249 lines
7.7 KiB
C++
249 lines
7.7 KiB
C++
#include <iostream>
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#include "simdjson.h"
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using namespace std;
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using namespace simdjson;
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using error_code=simdjson::error_code;
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void basics_1() {
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const char *filename = "x.txt";
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dom::parser parser;
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dom::element doc = parser.load(filename); // load and parse a file
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cout << doc;
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}
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void basics_2() {
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dom::parser parser;
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dom::element doc = parser.parse("[1,2,3]"_padded); // parse a string
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cout << doc;
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}
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void basics_dom_1() {
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auto cars_json = R"( [
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{ "make": "Toyota", "model": "Camry", "year": 2018, "tire_pressure": [ 40.1, 39.9, 37.7, 40.4 ] },
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{ "make": "Kia", "model": "Soul", "year": 2012, "tire_pressure": [ 30.1, 31.0, 28.6, 28.7 ] },
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{ "make": "Toyota", "model": "Tercel", "year": 1999, "tire_pressure": [ 29.8, 30.0, 30.2, 30.5 ] }
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] )"_padded;
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dom::parser parser;
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// Parse and iterate through each car
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for (dom::object car : parser.parse(cars_json)) {
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// Accessing a field by name
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cout << "Make/Model: " << car["make"] << "/" << car["model"] << endl;
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// Casting a JSON element to an integer
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uint64_t year = car["year"];
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cout << "- This car is " << 2020 - year << "years old." << endl;
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// Iterating through an array of floats
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double total_tire_pressure = 0;
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for (double tire_pressure : car["tire_pressure"]) {
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total_tire_pressure += tire_pressure;
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}
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cout << "- Average tire pressure: " << (total_tire_pressure / 4) << endl;
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// Writing out all the information about the car
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for (auto field : car) {
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cout << "- " << field.key << ": " << field.value << endl;
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}
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}
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}
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void basics_dom_2() {
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auto cars_json = R"( [
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{ "make": "Toyota", "model": "Camry", "year": 2018, "tire_pressure": [ 40.1, 39.9, 37.7, 40.4 ] },
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{ "make": "Kia", "model": "Soul", "year": 2012, "tire_pressure": [ 30.1, 31.0, 28.6, 28.7 ] },
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{ "make": "Toyota", "model": "Tercel", "year": 1999, "tire_pressure": [ 29.8, 30.0, 30.2, 30.5 ] }
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] )"_padded;
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dom::parser parser;
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dom::element cars = parser.parse(cars_json);
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cout << cars.at("0/tire_pressure/1") << endl; // Prints 39.9
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}
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void basics_dom_3() {
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auto abstract_json = R"( [
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{ "12345" : {"a":12.34, "b":56.78, "c": 9998877} },
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{ "12545" : {"a":11.44, "b":12.78, "c": 11111111} }
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] )"_padded;
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dom::parser parser;
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// Parse and iterate through an array of objects
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for (dom::object obj : parser.parse(abstract_json)) {
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for(const auto& key_value : obj) {
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cout << "key: " << key_value.key << " : ";
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dom::object innerobj = key_value.value;
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cout << "a: " << double(innerobj["a"]) << ", ";
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cout << "b: " << double(innerobj["b"]) << ", ";
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cout << "c: " << int64_t(innerobj["c"]) << endl;
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}
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}
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}
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void basics_dom_4() {
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auto abstract_json = R"(
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{ "str" : { "123" : {"abc" : 3.14 } } } )"_padded;
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dom::parser parser;
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double v = parser.parse(abstract_json)["str"]["123"]["abc"].get<double>();
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cout << "number: " << v << endl;
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}
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namespace treewalk_1 {
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void print_json(dom::element element) {
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switch (element.type()) {
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case dom::element_type::ARRAY:
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cout << "[";
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for (dom::element child : dom::array(element)) {
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print_json(child);
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cout << ",";
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}
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cout << "]";
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break;
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case dom::element_type::OBJECT:
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cout << "{";
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for (dom::key_value_pair field : dom::object(element)) {
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cout << "\"" << field.key << "\": ";
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print_json(field.value);
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}
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cout << "}";
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break;
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case dom::element_type::INT64:
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cout << int64_t(element) << endl;
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break;
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case dom::element_type::UINT64:
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cout << uint64_t(element) << endl;
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break;
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case dom::element_type::DOUBLE:
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cout << double(element) << endl;
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break;
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case dom::element_type::STRING:
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cout << std::string_view(element) << endl;
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break;
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case dom::element_type::BOOL:
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cout << bool(element) << endl;
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break;
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case dom::element_type::NULL_VALUE:
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cout << "null" << endl;
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break;
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}
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}
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void basics_treewalk_1() {
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dom::parser parser;
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print_json(parser.load("twitter.json"));
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}
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}
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#ifdef SIMDJSON_CPLUSPLUS17
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void basics_cpp17_1() {
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dom::parser parser;
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padded_string json = R"( { "foo": 1, "bar": 2 } )"_padded;
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auto [object, error] = parser.parse(json).get<dom::object>();
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if (error) { cerr << error << endl; return; }
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for (auto [key, value] : object) {
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cout << key << " = " << value << endl;
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}
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}
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#endif
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void basics_cpp17_2() {
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// C++ 11 version for comparison
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dom::parser parser;
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padded_string json = R"( { "foo": 1, "bar": 2 } )"_padded;
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dom::object object;
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simdjson::error_code error;
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parser.parse(json).get<dom::object>().tie(object, error);
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for (dom::key_value_pair field : object) {
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cout << field.key << " = " << field.value << endl;
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}
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}
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void basics_ndjson() {
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dom::parser parser;
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for (dom::element doc : parser.load_many("x.txt")) {
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cout << doc["foo"] << endl;
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}
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// Prints 1 2 3
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}
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void implementation_selection_1() {
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cout << "simdjson v" << STRINGIFY(SIMDJSON_VERSION) << endl;
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cout << "Detected the best implementation for your machine: " << simdjson::active_implementation->name();
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cout << "(" << simdjson::active_implementation->description() << ")" << endl;
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}
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void implementation_selection_2() {
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for (auto implementation : simdjson::available_implementations) {
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cout << implementation->name() << ": " << implementation->description() << endl;
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}
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}
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void implementation_selection_3() {
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cout << simdjson::available_implementations["fallback"]->description() << endl;
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}
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void implementation_selection_4() {
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// Use the fallback implementation, even though my machine is fast enough for anything
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simdjson::active_implementation = simdjson::available_implementations["fallback"];
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}
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void performance_1() {
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dom::parser parser;
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// This initializes buffers and a document big enough to handle this JSON.
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dom::element doc = parser.parse("[ true, false ]"_padded);
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cout << doc << endl;
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// This reuses the existing buffers, and reuses and *overwrites* the old document
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doc = parser.parse("[1, 2, 3]"_padded);
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cout << doc << endl;
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// This also reuses the existing buffers, and reuses and *overwrites* the old document
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dom::element doc2 = parser.parse("true"_padded);
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// Even if you keep the old reference around, doc and doc2 refer to the same document.
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cout << doc << endl;
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cout << doc2 << endl;
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}
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#ifdef SIMDJSON_CPLUSPLUS17
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SIMDJSON_PUSH_DISABLE_ALL_WARNINGS
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// The web_request part of this is aspirational, so we compile as much as we can here
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void performance_2() {
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dom::parser parser(1024*1024); // Never grow past documents > 1MB
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// for (web_request request : listen()) {
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auto [doc, error] = parser.parse("1"_padded/*request.body*/);
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// // If the document was above our limit, emit 413 = payload too large
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if (error == CAPACITY) { /* request.respond(413); continue; */ }
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// // ...
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// }
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}
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// The web_request part of this is aspirational, so we compile as much as we can here
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void performance_3() {
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dom::parser parser(0); // This parser will refuse to automatically grow capacity
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simdjson::error_code allocate_error = parser.allocate(1024*1024); // This allocates enough capacity to handle documents <= 1MB
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if (allocate_error) { cerr << allocate_error << endl; exit(1); }
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// for (web_request request : listen()) {
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auto [doc, error] = parser.parse("1"_padded/*request.body*/);
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// If the document was above our limit, emit 413 = payload too large
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if (error == CAPACITY) { /* request.respond(413); continue; */ }
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// ...
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// }
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}
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SIMDJSON_POP_DISABLE_WARNINGS
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#endif
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int main() {
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basics_dom_1();
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basics_dom_2();
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basics_dom_3();
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basics_dom_4();
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return 0;
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}
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