EinScott / json

An arbitrary JSON tree reader and writer for BeefLang.

Json for Beef

Read and write standard JSON in BeefLang. Focused on speed and usability.

Reading

The whole structure is contained within JsonTree. When the ReadJson call fails, tree is probably in an incomplete state, and might be partially invalid (e.g. .Object(let o)'s o might be null) but will always be correctly deletable. .Err(let err) will contain an error code, as well as column and line info.

The life time of all Dictionary, List and String objects within the tree is irreversably tied to it.

let tree = scope JsonTree();
switch (Json.ReadJson(jsonString, tree)
{
case .Err(let err):
    Debug.WriteLine(err);
    return .Err;
case .Ok:
}

// Use tree...
// - handle unexpected structures:

if (tree.root case .Object(let objData))
{
    if (rootObj.TryGetValue("answer", let truthBool)
        && truthBool case .Bool(let bool))
    {
        Debug.WriteLine(bool ? "Yup" : "Nup");
    }
    else return .Err;

    // ...
}
else return .Err;

// - just crash on unexpected structures:

let truthBool = tree.root.AsObject()["answer"].AsBool();
Debug.WriteLine(bool ? "Yeah" : "Nahh");

Options

• Json.readerMaxDepth Maximum allowed object/array depth, 256 by default
• Json.readerDuplicateKeyBehaviour Behaviour when encountering a duplicate key in an object. Can be .Override (default), or .Error

Writing

JsonTree can be modified and converted back to JSON. Dictionary, List and String objects that are used in the tree may be allocated, and thus be automatically deleted, with it (handy when storing or returning created trees). But this is not strictly required, meaning for example strings that are in scope at the time of writing the tree, as well as const strings can still be used as well.

let tree = scope JsonTree();

// Make object data, allocation life time is tied to tree
let rootObj = tree.MakeOwnedObject();
tree.root = .Object(rootObj); // Assign to structure

// Usual dicationary adding... for example:
rootObj["nothing here"] = .Null;

let treeBoundStr = tree.MakeOwnedString("keyValueThingBothYeaUseful");
rootObj[treeBoundStr] = .String(treeBoundStr);

let array = tree.MakeOwnedArray(8); // Already know required capacity!
rootObj["someArrayThing"] = .Array(array);
for (let i < 8)
{
    // Usual List adding...
    array.Add(.Number(Math.Pow(i, i) / 10));
}

// WriteJson just returns void, so we can just:
let jsonString = Json.WriteJson(tree, .. scope .(128));