Blob.js

/* Blob.js
 * A Blob implementation.
 * 2013-06-20
 * 
 * By Eli Grey, http://eligrey.com
 * By Devin Samarin, https://github.com/eboyjr
 * License: X11/MIT
 *   See LICENSE.md
 */

/*global self, unescape */
/*jslint bitwise: true, regexp: true, confusion: true, es5: true, vars: true, white: true,
  plusplus: true */

/*! @source http://purl.eligrey.com/github/Blob.js/blob/master/Blob.js */

if (typeof Blob !== "function" || typeof URL === "undefined")
if (typeof Blob === "function" && typeof webkitURL !== "undefined") self.URL = webkitURL;
else var Blob = (function (view) {
	"use strict";

	var BlobBuilder = view.BlobBuilder || view.WebKitBlobBuilder || view.MozBlobBuilder || view.MSBlobBuilder || (function(view) {
		var
			  get_class = function(object) {
				return Object.prototype.toString.call(object).match(/^\[object\s(.*)\]$/)[1];
			}
			, FakeBlobBuilder = function BlobBuilder() {
				this.data = [];
			}
			, FakeBlob = function Blob(data, type, encoding) {
				this.data = data;
				this.size = data.length;
				this.type = type;
				this.encoding = encoding;
			}
			, FBB_proto = FakeBlobBuilder.prototype
			, FB_proto = FakeBlob.prototype
			, FileReaderSync = view.FileReaderSync
			, FileException = function(type) {
				this.code = this[this.name = type];
			}
			, file_ex_codes = (
				  "NOT_FOUND_ERR SECURITY_ERR ABORT_ERR NOT_READABLE_ERR ENCODING_ERR "
				+ "NO_MODIFICATION_ALLOWED_ERR INVALID_STATE_ERR SYNTAX_ERR"
			).split(" ")
			, file_ex_code = file_ex_codes.length
			, real_URL = view.URL || view.webkitURL || view
			, real_create_object_URL = real_URL.createObjectURL
			, real_revoke_object_URL = real_URL.revokeObjectURL
			, URL = real_URL
			, btoa = view.btoa
			, atob = view.atob
			
			, ArrayBuffer = view.ArrayBuffer
			, Uint8Array = view.Uint8Array
		;
		FakeBlob.fake = FB_proto.fake = true;
		while (file_ex_code--) {
			FileException.prototype[file_ex_codes[file_ex_code]] = file_ex_code + 1;
		}
		if (!real_URL.createObjectURL) {
			URL = view.URL = {};
		}
		URL.createObjectURL = function(blob) {
			var
				  type = blob.type
				, data_URI_header
			;
			if (type === null) {
				type = "application/octet-stream";
			}
			if (blob instanceof FakeBlob) {
				data_URI_header = "data:" + type;
				if (blob.encoding === "base64") {
					return data_URI_header + ";base64," + blob.data;
				} else if (blob.encoding === "URI") {
					return data_URI_header + "," + decodeURIComponent(blob.data);
				} if (btoa) {
					return data_URI_header + ";base64," + btoa(blob.data);
				} else {
					return data_URI_header + "," + encodeURIComponent(blob.data);
				}
			} else if (real_create_object_URL) {
				return real_create_object_URL.call(real_URL, blob);
			}
		};
		URL.revokeObjectURL = function(object_URL) {
			if (object_URL.substring(0, 5) !== "data:" && real_revoke_object_URL) {
				real_revoke_object_URL.call(real_URL, object_URL);
			}
		};
		FBB_proto.append = function(data/*, endings*/) {
			var bb = this.data;
			// decode data to a binary string
			if (Uint8Array && (data instanceof ArrayBuffer || data instanceof Uint8Array)) {
				var
					  str = ""
					, buf = new Uint8Array(data)
					, i = 0
					, buf_len = buf.length
				;
				for (; i < buf_len; i++) {
					str += String.fromCharCode(buf[i]);
				}
				bb.push(str);
			} else if (get_class(data) === "Blob" || get_class(data) === "File") {
				if (FileReaderSync) {
					var fr = new FileReaderSync;
					bb.push(fr.readAsBinaryString(data));
				} else {
					// async FileReader won't work as BlobBuilder is sync
					throw new FileException("NOT_READABLE_ERR");
				}
			} else if (data instanceof FakeBlob) {
				if (data.encoding === "base64" && atob) {
					bb.push(atob(data.data));
				} else if (data.encoding === "URI") {
					bb.push(decodeURIComponent(data.data));
				} else if (data.encoding === "raw") {
					bb.push(data.data);
				}
			} else {
				if (typeof data !== "string") {
					data += ""; // convert unsupported types to strings
				}
				// decode UTF-16 to binary string
				bb.push(unescape(encodeURIComponent(data)));
			}
		};
		FBB_proto.getBlob = function(type) {
			if (!arguments.length) {
				type = null;
			}
			return new FakeBlob(this.data.join(""), type, "raw");
		};
		FBB_proto.toString = function() {
			return "[object BlobBuilder]";
		};
		FB_proto.slice = function(start, end, type) {
			var args = arguments.length;
			if (args < 3) {
				type = null;
			}
			return new FakeBlob(
				  this.data.slice(start, args > 1 ? end : this.data.length)
				, type
				, this.encoding
			);
		};
		FB_proto.toString = function() {
			return "[object Blob]";
		};
		return FakeBlobBuilder;
	}(view));

	return function Blob(blobParts, options) {
		var type = options ? (options.type || "") : "";
		var builder = new BlobBuilder();
		if (blobParts) {
			for (var i = 0, len = blobParts.length; i < len; i++) {
				builder.append(blobParts[i]);
			}
		}
		return builder.getBlob(type);
	};
}(self));