javascript - 即使 unconsumedBufferLength 为 0，DataReader.loadAsync 也正在完成

Question

我使用以下代码在 UWP WinRT 上使用 JSON 流:

async function connect() {
    let stream: MSStream;
    return new CancellableContext<void>(
        async (context) => {
            // this will be called immediately
            stream = await context.queue(() => getStreamByXHR()); // returns ms-stream object
            await consumeStream(stream);
        },
        {
            revert: () => {
                // this will be called when user cancels the task
                stream.msClose();
            }
        }
    ).feed();
}

async function consumeStream(stream: MSStream) {
    return new CancellableContext<void>(async (context) => {
        const input = stream.msDetachStream() as Windows.Storage.Streams.IInputStream;
        const reader = new Windows.Storage.Streams.DataReader(input);
        reader.inputStreamOptions = Windows.Storage.Streams.InputStreamOptions.partial;

        while (!context.canceled) {
            const content = await consumeString(1000);
            // ... some more codes
        }

        async function consumeString(count: number) {
            await reader.loadAsync(count); // will throw when the stream gets closed
            return reader.readString(reader.unconsumedBufferLength);
        }
    }).feed();
}

这里是关于InputStreamOptions.partial的文档说:

The asynchronous read operation completes when one or more bytes is available.

但是，即使 reader.unconsumedBufferLength 为 0，reader.loadAsync 也会完成，这会增加 CPU 负载。这是 API 错误还是我可以阻止此行为，以便 loadAsync 仅在 unconsumedBufferLength 大于 0 时才能完成？

PS:这是一个纯JS的复现:https://github.com/SaschaNaz/InputStreamOptionsBugRepro

Answer 1

Is this an API bug or can I prevent this behavior so that loadAsync can complete only when unconsumedBufferLength is greater than 0

最有可能它也在流的末尾 完成。因此，在那种情况下，unconsumedBufferLength 将为零并且需要满足。

事实上 https://msdn.microsoft.com/en-us/library/windows/apps/windows.storage.streams.datareader.aspx 的例子显示类似的东西(不可否认没有使用那个选项):

            // Once we have written the contents successfully we load the stream.
            await dataReader.LoadAsync((uint)stream.Size);

            var receivedStrings = "";

            // Keep reading until we consume the complete stream.
            while (dataReader.UnconsumedBufferLength > 0)

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