` (in)
: an input in BJData format convertible to an input adapter
`first` (in)
: iterator to start of the input
`last` (in)
: iterator to end of the input
`strict` (in)
: whether to expect the input to be consumed until EOF (`#!cpp true` by default)
`allow_exceptions` (in)
: whether to throw exceptions in case of a parse error (optional, `#!cpp true` by default)
## Return value
deserialized JSON value; in case of a parse error and `allow_exceptions` set to `#!cpp false`, the return value will be
`value_t::discarded`. The latter can be checked with [`is_discarded`](is_discarded.md).
## Exception safety
Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
## Exceptions
- Throws [parse_error.110](../../home/exceptions.md#jsonexceptionparse_error110) if the given input ends prematurely or
the end of file was not reached when `strict` was set to true
- Throws [parse_error.112](../../home/exceptions.md#jsonexceptionparse_error112) if a parse error occurs
- Throws [parse_error.113](../../home/exceptions.md#jsonexceptionparse_error113) if a string could not be parsed
successfully
## Complexity
Linear in the size of the input.
## Examples
??? example
The example shows the deserialization of a byte vector in BJData format to a JSON value.
```cpp
--8<-- "examples/from_bjdata.cpp"
```
Output:
```json
--8<-- "examples/from_bjdata.output"
```
## Version history
- Added in version 3.11.0.

View File

@ -10,10 +10,22 @@ Returns the allocator associated with the container.
associated allocator
## Examples
??? example
The example shows how `get_allocator()` is used to created `json` values.
```cpp
--8<-- "examples/get_allocator.cpp"
```
Output:
```json
--8<-- "examples/get_allocator.output"
```
## Version history
- Unknown.
!!! note
This documentation page is a stub.
- Added in version 1.0.0.

View File

@ -268,10 +268,12 @@ Access to the JSON value
### Binary formats
- [**from_bjdata**](from_bjdata.md) (_static_) - create a JSON value from an input in BJData format
- [**from_bson**](from_bson.md) (_static_) - create a JSON value from an input in BSON format
- [**from_cbor**](from_cbor.md) (_static_) - create a JSON value from an input in CBOR format
- [**from_msgpack**](from_msgpack.md) (_static_) - create a JSON value from an input in MessagePack format
- [**from_ubjson**](from_ubjson.md) (_static_) - create a JSON value from an input in UBJSON format
- [**to_bjdata**](to_bjdata.md) (_static_) - create a BJData serialization of a given JSON value
- [**to_bson**](to_bson.md) (_static_) - create a BSON serialization of a given JSON value
- [**to_cbor**](to_cbor.md) (_static_) - create a CBOR serialization of a given JSON value
- [**to_msgpack**](to_msgpack.md) (_static_) - create a MessagePack serialization of a given JSON value

View File

@ -6,7 +6,8 @@ enum class input_format_t {
cbor,
msgpack,
ubjson,
bson
bson,
bjdata
};
```
@ -27,6 +28,25 @@ ubjson
bson
: BSON (Binary JSON)
bjdata
: BJData (Binary JData)
## Examples
??? example
The example below shows how an `input_format_t` enum value is passed to `sax_parse` to set the input format to CBOR.
```cpp
--8<-- "examples/sax_parse__binary.cpp"
```
Output:
```json
--8<-- "examples/sax_parse__binary.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -1,6 +1,5 @@
# <small>nlohmann::basic_json::</small>object_comparator_t
```cpp
using object_comparator_t = typename object_t::key_compare;
// or
@ -10,6 +9,22 @@ using object_comparator_t = default_object_comparator_t;
The comparator used by [`object_t`](object_t.md). Defined as `#!cpp typename object_t::key_compare` if available,
and [`default_object_comparator_t`](default_object_comparator_t.md) otherwise.
## Examples
??? example
The example below demonstrates the used object comparator.
```cpp
--8<-- "examples/object_comparator_t.cpp"
```
Output:
```json
--8<-- "examples/object_comparator_t.output"
```
## Version history
- Added in version 3.0.0.

View File

@ -41,12 +41,9 @@ reference operator+=(initializer_list_t init);
## Exceptions
1. The function can throw the following exceptions:
- Throws [`type_error.308`](../../home/exceptions.md#jsonexceptiontype_error308) when called on a type other than
JSON array or null; example: `"cannot use operator+=() with number"`
2. The function can throw the following exceptions:
- Throws [`type_error.308`](../../home/exceptions.md#jsonexceptiontype_error308) when called on a type other than
JSON object or null; example: `"cannot use operator+=() with number"`
All functions can throw the following exception:
- Throws [`type_error.308`](../../home/exceptions.md#jsonexceptiontype_error308) when called on a type other than
JSON array or null; example: `"cannot use operator+=() with number"`
## Complexity

View File

@ -198,6 +198,8 @@ Strong exception safety: if an exception occurs, the original value stays intact
## See also
- documentation on [unchecked access](../../features/element_access/unchecked_access.md)
- documentation on [runtime assertions](../../features/assertions.md)
- see [`at`](at.md) for access by reference with range checking
- see [`value`](value.md) for access with default value

View File

@ -56,7 +56,6 @@ Linear in the size of the JSON value.
[`JSON_USE_IMPLICIT_CONVERSIONS`](../macros/json_use_implicit_conversions.md) to `0` and replace any implicit
conversions with calls to [`get`](../basic_json/get.md).
## Examples
??? example

View File

@ -44,13 +44,13 @@ Linear.
## Notes
!!! note
!!! note "Comparing special values"
- NaN values never compare equal to themselves or to other NaN values.
- JSON `#!cpp null` values are all equal.
- Discarded values never compare equal to themselves.
!!! note
!!! note "Comparing floating-point numbers"
Floating-point numbers inside JSON values numbers are compared with `json::number_float_t::operator==` which is
`double::operator==` by default. To compare floating-point while respecting an epsilon, an alternative

View File

@ -37,12 +37,9 @@ void push_back(initializer_list_t init);
## Exceptions
1. The function can throw the following exceptions:
- Throws [`type_error.308`](../../home/exceptions.md#jsonexceptiontype_error308) when called on a type other than
JSON array or null; example: `"cannot use push_back() with number"`
2. The function can throw the following exceptions:
- Throws [`type_error.308`](../../home/exceptions.md#jsonexceptiontype_error308) when called on a type other than
JSON object or null; example: `"cannot use push_back() with number"`
All functions can throw the following exception:
- Throws [`type_error.308`](../../home/exceptions.md#jsonexceptiontype_error308) when called on a type other than
JSON array or null; example: `"cannot use push_back() with number"`
## Complexity

View File

@ -0,0 +1,70 @@
# <small>nlohmann::basic_json::</small>to_bjdata
```cpp
// (1)
static std::vector<std::uint8_t> to_bjdata(const basic_json& j,
const bool use_size = false,
const bool use_type = false);
// (2)
static void to_bjdata(const basic_json& j, detail::output_adapter<std::uint8_t> o,
const bool use_size = false, const bool use_type = false);
static void to_bjdata(const basic_json& j, detail::output_adapter<char> o,
const bool use_size = false, const bool use_type = false);
```
Serializes a given JSON value `j` to a byte vector using the BJData (Binary JData) serialization format. BJData
aims to be more compact than JSON itself, yet more efficient to parse.
1. Returns a byte vector containing the BJData serialization.
2. Writes the BJData serialization to an output adapter.
The exact mapping and its limitations is described on a [dedicated page](../../features/binary_formats/bjdata.md).
## Parameters
`j` (in)
: JSON value to serialize
`o` (in)
: output adapter to write serialization to
`use_size` (in)
: whether to add size annotations to container types; optional, `#!cpp false` by default.
`use_type` (in)
: whether to add type annotations to container types (must be combined with `#!cpp use_size = true`); optional,
`#!cpp false` by default.
## Return value
1. BJData serialization as byte vector
2. (none)
## Exception safety
Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
## Complexity
Linear in the size of the JSON value `j`.
## Examples
??? example
The example shows the serialization of a JSON value to a byte vector in BJData format.
```cpp
--8<-- "examples/to_bjdata.cpp"
```
Output:
```json
--8<-- "examples/to_bjdata.output"
```
## Version history
- Added in version 3.11.0.

View File

@ -29,6 +29,22 @@ distinguishes these three types for numbers: [`number_unsigned_t`](number_unsign
[`number_integer_t`](number_integer_t.md) is used for signed integers, and [`number_float_t`](number_float_t.md) is used
for floating-point numbers or to approximate integers which do not fit in the limits of their respective type.
## Examples
??? example
The following code how `type()` queries the `value_t` for all JSON types.
```cpp
--8<-- "examples/type.cpp"
```
Output:
```json
--8<-- "examples/type.output"
```
## Version history
- Added in version 1.0.0.

View File

@ -25,6 +25,22 @@ byte_container_with_subtype(container_type&& container, subtype_type subtype);
`subtype` (in)
: subtype
## Examples
??? example
The example below demonstrates how byte containers can be created.
```cpp
--8<-- "examples/byte_container_with_subtype__byte_container_with_subtype.cpp"
```
Output:
```json
--8<-- "examples/byte_container_with_subtype__byte_container_with_subtype.output"
```
## Version history
Since version 3.8.0.

View File

@ -15,6 +15,22 @@ No-throw guarantee: this function never throws exceptions.
Constant.
## Examples
??? example
The example below demonstrates how `clear_subtype` can remove subtypes.
```cpp
--8<-- "examples/byte_container_with_subtype__clear_subtype.cpp"
```
Output:
```json
--8<-- "examples/byte_container_with_subtype__clear_subtype.output"
```
## Version history
Since version 3.8.0.

View File

@ -18,6 +18,22 @@ No-throw guarantee: this function never throws exceptions.
Constant.
## Examples
??? example
The example below demonstrates how `has_subtype` can check whether a subtype was set.
```cpp
--8<-- "examples/byte_container_with_subtype__has_subtype.cpp"
```
Output:
```json
--8<-- "examples/byte_container_with_subtype__has_subtype.output"
```
## Version history
Since version 3.8.0.

View File

@ -20,6 +20,22 @@ No-throw guarantee: this function never throws exceptions.
Constant.
## Examples
??? example
The example below demonstrates how a subtype can be set with `set_subtype`.
```cpp
--8<-- "examples/byte_container_with_subtype__set_subtype.cpp"
```
Output:
```json
--8<-- "examples/byte_container_with_subtype__set_subtype.output"
```
## Version history
Since version 3.8.0.

View File

@ -19,6 +19,23 @@ No-throw guarantee: this function never throws exceptions.
Constant.
## Examples
??? example
The example below demonstrates how the subtype can be retrieved with `subtype`. Note how `subtype_type(-1)` is
returned for container `c1`.
```cpp
--8<-- "examples/byte_container_with_subtype__subtype.cpp"
```
Output:
```json
--8<-- "examples/byte_container_with_subtype__subtype.output"
```
## Version history
- Added in version 3.8.0

View File

@ -7,6 +7,22 @@ using json = basic_json<>;
This type is the default specialization of the [basic_json](basic_json/index.md) class which uses the standard template
types.
## Examples
??? example
The example below demonstrates how to use the type `nlohmann::json`.
```cpp
--8<-- "examples/README.cpp"
```
Output:
```json
--8<-- "examples/README.output"
```
## Version history
Since version 1.0.0.

View File

@ -14,11 +14,11 @@ are the base for JSON patches.
`RefStringType`
: the string type used for the reference tokens making up the JSON pointer
## Notes
!!! warning "Deprecation"
For backwards compatibility `RefStringType` may also be a specialization of [`basic_json`](../basic_json/index.md) in
which case `string_t` will be deduced as [`basic_json::string_t`](../basic_json/string_t.md). This feature is deprecated
and may be removed in a future major version.
For backwards compatibility `RefStringType` may also be a specialization of [`basic_json`](../basic_json/index.md)
in which case `string_t` will be deduced as [`basic_json::string_t`](../basic_json/string_t.md). This feature is
deprecated and may be removed in a future major version.
## Member types

View File

@ -19,6 +19,22 @@ operator string_t() const
}
```
## Examples
??? example
The example shows how JSON Pointers can be implicitly converted to strings.
```cpp
--8<-- "examples/json_pointer__operator_string.cpp"
```
Output:
```json
--8<-- "examples/json_pointer__operator_string.output"
```
## Version history
- Since version 2.0.0.

View File

@ -7,6 +7,22 @@ The string type used for the reference tokens making up the JSON pointer.
See [`basic_json::string_t`](../basic_json/string_t.md) for more information.
## Examples
??? example
The example shows the type `string_t` and its relation to `basic_json::string_t`.
```cpp
--8<-- "examples/json_pointer__string_t.cpp"
```
Output:
```json
--8<-- "examples/json_pointer__string_t.output"
```
## Version history
- Added in version 3.11.0.

View File

@ -19,6 +19,22 @@ Whether parsing should proceed.
It is safe to move the passed binary value.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse__binary.cpp"
```
Output:
```json
--8<-- "examples/sax_parse__binary.output"
```
## Version history
- Added in version 3.8.0.

View File

@ -15,6 +15,22 @@ A boolean value was read.
Whether parsing should proceed.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -10,6 +10,22 @@ The end of an array was read.
Whether parsing should proceed.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -10,6 +10,22 @@ The end of an object was read.
Whether parsing should proceed.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -19,6 +19,22 @@ Whether parsing should proceed.
It is safe to move the passed object key value.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -10,6 +10,22 @@ A null value was read.
Whether parsing should proceed.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -18,6 +18,22 @@ A floating-point number was read.
Whether parsing should proceed.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -15,6 +15,22 @@ An integer number was read.
Whether parsing should proceed.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -15,6 +15,22 @@ An unsigned integer number was read.
Whether parsing should proceed.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -23,6 +23,22 @@ A parse error occurred.
Whether parsing should proceed (**must return `#!cpp false`**).
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -19,6 +19,22 @@ Whether parsing should proceed.
Binary formats may report the number of elements.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -19,6 +19,22 @@ Whether parsing should proceed.
Binary formats may report the number of elements.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -19,6 +19,22 @@ Whether parsing should proceed.
It is safe to move the passed string value.
## Examples
??? example
.The example below shows how the SAX interface is used.
```cpp
--8<-- "examples/sax_parse.cpp"
```
Output:
```json
--8<-- "examples/sax_parse.output"
```
## Version history
- Added in version 3.2.0.

View File

@ -23,6 +23,19 @@ The default value is detected based on preprocessor macros such as `#!cpp __cplu
- `#!cpp JSON_HAS_CPP_11` is always defined.
- All macros are undefined outside the library.
## Examples
??? example
The code below forces the library to use the C++14 standard:
```cpp
#define JSON_HAS_CPP_14 1
#include <nlohmann/json.hpp>
...
```
## Version history
- Added in version 3.10.5.

View File

@ -25,6 +25,19 @@ The default value is detected based on the preprocessor macros `#!cpp __cpp_lib_
filesystem support.
- Both macros are undefined outside the library.
## Examples
??? example
The code below forces the library to use the header `<experimental/filesystem>`.
```cpp
#define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
#include <nlohmann/json.hpp>
...
```
## Version history
- Added in version 3.10.5.

View File

@ -16,6 +16,20 @@ By default, `#!cpp JSON_NO_IO` is not defined.
#undef JSON_NO_IO
```
## Examples
??? example
The code below forces the library not to use the headers `<cstdio>`, `<ios>`, `<iosfwd>`, `<istream>`, and
`<ostream>`.
```cpp
#define JSON_NO_IO 1
#include <nlohmann/json.hpp>
...
```
## Version history
- Added in version 3.10.0.

View File

@ -23,6 +23,19 @@ By default, the macro is not defined.
The explanatory [`what()`](https://en.cppreference.com/w/cpp/error/exception/what) string of exceptions is not
available for MSVC if exceptions are disabled, see [#2824](https://github.com/nlohmann/json/discussions/2824).
## Examples
??? example
The code below switches off exceptions in the library.
```cpp
#define JSON_NOEXCEPTION 1
#include <nlohmann/json.hpp>
...
```
## See also
- [Switch off exceptions](../../home/exceptions.md#switch-off-exceptions) for more information how to switch off exceptions

View File

@ -15,6 +15,19 @@ By default, the macro is not defined.
#undef JSON_SKIP_UNSUPPORTED_COMPILER_CHECK
```
## Examples
??? example
The code below switches off the check whether the compiler is supported.
```cpp
#define JSON_SKIP_UNSUPPORTED_COMPILER_CHECK 1
#include <nlohmann/json.hpp>
...
```
## Version history
Added in version 3.2.0.

View File

@ -13,6 +13,23 @@ These macros are defined by the library and contain the version numbers accordin
The macros are defined according to the current library version.
## Examples
??? example
The example below shows how `NLOHMANN_JSON_VERSION_MAJOR`, `NLOHMANN_JSON_VERSION_MINOR`, and
`NLOHMANN_JSON_VERSION_PATCH` are defined by the library.
```cpp
--8<-- "examples/nlohmann_json_version.cpp"
```
Output:
```json
--8<-- "examples/nlohmann_json_version.output"
```
## See also
- [meta](../basic_json/meta.md) - returns version information on the library

View File

@ -6,9 +6,26 @@ using ordered_json = basic_json<ordered_map>;
This type preserves the insertion order of object keys.
## Examples
??? example
The example below demonstrates how `ordered_json` preserves the insertion order of object keys.
```cpp
--8<-- "examples/ordered_json.cpp"
```
Output:
```json
--8<-- "examples/ordered_json.output"
```
## See also
- [ordered_map](ordered_map.md)
- [Object Order](../features/object_order.md)
## Version history

View File

@ -0,0 +1,209 @@
# BJData
The [BJData format](https://neurojson.org) was derived from and improved upon
[Universal Binary JSON(UBJSON)](https://ubjson.org) specification (Draft 12).
Specifically, it introduces an optimized array container for efficient storage
of N-dimensional packed arrays (**ND-arrays**); it also adds 4 new type markers -
`[u] - uint16`, `[m] - uint32`, `[M] - uint64` and `[h] - float16` - to
unambigiously map common binary numeric types; furthermore, it uses little-endian
(LE) to store all numerics instead of big-endian (BE) as in UBJSON to avoid
unnecessary conversions on commonly available platforms.
Compared to other binary-JSON-like formats such as MessagePack and CBOR, both BJData and
UBJSON demonstrate a rare combination of being both binary and **quasi-human-readable**. This
is because all semantic elements in BJData and UBJSON, including the data-type markers
and name/string types are directly human-readable. Data stored in the BJData/UBJSON format
are not only compact in size, fast to read/write, but also can be directly searched
or read using simple processing.
!!! abstract "References"
- [BJData Specification](https://neurojson.org/bjdata/draft2)
## Serialization
The library uses the following mapping from JSON values types to BJData types according to the BJData specification:
| JSON value type | value/range | BJData type | marker |
|-----------------|-------------------------------------------|----------------|--------|
| null | `null` | null | `Z` |
| boolean | `true` | true | `T` |
| boolean | `false` | false | `F` |
| number_integer | -9223372036854775808..-2147483649 | int64 | `L` |
| number_integer | -2147483648..-32769 | int32 | `l` |
| number_integer | -32768..-129 | int16 | `I` |
| number_integer | -128..127 | int8 | `i` |
| number_integer | 128..255 | uint8 | `U` |
| number_integer | 256..32767 | int16 | `I` |
| number_integer | 32768..65535 | uint16 | `u` |
| number_integer | 65536..2147483647 | int32 | `l` |
| number_integer | 2147483648..4294967295 | uint32 | `m` |
| number_integer | 4294967296..9223372036854775807 | int64 | `L` |
| number_integer | 9223372036854775808..18446744073709551615 | uint64 | `M` |
| number_unsigned | 0..127 | int8 | `i` |
| number_unsigned | 128..255 | uint8 | `U` |
| number_unsigned | 256..32767 | int16 | `I` |
| number_unsigned | 32768..65535 | uint16 | `u` |
| number_unsigned | 65536..2147483647 | int32 | `l` |
| number_unsigned | 2147483648..4294967295 | uint32 | `m` |
| number_unsigned | 4294967296..9223372036854775807 | int64 | `L` |
| number_unsigned | 9223372036854775808..18446744073709551615 | uint64 | `M` |
| number_float | *any value* | float64 | `D` |
| string | *with shortest length indicator* | string | `S` |
| array | *see notes on optimized format/ND-array* | array | `[` |
| object | *see notes on optimized format* | map | `{` |
!!! success "Complete mapping"
The mapping is **complete** in the sense that any JSON value type can be converted to a BJData value.
Any BJData output created by `to_bjdata` can be successfully parsed by `from_bjdata`.
!!! warning "Size constraints"
The following values can **not** be converted to a BJData value:
- strings with more than 18446744073709551615 bytes (theoretical)
!!! info "Unused BJData markers"
The following markers are not used in the conversion:
- `Z`: no-op values are not created.
- `C`: single-byte strings are serialized with `S` markers.
!!! info "NaN/infinity handling"
If NaN or Infinity are stored inside a JSON number, they are
serialized properly. This behavior differs from the `dump()`
function which serializes NaN or Infinity to `null`.
!!! info "Endianness"
A breaking difference between BJData and UBJSON is the endianness
of numerical values. In BJData, all numerical data types (integers
`UiuImlML` and floating-point values `hdD`) are stored in the little-endian (LE)
byte order as opposed to big-endian as used by UBJSON. To adopt LE
to store numeric records avoids unnecessary byte swapping on most modern
computers where LE is used as the default byte order.
!!! info "Optimized formats"
The optimized formats for containers are supported: Parameter
`use_size` adds size information to the beginning of a container and
removes the closing marker. Parameter `use_type` further checks
whether all elements of a container have the same type and adds the
type marker to the beginning of the container. The `use_type`
parameter must only be used together with `use_size = true`.
Note that `use_size = true` alone may result in larger representations -
the benefit of this parameter is that the receiving side is
immediately informed on the number of elements of the container.
!!! info "ND-array optimized format"
BJData extends UBJSON's optimized array **size** marker to support
ND-array of uniform numerical data types (referred to as the *packed array*).
For example, 2-D `uint8` integer array `[[1,2],[3,4],[5,6]]` that can be stored
as nested optimized array in UBJSON `[ [$U#i2 1 2 [$U#i2 3 4 [$U#i2 5 6 ]`,
can be further compressed in BJData and stored as `[$U#[$i#i2 2 3 1 2 3 4 5 6`
or `[$U#[i2 i3] 1 2 3 4 5 6`.
In order to maintain the type and dimension information of an ND-array,
when this library parses a BJData ND-array via `from_bjdata`, it converts the
data into a JSON object, following the **annotated array format** as defined in the
[JData specification (Draft 3)](https://github.com/NeuroJSON/jdata/blob/master/JData_specification.md#annotated-storage-of-n-d-arrays).
For example, the above 2-D `uint8` array can be parsed and accessed as
```json
{
"_ArrayType_": "uint8",
"_ArraySize_": [2,3],
"_ArrayData_": [1,2,3,4,5,6]
}
```
In the reversed direction, when `to_bjdata` detects a JSON object in the
above form, it automatically converts such object into a BJData ND-array
to generate compact output. The only exception is that when the 1-D dimensional
vector stored in `"_ArraySize_"` contains a single integer, or two integers with
one being 1, a regular 1-D optimized array is generated.
The current version of this library has not yet supported automatic
recognition and conversion from a nested JSON array input to a BJData ND-array.
!!! info "Restrictions in optimized data types for arrays and objects"
Due to diminished space saving, hampered readability, and increased
security risks, in BJData, the allowed data types following the `$` marker
in an optimized array and object container are restricted to
**non-zero-fixed-length** data types. Therefore, the valid optimized
type markers can only be one of `UiuImlMLhdDC`. This also means other
variable (`[{SH`) or zero-length types (`TFN`) can not be used in an
optimized array or object in BJData.
!!! info "Binary values"
If the JSON data contains the binary type, the value stored is a list
of integers, as suggested by the BJData documentation. In particular,
this means that serialization and the deserialization of a JSON
containing binary values into BJData and back will result in a
different JSON object.
??? example
```cpp
--8<-- "examples/to_bjdata.cpp"
```
Output:
```c
--8<-- "examples/to_bjdata.output"
```
## Deserialization
The library maps BJData types to JSON value types as follows:
| BJData type | JSON value type | marker |
|-------------|-----------------------------------------|--------|
| no-op | *no value, next value is read* | `N` |
| null | `null` | `Z` |
| false | `false` | `F` |
| true | `true` | `T` |
| float16 | number_float | `h` |
| float32 | number_float | `d` |
| float64 | number_float | `D` |
| uint8 | number_unsigned | `U` |
| int8 | number_integer | `i` |
| uint16 | number_unsigned | `u` |
| int16 | number_integer | `I` |
| uint32 | number_unsigned | `m` |
| int32 | number_integer | `l` |
| uint64 | number_unsigned | `M` |
| int64 | number_integer | `L` |
| string | string | `S` |
| char | string | `C` |
| array | array (optimized values are supported) | `[` |
| ND-array | object (in JData annotated array format)|`[$.#[.`|
| object | object (optimized values are supported) | `{` |
!!! success "Complete mapping"
The mapping is **complete** in the sense that any BJData value can be converted to a JSON value.
??? example
```cpp
--8<-- "examples/from_bjdata.cpp"
```
Output:
```json
--8<-- "examples/from_bjdata.output"
```

View File

@ -1,7 +1,9 @@
# Binary Formats
Though JSON is a ubiquitous data format, it is not a very compact format suitable for data exchange, for instance over a network. Hence, the library supports
Though JSON is a ubiquitous data format, it is not a very compact format suitable for data exchange, for instance over
a network. Hence, the library supports
- [BJData](bjdata.md) (Binary JData),
- [BSON](bson.md) (Binary JSON),
- [CBOR](cbor.md) (Concise Binary Object Representation),
- [MessagePack](messagepack.md), and
@ -15,6 +17,7 @@ to efficiently encode JSON values to byte vectors and to decode such vectors.
| Format | Serialization | Deserialization |
|-------------|-----------------------------------------------|----------------------------------------------|
| BJData | complete | complete |
| BSON | incomplete: top-level value must be an object | incomplete, but all JSON types are supported |
| CBOR | complete | incomplete, but all JSON types are supported |
| MessagePack | complete | complete |
@ -24,6 +27,7 @@ to efficiently encode JSON values to byte vectors and to decode such vectors.
| Format | Binary values | Binary subtypes |
|-------------|---------------|-----------------|
| BJData | not supported | not supported |
| BSON | supported | supported |
| CBOR | supported | supported |
| MessagePack | supported | supported |
@ -35,11 +39,14 @@ See [binary values](../binary_values.md) for more information.
| Format | canada.json | twitter.json | citm_catalog.json | jeopardy.json |
|--------------------|-------------|--------------|-------------------|---------------|
| BSON | 85,8 % | 95,2 % | 95,8 % | 106,7 % |
| CBOR | 50,5 % | 86,3 % | 68,4 % | 88,0 % |
| MessagePack | 50,6 % | 86,0 % | 68,5 % | 87,9 % |
| UBJSON | 53,2 % | 91,3 % | 78,2 % | 96,6 % |
| UBJSON (size) | 58,6 % | 92,3 % | 86,8 % | 97,4 % |
| UBJSON (size+type) | 55,9 % | 92,3 % | 85,0 % | 95,0 % |
| BJData | 53.2 % | 91.1 % | 78.1 % | 96.6 % |
| BJData (size) | 58.6 % | 92.1 % | 86.7 % | 97.4 % |
| BJData (size+tyoe) | 58.6 % | 92.1 % | 86.5 % | 97.4 % |
| BSON | 85.8 % | 95.2 % | 95.8 % | 106.7 % |
| CBOR | 50.5 % | 86.3 % | 68.4 % | 88.0 % |
| MessagePack | 50.5 % | 86.0 % | 68.5 % | 87.9 % |
| UBJSON | 53.2 % | 91.3 % | 78.2 % | 96.6 % |
| UBJSON (size) | 58.6 % | 92.3 % | 86.8 % | 97.4 % |
| UBJSON (size+type) | 55.9 % | 92.3 % | 85.0 % | 95.0 % |
Sizes compared to minified JSON value.

View File

@ -1,8 +1,12 @@
# Binary Values
The library implements several [binary formats](binary_formats/index.md) that encode JSON in an efficient way. Most of these formats support binary values; that is, values that have semantics define outside the library and only define a sequence of bytes to be stored.
The library implements several [binary formats](binary_formats/index.md) that encode JSON in an efficient way. Most of
these formats support binary values; that is, values that have semantics define outside the library and only define a
sequence of bytes to be stored.
JSON itself does not have a binary value. As such, binary values are an extension that this library implements to store values received by a binary format. Binary values are never created by the JSON parser, and are only part of a serialized JSON text if they have been created manually or via a binary format.
JSON itself does not have a binary value. As such, binary values are an extension that this library implements to store
values received by a binary format. Binary values are never created by the JSON parser, and are only part of a
serialized JSON text if they have been created manually or via a binary format.
## API for binary values
@ -19,7 +23,9 @@ class json::binary_t {
"std::vector<uint8_t>" <|-- json::binary_t
```
By default, binary values are stored as `std::vector<std::uint8_t>`. This type can be changed by providing a template parameter to the `basic_json` type. To store binary subtypes, the storage type is extended and exposed as `json::binary_t`:
By default, binary values are stored as `std::vector<std::uint8_t>`. This type can be changed by providing a template
parameter to the `basic_json` type. To store binary subtypes, the storage type is extended and exposed as
`json::binary_t`:
```cpp
auto binary = json::binary_t({0xCA, 0xFE, 0xBA, 0xBE});
@ -87,7 +93,9 @@ Binary values are serialized differently according to the formats.
### JSON
JSON does not have a binary type, and this library does not introduce a new type as this would break conformance. Instead, binary values are serialized as an object with two keys: `bytes` holds an array of integers, and `subtype` is an integer or `null`.
JSON does not have a binary type, and this library does not introduce a new type as this would break conformance.
Instead, binary values are serialized as an object with two keys: `bytes` holds an array of integers, and `subtype`
is an integer or `null`.
??? example
@ -115,11 +123,72 @@ JSON does not have a binary type, and this library does not introduce a new type
!!! warning "No roundtrip for binary values"
The JSON parser will not parse the objects generated by binary values back to binary values. This is by design to remain standards compliant. Serializing binary values to JSON is only implemented for debugging purposes.
The JSON parser will not parse the objects generated by binary values back to binary values. This is by design to
remain standards compliant. Serializing binary values to JSON is only implemented for debugging purposes.
### BJData
[BJData](binary_formats/bjdata.md) neither supports binary values nor subtypes, and proposes to serialize binary values
as array of uint8 values. This translation is implemented by the library.
??? example
Code:
```cpp
// create a binary value of subtype 42 (will be ignored in BJData)
json j;
j["binary"] = json::binary({0xCA, 0xFE, 0xBA, 0xBE}, 42);
// convert to BJData
auto v = json::to_bjdata(j);
```
`v` is a `std::vector<std::uint8t>` with the following 20 elements:
```c
0x7B // '{'
0x69 0x06 // i 6 (length of the key)
0x62 0x69 0x6E 0x61 0x72 0x79 // "binary"
0x5B // '['
0x55 0xCA 0x55 0xFE 0x55 0xBA 0x55 0xBE // content (each byte prefixed with 'U')
0x5D // ']'
0x7D // '}'
```
The following code uses the type and size optimization for UBJSON:
```cpp
// convert to UBJSON using the size and type optimization
auto v = json::to_bjdata(j, true, true);
```
The resulting vector has 22 elements; the optimization is not effective for examples with few values:
```c
0x7B // '{'
0x23 0x69 0x01 // '#' 'i' type of the array elements: unsigned integers
0x69 0x06 // i 6 (length of the key)
0x62 0x69 0x6E 0x61 0x72 0x79 // "binary"
0x5B // '[' array
0x24 0x55 // '$' 'U' type of the array elements: unsigned integers
0x23 0x69 0x04 // '#' i 4 number of array elements
0xCA 0xFE 0xBA 0xBE // content
```
Note that subtype (42) is **not** serialized and that UBJSON has **no binary type**, and deserializing `v` would
yield the following value:
```json
{
"binary": [202, 254, 186, 190]
}
```
### BSON
[BSON](binary_formats/bson.md) supports binary values and subtypes. If a subtype is given, it is used and added as unsigned 8-bit integer. If no subtype is given, the generic binary subtype 0x00 is used.
[BSON](binary_formats/bson.md) supports binary values and subtypes. If a subtype is given, it is used and added as
unsigned 8-bit integer. If no subtype is given, the generic binary subtype 0x00 is used.
??? example
@ -159,7 +228,9 @@ JSON does not have a binary type, and this library does not introduce a new type
### CBOR
[CBOR](binary_formats/cbor.md) supports binary values, but no subtypes. Subtypes will be serialized as tags. Any binary value will be serialized as byte strings. The library will choose the smallest representation using the length of the byte array.
[CBOR](binary_formats/cbor.md) supports binary values, but no subtypes. Subtypes will be serialized as tags. Any binary
value will be serialized as byte strings. The library will choose the smallest representation using the length of the
byte array.
??? example
@ -185,7 +256,8 @@ JSON does not have a binary type, and this library does not introduce a new type
0xCA 0xFE 0xBA 0xBE // content
```
Note that the subtype is serialized as tag. However, parsing tagged values yield a parse error unless `json::cbor_tag_handler_t::ignore` or `json::cbor_tag_handler_t::store` is passed to `json::from_cbor`.
Note that the subtype is serialized as tag. However, parsing tagged values yield a parse error unless
`json::cbor_tag_handler_t::ignore` or `json::cbor_tag_handler_t::store` is passed to `json::from_cbor`.
```json
{
@ -198,7 +270,9 @@ JSON does not have a binary type, and this library does not introduce a new type
### MessagePack
[MessagePack](binary_formats/messagepack.md) supports binary values and subtypes. If a subtype is given, the ext family is used. The library will choose the smallest representation among fixext1, fixext2, fixext4, fixext8, ext8, ext16, and ext32. The subtype is then added as signed 8-bit integer.
[MessagePack](binary_formats/messagepack.md) supports binary values and subtypes. If a subtype is given, the ext family
is used. The library will choose the smallest representation among fixext1, fixext2, fixext4, fixext8, ext8, ext16, and
ext32. The subtype is then added as signed 8-bit integer.
If no subtype is given, the bin family (bin8, bin16, bin32) is used.
@ -239,7 +313,8 @@ If no subtype is given, the bin family (bin8, bin16, bin32) is used.
### UBJSON
[UBJSON](binary_formats/ubjson.md) neither supports binary values nor subtypes, and proposes to serialize binary values as array of uint8 values. This translation is implemented by the library.
[UBJSON](binary_formats/ubjson.md) neither supports binary values nor subtypes, and proposes to serialize binary values
as array of uint8 values. This translation is implemented by the library.
??? example
@ -251,7 +326,7 @@ If no subtype is given, the bin family (bin8, bin16, bin32) is used.
j["binary"] = json::binary({0xCA, 0xFE, 0xBA, 0xBE}, 42);
// convert to UBJSON
auto v = json::to_msgpack(j);
auto v = json::to_ubjson(j);
```
`v` is a `std::vector<std::uint8t>` with the following 20 elements:
@ -287,7 +362,8 @@ If no subtype is given, the bin family (bin8, bin16, bin32) is used.
0xCA 0xFE 0xBA 0xBE // content
```
Note that subtype (42) is **not** serialized and that UBJSON has **no binary type**, and deserializing `v` would yield the following value:
Note that subtype (42) is **not** serialized and that UBJSON has **no binary type**, and deserializing `v` would
yield the following value:
```json
{

View File

@ -2,9 +2,11 @@
## Overview
The `#!cpp at()` member function performs checked access; that is, it returns a reference to the desired value if it exists and throws a [`basic_json::out_of_range` exception](../../home/exceptions.md#out-of-range) otherwise.
The [`at`](../../api/basic_json/at.md) member function performs checked access; that is, it returns a reference to the
desired value if it exists and throws a [`basic_json::out_of_range` exception](../../home/exceptions.md#out-of-range)
otherwise.
??? example
??? example "Read access"
Consider the following JSON value:
@ -18,18 +20,18 @@ The `#!cpp at()` member function performs checked access; that is, it returns a
Assume the value is parsed to a `json` variable `j`.
| expression | value |
| ---------- | ----- |
| `#!cpp j` | `#!json {"name": "Mary Smith", "age": 42, "hobbies": ["hiking", "reading"]}` |
| `#!cpp j.at("name")` | `#!json "Mary Smith"` |
| `#!cpp j.at("age")` | `#!json 42` |
| `#!cpp j.at("hobbies")` | `#!json ["hiking", "reading"]` |
| `#!cpp j.at("hobbies").at(0)` | `#!json "hiking"` |
| `#!cpp j.at("hobbies").at(1)` | `#!json "reading"` |
| expression | value |
|-------------------------------|------------------------------------------------------------------------------|
| `#!cpp j` | `#!json {"name": "Mary Smith", "age": 42, "hobbies": ["hiking", "reading"]}` |
| `#!cpp j.at("name")` | `#!json "Mary Smith"` |
| `#!cpp j.at("age")` | `#!json 42` |
| `#!cpp j.at("hobbies")` | `#!json ["hiking", "reading"]` |
| `#!cpp j.at("hobbies").at(0)` | `#!json "hiking"` |
| `#!cpp j.at("hobbies").at(1)` | `#!json "reading"` |
The return value is a reference, so it can be modified by the original value.
??? example
??? example "Write access"
```cpp
j.at("name") = "John Smith";
@ -45,9 +47,10 @@ The return value is a reference, so it can be modified by the original value.
}
```
When accessing an invalid index (i.e., an index greater than or equal to the array size) or the passed object key is non-existing, an exception is thrown.
When accessing an invalid index (i.e., an index greater than or equal to the array size) or the passed object key is
non-existing, an exception is thrown.
??? example
??? example "Accessing via invalid index or missing key"
```cpp
j.at("hobbies").at(3) = "cooking";
@ -59,13 +62,24 @@ When accessing an invalid index (i.e., an index greater than or equal to the arr
[json.exception.out_of_range.401] array index 3 is out of range
```
When you [extended diagnostic messages](../../home/exceptions.md#extended-diagnostic-messages) are enabled by
defining [`JSON_DIAGNOSTICS`](../../api/macros/json_diagnostics.md), the exception further gives information where
the key or index is missing or out of range.
```
[json.exception.out_of_range.401] (/hobbies) array index 3 is out of range
```
## Notes
!!! failure "Exceptions"
- `at` can only be used with objects (with a string argument) or with arrays (with a numeric argument). For other types, a [`basic_json::type_error`](../../home/exceptions.md#jsonexceptiontype_error304) is thrown.
- [`basic_json::out_of_range` exception](../../home/exceptions.md#out-of-range) exceptions are thrown if the provided key is not found in an object or the provided index is invalid.
- [`at`](../../api/basic_json/at.md) can only be used with objects (with a string argument) or with arrays (with a
numeric argument). For other types, a [`basic_json::type_error`](../../home/exceptions.md#jsonexceptiontype_error304)
is thrown.
- [`basic_json::out_of_range` exception](../../home/exceptions.md#out-of-range) exceptions are thrown if the
provided key is not found in an object or the provided index is invalid.
## Summary

View File

@ -2,9 +2,10 @@
## Overview
Elements in a JSON object and a JSON array can be accessed via `#!cpp operator[]` similar to a `#!cpp std::map` and a `#!cpp std::vector`, respectively.
Elements in a JSON object and a JSON array can be accessed via [`operator[]`](../../api/basic_json/operator%5B%5D.md)
similar to a `#!cpp std::map` and a `#!cpp std::vector`, respectively.
??? example
??? example "Read access"
Consider the following JSON value:
@ -18,18 +19,19 @@ Elements in a JSON object and a JSON array can be accessed via `#!cpp operator[]
Assume the value is parsed to a `json` variable `j`.
| expression | value |
| ---------- | ----- |
| `#!cpp j` | `#!json {"name": "Mary Smith", "age": 42, "hobbies": ["hiking", "reading"]}` |
| `#!cpp j["name"]` | `#!json "Mary Smith"` |
| `#!cpp j["age"]` | `#!json 42` |
| `#!cpp j["hobbies"]` | `#!json ["hiking", "reading"]` |
| `#!cpp j["hobbies"][0]` | `#!json "hiking"` |
| `#!cpp j["hobbies"][1]` | `#!json "reading"` |
| expression | value |
|-------------------------|------------------------------------------------------------------------------|
| `#!cpp j` | `#!json {"name": "Mary Smith", "age": 42, "hobbies": ["hiking", "reading"]}` |
| `#!cpp j["name"]` | `#!json "Mary Smith"` |
| `#!cpp j["age"]` | `#!json 42` |
| `#!cpp j["hobbies"]` | `#!json ["hiking", "reading"]` |
| `#!cpp j["hobbies"][0]` | `#!json "hiking"` |
| `#!cpp j["hobbies"][1]` | `#!json "reading"` |
The return value is a reference, so it can modify the original value. In case the passed object key is non-existing, a `#!json null` value is inserted which can be immediately be overwritten.
The return value is a reference, so it can modify the original value. In case the passed object key is non-existing, a
`#!json null` value is inserted which can be immediately be overwritten.
??? example
??? example "Write access"
```cpp
j["name"] = "John Smith";
@ -47,9 +49,10 @@ The return value is a reference, so it can modify the original value. In case th
}
```
When accessing an invalid index (i.e., an index greater than or equal to the array size), the JSON array is resized such that the passed index is the new maximal index. Intermediate values are filled with `#!json null`.
When accessing an invalid index (i.e., an index greater than or equal to the array size), the JSON array is resized such
that the passed index is the new maximal index. Intermediate values are filled with `#!json null`.
??? example
??? example "Filling up arrays with `#!json null` values"
```cpp
j["hobbies"][0] = "running";
@ -76,17 +79,23 @@ When accessing an invalid index (i.e., an index greater than or equal to the arr
- `#!cpp std::vector::operator[]` never inserts a new element.
- `#!cpp std::map::operator[]` is not available for const values.
The type `#!cpp json` wraps all JSON value types. It would be impossible to remove `operator[]` for const objects. At the same time, inserting elements for non-const objects is really convenient as it avoids awkward `insert` calls. To this end, we decided to have an inserting non-const behavior for both arrays and objects.
The type `#!cpp json` wraps all JSON value types. It would be impossible to remove
[`operator[]`](../../api/basic_json/operator%5B%5D.md) for const objects. At the same time, inserting elements for
non-const objects is really convenient as it avoids awkward `insert` calls. To this end, we decided to have an
inserting non-const behavior for both arrays and objects.
!!! info
The access is unchecked. In case the passed object key does not exist or the passed array index is invalid, no exception is thrown.
The access is unchecked. In case the passed object key does not exist or the passed array index is invalid, no
exception is thrown.
!!! danger
- It is **undefined behavior** to access a const object with a non-existing key.
- It is **undefined behavior** to access a const array with an invalid index.
- In debug mode, an **assertion** will fire in both cases. You can disable assertions by defining the preprocessor symbol `#!cpp NDEBUG` or redefine the macro [`JSON_ASSERT(x)`](../macros.md#json_assertx).
- In debug mode, an **assertion** will fire in both cases. You can disable assertions by defining the preprocessor
symbol `#!cpp NDEBUG` or redefine the macro [`JSON_ASSERT(x)`](../macros.md#json_assertx). See the documentation
on [runtime assertions](../assertions.md) for more information.
!!! failure "Exceptions"

View File

@ -113,7 +113,7 @@ for (auto& [key, val] : j_object.items())
```cpp
json j = {1, 2, 3, 4};
for (auto it = j.begin(); it != j.end(); ++it)
for (auto it = j.rbegin(); it != j.rend(); ++it)
{
std::cout << *it << std::endl;
}

View File

@ -42,30 +42,13 @@ If you do want to preserve the **insertion order**, you can try the type [`nlohm
??? example
```cpp
#include <iostream>
#include <nlohmann/json.hpp>
using ordered_json = nlohmann::ordered_json;
int main()
{
ordered_json j;
j["one"] = 1;
j["two"] = 2;
j["three"] = 3;
std::cout << j.dump(2) << '\n';
}
--8<-- "examples/ordered_json.cpp"
```
Output:
```json
{
"one": 1,
"two": 2,
"three": 3
}
--8<-- "examples/ordered_json.output"
```
Alternatively, you can use a more sophisticated ordered map like [`tsl::ordered_map`](https://github.com/Tessil/ordered-map) ([integration](https://github.com/nlohmann/json/issues/546#issuecomment-304447518)) or [`nlohmann::fifo_map`](https://github.com/nlohmann/fifo_map) ([integration](https://github.com/nlohmann/json/issues/485#issuecomment-333652309)).

View File

@ -271,7 +271,7 @@ In a JSON Pointer, only `~0` and `~1` are valid escape sequences.
A JSON Pointer array index must be a number.
!!! failure "Example message"
!!! failure "Example messages"
```
[json.exception.parse_error.109] parse error: array index 'one' is not a number
@ -295,19 +295,34 @@ When parsing CBOR or MessagePack, the byte vector ends before the complete value
### json.exception.parse_error.112
Not all types of CBOR or MessagePack are supported. This exception occurs if an unsupported byte was read.
An unexpected byte was read in a [binary format](../features/binary_formats/index.md) or length information is invalid ([BSON](../features/binary_formats/bson.md)).
!!! failure "Example message"
!!! failure "Example messages"
```
[json.exception.parse_error.112] parse error at byte 1: syntax error while parsing CBOR value: invalid byte: 0x1C
```
```
[json.exception.parse_error.112] parse error at byte 1: syntax error while parsing MessagePack value: invalid byte: 0xC1
```
```
[json.exception.parse_error.112] parse error at byte 4: syntax error while parsing BJData size: expected '#' after type information; last byte: 0x02
```
```
[json.exception.parse_error.112] parse error at byte 4: syntax error while parsing UBJSON size: expected '#' after type information; last byte: 0x02
```
```
[json.exception.parse_error.112] parse error at byte 10: syntax error while parsing BSON string: string length must be at least 1, is -2147483648
```
```
[json.exception.parse_error.112] parse error at byte 15: syntax error while parsing BSON binary: byte array length cannot be negative, is -1
```
### json.exception.parse_error.113
While parsing a map key, a value that is not a string has been read.
!!! failure "Example message"
!!! failure "Example messages"
```
[json.exception.parse_error.113] parse error at byte 2: syntax error while parsing CBOR string: expected length specification (0x60-0x7B) or indefinite string type (0x7F); last byte: 0xFF
@ -374,7 +389,7 @@ The iterators passed to constructor `basic_json(InputIT first, InputIT last)` ar
In the [erase](../api/basic_json/erase.md) or insert function, the passed iterator `pos` does not belong to the JSON value for which the function was called. It hence does not define a valid position for the deletion/insertion.
!!! failure "Example message"
!!! failure "Example messages"
```
[json.exception.invalid_iterator.202] iterator does not fit current value
@ -538,7 +553,7 @@ To create an object from an initializer list, the initializer list must consist
During implicit or explicit value conversion, the JSON type must be compatible to the target type. For instance, a JSON string can only be converted into string types, but not into numbers or boolean types.
!!! failure "Example message"
!!! failure "Example messages"
```
[json.exception.type_error.302] type must be object, but is null
@ -551,7 +566,7 @@ During implicit or explicit value conversion, the JSON type must be compatible t
To retrieve a reference to a value stored in a `basic_json` object with `get_ref`, the type of the reference must match the value type. For instance, for a JSON array, the `ReferenceType` must be `array_t &`.
!!! failure "Example message"
!!! failure "Example messages"
```
[json.exception.type_error.303] incompatible ReferenceType for get_ref, actual type is object
@ -564,7 +579,7 @@ To retrieve a reference to a value stored in a `basic_json` object with `get_ref
The `at()` member functions can only be executed for certain JSON types.
!!! failure "Example message"
!!! failure "Example messages"
```
[json.exception.type_error.304] cannot use at() with string
@ -577,7 +592,7 @@ The `at()` member functions can only be executed for certain JSON types.
The `operator[]` member functions can only be executed for certain JSON types.
!!! failure "Example message"
!!! failure "Example messages"
```
[json.exception.type_error.305] cannot use operator[] with a string argument with array
@ -620,7 +635,7 @@ The `push_back()` and `operator+=` member functions can only be executed for cer
The `insert()` member functions can only be executed for certain JSON types.
!!! failure "Example message"
!!! failure "Example messages"
```
[json.exception.type_error.309] cannot use insert() with array
@ -643,7 +658,7 @@ The `swap()` member functions can only be executed for certain JSON types.
The `emplace()` and `emplace_back()` member functions can only be executed for certain JSON types.
!!! failure "Example message"
!!! failure "Example messages"
```
[json.exception.type_error.311] cannot use emplace() with number
@ -718,7 +733,7 @@ The `dump()` function only works with UTF-8 encoded strings; that is, if you ass
The dynamic type of the object cannot be represented in the requested serialization format (e.g. a raw `true` or `null` JSON object cannot be serialized to BSON)
!!! failure "Example message"
!!! failure "Example messages"
Serializing `#!json null` to BSON:
```

View File

@ -42,6 +42,7 @@ nav:
- features/arbitrary_types.md
- Binary Formats:
- features/binary_formats/index.md
- features/binary_formats/bjdata.md
- features/binary_formats/bson.md
- features/binary_formats/cbor.md
- features/binary_formats/messagepack.md
@ -109,6 +110,7 @@ nav:
- 'exception': api/basic_json/exception.md
- 'find': api/basic_json/find.md
- 'flatten': api/basic_json/flatten.md
- 'from_bjdata': api/basic_json/from_bjdata.md
- 'from_bson': api/basic_json/from_bson.md
- 'from_cbor': api/basic_json/from_cbor.md
- 'from_msgpack': api/basic_json/from_msgpack.md
@ -178,6 +180,7 @@ nav:
- 'string_t': api/basic_json/string_t.md
- 'swap': api/basic_json/swap.md
- 'std::swap&lt;basic_json&gt;': api/basic_json/std_swap.md
- 'to_bjdata': api/basic_json/to_bjdata.md
- 'to_bson': api/basic_json/to_bson.md
- 'to_cbor': api/basic_json/to_cbor.md
- 'to_msgpack': api/basic_json/to_msgpack.md

View File

@ -47,14 +47,17 @@ def check_structure():
files = sorted(glob.glob('api/**/*.md', recursive=True))
for file in files:
with open(file) as file_content:
section_idx = -1
existing_sections = []
in_initial_code_example = False
previous_line = None
h1sections = 0
section_idx = -1 # the index of the current h2 section
existing_sections = [] # the list of h2 sections in the file
in_initial_code_example = False # whether we are inside the first code example block
previous_line = None # the previous read line
h1sections = 0 # the number of h1 sections in the file
last_overload = 0 # the last seen overload number in the code example
documented_overloads = {} # the overloads that have been documented in the current block
current_section = None # the name of the current section
for lineno, line in enumerate(file_content.readlines()):
line = line.strip()
for lineno, original_line in enumerate(file_content.readlines()):
line = original_line.strip()
if line.startswith('# '):
h1sections += 1
@ -70,10 +73,21 @@ def check_structure():
# lines longer than 160 characters are bad (unless they are tables)
if len(line) > 160 and '|' not in line:
report('whitespace/line_length', f'{file}:{lineno+1}', f'line is too long ({len(line)} vs. 160 chars)')
report('whitespace/line_length', f'{file}:{lineno+1} ({current_section})', f'line is too long ({len(line)} vs. 160 chars)')
# check if sections are correct
if line.startswith('## '):
# before starting a new section, check if the previous one documented all overloads
if current_section in documented_overloads and last_overload != 0:
if len(documented_overloads[current_section]) > 0 and len(documented_overloads[current_section]) != last_overload:
expected = list(range(1, last_overload+1))
undocumented = [x for x in expected if x not in documented_overloads[current_section]]
unexpected = [x for x in documented_overloads[current_section] if x not in expected]
if len(undocumented):
report('style/numbering', f'{file}:{lineno} ({current_section})', f'undocumented overloads: {", ".join([f"({x})" for x in undocumented])}')
if len(unexpected):
report('style/numbering', f'{file}:{lineno} ({current_section})', f'unexpected overloads: {", ".join([f"({x})" for x in unexpected])}')
current_section = line.strip('## ')
existing_sections.append(current_section)
@ -83,13 +97,29 @@ def check_structure():
report('structure/section_order', f'{file}:{lineno+1}', f'section "{current_section}" is in an unexpected order (should be before "{expected_sections[section_idx]}")')
section_idx = idx
else:
report('structure/unknown_section', f'{file}:{lineno+1}', f'section "{current_section}" is not part of the expected sections')
if 'index.md' not in file: # index.md files may have a different structure
report('structure/unknown_section', f'{file}:{lineno+1}', f'section "{current_section}" is not part of the expected sections')
# collect the numbered items of the current section to later check if they match the number of overloads
if last_overload != 0 and not in_initial_code_example:
if len(original_line) and original_line[0].isdigit():
number = int(re.findall(r"^(\d+).", original_line)[0])
if current_section not in documented_overloads:
documented_overloads[current_section] = []
documented_overloads[current_section].append(number)
# code example
if line == '```cpp' and section_idx == -1:
in_initial_code_example = True
if in_initial_code_example and line.startswith('//'):
# check numbering of overloads
if any(map(str.isdigit, line)):
number = int(re.findall(r'\d+', line)[0])
if number != last_overload + 1:
report('style/numbering', f'{file}:{lineno+1}', f'expected number ({number}) to be ({last_overload +1 })')
last_overload = number
if any(map(str.isdigit, line)) and '(' not in line:
report('style/numbering', f'{file}:{lineno+1}', 'number should be in parentheses: {line}')
@ -98,18 +128,19 @@ def check_structure():
# consecutive blank lines are bad
if line == '' and previous_line == '':
report('whitespace/blank_lines', f'{file}:{lineno}-{lineno+1}', 'consecutive blank lines')
report('whitespace/blank_lines', f'{file}:{lineno}-{lineno+1} ({current_section})', 'consecutive blank lines')
# check that non-example admonitions have titles
untitled_admonition = re.match(r'^(\?\?\?|!!!) ([^ ]+)$', line)
if untitled_admonition and untitled_admonition.group(2) != 'example':
report('style/admonition_title', f'{file}:{lineno}', f'"{untitled_admonition.group(2)}" admonitions should have a title')
report('style/admonition_title', f'{file}:{lineno} ({current_section})', f'"{untitled_admonition.group(2)}" admonitions should have a title')
previous_line = line
for required_section in required_sections:
if required_section not in existing_sections:
report('structure/missing_section', f'{file}:{lineno+1}', f'required section "{required_section}" was not found')
if 'index.md' not in file: # index.md files may have a different structure
for required_section in required_sections:
if required_section not in existing_sections:
report('structure/missing_section', f'{file}:{lineno+1}', f'required section "{required_section}" was not found')
def check_examples():

View File

@ -4403,29 +4403,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
return res ? result : basic_json(value_t::discarded);
}
template<typename T>
JSON_HEDLEY_WARN_UNUSED_RESULT
static basic_json from_bjdata(const T* ptr, std::size_t len,
const bool strict = true,
const bool allow_exceptions = true)
{
return from_bjdata(ptr, ptr + len, strict, allow_exceptions);
}
JSON_HEDLEY_WARN_UNUSED_RESULT
static basic_json from_bjdata(detail::span_input_adapter&& i,
const bool strict = true,
const bool allow_exceptions = true)
{
basic_json result;
detail::json_sax_dom_parser<basic_json> sdp(result, allow_exceptions);
auto ia = i.get();
// NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(input_format_t::bjdata, &sdp, strict);
return res ? result : basic_json(value_t::discarded);
}
/// @brief create a JSON value from an input in BSON format
/// @sa https://json.nlohmann.me/api/basic_json/from_bson/
template<typename InputType>

View File

@ -22512,29 +22512,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
return res ? result : basic_json(value_t::discarded);
}
template<typename T>
JSON_HEDLEY_WARN_UNUSED_RESULT
static basic_json from_bjdata(const T* ptr, std::size_t len,
const bool strict = true,
const bool allow_exceptions = true)
{
return from_bjdata(ptr, ptr + len, strict, allow_exceptions);
}
JSON_HEDLEY_WARN_UNUSED_RESULT
static basic_json from_bjdata(detail::span_input_adapter&& i,
const bool strict = true,
const bool allow_exceptions = true)
{
basic_json result;
detail::json_sax_dom_parser<basic_json> sdp(result, allow_exceptions);
auto ia = i.get();
// NOLINTNEXTLINE(hicpp-move-const-arg,performance-move-const-arg)
const bool res = binary_reader<decltype(ia)>(std::move(ia), input_format_t::bjdata).sax_parse(input_format_t::bjdata, &sdp, strict);
return res ? result : basic_json(value_t::discarded);
}
/// @brief create a JSON value from an input in BSON format
/// @sa https://json.nlohmann.me/api/basic_json/from_bson/
template<typename InputType>

View File

@ -76,7 +76,7 @@ endif()
if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
# avoid stack overflow, see https://github.com/nlohmann/json/issues/2955
json_test_set_test_options("test-cbor;test-msgpack;test-ubjson;test-bjdata" LINK_OPTIONS /STACK:4000000)
json_test_set_test_options("test-cbor;test-msgpack;test-ubjson;test-bjdata;test-binary_formats" LINK_OPTIONS /STACK:4000000)
endif()
# disable exceptions for test-disabled_exceptions

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