Javascript 使用XMLHttpRequest和FileReader whyle设置自定义内容类型和边界上载二进制文件

我正在尝试使用XMLHttpRequest和FileReader将（DICOM）二进制文件上载到服务器

根据DICOM标准，内容类型muss应

多部分/相关；type=application/dicom

已定义，并且请求负载中必须是

内容类型：application/dicom

同样，我已设法用以下代码构建该结构：

    let boundary = Math.random().toString().substr(2);
    let reader = new FileReader();
    reader.readAsBinaryString(fileList[0]);

    reader.onload = function(e) {

        var xmlHttpRequest = new XMLHttpRequest();
        xmlHttpRequest.open("POST", "myurl", true);
        var dashes = '--';
        var crlf = "\r\n";
        if ( fileList[0].type == '' ){
            filetype = 'application/dicom';
        } else {
            filetype = fileList[0].type;
        }
        let content = e.target["result"];
        var data = dashes + boundary + crlf + "Content-Type: " + filetype + crlf + crlf + content + crlf + dashes + boundary + dashes;
        xmlHttpRequest.setRequestHeader("Content-Type", "multipart/related;type=application/dicom;boundary=" + boundary+";");
        xmlHttpRequest.setRequestHeader("Accept", "application/dicom+json");
        xmlHttpRequest.send(data);
    }; xmlHttpRequest.send(data);
        };

这种方法的问题在于，XMLHttpRequest似乎进行了UTF-8编码，这破坏了二进制数据（见下文）

• 问题是如何使用reader.readAsArrayBuffer（）并设置正文内容类型和边界？或
• 如何防止XMLHttpRequest进行UTF-8编码

我的第二个问题是如何使用这种方法处理大文件（约1 TB）？

我找到了我（第一部分）问题的答案。多亏了这一点，现在我的代码是：

var boundary = Math.random().toString().substr(2);
var reader = new FileReader();
reader.readAsArrayBuffer(fileList[0]);
reader.onload = function(e) {
    var xmlHttpRequest = new XMLHttpRequest();
    xmlHttpRequest.open("POST", "myurl", true);
    var dashes = '--';
    var crlf = "\r\n";
    if ( fileList[0].type == '' ){
        filetype = 'application/dicom';
    } else {
        filetype = fileList[0].type;
    }
    var content = e.target["result"];
    var dataView = new DataView(e.target["result"]);
    var postDataStart = dashes + boundary + crlf + "Content-Disposition: form-data;" + "name=\"file\";" + "filename=\"" + encodeURIComponent(fileList[0].name) + "\"" + crlf + "Content-Type: " + filetype + crlf + crlf;
    var postDataEnd = crlf + dashes + boundary + dashes;
    var size = postDataStart.length + dataView.byteLength + postDataEnd.length;
    var uint8Array = new Uint8Array(size);
    var i = 0;

    for (; i < postDataStart.length; i++) {
          uint8Array[i] = postDataStart.charCodeAt(i) & 0xFF;
    }
    for (let j = 0; j < dataView.byteLength; i++, j++) {
          uint8Array[i] = dataView.getUint8(j);
    }
    for (let j = 0; j < postDataEnd.length; i++, j++) {
         uint8Array[i] = postDataEnd.charCodeAt(j) & 0xFF;
    }
    var payload = uint8Array.buffer;
    xmlHttpRequest.setRequestHeader("Content-Type", "multipart/related;type=application/dicom;boundary=" + boundary+";");
    xmlHttpRequest.setRequestHeader("Accept", "application/dicom+json");
    xmlHttpRequest.send(payload);
};

    var boundary = Math.random().toString().substr(2);
    var xmlHttpRequest = new XMLHttpRequest();
    xmlHttpRequest.open("POST", "myurl", true);
    var dashes = '--';
    var crlf = "\r\n";
    filetype = fileList[0].type;

    var postDataStart = dashes + boundary + crlf + "Content-Disposition: form-data;" + "name=\"file\";" + "filename=\"" + encodeURIComponent(fileList[0].name) + "\"" + crlf + "Content-Type: " + filetype + crlf + crlf;
    var postDataEnd = crlf + dashes + boundary + dashes;

    xmlHttpRequest.setRequestHeader("Content-Type", "multipart/related;type=application/dicom;boundary=" + boundary+";");
    xmlHttpRequest.setRequestHeader("Accept", "application/dicom+json");
    xmlHttpRequest.send(new Blob([new Blob([postDataStart]),fileList[0], new Blob([postDataEnd])]));