sebastienros.jint/Jint/Native/DataView/DataViewConstructor.cs

using Jint.Native.Function;
using Jint.Native.Object;
using Jint.Runtime;
using Jint.Runtime.Descriptors;

namespace Jint.Native.DataView;

/// <summary>
/// https://tc39.es/ecma262/#sec-dataview-constructor
/// </summary>
internal sealed class DataViewConstructor : Constructor
{
    private static readonly JsString _functionName = new("DataView");

    internal DataViewConstructor(
        Engine engine,
        Realm realm,
        FunctionPrototype functionPrototype,
        ObjectPrototype objectPrototype)
        : base(engine, realm, _functionName)
    {
        _prototype = functionPrototype;
        PrototypeObject = new DataViewPrototype(engine, this, objectPrototype);
        _length = new PropertyDescriptor(1, PropertyFlag.Configurable);
        _prototypeDescriptor = new PropertyDescriptor(PrototypeObject, PropertyFlag.AllForbidden);
    }

    private DataViewPrototype PrototypeObject { get; }

    public override ObjectInstance Construct(JsCallArguments arguments, JsValue newTarget)
    {
        if (newTarget.IsUndefined())
        {
            Throw.TypeError(_realm);
        }

        var buffer = arguments.At(0) as JsArrayBuffer;
        var byteOffset = arguments.At(1);
        var byteLength = arguments.At(2);

        if (buffer is null)
        {
            Throw.TypeError(_realm, "First argument to DataView constructor must be an ArrayBuffer");
        }

        var offset = TypeConverter.ToIndex(_realm, byteOffset);

        if (buffer.IsDetachedBuffer)
        {
            Throw.TypeError(_realm);
        }

        var bufferByteLength = (uint) buffer.ArrayBufferByteLength;
        if (offset > bufferByteLength)
        {
            Throw.RangeError(_realm, "Start offset " + offset + " is outside the bounds of the buffer");
        }

        var bufferIsFixedLength = buffer.IsFixedLengthArrayBuffer;
        uint viewByteLength;
        if (byteLength.IsUndefined())
        {
            if (bufferIsFixedLength)
            {
                viewByteLength = bufferByteLength - offset;
            }
            else
            {
                viewByteLength = JsTypedArray.LengthAuto;
            }
        }
        else
        {
            viewByteLength = TypeConverter.ToIndex(_realm, byteLength);
            if (offset + viewByteLength > bufferByteLength)
            {
                Throw.RangeError(_realm, "Invalid DataView length");
            }
        }

        var o = OrdinaryCreateFromConstructor(
            newTarget,
            static intrinsics => intrinsics.DataView.PrototypeObject,
            static (Engine engine, Realm _, object? _) => new JsDataView(engine));

        if (buffer.IsDetachedBuffer)
        {
            Throw.TypeError(_realm);
        }

        bufferByteLength = (uint) buffer.ArrayBufferByteLength;
        if (offset > bufferByteLength)
        {
            Throw.RangeError(_realm, "Invalid DataView offset");
        }

        if (!byteLength.IsUndefined())
        {
            if (offset + viewByteLength > bufferByteLength)
            {
                Throw.RangeError(_realm, "Invalid DataView length");
            }
        }

        o._viewedArrayBuffer = buffer;
        o._byteLength = viewByteLength;
        o._byteOffset = offset;

        return o;
    }
}