ArduinoJStream

A Arduino/C++ library for parsing Json Streams with minimal memory usage.

Why Json Stream?

Some Web-API Json responses can be huge which makes it impractical to save them, especially on devices with small memory capacity (e.g. ESP8266).
This library tries to solve that issue by not saving the whole response and instead extracting only the important data.

Example usage

Lets consider the Json String:

    {
        "books": [
            {
                "title": "The Hobbit",
                "author": "J. R. R. Tolkien"
            },
            {
                "title": "The NeverEnding Story",
                "author": "Michael Ende"
            }
        ]
    }

We want to known the author of the second book, For simplicity lets assume we already made a request to the API and now have a stream object stream as a response.

    char* authorOfSecondBook = malloc(20);

    JsonParser parser;
    parser.parse(stream);

    parser.enterObj(); // Enter root Object
    parser.findKey("books"); // Find "books" key
    parser.enterObj(); // Enter "books" array

    parser.nextVal(); // Skip to second array element
    parser.enterObj(); // Enter book object
    
    parser.findKey("author"); // Find the "author" key
    parser.readString(authorOfSecondBook) // Read the author from stream into authorOfSecondBook

Alternatively a path can used instead:

    char* authorOfSecondBook = malloc(20);

    JsonParser parser;
    parser.parse(stream);
    
    parser.enterObj() // Enter root object
    parser.find("books[1]/author") // Find the author of the second book
    parser.readString(authorOfSecondBook) // Read the author from stream into authorOfSecondBook