WinJS中的文件到字节数组 [英] File to Byte Array in WinJS

问题描述

我正在用JavaScript改进Windows商店的开发，而且我似乎对如何从二进制文件中获取字节数组一无所知.我在网上找到了几个示例，但是它们似乎都只能阅读文本，而我的文件是图像.我正在这样打开文件:

I'm tinkering with some Windows Store development in JavaScript and I seem to be stuck on how to get a byte array from a binary file. I've found a couple of examples online, but they all seem to only read in text whereas my file is an image. I'm opening the file like this:

Windows.Storage.FileIO.readBufferAsync(photos[currentIndex]).done(function (buffer) {

    var dataReader = Windows.Storage.Streams.DataReader.fromBuffer(buffer);
    var fileContent = dataReader.readString(buffer.length);
    dataReader.close();

    // do something with fileContent

});

其中photos[currentIndex]是文件(从getFilesAsync()加载).当然，这种情况下的错误是readString在二进制数据上失败.它不能将字符"映射为字符串.我也尝试过这个:

Where photos[currentIndex] is a file (loaded from getFilesAsync()). The error in this case, of course, is that readString fails on binary data. It can't map the "characters" into a string. I also tried this:

Windows.Storage.FileIO.readBufferAsync(photos[currentIndex]).done(function (buffer) {

    var bytes = [];
    var dataReader = Windows.Storage.Streams.DataReader.fromBuffer(buffer);
    dataReader.readBytes(bytes);
    dataReader.close();

    // do something with bytes

});

但是bytes为空，所以我认为我使用的不正确.我想我只是在这里忽略了一些简单的事情，但是由于某种原因，我似乎找不到正确的方法将二进制文件读入字节数组.有人可以帮忙吗?

But bytes is empty, so I think I'm using this incorrectly. I imagine I'm just overlooking something simple here, but for some reason I just can't seem to find the right way to read a binary file into a byte array. Can somebody offer a second set of eyes to help?

推荐答案

在发布问题后几乎立即想出了答案，但我认为我将在此处保留答案以供后代之用...

Figured it out almost immediately after posting the question, but I figure I'll leave the answer here for posterity...

我需要在第二个示例中以不同的方式声明数组:

I needed to declare the array in the second example differently:

Windows.Storage.FileIO.readBufferAsync(photos[currentIndex]).done(function (buffer) {

    var bytes = new Uint8Array(buffer.length);
    var dataReader = Windows.Storage.Streams.DataReader.fromBuffer(buffer);
    dataReader.readBytes(bytes);
    dataReader.close();

    // do something with bytes

});

我的JavaScript不够完善，所以我想我不明白数组声明应该如何工作. (当我在浏览器中使用普通JavaScript时，我总是只像最初那样声明空数组并追加到它们.)但这确实可以解决问题.

My JavaScript isn't quite up to par, so I guess I didn't understand how the array declaration was supposed to work. (When I do vanilla JavaScript in a browser, I always just declare empty arrays like I originally did and append to them.) But this does the trick.

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