是的，我想通过IE中的XHR读取二进制数据的答案是使用VBScript注入。一开始这对我来说很令人讨厌，但是，我将其视为仅仅是一个依赖于浏览器的代码。（常规XHR和responseText在其他浏览器中可以正常工作；您可能必须使用来强制MIME类型。IEXMLHttpRequest.overrideMimeType()]上不提供此功能）。
这就是我得到的东西responseText即使在二进制数据中也可以在IE中工作的方式。首先，一次性注入一些VBScript，如下所示：
if(/msie/i.test(navigator.userAgent) && !/opera/i.test(navigator.userAgent)) {
var IEBinaryToArray_ByteStr_Script =
"<!-- IEBinaryToArray_ByteStr -->\r\n"+
"<script type='text/vbscript' language='VBScript'>\r\n"+
"Function IEBinaryToArray_ByteStr(Binary)\r\n"+
" IEBinaryToArray_ByteStr = CStr(Binary)\r\n"+
"End Function\r\n"+
"Function IEBinaryToArray_ByteStr_Last(Binary)\r\n"+
" Dim lastIndex\r\n"+
" lastIndex = LenB(Binary)\r\n"+
" if lastIndex mod 2 Then\r\n"+
" IEBinaryToArray_ByteStr_Last = Chr( AscB( MidB( Binary, lastIndex, 1 ) ) )\r\n"+
" Else\r\n"+
" IEBinaryToArray_ByteStr_Last = "+'""'+"\r\n"+
" End If\r\n"+
"End Function\r\n"+
"</script>\r\n";
// inject VBScript
document.write(IEBinaryToArray_ByteStr_Script);
}
我正在使用的读取二进制文件的JS类公开了一个有趣的方法readCharAt(i)，该方法读取第i个索引处的字符（实际上是一个字节）。这是我的设置方式：
// see doc on http://msdn.microsoft.com/en-us/library/ms535874(VS.85).aspx
function getXMLHttpRequest()
{
if (window.XMLHttpRequest) {
return new window.XMLHttpRequest;
}
else {
try {
return new ActiveXObject("MSXML2.XMLHTTP");
}
catch(ex) {
return null;
}
}
}
// this fn is invoked if IE
function IeBinFileReaderImpl(fileURL){
this.req = getXMLHttpRequest();
this.req.open("GET", fileURL, true);
this.req.setRequestHeader("Accept-Charset", "x-user-defined");
// my helper to convert from responseBody to a "responseText" like thing
var convertResponseBodyToText = function (binary) {
var byteMapping = {};
for ( var i = 0; i < 256; i++ ) {
for ( var j = 0; j < 256; j++ ) {
byteMapping[ String.fromCharCode( i + j * 256 ) ] =
String.fromCharCode(i) + String.fromCharCode(j);
}
}
// call into VBScript utility fns
var rawBytes = IEBinaryToArray_ByteStr(binary);
var lastChr = IEBinaryToArray_ByteStr_Last(binary);
return rawBytes.replace(/[\s\S]/g,
function( match ) { return byteMapping[match]; }) + lastChr;
};
this.req.onreadystatechange = function(event){
if (that.req.readyState == 4) {
that.status = "Status: " + that.req.status;
//that.httpStatus = that.req.status;
if (that.req.status == 200) {
// this doesn't work
//fileContents = that.req.responseBody.toArray();
// this doesn't work
//fileContents = new VBArray(that.req.responseBody).toArray();
// this works...
var fileContents = convertResponseBodyToText(that.req.responseBody);
fileSize = fileContents.length-1;
if(that.fileSize < 0) throwException(_exception.FileLoadFailed);
that.readByteAt = function(i){
return fileContents.charCodeAt(i) & 0xff;
};
}
if (typeof callback == "function"){ callback(that);}
}
};
this.req.send();
}
// this fn is invoked if non IE
function NormalBinFileReaderImpl(fileURL){
this.req = new XMLHttpRequest();
this.req.open('GET', fileURL, true);
this.req.onreadystatechange = function(aEvt) {
if (that.req.readyState == 4) {
if(that.req.status == 200){
var fileContents = that.req.responseText;
fileSize = fileContents.length;
that.readByteAt = function(i){
return fileContents.charCodeAt(i) & 0xff;
}
if (typeof callback == "function"){ callback(that);}
}
else
throwException(_exception.FileLoadFailed);
}
};
//XHR binary charset opt by Marcus Granado 2006 [http://mgran.blogspot.com]
this.req.overrideMimeType('text/plain; charset=x-user-defined');
this.req.send(null);
}
转换码被提供Miskun。
效果很好。
我使用此方法从Javascript读取和提取zip文件，并且还在使用Javascript读取和显示EPUB文件的类中使用了该方法。性能非常合理。500kb文件大约需要半秒钟。
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