Javascript：Uint16Array（length）返回无效的参数

Question

I'm trying to read a file in order to perform certain actions on the binary data before sending it to a server.

At a certain point I'm trying to convert the data returned by FileReader.readAsArrayBuffer() to an Uint16Array(). However upon doing so the code allocating the array fails with: 'Error: invalid arguments'. I need the data to be a hex string representing the entire binary.

This is the code I'm using:

function HexToHexString(ByteBuffer)
{
    //Similar constructs like: 'var Array = new Uint16Array(ByteBuffer);' also fail
    var View = new DataView(ByteBuffer);
    var Array = new Uint16Array((ByteBuffer.byteLength / 2));  // <- this line fails

    for(var i = 0; i < Array.length; i++)
    {
        Array[i] = View.getUint16(i*2);
    }

    return String.fromCharCode.apply(null, Array);
}

function OnReadFileCompletion(FileReadEvent)
{
    if(FileReadEvent.target.readyState == FileReader.DONE)
    {
        // Debug code, will be replaced:
        document.getElementById('byte_content').textContent = HexToHexString(FileReadEvent.target.result);
        //FileReadEvent.target.result;
    }
}

function ReadFile(File, ResultFunction)
{
    var Reader = new FileReader();

    Reader.onloadend = ResultFunction;

    Reader.readAsArrayBuffer(File.slice(0, File.size - 1));
}

File Is a file object, ResultFunction is OnReadFileCompletion(), ByteBuffer is an '[object ArrayBuffer]'.

When I output the size of the ArrayBuffer it matches the size of the file (82kb). I'm on firefox 32 with no plugins installed.

I'm not a javascript programmer, does anyone know what I'm doing wrong?

Edit1:

It appears to have something to-do with the size of the file I'm trying to read, using a 1kb text file appears to work while a 82kb binary file does not.

Edit2

I spoke too soon, perhaps it has something to do with file types. An image file of 200kb works, while an executable of 82 does not.

It appears that javascript does not allow executable files to be accesed this way, does anybody know of any way where I could possibly access the data in hex form?

Answer 1

尝试使用.length而不是byteLength

Answer 2

I've hacked together code that works for me, I don't know why this works or what I did wrong the other time. But it works.

function ApplyPadding(Number, PaddingLength)
{
    var s = Number + "";
    while (s.length < PaddingLength)
        s = "0" + s;
    return s;
}

function HexToHexString(ByteBuffers)
{
    var AnArray = new Uint8Array(ByteBuffers);
    var Result = "";

    for(var i = 0; i < AnArray.length; i++)
    {
        if(i%2==0)
            Result += ApplyPadding(AnArray[i].toString(16), 2);
    }

    return Result;
}

function HexStringToHex(aString)
{
    var Buffer = new ArrayBuffer(aString.length*2); // 2 bytes for each char
    var BufferView = new Uint16Array(Buffer);

    for (var i = 0;i < aString.length; i++)
    {
        BufferView[i] = aString.charCodeAt(i);
    }
    return Buffer;
}

function OnReadFileCompletion(FileReadEvent)
{
    if(FileReadEvent.target.readyState == FileReader.DONE)
    {
        //document.getElementById('byte_content').textContent =FileReadEvent.target.result;
        var DataOfFile = HexStringToHex(FileReadEvent.target.result);
        var FinalData = HexToHexString(DataOfFile);
        document.getElementById('byte_content').textContent = FinalData;
        //FileReadEvent.target.result;
    }
}

function ReadFile(File, ResultFunction)
{
    var Reader = new FileReader();

    Reader.onloadend = ResultFunction;

    Reader.readAsBinaryString(File.slice(0, File.size - 1));
}