Base64 - 文件損壞

Question

我想通過javascript上傳一個pdf文件。我有該文件的base64表示，我解碼它。該文件已上傳，但該數據似乎已損壞。

當我嘗試打開文件時，出現錯誤消息「文件已損壞，無法修復」。

我得到的base64字符串服務器端是這樣的...

byte[] buffer = new byte[length]; 
var postedFile = httpRequest.Files[file];     
postedFile.InputStream.Read(buffer, 0, length); 
string encodedString = Convert.ToBase64String(buffer); 

這裏是Ajax調用我對該文件進行上傳

var data= Base64.decode(result); //result is the base64 encoded string 
$.ajax({ 
        url: url, 
        type: "POST", 
        data: data, 
        processData: false, 
        headers: { 
         "accept": "application/json;odata=verbose", 
         "X-RequestDigest": _digetsValue, 
         "content-length": length 

        }, 
        success: function (data) 
        { 
         alert("it worked"); 

        }, 
        error: function (err) 
        { 

        } 
       }); 

用於解碼，我使用這個塊代碼... 或從這裏How can you encode a string to Base64 in JavaScript?

var Base64 = { 
     // private property 
     _keyStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz/=", 

     // public method for encoding 
     encode: function (input) 
     { 
      var output = ""; 
      var chr1, chr2, chr3, enc1, enc2, enc3, enc4; 
      var i = 0; 

      input = Base64._utf8_encode(input); 

      while (i < input.length) 
      { 

       chr1 = input.charCodeAt(i++); 
       chr2 = input.charCodeAt(i++); 
       chr3 = input.charCodeAt(i++); 

       enc1 = chr1 >> 2; 
       enc2 = ((chr1 & 3) << 4) | (chr2 >> 4); 
       enc3 = ((chr2 & 15) << 2) | (chr3 >> 6); 
       enc4 = chr3 & 63; 

       if (isNaN(chr2)) 
       { 
        enc3 = enc4 = 64; 
       } else if (isNaN(chr3)) 
       { 
        enc4 = 64; 
       } 

       output = output + 
       Base64._keyStr.charAt(enc1) + Base64._keyStr.charAt(enc2) + 
       Base64._keyStr.charAt(enc3) + Base64._keyStr.charAt(enc4); 

      } 

      return output; 
     }, 

     // public method for decoding 
     decode: function (input) 
     { 
      var output = ""; 
      var chr1, chr2, chr3; 
      var enc1, enc2, enc3, enc4; 
      var i = 0; 

      input = input.replace(/[^A-Za-z0-9\+\/\=]/g, ""); 

      while (i < input.length) 
      { 

       enc1 = Base64._keyStr.indexOf(input.charAt(i++)); 
       enc2 = Base64._keyStr.indexOf(input.charAt(i++)); 
       enc3 = Base64._keyStr.indexOf(input.charAt(i++)); 
       enc4 = Base64._keyStr.indexOf(input.charAt(i++)); 

       chr1 = (enc1 << 2) | (enc2 >> 4); 
       chr2 = ((enc2 & 15) << 4) | (enc3 >> 2); 
       chr3 = ((enc3 & 3) << 6) | enc4; 

       output = output + String.fromCharCode(chr1); 

       if (enc3 != 64) 
       { 
        output = output + String.fromCharCode(chr2); 
       } 
       if (enc4 != 64) 
       { 
        output = output + String.fromCharCode(chr3); 
       } 

      } 

      output = Base64._utf8_decode(output); 

      return output; 

     }, 

     // private method for UTF-8 encoding 
     _utf8_encode: function (string) 
     { 
      string = string.replace(/\r\n/g, "\n"); 
      var utftext = ""; 

      for (var n = 0; n < string.length; n++) 
      { 

       var c = string.charCodeAt(n); 

       if (c < 128) 
       { 
        utftext += String.fromCharCode(c); 
       } 
       else if ((c > 127) && (c < 2048)) 
       { 
        utftext += String.fromCharCode((c >> 6) | 192); 
        utftext += String.fromCharCode((c & 63) | 128); 
       } 
       else 
       { 
        utftext += String.fromCharCode((c >> 12) | 224); 
        utftext += String.fromCharCode(((c >> 6) & 63) | 128); 
        utftext += String.fromCharCode((c & 63) | 128); 
       } 

      } 

      return utftext; 
     }, 

     // private method for UTF-8 decoding 
     _utf8_decode: function (utftext) 
     { 
      var string = ""; 
      var i = 0; 
      var c = c1 = c2 = 0; 

      while (i < utftext.length) 
      { 

       c = utftext.charCodeAt(i); 

       if (c < 128) 
       { 
        string += String.fromCharCode(c); 
        i++; 
       } 
       else if ((c > 191) && (c < 224)) 
       { 
        c2 = utftext.charCodeAt(i + 1); 
        string += String.fromCharCode(((c & 31) << 6) | (c2 & 63)); 
        i += 2; 
       } 
       else 
       { 
        c2 = utftext.charCodeAt(i + 1); 
        c3 = utftext.charCodeAt(i + 2); 
        string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63)); 
        i += 3; 
       } 

      } 
      return string; 
     } 
    } 

本來我是DOI ng這樣的東西...

getFileBuffer = function (file) 
{ 
    var deferred = $.Deferred(); 
    var reader = new FileReader(); 
    reader.onload = function (e) 
    { 
     deferred.resolve(e.target.result); 
    } 
    reader.onerror = function (e) 
    { 
     deferred.reject(e.target.error); 
    } 
    reader.readAsArrayBuffer(file); 

    return deferred.promise(); 
}; 

但當然這是HTML5和什麼都不排除。所以當我打電話給我的ajax函數時，我會從文件讀取器中傳入這個數組緩衝區，瞧！它會工作。現在我試圖用IE8模仿相同的功能。這可能嗎？

感謝

Answer 1

我寫了一些功能，前一段時間我認爲是二進制安全的，這裏爲大家介紹相關的人; base64To6和（可能命名不清）base6To8。

var chars = (
     'ABCDEFGHIJKLMNOPQRSTUVWXYZ' + 
     'abcdefghijklmnopqrstuvwxyz' + 
     '/' 
    ), 
    inver = {}, i; 
for (i = 0; i < chars.length; ++i) { 
    inver[chars[i]] = i; 
} 

function base64To6(b64) { 
    var arr6 = [], 
     i = b64.length, lenMod = 0; 
    while (b64.charAt(--i) === '=') 
     ++lenMod; 
    for (i = 0; i < b64.length - lenMod; ++i) 
     arr6.push(inver[b64.charAt(i)]); 
    i = b64.length & 3; 
    if (i) i = 4 - i; 
    i = i + b64.length; 
    arr6.byteLength = 3 * i/4 - lenMod; 
    return arr6; 
} 

function base6To8(arr6) { 
    var arr8 = [], i, 
     e1, e2, e3, 
     s1, s2, s3, s4, 
     d1, d2, d3, d4; 
    for (i = 0; i < arr6.length; i += 4) { 
     s1 = (d1 = arr6[i] ) & 63; 
     s2 = (d2 = arr6[i + 1]) & 63; 
     s3 = (d3 = arr6[i + 2]) & 63; 
     s4 = (d4 = arr6[i + 3]) & 63; 
     // xxxxxx xxyyyy yyyyzz zzzzzz 
     e1 = (s1  << 2) + (s2 >>> 4); 
     e2 = ((s2 & 15) << 4) + (s3 >>> 2); 
     e3 = ((s3 & 3) << 6) + s4  ; 
     arr8.push(e1); 
     if (d3 !== undefined) 
      arr8.push(e2, e3); 
     else if (d2 !== undefined) 
      arr8.push(e2); 
    } 
    if (arr6.byteLength !== undefined) 
     arr8.length = +arr6.byteLength; 
    return arr8; 
} 

現在，如果你這樣做

var int8arr = base6to8(base64to6(data)); 

您將有整數的陣列（最多8位數字），其中Base64編碼是代表。 JavaScript不使用Int8對於編號因此您不能立即使用此數組。

不幸的是，據我所知，IE8不支持UInt8Array或Blob，這將讓你便愉快地與二進制數據的工作，所以我不知道究竟在何處，你會希望把它從這裏。