New base64 string encoder. Old one sometimes gave wrong results.

mobl/imagefetch.mobl

@@ -6,57 +6,84 @@ module mobl::imagefetch
 external function downloadImageAsBase64(url : String) : String
 
 <javascript>
+/*
+ * getByteAt and encodeBinary inspired by base64 string encoder:
+ *
+ * Copyright (c) 2010 Nick Galbreath
+ * http://code.google.com/p/stringencoders/source/browse/#svn/trunk/javascript
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following
+ * conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
 mobl.imagefetch.Base64 = {
   // private property
-  _keyStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
-
+  _alphaStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
+
+  _padChar: '=',
+
+  getByteAt: function(str, idx) {
+  	var x = str.charCodeAt(idx) & 0xff; // throw away high-order byte, as documented at: https://developer.mozilla.org/En/Using_XMLHttpRequest#Handling_binary_data
+    if (x > 255) {
+        throw new Error();
+    }
+    return x;
+  },
+
   encodeBinary: function(input){
-    var output = "";
-    var bytebuffer;
-    var encodedCharIndexes = new Array(4);
-    var inx = 0;
-    var paddingBytes = 0;
+  	if (arguments.length !== 1) {
+        throw new SyntaxError("Not enough arguments");
+    }
+
+    var i, b10;
+    var x = [];
 
-    while (inx < input.length) {
-      // Fill byte buffer array
-      bytebuffer = new Array(3);
-      for (jnx = 0; jnx < bytebuffer.length; jnx++)
-        if (inx < input.length)
-          bytebuffer[jnx] = input.charCodeAt(inx++) & 0xff; // throw away high-order byte, as documented at: https://developer.mozilla.org/En/Using_XMLHttpRequest#Handling_binary_data
-        else
-          bytebuffer[jnx] = 0;
+    // convert to string
+    input = '' + input;
 
-      // Get each encoded character, 6 bits at a time
-      // index 1: first 6 bits
-      encodedCharIndexes[0] = bytebuffer[0] >> 2;
-      // index 2: second 6 bits (2 least significant bits from input byte 1 + 4 most significant bits from byte 2)
-      encodedCharIndexes[1] = ((bytebuffer[0] & 0x3) << 4) | (bytebuffer[1] >> 4);
-      // index 3: third 6 bits (4 least significant bits from input byte 2 + 2 most significant bits from byte 3)
-      encodedCharIndexes[2] = ((bytebuffer[1] & 0x0f) << 2) | (bytebuffer[2] >> 6);
-      // index 3: forth 6 bits (6 least significant bits from input byte 3)
-      encodedCharIndexes[3] = bytebuffer[2] & 0x3f;
+    var imax = input.length - input.length % 3;
 
-      // Determine whether padding happened, and adjust accordingly
-      paddingBytes = inx - (input.length - 1);
-      switch (paddingBytes) {
-        case 2:
-          // Set last 2 characters to padding char
-          encodedCharIndexes[3] = 64;
-          encodedCharIndexes[2] = 64;
-          break;
-        case 1:
-          // Set last character to padding char
-          encodedCharIndexes[3] = 64;
-          break;
-        default:
-          break; // No padding - proceed
-      }
-      // Now we will grab each appropriate character out of our keystring
-      // based on our index array and append it to the output string
-      for (jnx = 0; jnx < encodedCharIndexes.length; jnx++)
-        output += this._keyStr.charAt(encodedCharIndexes[jnx]);
+    if (input.length === 0) {
+        return input;
+    }
+    for (i = 0; i < imax; i += 3) {
+        b10 = (this.getByteAt(input,i) << 16) | (this.getByteAt(input,i+1) << 8) | this.getByteAt(input,i+2);
+        x.push(this._alphaStr.charAt(b10 >> 18));
+        x.push(this._alphaStr.charAt((b10 >> 12) & 0x3F));
+        x.push(this._alphaStr.charAt((b10 >> 6) & 0x3f));
+        x.push(this._alphaStr.charAt(b10 & 0x3f));
+    }
+    switch (input.length - imax) {
+    case 1:
+        b10 = this.getByteAt(input,i) << 16;
+        x.push(this._alphaStr.charAt(b10 >> 18) + this._alphaStr.charAt((b10 >> 12) & 0x3F) +
+               this._padChar + this._padChar);
+        break;
+    case 2:
+        b10 = (this.getByteAt(input,i) << 16) | (this.getByteAt(input,i+1) << 8);
+        x.push(this._alphaStr.charAt(b10 >> 18) + this._alphaStr.charAt((b10 >> 12) & 0x3F) +
+               this._alphaStr.charAt((b10 >> 6) & 0x3f) + this._padChar);
+        break;
     }
-    return output;
+    return x.join('');
   }
 };
 
@@ -71,7 +98,7 @@ mobl.imagefetch.downloadImageAsBase64 = function(url, callback) {
       xhr.overrideMimeType('text/plain; charset=x-user-defined');
     },
     success: function(data) {
-      var b64 = mobl.imagefetch.Base64.encodeBinary(data);
+      var data = mobl.imagefetch.Base64.encodeBinary(data);
       // my super image-type detection code
       var fileType = 'image/png';
       var firstPart = data.substring(0, 100);
@@ -80,7 +107,7 @@ mobl.imagefetch.downloadImageAsBase64 = function(url, callback) {
       } else if(firstPart.indexOf('JFIF') !== -1) {
         fileType = 'image/jpeg';
       }
-      callback("data:" + fileType + ";base64," + b64);
+      callback("data:" + fileType + ";base64," + data);
     },
     error: function() {
       callback(null);