Commit 60b7299f authored by Niels Lohmann's avatar Niels Lohmann
Browse files

📝 updated README

parent 8f563a5f
......@@ -25,7 +25,7 @@ Other aspects were not so important to us:
- **Memory efficiency**. Each JSON object has an overhead of one pointer (the maximal size of a union) and one enumeration element (1 byte). The default generalization uses the following C++ data types: `std::string` for strings, `int64_t`, `uint64_t` or `double` for numbers, `std::map` for objects, `std::vector` for arrays, and `bool` for Booleans. However, you can template the generalized class `basic_json` to your needs.
- **Speed**. We currently implement the parser as naive [recursive descent parser]( with hand coded string handling. It is fast enough, but a [LALR-parser]( may be even faster (but would consist of more files which makes the integration harder).
- **Speed**. There are certainly [faster JSON libraries]( out there. However, if your goal is to speed up your development by adding JSON support with a single header, then this library is the way to go. If you know how to use a `std::vector` or `std::map`, you are already set.
See the [contribution guidelines]( for more information.
......@@ -130,6 +130,8 @@ json array_not_object = { json::array({"currency", "USD"}), json::array({"value"
### Serialization / Deserialization
#### To/from strings
You can create an object (deserialization) by appending `_json` to a string literal:
......@@ -163,6 +165,8 @@ std::cout << j.dump(4) << std::endl;
// }
#### To/from streams (e.g. files, string streams)
You can also use streams to serialize and deserialize:
......@@ -177,10 +181,37 @@ std::cout << j;
std::cout << std::setw(4) << j << std::endl;
These operators work for any subclasses of `std::istream` or `std::ostream`.
These operators work for any subclasses of `std::istream` or `std::ostream`. Here is the same example with files:
// read a JSON file
std::ifstream i("file.json");
json j;
i >> j;
// write prettified JSON to another file
std::ofstream o("pretty.json");
o << std::setw(4) << j << std::endl;
Please note that setting the exception bit for `failbit` is inappropriate for this use case. It will result in program termination due to the `noexcept` specifier in use.
#### Read from iterator range
You can also read JSON from an iterator range; that is, from any container accessible by iterators whose content is stored as contiguous byte sequence, for instance a `std::vector<uint8_t>`:
std::vector<uint8_t> v = {'t', 'r', 'u', 'e'};
json j = json::parse(v.begin(), v.end());
You may leave the iterators for the range [begin, end):
std::vector<uint8_t> v = {'t', 'r', 'u', 'e'};
json j = json::parse(v);
### STL-like access
......@@ -193,6 +224,9 @@ j.push_back("foo");
// also use emplace_back
// iterate the array
for (json::iterator it = j.begin(); it != j.end(); ++it) {
std::cout << *it << '\n';
......@@ -231,6 +265,9 @@ o["foo"] = 23;
o["bar"] = false;
o["baz"] = 3.141;
// also use emplace
o.emplace("weather", "sunny");
// special iterator member functions for objects
for (json::iterator it = o.begin(); it != o.end(); ++it) {
std::cout << it.key() << " : " << it.value() << "\n";
......@@ -523,7 +560,7 @@ To compile and run the tests, you need to execute
$ make check
All tests passed (8905491 assertions in 36 test cases)
All tests passed (8905518 assertions in 36 test cases)
Alternatively, you can use [CMake]( and run
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