sebastienros.jint/Jint/Native/Iterator/IteratorProtocol.cs

using Jint.Native.Object;
using Jint.Runtime;

namespace Jint.Native.Iterator;

/// <summary>
/// Handles looping of iterator values, sub-classes can use to implement wanted actions.
/// </summary>
internal abstract class IteratorProtocol
{
    private readonly Engine _engine;
    private readonly IteratorInstance _iterator;
    private readonly int _argCount;

    protected IteratorProtocol(
        Engine engine,
        IteratorInstance iterator,
        int argCount)
    {
        _engine = engine;
        _iterator = iterator;
        _argCount = argCount;
    }

    internal bool Execute()
    {
        var args = _engine._jsValueArrayPool.RentArray(_argCount);
        var done = false;
        try
        {
            while (ShouldContinue)
            {
                if (!_iterator.TryIteratorStep(out var item))
                {
                    done = true;
                    break;
                }

                var currentValue = item.Get(CommonProperties.Value);

                ProcessItem(args, currentValue);
            }
        }
        catch
        {
            IteratorClose(CompletionType.Throw);
            throw;
        }
        finally
        {
            _engine._jsValueArrayPool.ReturnArray(args);
        }

        IterationEnd();
        return done;
    }

    protected void IteratorClose(CompletionType completionType)
    {
        _iterator.Close(completionType);
    }

    protected virtual bool ShouldContinue => true;

    protected virtual void IterationEnd()
    {
    }

    protected abstract void ProcessItem(JsValue[] arguments, JsValue currentValue);

    internal static void AddEntriesFromIterable(ObjectInstance target, IteratorInstance iterable, object adder)
    {
        var callable = adder as ICallable;
        if (callable is null)
        {
            ExceptionHelper.ThrowTypeError(target.Engine.Realm, "adder must be callable");
        }

        var args = target.Engine._jsValueArrayPool.RentArray(2);

        var skipClose = true;
        try
        {
            do
            {
                if (!iterable.TryIteratorStep(out var nextItem))
                {
                    return;
                }

                var temp = nextItem.Get(CommonProperties.Value);

                skipClose = false;
                var oi = temp as ObjectInstance;
                if (oi is null)
                {
                    ExceptionHelper.ThrowTypeError(target.Engine.Realm, "iterator's value must be an object");
                }

                var k = oi.Get(JsString.NumberZeroString);
                var v = oi.Get(JsString.NumberOneString);

                args[0] = k;
                args[1] = v;

                callable.Call(target, args);
            } while (true);
        }
        catch
        {
            if (!skipClose)
            {
                iterable.Close(CompletionType.Throw);
            }
            throw;
        }
        finally
        {
            target.Engine._jsValueArrayPool.ReturnArray(args);
        }
    }
}