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Up to [Public] / 2006 / webapi / FileAPI|
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1.80 dom 1:
1.1 arangana 2:
3:
11:
12:
13:
14:
15:
16:
17: File API
1.96 arangana 18:
1.130 ! arangana 19:
1.96 arangana 20:
1.1 arangana 21:
22:
23:
24:
32:
33:
34:
35:
40:
41:
42: Arun Ranganathan
43: Mozilla Corporation
44:
1.28 arangana 45:
46: Jonas Sicking
47: Mozilla Corporation
48:
1.1 arangana 49:
1.129 arangana 50: WD
1.116 arangana 51:
53:
54:
55:
56:
57:
58:
59: Abstract
60:
61: This specification provides an API
62: for representing file objects in web applications, as well as programmatically selecting them and accessing their data. This includes:
63:
64:
65:
1.48 arangana 66: - A FileList interface, which represents an array of individually selected files from the underlying system.
1.1 arangana 67: The user interface for selection can be invoked via
<input type="file">, i.e. when the
1.55 arangana 68: input element is in the File Upload state [HTML] .
1.48 arangana 69: - A Blob interface, which represents immutable raw binary data, and allows access to ranges of bytes within the
70:
Blob object as a separate Blob.
1.1 arangana 71: - A File interface, which includes readonly informational attributes about a file
1.35 arangana 72: such as its name and the date of the last modification (on disk) of the file.
1.28 arangana 73: - A FileReader interface, which provides methods to read a
1.18 arangana 74: File or a Blob, and an event model to obtain the results of these reads.
1.35 arangana 75: - A URI scheme for use with binary data such as files, so that they can be referenced within web applications.
1.1 arangana 76:
77:
78:
1.4 arangana 79: Additionally, this specification defines objects to be used within threaded web applications for the synchronous reading of files.
1.1 arangana 80:
81: The section on Requirements and Use Cases [REQ] covers the motivation behind this specification.
82:
83: This API is designed to be used in conjunction with other APIs and elements on the web platform,
84: notably: XMLHttpRequest (e.g. with an overloaded send()
1.35 arangana 85: method for File or Blob objects), postMessage, DataTransfer (part
1.55 arangana 86: of the drag and drop API defined in [HTML,]) and
1.12 arangana 87: Web Workers. Additionally, it should be possible to programmatically obtain a list of files from the
1.14 arangana 88: input element when it is
1.55 arangana 89: in the File Upload state[HTML].
1.1 arangana 90: These kinds of behaviors are defined in the appropriate affiliated specifications.
91:
92:
93:
94:
95:
96:
97: Status of this Document
98: public-webapps@w3.org http://lists.w3.org/Archives/Public/public-webapps/?>
99:
100: Previous discussion of this specification has taken place on two other
101: mailing lists: public-webapps@w3.org">public-webapps@w3.org
102: (http://lists.w3.org/Archives/Public/public-webapps/">archive)
103: and public-webapi@w3.org">public-webapi@w3.org
104: (http://lists.w3.org/Archives/Public/public-webapi/">archive). Ongoing
105: discussion will be on the public-webapps@w3.org">public-webapps@w3.org
106: mailing list.
107:
108:
109:
110: This section describes the status of this document at the time of its publication.
111: Other documents may supersede this document, since it is only an editor's draft.
112: A list of current W3C
113: publications and the latest revision of this technical report can be found in the
114: http://www.w3.org/TR/">W3C
1.96 arangana 115: technical reports index at http://www.w3.org/TR/">http://www.w3.org/TR/.
1.1 arangana 116:
117:
118:
119: This document is produced by the http://www.w3.org/2008/webapps">Web Applications
120: WG in the W3C
121: http://www.w3.org/Interaction/">Interaction Domain.
122:
123:
124: Web content and browser developers are encouraged to review this draft. Please send comments to
125: public-webapps@w3.org">public-webapps@w3.org, the W3C's
126: public email list for issues related to Web APIs.
127: http://lists.w3.org/Archives/Public/public-webapps/">Archives of the
128: list are available.
129:
130:
131: This document is produced by the Web Applications Working Group,
132: part of the Rich Web Clients Activity
133: in the W3C Interaction Domain.
134: Changes made to this document can be found in the
1.35 arangana 135: W3C public CVS server.
1.1 arangana 136:
137: http://www.w3.org/2004/01/pp-impl/42538/status?>
138:
139:
140:
141: Table of Contents
142:
143:
144:
145:
146:
147: Introduction
148:
149: This section is informative.
150:
151:
1.4 arangana 152: Web applications should have the ability to manipulate as wide
1.1 arangana 153: as possible a range of user input, including files that a user may wish to upload
154: to a remote server or manipulate inside a rich web application. This specification
155: defines the basic representations for files, lists of files, errors raised by access to files,
1.35 arangana 156: and programmatic ways to read files. Additionally, this specification also defines an interface that represents
157: "raw data" which can be asynchronously processed on the main thread of conforming user agents. The interfaces and API defined in this
1.4 arangana 158: specification can be used with other interfaces and APIs exposed to the web platform.
159:
1.1 arangana 160:
1.4 arangana 161:
1.35 arangana 162: The File interface represents file data typically obtained from the underlying file system, and the Blob interface
1.110 arangana 163: ("Binary Large Object" - a name originally introduced to web APIs in Google Gears) represents immutable raw data. File or
1.35 arangana 164: Blob reads should happen asynchronously on the main thread, with an optional synchronous API used
1.4 arangana 165: within threaded web applications. An asynchronous API for reading files prevents blocking and UI "freezing" on a user
1.110 arangana 166: agent's main thread. This specification defines an asynchronous API based on an event model to read and access a File or Blob's
1.35 arangana 167: data. A FileReader
1.4 arangana 168: object provides asynchronous read methods to
169: access that file's data through event handler attributes and the firing of events. The use of events and event handlers allows separate code blocks the ability
1.35 arangana 170: to monitor the progress of the read (which is particularly useful for remote drives or mounted drives, where file access performance may vary from local drives)
171: and error conditions that may arise during reading of a file. An example will be illustrative.
1.4 arangana 172:
173: In the example below, different code blocks handle progress, error, and success conditions.
174:
175: function startRead() {
176: // obtain input element through DOM
177:
178: var file = document.getElementById('file').files[0];
179: if(file){
180: getAsText(file);
181: }
182: }
183:
184: function getAsText(readFile) {
185:
1.28 arangana 186: var reader = new FileReader();
1.4 arangana 187:
188: // Read file into memory as UTF-16
189: reader.readAsText(readFile, "UTF-16");
190:
191: // Handle progress, success, and errors
192: reader.onprogress = updateProgress;
193: reader.onload = loaded;
194: reader.onerror = errorHandler;
195: }
196:
197: function updateProgress(evt) {
198: if (evt.lengthComputable) {
199: // evt.loaded and evt.total are ProgressEvent properties
200: var loaded = (evt.loaded / evt.total);
201: if (loaded < 1) {
202: // Increase the prog bar length
1.11 arangana 203: // style.width = (loaded * 200) + "px";
1.4 arangana 204: }
205: }
206: }
207:
208: function loaded(evt) {
209: // Obtain the read file data
1.8 arangana 210: var fileString = evt.target.result;
1.4 arangana 211: // Handle UTF-16 file dump
212: if(utils.regexp.isChinese(fileString)) {
213: //Chinese Characters + Name validation
214: }
215: else {
216: // run other charset test
217: }
218: // xhr.send(fileString)
219: }
220:
221: function errorHandler(evt) {
1.110 arangana 222: if(evt.target.error.name == "NotReadableErr") {
1.4 arangana 223: // The file could not be read
224: }
225: }
226:
227:
228:
1.1 arangana 229:
230:
231: Conformance
232:
233:
234: Everything in this specification is normative except for
235: examples and sections marked as being informative.
236:
237:
238: The keywords “MUST”,
239: “MUST NOT”,
240: “REQUIRED”,
241: “SHALL”,
242: “SHALL NOT”,
243: “RECOMMENDED”,
244: “MAY” and
245: “OPTIONAL” in this document are to be
246: interpreted as described in
247: Key words for use in RFCs to
248: Indicate Requirement Levels
1.12 arangana 249: [RFC2119].
1.1 arangana 250:
251:
252: The following conformance classes are defined by this specification:
253:
254:
1.55 arangana 255: - conforming user agent
1.1 arangana 256: -
257:
258: A user agent is considered to be a
1.55 arangana 259: conforming user agent
1.1 arangana 260: if it satisfies all of the MUST-,
261: REQUIRED- and SHALL-level
1.55 arangana 262: criteria in this specification that apply to implementations. This specification uses both the terms "conforming user agent" and "user agent" to refer to this product class.
1.1 arangana 263:
1.123 arangana 264: User agents may implement algorithms in this specifications in any way desired, so long as the end result is indistinguishable from the result that would be obtained
1.55 arangana 265: from the specification's algorithms.
1.1 arangana 266:
267:
1.123 arangana 268: User agents that use ECMAScript to implement the APIs defined in this specification must implement them in a manner consistent with the
1.55 arangana 269: ECMAScript Bindings defined in the Web IDL specification [WEBIDL] as this specification uses that specification and terminology.
270:
1.1 arangana 271:
1.55 arangana 272:
273: Dependencies
274: This specification relies on underlying specifications.
275: - DOM
1.123 arangana 276: A conforming user agent must support at least the subset of the functionality defined in DOM4 that this specification relies upon; in particular,
1.110 arangana 277: it must support EventTarget. [DOM4]
- Progress Events
1.123 arangana 279: A conforming user agent must support the Progress Events specification. Data access on read operations is enabled via Progress Events.[ProgressEvents]
- HTML
1.123 arangana 281: A conforming user agent must support at least the subset of the functionality defined in HTML that this specification relies upon;
1.75 arangana 282: in particular, it must support event loops and event handler attributes. [HTML]
- Web IDL
284: A conforming user agent must also be a conforming implementation of the IDL fragments in this specification,
1.75 arangana 285: as described in the Web IDL specification. [WebIDL]
- Typed Arrays
287: A conforming user agent must support the Typed Arrays specification [TypedArrays].
1.55 arangana 288: Parts of this specification rely on the Web Workers specification; for those parts of this specification, the Web Workers specification is a normative dependency.
289: [Workers]
290:
1.2 arangana 291:
1.1 arangana 292: Terminology and Algorithms
1.40 arangana 293: The terms and algorithms <fragment>, <scheme>, document,
1.75 arangana 294: unloading document cleanup steps, event handler attributes,
295: event handler event type,
296: origin, same origin, event loops,
1.116 arangana 297: task, task source, URL,
1.124 arangana 298: queue a task, neuter, UTF-8, and UTF-16 are as defined by the HTML specification [HTML].
1.79 arangana 299: When this specification says to terminate an algorithm the user agent must terminate the algorithm after finishing the step it is on. Asynchronous read methods defined in this specification may return before the algorithm in question is terminated, and can be terminated by an abort() call.
1.110 arangana 300: The term throw in this specification, as it pertains to exceptions, is used as defined in the DOM4 specification [DOM4].
1.46 arangana 301: The algorithms and steps in this specification use the following mathematical operations:
302:
303: max(a,b) returns the maximum of a and b, and is always performed on integers as they are defined in WebIDL [WebIDL]; in the case of max(6,4) the result is 6.
304: This operation is also defined in ECMAScript [ECMA-262].
min(a,b) returns the minimum of a and b, and is always performed on integers as they are defined in WebIDL [WebIDL]; in the case of min(6,4) the result is 4.
306: This operation is also defined in ECMAScript [ECMA-262].
Mathematical comparisons such as < (less than), ≤ (less than or equal to) and > (greater than) are as in ECMAScript
1.46 arangana 308: [ECMA-262].
1.1 arangana 310:
1.12 arangana 311:
1.46 arangana 312: The FileList Interface
1.1 arangana 313:
314:
1.110 arangana 315: This interface is a collection [DOM4] of File objects.
1.1 arangana 316:
317:
1.46 arangana 318: interface FileList {
1.78 arangana 319: getter File? item(unsigned long index);
1.48 arangana 320: readonly attribute unsigned long length;
1.62 arangana 321: };
1.1 arangana 322:
323:
324:
1.4 arangana 325: Sample usage typically involves DOM access to the <input type="file"> element within a form, and then accessing selected files.
1.1 arangana 326:
327:
328: // uploadData is a form element
329: // fileChooser is input element of type 'file'
330: var file = document.forms['uploadData']['fileChooser'].files[0];
331:
1.48 arangana 332: // alternative syntax can be
333: // var file = document.forms['uploadData']['fileChooser'].files.item(0);
334:
1.1 arangana 335: if(file)
336: {
337: // Perform file ops
338: }
339:
340:
1.48 arangana 341:
342: Attributes
343:
346:
347:
348: Methods and Parameters
349:
1.123 arangana 350: item(index)must return the indexth File object in
1.48 arangana 351: the FileList. If there is no indexth File object in the
352: FileList, then this method must return null.
1.123 arangana 353: index must be treated by user agents as value for the position of a File
1.110 arangana 354: object in the FileList collection, with 0 representing the first file in the collection. Supported property indices [WebIDL] are the numbers in the range zero to one less than the number of File objects represented by the collection [DOM4].
1.91 arangana 355: If there are no such File objects, then there are no supported property indices [WebIDL].
1.48 arangana 356:
359:
1.1 arangana 360:
1.55 arangana 361: The HTMLInputElement interface [HTML] has a readonly attribute of type FileList, which is what is
1.43 arangana 362: being accessed in the above example. Other interfaces with a readonly attribute of type FileList include the DataTransfer
1.55 arangana 363: interface [HTML].
1.42 arangana 364:
1.1 arangana 365:
1.2 arangana 366:
1.1 arangana 367: The Blob Interface
368:
1.83 arangana 369: This interface represents immutable raw data. It provides a method to slice data objects between ranges of bytes into further chunks of raw data. It also provides an attribute representing the size of the chunk of data.
1.55 arangana 370: The File interface inherits from this interface.
1.1 arangana 371:
372:
1.128 arangana 373: [Constructor, Constructor((ArrayBufferView or Blob or DOMString)[] blobParts, optional BlobPropertyBag options)]
1.120 arangana 374: interface Blob {
1.1 arangana 375:
1.48 arangana 376: readonly attribute unsigned long long size;
1.54 arangana 377: readonly attribute DOMString type;
378:
1.1 arangana 379: //slice Blob into byte-ranged chunks
380:
1.80 dom 381: Blob slice(optional long long start,
382: optional long long end,
1.124 arangana 383: optional DOMString contentType);
384: void close();
1.1 arangana 385:
1.7 arangana 386: };
1.97 arangana 387:
1.118 arangana 388: enum EndingTypes{"transparent", "native"};
1.117 arangana 389:
1.97 arangana 390: dictionary BlobPropertyBag {
391:
1.118 arangana 392: DOMString type = "";
1.117 arangana 393: EndingTypes endings = "transparent";
1.97 arangana 394:
395: };
1.1 arangana 396:
1.97 arangana 397:
398: Constructors
1.123 arangana 399: The Blob() constructor can be invoked with zero, one, or two parameters. When the Blob() constructor is invoked, user agents must run the following steps:
1.118 arangana 400:
401: If invoked with zero parameters, return a new Blob object consisting of 0 bytes, with size set to 0, and with type set to the empty string.
Otherwise, the constructor is invoked with a blobParts array. Let a be that array.
Let bytes be an empty sequence of bytes.
Let length be a's length. For 0 ≤ i < length, repeat the following steps:
1.118 arangana 405:
1.127 arangana 406: Let element be the ith element of a.
If element is a DOMString, run the following substeps:
1.118 arangana 408:
1.127 arangana 409: Let s be the result of converting element to a sequence of Unicode characters [Unicode] using the algorithm for doing so in WebIDL [WebIDL].
If the endings dictionary member of the options argument is set to "native", transform all newlines in s to the default line-ending representation of the underlying host operating system.
Encode s as UTF-8 and append the resulting bytes to bytes.
413:
416: If element is an ArrayBufferView [TypedArrays], convert it to a sequence of byteLength bytes from the underlying ArrayBuffer, starting at the byteOffset of the ArrayBufferView [TypedArrays], and append those bytes to bytes.
If element is a Blob, append the bytes it represents to bytes. The type of the Blob array element is ignored.
420: If the type member of the options argument is not the empty string, run the following substeps:
422:
423: Let s be the type dictionary member. If s contains any non-ASCII characters, throw a SyntaxError (per [RFC2616]) and return from this algorithm.
Convert every character in s to lower case.
Parse s as an RFC2616 media-type, tokenizing it according to the ABNF for media-type [RFC2616] with the ASCII "/" character separating tokens representing the type and subtype productions. If s cannot be tokenized according to the ABNF for media-type [RFC2616], throw a SyntaxError and return from this algorithm.
If the type and subtype tokens consist of any CTLs or separators, throw a SyntaxError and return from this algorithm (per [RFC2616]).
1.127 arangana 428: Return a Blob object consisting of bytes, with its size set to the length of bytes, and its type set to the type member of the options argument.
1.118 arangana 431:
1.97 arangana 432:
433:
434: Constructor Parameters
1.118 arangana 435: The Blob() constructor can be invoked with the parameters below:
1.97 arangana 436:
1.110 arangana 437: - A
blobParts Array
1.116 arangana 438: - which takes any number of the following types of array elements, and in any order:
1.97 arangana 439:
1.121 arangana 440: ArrayBufferView [TypedArrays] array elements
Blob array elements
DOMString [WebIDL] array elements
1.97 arangana 444:
445: - An optional
BlobPropertyBag
1.118 arangana 446: - which takes two members:
1.97 arangana 447:
1.118 arangana 448: type, a DOMString which corresponds to the Blob object's type attribute. endings, an enum which can take the values "transparent" which is set by default, or "native". A description of both is given in the table below.
1.97 arangana 450: Value Description
1.123 arangana 452: transparent
1.97 arangana 453:
1.123 arangana 454: Code points from the string arguments must remain unchanged.
1.97 arangana 455:
456:
457:
458:
459:
1.123 arangana 460: native
1.97 arangana 461:
1.123 arangana 462: Newlines must be transformed to the default line-ending
1.97 arangana 463: representation of the underlying host operating system. For
464: example, if the underlying OS is Windows, newlines will be
465: transformed into \r\n pairs as the text is
466: appended to the newly minted Blob object.
467:
468:
469:
470:
471:
1.105 arangana 473:
474:
1.97 arangana 475:
476:
477: Examples of constructor usage follow.
478:
1.105 arangana 479: // Create a new Blob object
480:
1.97 arangana 481: var a = new Blob();
482:
1.118 arangana 483: // Create a 1024-byte ArrayBuffer
484: // buffer could also come from reading a File
485:
486: var buffer = new ArrayBuffer(1024);
1.101 arangana 487:
1.118 arangana 488: // Create ArrayBufferView objects based on buffer
489:
490: var shorts = new Uint16Array(buffer, 512, 128);
491: var bytes = new Uint8Array(buffer, shorts.byteOffset + shorts.byteLength);
1.97 arangana 492:
493: // b has line endings of type "transparent" by default
1.102 arangana 494:
1.105 arangana 495: var b = new Blob(["foobarbazetcetc", "birdiebirdieboo"], {type: "text/plain;charset=UTF-8"});
1.97 arangana 496:
1.118 arangana 497: // c appends b and shorts and has line endings of type "transparent"
1.102 arangana 498:
1.118 arangana 499: var c = new Blob([b, shorts]);
1.97 arangana 500:
1.101 arangana 501: // a has native endings depending on platform
1.102 arangana 502:
1.118 arangana 503: var a = new Blob([b, c, bytes], {endings: "native"});
1.102 arangana 504:
1.97 arangana 505:
506:
507:
508:
509:
1.2 arangana 510:
1.1 arangana 511: Attributes
1.123 arangana 512: sizeReturns the size of the Blob object in bytes. On getting, conforming user agents must return the total
1.46 arangana 513: number of bytes that can be read by a FileReader or FileReaderSync object, or 0 if the
1.43 arangana 514: Blob has no bytes to be read.
typeThe ASCII-encoded string in lower case representing the media type of the Blob, expressed as an RFC2046 MIME type [RFC2046].
1.123 arangana 517: On getting, conforming user agents must return the MIME type of the Blob,
518: if it is known. If conforming user agents cannot determine the media type of the Blob, they must return the empty string.
1.35 arangana 519: A string is a valid MIME type if it matches the media-type
1.14 arangana 520: token defined in section 3.7 "Media Types" of RFC 2616 [HTTP].
1.55 arangana 522:
1.87 arangana 523: Use of the type attribute informs the encoding determination and parsing the Content-Type header when dereferencing blob: URIs.
1.55 arangana 524:
1.1 arangana 525:
1.2 arangana 526:
1.1 arangana 527: Methods and Parameters
1.83 arangana 528:
1.130 ! arangana 529:
! 530: The slice method
! 531: The slice method returns a new Blob object with bytes ranging from the optional start
! 532: parameter upto but not including the optional end parameter, and with a
! 533: type attribute that is the value of the optional contentType parameter. It must act as follows :
! 534:
! 535: Let O be the Blob object on which the slice method is being called.
The optional start parameter is a value for the start point of a slice call, and must be treated as a byte-order position, with the zeroth position representing the first byte.
slice with
1.46 arangana 538: start normalized according to the following:
1.130 ! arangana 539:
1.119 arangana 540: If the optional start parameter is not used as a parameter when making this call, let relativeStart be 0.
If start is negative, let relativeStart be max((size + start), 0)).
Else, let relativeStart be min(start, size).
This defines the normalization of the start parameter. When processing the slice call,
1.119 arangana 544: user agents must normalize start to relativeStart.
The optional end parameter is a value for the end point of a
slice call. The following requirements
1.123 arangana 549: are normative for this parameter, and user agents must process slice with end normalized according to the following:
1.130 ! arangana 550:
1.119 arangana 551: If the optional end parameter is not used as a parameter when making this call, let relativeEnd be size.
If end is negative, let relativeEnd be max((size + end), 0)
Else, let relativeEnd be min(end, size)
This defines the normalization of the end parameter. When processing the slice call,
1.119 arangana 555: user agents must normalize end to relativeEnd.
The optional contentType parameter is used to set a value identical to one that is set with the
Blob returned by the slice call. The following requirements are normative for this
1.123 arangana 561: parameter, and user agents must process the slice with contentType normalized according to the following:
1.46 arangana 562:
1.130 ! arangana 563:
1.119 arangana 564: If the contentType parameter is not provided, let relativeContentType be set to the empty string .
Else let relativeContentType be set to contentType and run the following substeps:
1.130 ! arangana 566:
1.122 arangana 567: If relativeContentType consists of any non-ASCII characters, throw a SyntaxError (per [RFC2616]) and return from this algorithm.
Convert every character in relativeContentType to lower case.
Parse relativeContentType as an RFC2616 media-type, tokenizing it according to the ABNF for media-type [RFC2616] with the ASCII "/" character separating tokens representing the type and subtype productions. If relativeContentType cannot be tokenized according to the ABNF for media-type [RFC2616], throw a SyntaxError and return from this algorithm.
If the type and subtype tokens consist of any CTLs or separators, throw a SyntaxError and return from this algorithm (per [RFC2616]).
This defines the normalization of the contentType parameter. When processing the slice call,
1.119 arangana 574: user agents must normalize contentType to relativeContentType.
Let span be max((relativeEnd - relativeStart), 0).
Return a new Blob object S with the following characteristics:
1.130 ! arangana 580: S consists of span consecutive bytes from O, beginning with the byte at byte-order position relativeStart.
S.size = span.
S.type = relativeContentType.
584:
585:
1.48 arangana 586:
587:
588: The examples below illustrate the different types of slice calls possible. Since the
589: File interface inherits from the Blob interface, examples are based on the use of the File interface.
590:
591:
592: // obtain input element through DOM
593:
594: var file = document.getElementById('file').files[0];
595: if(file)
596: {
597: // create an identical copy of file
598: // the two calls below are equivalent
599:
600: var fileClone = file.slice();
601: var fileClone2 = file.slice(0, file.size);
602:
603: // slice file into 1/2 chunk starting at middle of file
604: // Note the use of negative number
605:
606: var fileChunkFromEnd = file.slice(-(Math.round(file.size/2)));
607:
608: // slice file into 1/2 chunk starting at beginning of file
609:
610: var fileChunkFromStart = file.slice(0, Math.round(file.size/2));
611:
612: // slice file from beginning till 150 bytes before end
613:
614: var fileNoMetadata = file.slice(0, -150, "application/experimental");
615: }
616:
1.89 arangana 617:
618:
1.124 arangana 619:
620: The close method
1.126 arangana 621: Calling the close method must permanently neuter the original Blob object. This is an irreversible and non-idempotent operation; once a Blob has been neutered, it cannot be used again; dereferencing a Blob URI bound to a Blob object on which close has been called results in a 500 Error. This must not affect any ongoing read operation via any asynchronous read methods or any synchronous read methods. This must not affect any Blob objects created by a slice call on the Blob object on which close has been called.
1.124 arangana 622:
1.1 arangana 623:
624:
1.88 arangana 625:
626:
627: The File Interface
628:
629: This interface describes a single file in a FileList and exposes its name.
630: It inherits from Blob.
631:
1.110 arangana 632:
633: interface File : Blob {
1.88 arangana 634:
1.110 arangana 635: readonly attribute DOMString name;
636: readonly attribute Date? lastModifiedDate;
637:
638: };
1.88 arangana 639:
640:
641: Attributes
642:
643: nameThe name of the file; on getting, this must return the name of the file as a string. There are numerous file name variations on different systems;
645: this is merely the name of the file, without path information. On getting, if user agents cannot make this information available, they must return the empty string.
lastModifiedDateThe last modified date of the file. On getting, if user agents can make this information available, this must return a new Date[HTML] object
648: initialized to the last modified date of the file; otherwise, this must return null.
1.88 arangana 649:
651:
1.110 arangana 652:
1.88 arangana 653: The File interface is available on objects that expose an attribute of type FileList; these objects are defined in
654: HTML [HTML]. The File interface, which inherits from Blob, is immutable, and thus represents file data that can be
1.123 arangana 655: read into memory at the time a read operation is initiated. For synchronous reads on a Web Worker [Workers], if the file has been modified on disk since the File object reference is created, user agents must throw a NotReadableError; for asynchronous reads, user agents must fire an error event with the error
656: attribute returning a NotReadableError DOMError. User agents must process reads on files that no longer exist at the time of read as
1.89 arangana 657: errors, throwing a NotFoundError exception if using a FileReaderSync on a Web Worker [Workers] or firing an error event with the error
658: attribute returning a NotFoundError DOMError.
1.88 arangana 659:
660:
661: The FileReader Interface
662:
663: This interface provides methods to read File objects or Blob objects into memory, and to access the data from those
664: Files or Blobs using progress events and
1.110 arangana 665: event handler attributes; it inherits from EventTarget [DOM4].
1.88 arangana 666: It is desirable to read data from file systems asynchronously in the main thread of user agents. This interface provides such an asynchronous API, and is specified to be used
667: with the global object (Window [HTML]).
668:
669:
670:
671: [Constructor]
672: interface FileReader: EventTarget {
673:
674: // async read methods
675: void readAsArrayBuffer(Blob blob);
676: void readAsText(Blob blob, optional DOMString encoding);
677: void readAsDataURL(Blob blob);
678:
679: void abort();
680:
681: // states
682: const unsigned short EMPTY = 0;
683: const unsigned short LOADING = 1;
684: const unsigned short DONE = 2;
685:
686:
1.94 arangana 687: readonly attribute unsigned short readyState;
1.88 arangana 688:
689: // File or Blob data
1.110 arangana 690: readonly attribute (DOMString or ArrayBuffer)? result;
1.88 arangana 691:
692: readonly attribute DOMError error;
693:
694: // event handler attributes
1.95 dom 695: [TreatNonCallableAsNull] attribute Function? onloadstart;
696: [TreatNonCallableAsNull] attribute Function? onprogress;
697: [TreatNonCallableAsNull] attribute Function? onload;
698: [TreatNonCallableAsNull] attribute Function? onabort;
699: [TreatNonCallableAsNull] attribute Function? onerror;
700: [TreatNonCallableAsNull] attribute Function? onloadend;
1.88 arangana 701:
702: };
703:
704:
705: The FileReader Task Source
706: The FileReader interface enables asynchronous reads on individual Blob objects by
1.110 arangana 707: firing progress events as the read occurs.
1.88 arangana 708: Unless stated otherwise, the task source that is used in this specification is the
709: FileReader. This task source is used for events that are asynchronously fired, and for
710: event tasks that are queued for firing, and for the read methods, which queue tasks
711: to update the result.
712:
713:
714: Constructors
1.123 arangana 715: When the FileReader() constructor is invoked, the user agent must return a new FileReader object.
1.88 arangana 716: In environments where the global object is represented by a Window or a WorkerGlobalScope object, the FileReader constructor
1.123 arangana 717: must be available.
1.88 arangana 718:
719:
720: Event Handler Attributes
721:
722: The following are the event
723: handler attributes (and their corresponding event
1.123 arangana 724: handler event types) that user agents must support on
1.88 arangana 725: FileReader as
726: DOM attributes:
727:
728:
729:
730:
731:
732: event handler attribute
734:
735: event handler event type
736:
737:
738:
739:
740: onloadstart
741:
742: loadstart
743:
744:
745: onprogress
746:
747: progress
748:
749:
750: onabort
751:
752: abort
753:
754:
755: onerror
756:
757: error
758:
759:
760: onload
761:
762: load
763:
764:
765: onloadend
766:
767: loadend
768:
769:
770:
771:
772:
773: FileReader States
774: The FileReader object can be in one of 3 states. The
1.94 arangana 775: readyState attribute, on getting,
1.123 arangana 776: must return the current state, which must be one of the following values:
1.88 arangana 777:
778: EMPTY (numeric value 0)The FileReader object has been constructed, and there are no pending reads. None of the read methods have been called. This is the
780: default state of a newly minted FileReader object, until one of the read methods have been called on it.
LOADING (numeric value 1)A File or Blob is being read. One of the read methods is being processed,
783: and no error has occurred during the read.
DONE (numeric value 2)The entire File or Blob has been read into memory,
786: OR a file error occurred during read, OR the read was
787: aborted using abort().
788: The FileReader
789: is no longer reading a File or Blob. If readyState is set to DONE it means
790: at least one of the read methods have been called on this FileReader.
792:
793:
794: Reading a File or Blob
795:
796: Multiple Reads
797:
1.123 arangana 798: The FileReader interface makes available three asynchronous read methods - readAsArrayBuffer, readAsText, and readAsDataURL, which read files into memory. If multiple concurrent read methods are called on the same FileReader object, user agents must throw an InvalidStateError [DOM4] on any of the read methods that occur when readyState = LOADING.
1.88 arangana 799:
800:
801:
802: The result attribute
803: On getting, the result attribute returns a Blob's data as a DOMString, or as
804: an ArrayBuffer [TypedArrays], or null, depending on the read method
805: that has been called on the FileReader, and any errors that may have occurred.
806: It can also return partial Blob data.
807: Partial Blob data is the part of the File or Blob
808: that has been read into memory currently;
1.104 arangana 809: when processing the read method
1.88 arangana 810: readAsText, partial Blob data is a DOMString that is incremented as more bytes
811: are loaded (a portion of the total) [ProgressEvents], and
812: when processing readAsArrayBuffer partial Blob data is an
813: ArrayBuffer [TypedArrays] object consisting of the bytes loaded so far (a portion of the
814: total)[ProgressEvents].
1.89 arangana 815: The list below is normative for the result attribute and is the conformance criteria for this attribute:
1.88 arangana 816:
817:
1.94 arangana 818: On getting, if the readyState is EMPTY (no read method has been called)
1.123 arangana 819: then the result attribute must return null.
On getting, if an error in reading the File or Blob has
821: occurred (using any read method),
1.123 arangana 822: then the result attribute must return null.
On getting, if the readAsDataURL read method is
1.123 arangana 824: used, the result attribute must return a DOMString that is a Data URL [DataURL] encoding of the
1.88 arangana 825: File or Blob's data.
On getting, if the readAsText read method is called
827: and no error in reading the File or Blob has occurred,
1.123 arangana 828: then the result attribute must return a string representing the File or Blob's
829: data as a text string, and should decode the string into memory in the format specified
1.88 arangana 830: by the encoding determination. On getting, while processing the
1.123 arangana 831: readAsText read method, this attibute should return
1.88 arangana 832: partial Blob data in the format specified by
833: the encoding determination as a DOMString that is incremented as more data is read.
1.123 arangana 834: User agents must return at least one such result, with the final result returned at completion of the read. See the caveat about
1.90 arangana 835: partial Blob data being valid within a giving encoding.
1.88 arangana 836:
On getting, if the readAsArrayBuffer read method is called
838: and no error in reading the File or Blob has occurred,
1.123 arangana 839: then the result attribute must return an ArrayBuffer [TypedArrays] object. On getting, while processing the
1.88 arangana 840: readAsArrayBuffer read method, the result
1.123 arangana 841: attribute should return partial Blob data as an ArrayBuffer [TypedArrays]. User agents must return at least one such result,
1.88 arangana 842: with the final result returned at completion of the read.
1.123 arangana 844: If a read is successful, the result attribute must return a non-null value only after a progress event (see also [ProgressEvents]) has fired,
1.88 arangana 845: since all the read methods access Blob data asynchronously. Tasks are queued to update
846: the result attribute as Blob data is made available.
847:
848:
849: The readAsDataURL(blob) method
1.123 arangana 850: When the readAsDataURL(blob) method is called, the user agent must run the steps below (unless otherwise indicated).
1.88 arangana 851:
1.110 arangana 852: If readyState = LOADING throw an InvalidStateError exception [DOM4] and terminate this algorithm.
1.88 arangana 853:
854: Note: The readAsDataURL() method returns due to the algorithm being terminated.
855: If an error occurs during reading of the blob parameter, OR if a user agent's URL length limitations prevent returning
1.94 arangana 857: data as a Data URL [DataURL], set readyState to
1.88 arangana 858: DONE and set result to null. Proceed to the error steps below.
859:
860: Fire a progress event called
861: error. Set the error attribute; on getting, the
1.123 arangana 862: error attribute must be a
1.88 arangana 863: a DOMError object that indicates the kind of
864: file error that has occurred.
Fire a progress event called
866: loadend.
-
868:
869:
Note: The readAsDataURL() method returns due to the algorithm being terminated.
870:
871:
872: If no error has occurred, set readyState to LOADING
Fire a progress event called loadstart.
Return the readAsDataURL() method, but continue to process the steps in this algorithm.
Fire a progress event called progress at completion of the read.
Queue a task to update the result attribute with the blob as a
878: DataURL [DataURL] after it has been fully read into memory; on getting, the result attribute returns the (complete) data of blob as a
879: Data URL [DataURL].
880:
881: - Use the
blob's type
882: attribute as part of the Data URL if it is available in keeping with the Data URL specification [DataURL] .
883: - If the
type attribute is not available on the blob return a Data URL without a media-type.
884: [DataURL].
1.123 arangana 885: Data URLs that do not have media-types [RFC2046] must be treated as plain text by conforming user agents. [DataURL].
1.110 arangana 886:
1.88 arangana 887:
888:
889: Set readyState to
1.88 arangana 891: DONE
Fire a progress event called load.
Fire a progress event called loadend.
896:
897:
898: The readAsText(blob, encoding) method
899:
900: When the readAsText(blob, encoding) method is called (the encoding argument is optional),
1.123 arangana 901: the user agent must run the steps below (unless otherwise indicated).
1.88 arangana 902:
903:
1.110 arangana 904: If readyState = LOADING throw an InvalidStateError [DOM4] and terminate these steps.
1.88 arangana 905:
1.79 arangana 906:
907: Note: The readAsText() method returns due to the algorithm being terminated.
1.88 arangana 908: If an error occurs during reading the blob parameter,
1.94 arangana 910: set readyState to
1.88 arangana 911: DONE and set result to null. Proceed to the error steps below.
912:
913: Fire a progress event called
914: error. Set the error attribute; on getting, the
1.123 arangana 915: error attribute must be a
1.88 arangana 916: a DOMError object that indicates the kind of
917: file error that has occurred.
918: Fire a progress event called
920: loadend.
-
922:
923:
Note: The readAsText() method returns due to the algorithm being terminated.
924:
925:
926: If no error has occurred, set readyState to LOADING
Fire a progress event called loadstart.
Return the readAsText() method, but continue to process the steps in this algorithm
While processing the read, as data from the blob becomes available, user agents should queue tasks to update the result with partial Blob data represented as a string in a format determined by the encoding determination until the read is complete, to accompany the firing of progress events. On getting, the result attribute returns partial Blob data representing the number of bytes currently loaded (as a fraction of the total) [ProgressEvents], decoded into
932: memory according to the encoding determination; user agents must return at least one such result while processing this read method. The last returned value is at completion of the read.
1.88 arangana 933:
1.123 arangana 934: Partial Blob data must be returned such that where possible, the bytes read thus far should be valid code points
1.88 arangana 935: within the encoding; in particular, when executing the encoding determination for
1.123 arangana 936: Partial Blob data, user agents must NOT return the U+FFFD character for bytes that are invalid within an encoding
1.88 arangana 937: till the entire codepoint has been read. For example:
938:
1.116 arangana 939: Suppose a file resource is to be read in UTF-8, and in hexadecimal the bytes in this file are E3 83 91 E3 83 91, which is effectively 0x30D1 0x30D1.
1.123 arangana 940: Suppose the first 5 bytes have been read. The result returned here must be 0x30D1 and have result.length == 1 ,
1.88 arangana 941: and NOT be 0x30D1 0xFFFD with result.length == 2 .
1.123 arangana 942: Even though the trailing E3 83 is not a valid code point in UTF-8 at the fifth byte, user agents must NOT return a result with such invalid code points
1.88 arangana 943: replaced with U+FFFD till it can be determined definitively that the codepoint is invalid.
944:
945: When the blob has been read into memory fully, set readyState to DONE
Terminate this algorithm.
948:
950:
951:
952: The readAsArrayBuffer(blob) method
953:
1.123 arangana 954: When the readAsArrayBuffer(blob) method is called, the user agent must run the steps below (unless otherwise indicated).
1.88 arangana 955:
956:
1.110 arangana 957: If readyState = LOADING throw an InvalidStateError exception [DOM4] and terminate these steps.
1.88 arangana 958:
1.2 arangana 959:
1.88 arangana 960: Note: The readAsArrayBuffer() method returns due to the algorithm being terminated.
961: If an error occurs during reading the blob parameter, set readyState to
1.88 arangana 963: DONE and set result to null. Proceed to the error steps below.
964:
965: Fire a progress event called
966: error. Set the error attribute; on getting, the
1.123 arangana 967: error attribute must be a
1.88 arangana 968: a DOMError that indicates the kind of
969: file error that has occurred.
970: Fire a progress event called
972: loadend.
-
974:
Note: The readAsArrayBuffer() method returns due to the algorithm being terminated.
975:
976:
977: If no error has occurred, set readyState to LOADING
Fire a progress event called loadstart.
Return the readAsArrayBuffer() method, but continue to process the steps in this algorithm.
While processing the read, as data from the blob becomes available, user agents should queue tasks to update the
1.88 arangana 984: result with partial Blob data as an ArrayBuffer [TypedArrays]
985: object containing the bytes read until the read is complete, to accompany the firing of progress events. On getting,
986: the result attribute returns partial Blob data representing the number of bytes currently loaded
987: (as a fraction of the total) [ProgressEvents], as an ArrayBuffer [TypedArrays] object;
1.123 arangana 988: user agents must return at least one such ArrayBuffer [TypedArrays] while processing this read method. The last returned value is at completion of
1.88 arangana 989: the read.
When the blob has been read into memory fully, set readyState to DONE
993:
994:
995: The abort() method
996:
1.123 arangana 997: When the abort() method is called, the user agent must run the steps below:
1.88 arangana 998:
999: If readyState = EMPTY or if readyState = DONE set result to null
1000: and terminate this overall set of steps without doing anything else.
If readyState = LOADING set readyState to
1.88 arangana 1002: DONE and result to null.
If there are any tasks from the object's FileReader task source in one of the
1004: task queues, then remove those tasks.
Terminate the algorithm for the read method being processed.
Fire a progress event called abort
Fire a progress event called loadend
1009:
1010:
1011:
1012: Blob Parameters
1.110 arangana 1013: The three asynchronous read methods, the three synchronous read methods, and createObjectURL take a mandatory
1014: Blob parameter. This section defines this parameter.
1.88 arangana 1015:
1016:
1021:
1022:
1023: Determining Encoding
1.123 arangana 1024: When reading blob objects using the readAsText() read method, the following encoding determination steps must be followed:
1.88 arangana 1025:
1.96 arangana 1026: Let charset be null
If the encoding argument is present, and is the name or alias of a character set used on the Internet
1028: [IANACHARSET], let charset be set to the value of the encoding parameter.
If charset is null, then for each of the rows in the
1.88 arangana 1030: following table, starting with the first one and going down, if the
1031: first bytes of blob match the bytes given in the first
1032: column, then let charset be the encoding given in the cell in
1.111 arangana 1033: the second column of that row. If there is no match then charset
1.112 arangana 1034: remains null.
1.88 arangana 1035:
1036:
1037:
1038: Bytes in Hexadecimal
1039:
1040: Description
1041:
1042:
1049:
1050:
1051: FE FF
1052:
1053: UTF-16BE BOM
1054:
1055:
1056:
1057: FF FE
1058:
1059: UTF-16LE BOM
1060:
1061:
1062: EF BB BF
1063:
1064: UTF-8 BOM
1069:
1070:
1071:
1.96 arangana 1072: If charset is null, and the blob argument's type attribute is present, and its Charset Parameter [RFC2046] is the name or alias of a character set used on the Internet [IANACHARSET], let charset be set to its Charset Parameter.
1074:
1077: If charset is null let charset be UTF-8.
1.113 arangana 1079:
Return the result of decoding the blob using
1.88 arangana 1082: charset; on getting, the result attribute of the FileReader
1083: object returns a string in charset format. The synchronous
1084: readAsText method of the FileReaderSync object returns a string in charset format.
1085: Replace bytes or sequences of bytes that are not
1086: valid according to the charset with a single U+FFFD character [Unicode].
1087: When processing Partial Blob Data, use the encoding caveat, if applicable.
1088:
1090:
1091:
1092: Events
1093: When this specification says to make progress notifications for a read method,
1.123 arangana 1094: the following steps must be followed:
1.88 arangana 1095:
1096:
1097: While the read method is processing, queue a task to
1098: fire a progress event called progress at the
1.123 arangana 1099: FileReader object about every 50ms or for every byte read into memory, whichever is least frequent. At least one event called progress must fire before load is fired, and at 100% completion of the read operation; if 100% of blob can be read into memory in less than 50ms, user agents must fire a progress event called progress at completion.
1.88 arangana 1100:
1.123 arangana 1101: If a given implementation uses buffers of size 65536 bytes to read files, and thus limits reading operations to that size, and a read method is called on a file that is 65537 bytes, then that implementation must fire one progress event for the 65536 first bytes, one progress event for the 65537th byte (which is at completion of read), one load event and one loadend event.
1.88 arangana 1102:
1103: When the data from the blob
1105: has been completely read into memory, queue a task to fire a progress event called
1.91 arangana 1106: load at the FileReader object.
When the data from the blob
1108: has been completely read into memory, queue a task to fire a progress event called
1.91 arangana 1109: loadend at the FileReader object.
1111:
1112: When this specification says to fire a progress event called e (for some
1113: ProgressEvent e at a FileReader reader),
1114: the following are normative:
1115:
1.123 arangana 1116: The progress event e does not bubble. e.bubbles must be false [DOM4]
The progress event e is NOT cancelable. e.cancelable must be false [DOM4]
The term "fire an event" is defined in DOM Core [DOM4]. Progress Events are defined in Progress Events
1.88 arangana 1119: [ProgressEvents].
1121:
1122: Event Summary
1123: The following are the events that are fired at FileReader objects; firing events is defined in
1.110 arangana 1124: DOM Core [DOM4].
1.88 arangana 1125:
1126:
1127:
1128:
1129: Event name
1130:
1131: Interface
1132:
1133: Fired when…
1134:
1135:
1136:
1137: loadstart
1138:
1139: ProgressEvent
1140:
1141: When the read starts.
1142:
1143:
1144:
1145: progress
1146:
1147: ProgressEvent
1148:
1149: While reading (and decoding) blob, and reporting partial Blob data (progess.loaded/progress.total)
1150:
1151:
1152: abort
1153:
1154: ProgressEvent
1155:
1156: When the read has been aborted. For instance, by invoking the
1157: abort() method.
1158:
1159:
1160: error
1161:
1162: ProgressEvent
1163:
1164: When the read has failed (see errors).
1165:
1166:
1167:
1168: load
1169:
1170: ProgressEvent
1171:
1172: When the read has successfully completed.
1173:
1174:
1175: loadend
1176:
1177: ProgressEvent
1178:
1179: When the request has completed (either in success or failure).
1180:
1181:
1182:
1183:
1184: Summary of Event Invariants
1185:
1.110 arangana 1186: This section is informative. The following are invariants applicable to event firing for a given asynchronous read method in this specification:
1.88 arangana 1187:
1188:
1.94 arangana 1189: Once a loadstart has been fired, a corresponding loadend fires at completion of the read, EXCEPT if the read method has been cancelled using abort() and a new read method has been invoked.
1.88 arangana 1190:
1193: One progress event will fire when blob has been completely read into memory.
No progress event fires after any one of abort, load, and error have fired. At most one of abort, load, and error fire for a given read.
1199:
1200:
1201:
1202:
1203:
1204: Reading on Threads
1205: Web Workers allow for the use of synchronous File or Blob read APIs,
1206: since such reads on threads do not block the main thread.
1207: This section defines a synchronous API, which can be used within Workers [Web Workers]. Workers can avail of both the asynchronous API (the
1208: FileReader
1209: object) and the synchronous API (the FileReaderSync object).
1210:
1211: The FileReaderSync Interface
1.94 arangana 1212: This interface provides methods to synchronously read File or Blob objects into memory.
1.88 arangana 1213:
1214:
1215: [Constructor]
1216: interface FileReaderSync {
1217:
1218: // Synchronously return strings
1219:
1.104 arangana 1220: ArrayBuffer readAsArrayBuffer(Blob blob);
1.88 arangana 1221: DOMString readAsText(Blob blob, optional DOMString encoding);
1222: DOMString readAsDataURL(Blob blob);
1223: };
1224:
1225:
1226:
1227: Constructors
1.123 arangana 1228: When the FileReaderSync() constructor is invoked, the user agent must return a new FileReaderSync object.
1229: In environments where the global object is represented by a WorkerGlobalScope object, the FileReaderSync constructor must be available.
1.88 arangana 1230:
1231:
1232: The readAsText method
1233: When the readAsText(blob, encoding) method is called (the
1.123 arangana 1234: encoding argument is optional), the following steps must be followed:
1.88 arangana 1235:
1236: If an error occurs during reading of the blob parameter, throw the appropriate
1237: exception. Terminate these overall steps.
If no error has occurred, read blob into memory. Return the data contents of blob
1239: using the encoding determination algorithm.
1241:
1242:
1243: The readAsDataURL method
1244:
1.123 arangana 1245: When the readAsDataURL(blob) method is called, the following steps must be followed:
1.88 arangana 1246:
1247: If an error occurs during reading of the blob parameter, throw the appropriate exception. Terminate these overall steps.
If no error has occurred, read blob into memory. Return the data contents of blob
1249: as a Data URL [DataURL]
1250:
1251: - Use the
blob's type
1252: attribute as part of the Data URL if it is available in keeping with the Data URL specification [DataURL] .
1253: - If the
type attribute is not available on the blob return a Data URL without a media-type.
1254: [DataURL].
1.123 arangana 1255: Data URLs that do not have media-types [RFC2046] must be treated as plain text by conforming user agents. [DataURL].
1.110 arangana 1256:
1.88 arangana 1257:
1258:
1.87 arangana 1259:
1261:
1262:
1263: The readAsArrayBuffer method
1.123 arangana 1264: When the readAsArrayBuffer(blob) method is called, the following steps must be followed:
1.88 arangana 1265:
1266: If an error occurs during reading the blob parameter, throw the appropriate
1.86 arangana 1267: exception. Terminate these overall steps.
If no error has occurred, read blob into memory. Return the data contents of
1269: blob as an ArrayBuffer [TypedArrays]
1271:
1272:
1273:
1274:
1275: Errors and Exceptions
1276: Error conditions can occur when reading files from the underlying filesystem. The list below of potential error conditions is informative.
1277:
1278: The File or Blob being accessed may not exist at the time one of the asynchronous read methods or synchronous
1279: read methods
1280: are called. This may be due to it having been moved or deleted after a reference to it was acquired (e.g. concurrent modification with another application). See
1281: NotFoundError
A File or Blob may be unreadable. This may be due to permission problems that occur after a reference to a File or Blob has been acquired
1283: (e.g. concurrent lock with another application). See NotReadableError
User agents MAY determine that some files are unsafe for use within Web applications. A file may change on disk since the original file selection,
1285: thus resulting in an invalid read. Additionally, some file and directory structures may be considered restricted
1286: by the underlying filesystem; attempts to read from them may be considered a security violation. See the security considerations.
1287: See SecurityError
Files may be too large to return to the data structures of a Web application. An example might be that URL length limitations imposed by user agents on Data URLs may
1289: make obtaining large files encoded as Data URLs impossible to return [DataURL]. See EncodingError
1291:
1292: Throwing an Exception or Returning an Error
1293: This section is normative. Error conditions can arise when reading a file.
1.110 arangana 1294: Synchronous read methods throw exceptions of the type in the table below if there has been an error with reading.
1.88 arangana 1295:
1.123 arangana 1296: The error attribute of the FileReader object must return a DOMError object [DOM4] of the most appropriate type from the table below if there has been an error, and otherwise returns null.
1.88 arangana 1297:
1298: Type
1299: Description
1300: NotFoundError
1.123 arangana 1301: If the File or Blob resource could not be found at the time the read was processed, then for asynchronous read methods the error attribute must return a "NotFoundError" DOMError and synchronous read methods must throw a NotFoundError exception.
1.88 arangana 1302:
1303: SecurityError
1304: If:
1305: - it is determined that certain files are unsafe for access within a Web application
1306: - it is determined that too many read calls are being made on
File or Blob resources
1307: - it is determined that the file has changed on disk since the user selected it
1308:
1.123 arangana 1309: then for asynchronous read methods the error attribute may return a "SecurityError" DOMError and synchronous read methods may throw a SecurityError exception.
1.88 arangana 1310: This is a security error to be used in situations not covered by any other exception type.
1311:
1312: NotReadableError
1313: If the File or Blob cannot be read, typically due due to permission problems that occur after a
1.123 arangana 1314: reference to a File or Blob has been acquired (e.g. concurrent lock with another application) then for asynchronous read methods the error attribute must return a "NotFoundError" DOMError and synchronous read methods must throw a NotFoundError exception.
1.88 arangana 1315: EncodingError
1.123 arangana 1316: If the File or Blob cannot be encoded as Base64 for a Data URL [DataURL] owing to URL length limitations in implementations, then for asynchronous read methods the error attribute must return a "EncodingError" DOMError, and synchronous read methods must throw an EncodingError exception.
1.110 arangana 1317:
1.88 arangana 1318:
1319:
1320:
1321: A URI for Blob and File reference
1322: This section defines a scheme for a URI used to refer to Blob objects (and File objects).
1323:
1324:
1325: Requirements for a New Scheme
1326: This specification defines a scheme with URIs of the sort: blob:550e8400-e29b-41d4-a716-446655440000#aboutABBA.
1327: This section provides some requirements and is an informative discussion.
1328:
1329: This scheme should be able to be used with web APIs such as XMLHttpRequest [XHR2], and with elements that are designed to be used with HTTP URIs, such as the
1330: img element [HTML]. In general, this scheme should be designed to be used wherever URIs can be used on the web.
1331: This scheme should have defined response codes, so that web applications can respond to scenarios where the resource is not found, or raises an error, etc.
1332:
This scheme should have an origin policy and a
1.94 arangana 1334: lifetime stipulation, to allow safe access to binary data from web applications.
1.88 arangana 1335: URIs in this scheme should be used as a references to "in-memory" Blobs, and also be re-used elsewhere on the platform to refer to binary
1336: resources (e.g. for video-conferencing
1337: [Stream API]).
1338: URIs in this scheme are designed for impermanence, since they will be typically used to access "in memory" resources.
Developers should have the ability to revoke URIs in this scheme, so that they no longer refer to Blob objects. This includes scenarios
1340: where file references are no longer needed by a program, but also other uses of Blob objects.
1341: Consider a scenario where a Blob object can be exported from a drawing program which uses the canvas element and API [HTML]. A snapshot of the drawing can be created by
1.110 arangana 1342: exporting a Blob. This scheme can be used with the img [HTML] element to display the snapshot;
1.88 arangana 1343: if the user deletes the snapshot, any reference to the snapshot in memory via a URI should be invalid, and hence the need to be able to revoke such a URI.
1345:
1346:
1347: Discussion of Existing Schemes
1348:
1349: This section is an informative discussion of existing schemes that may have been repurposed or reused for the use cases for URIs above, and justification for why a new scheme
1350: is considered preferable. These schemes include HTTP [HTTP], file [RFC1630][RFC1738], and a scheme such as
1.94 arangana 1351: urn:uuid [RFC4122]. One broad consideration in determining what scheme to use is providing something with intuitive appeal to web developers.
1.88 arangana 1352:
1353:
1354: HTTP could be repurposed for the use cases mentioned above; it already comes with well-defined request-response semantics that are already used by web applications.
1355: But Blob resources are typically "in-memory"
1356: resident (e.g. after a file has been read into memory), and are thus unlike "traditional" HTTP resources that are dereferenced via DNS. While some user agents automatically
1357: "proxy" the underlying file system on the local machine via an HTTP server (e.g. with URLs of the sort http://localhost), HTTP is not traditionally used with local resources.
1358: Moreover, an important use case for these URIs are that they can be revoked with an API call. HTTP URIs have traditionally been used for resources that may be more permanent
1359: (and that are certainly not chiefly memory-resident, such as files that a web application can read). Reusing the HTTP scheme might be confusing for web developers owing to well-established
1360: practice.
The reuse of file URIs would involve changes to file URI use today, such as adding response codes. While they are used inconsistently in web applications,
1362: the structure of the URIs would change, and request-response behavior would have to be superimposed on what already works in a more-or-less ad-hoc manner. Modifying this for the use cases
1363: cited above is imprudent, given legacy usage. Additionally, the use cases for a Blob URI scheme call for uses beyond the file system.
A scheme of the sort urn:uuid could be used, though use of this scheme is unprecedented in HTML and JavaScript web applications. The urn:uuid scheme is very generic. URIs in the scheme urn:uuid have the disadvantage of unfamiliarity and inconsistency across the web platform. A new scheme has the advantage of being explicit about what is being referenced. In theory, URIs make no guarantee about what sort of resource is obtained when they are dereferenced; that is left to content labeling and media type. But in practice, the name of the scheme creates an expectation about both the resource and the protocol of the request-response transaction. Choosing a name that clarifies the primary use case - namely, access to memory-resident Blob resources - is a worthwhile compromise, and favors clarity, familiarity, and consistency across the web platform.
1.88 arangana 1365:
1367:
1368:
1369:
1370: Definition of blob URI Scheme
1371: This section defines a blob: URI scheme using a formal grammar. A blob: URI consists of the blob: scheme and an opaque string, along with an optional fragment identifier.
1372: In this specification an opaque string is a unique string which can be heuristically generated upon demand such that the probability that two are alike is small, and which is hard to guess (e.g.
1373: the Universally Unique IDentifier (UUID) as defined in [RFC4122] is an opaque string). A fragment identifier is optional, and if used,
1374: has a distinct interpretation depending on the media type of the Blob or File resource in question [RFC2046].
1.123 arangana 1375: This section uses the Augmented Backus-Naur Form (ABNF), defined in [RFC5234]. All blob: URLs must follow this ABNF.
1.88 arangana 1376:
1377:
1378:
1379:
1380: blob = scheme ":" opaqueString [fragIdentifier]
1381:
1382: scheme = "blob"
1383:
1384: ; scheme is always "blob"
1385:
1.123 arangana 1386: ; opaqueString tokens must be globally unique
1.88 arangana 1387: ; opaqueString could be a UUID in its canonical form
1388:
1389:
1390:
1391: The Opaque String
1.123 arangana 1392: Opaque strings must NOT include any reserved characters from [RFC3986] without percent-encoding them.
1393: Opaque strings must be globally unique. Such strings should only use characters in the ranges U+002A to U+002B, U+002D to U+002E, U+0030 to U+0039,
1394: U+0041 to U+005A, U+005E to U+007E [Unicode], and should be at least 36 characters long.
1.88 arangana 1395: UUID is one potential option available to user agents for use with Blob URIs as opaque strings, and their use is strongly encouraged.
1396: UUIDs are defined in [RFC4122]. For an ABNF of UUID, see Appendix A.
1397:
1398:
1399:
1400:
1401:
1402:
1403: Discussion of Fragment Identifier
1404:
1405: The fragment's format, resolution and processing directives depend on the media type [RFC2046] of a potentially retrieved representation, even though such
1406: a retrieval is only performed if the blob: URI is dereferenced. For example, in an HTML file [HTML] the fragment identifier
1407: could be used to refer to an anchor within the file. If the user agent does not recognize the media type of the resource, OR if a fragment identifer is not
1.123 arangana 1408: meaningful within the resource, it must ignore the fragment identifier. Additionally, user agents must honor additional fragment processing directives given in
1.88 arangana 1409: the relevant media format specifications; in particular, this includes any modifications to the fragment production given in HTML [HTML]. The following
1410: section is normative for fragment identifers in general, though it should be noted that affiliated specifications may extend this definition.
1411:
1412:
1413: fragIdentifier = "#" fragment
1414:
1415: ; Fragment Identifiers depend on the media type of the Blob
1416: ; fragment is defined in [RFC3986]
1417: ; fragment processing for HTML is defined in [HTML]
1418:
1419: fragment = *( pchar / "/" / "?" )
1420:
1421: pchar = unreserved / pct-encoded / sub-delims / ":" / "@"
1422:
1423: unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
1424:
1425: pct-encoded = "%" HEXDIG HEXDIG
1426:
1427: sub-delims = "!" / "$" / "&" / "'" / "(" / ")"
1428: / "*" / "+" / "," / ";" / "="
1429:
1430:
1431: A valid Blob URI reference could look like: blob:550e8400-e29b-41d4-a716-446655440000#aboutABBA where "#aboutABBA" might be an HTML fragment identifier referring to an
1432: element with an id attribute of "aboutABBA".
1433:
1434:
1435: Origin of Blob URIs
1.123 arangana 1436: The origin of a Blob URI must be the origin of the script that called URL.createObjectURL.
1437: Blob URIs must only be valid within this origin.
1.88 arangana 1438:
1439:
1440:
1441: Lifetime of Blob URIs
1442: This specification defines the following lifetime conditions on Blob URIs:
1.123 arangana 1443: This specification adds an additional unloading document cleanup step: user agents must revoke any Blob URIs created with URL.createObjectURL from within that document.
1.92 arangana 1444: If these Blob URIs are dereferenced, user agents must respond with 500 Error Condition.
A Blob URI created with URL.createObjectURL using the optional options parameter with oneTimeOnly set to true must be revoked after its first use; subsequent attempts to dereference that Blob URI must return a 500 Error Condition.
User agents must ensure that any Blob URIs are revoked after URL.revokeObjectURL is called with that
1447: Blob URI as an argument. User agents must respond with a 500 Error Condition if a Blob URI is
1.88 arangana 1448: dereferenced after URL.revokeObjectURL is called on that particular Blob URI.
1450:
1451:
1452: Dereferencing Model for Blob URIs
1453:
1454:
1.123 arangana 1455: User agents must only support requests with GET [HTTP]. If the Blob has a
1.88 arangana 1456: type attribute, or if the Blob has been created with a slice call which
1457: uses a contentType argument, responses to dereferencing the Blob URI must include the Content-Type header from HTTP [HTTP] with the value of the type
1.123 arangana 1458: attribute or contentType argument. Specifically, responses must only support a subset of responses that are equivalent to the following from HTTP [HTTP]:
1.88 arangana 1459:
1460: 200 OK
1.123 arangana 1461: This response [HTTP] must be used if the request has succeeded, namely the blob: URI has been requested with a GET,
1.88 arangana 1462: satisfies the origin requirement, and satisfies the lifetime requirement. If this response code is used,
1.123 arangana 1463: the user agent must also use a Content-Type header [HTTP] with a value equal to the Blob object's type attribute. See blob: protocol examples.
1.88 arangana 1464:
1465:
1466:
1.92 arangana 1467: 500 Error Condition
1.88 arangana 1468:
1.123 arangana 1469: This response [HTTP] must be used if:
1.88 arangana 1470:
1471:
1472: Any request method other than GET is used to dereference the URL.
The request violates the origin requirement. In this case, the response should be accompanied by clarifying text alongside the 500 response, e.g. "500 Origin Violation."
The request does not satisfy the lifetime requirement. In this case, the response should be accompanied by clarifying text alongside the 500 response, e.g. "500 Expired URI."
The underlying resource has changed, moved, been deleted or has become invalid. In this case, the response should be accompanied by clarifying text alongside the 500 response, e.g. "500 Invalid Resource."
The permissions surrounding the underlying resource do not permit access. In this case, the response should be accompanied by clarifying text alongside the 500 response, e.g. "500 Access Violation."
A security error has occurred. In this case, the response should be accompanied by clarifying text alongside the 500 response, e.g. "500 Security Violation."
1.123 arangana 1479: This response may be accompanied by additional messages in the response indicating why the Blob resource could not be served. See blob: protocol examples.
1.92 arangana 1480: The 500 Error Condition provides a response code, but not a fixed status. User agents MAY leave it as simply "500 Error Condition" or supply additional status information (e.g. "500 Origin Violation"). Implementers are strongly encouraged to provide messages to developers along with the response code.
1481:
1.88 arangana 1482:
1483: Request and Response Headers
1.92 arangana 1484: This section provides sample exchanges between web applications and user agents using the blob: protocol. A request can be triggered using HTML markup of the sort <img src="blob:550e8400-e29b-41d4-a716-446655440000">, after a web application calls URL.createObjectURL on a given blob, which returns blob:550e8400-e29b-41d4-a716-446655440000 to dereference that blob. These examples merely illustrate the protocol; web developers are not likely to interact with all the headers, but the getAllResponseHeaders() method of XMLHttpRequest, if used, will show relevant response headers [XHR2].
1.88 arangana 1485:
1486: Requests could look like this:
1487:
1.100 arangana 1488: GET 550e8400-e29b-41d4-a716-446655440000
1.88 arangana 1489:
1490: If the blob has an affiliated media type [RFC2046] represented by its type attribute, then the response message should include the Content-Type header from HTTP [HTTP]. See processing media types.
1491:
1.99 arangana 1492: 200 OK
1.88 arangana 1493: Content-Type: image/jpeg
1494:
1495: ....
1496:
1.92 arangana 1497: If there is a file error or any other kind of error associated with the blob, then a user agent can respond with a 500 Error Condition as the response message. This should also be used if any method other than GET is used to make the request.
1.88 arangana 1498:
1.99 arangana 1499: 500 Error Condition
1.88 arangana 1500:
1501: This file cannot be read.
1502:
1503:
1504:
1505: Processing Media Types
1506:
1.123 arangana 1507: If a Content-Type header [HTTP] is provided (e.g. if the blob has an affiliated type attribute), then user agents should obtain and process that media type in a manner consistent with the Media Type Sniffing specification [MIMESNIFF].
1.88 arangana 1508:
1509:
1510:
1511:
1512:
1513:
1514:
1515: Creating and Revoking a Blob URI
1516: Blob URIs are created and revoked using methods exposed on the URL object, supported by
1517: global objects Window [HTML] and WorkerGlobalScope [Web Workers]. Revocation of a Blob URI
1.123 arangana 1518: decouples the Blob URI from the resource it refers to, and if it is dereferenced after it is revoked, user agents must return a 500 response.
1.109 arangana 1519: This section describes a supplemental interface to the URL specification [URL API] and presents methods for Blob URI creation and revocation.
1.88 arangana 1520:
1.106 arangana 1521: partial interface URL {
1.88 arangana 1522:
1.106 arangana 1523: static DOMString createObjectURL(Blob blob, optional objectURLOptions options);
1.88 arangana 1524: static void revokeObjectURL(DOMString url);
1525: };
1.106 arangana 1526:
1.109 arangana 1527: dictionary objectURLOptions
1.106 arangana 1528: {
1529: boolean oneTimeOnly = false;
1530:
1531: };
1532:
1.88 arangana 1533:
1.123 arangana 1534: ECMAScript user agents of this specification must ensure that they do not expose a prototype property on the URL interface
1535: object unless the user agent also implements the URL [URL API] specification. In other words, URL.prototype must
1536: evaluate to true if the user agent implements the URL [URL API] specification, and must NOT evaluate to true otherwise.
1.106 arangana 1537:
1538:
1539: Methods and Parameters
1.109 arangana 1540: - The
createObjectURL static method Returns a unique Blob URI each time it is called on a
1.88 arangana 1541: valid blob argument, which is a non-null Blob in scope of the global
1542: object's URL property from which this static method is called.
1543:
1.123 arangana 1544: If this method is called with a Blob argument that is NOT valid, then user agents must return null.
If this method is called with a valid Blob argument, user agents must return
1.88 arangana 1546: a unique Blob URI that can be used to dereference the blob argument.
1.123 arangana 1548: The optional options dictionary argument contains a key, oneTimeOnly that defaults to false. If set to true, then the first time the Blob URI is dereferenced, user agents must automatically revoke that Blob URI without needing a call to revokeObjectURL() on the Blob URI.
1.88 arangana 1549:
1.109 arangana 1550: In the example below, after obtaining a reference to a Blob object (in this case, a user-selected File from the underlying file system), the static method URL.createObjectURL() is called on that Blob object.
1.88 arangana 1551:
1552: var file = document.getElementById('file').files[0];
1553: if(file){
1554: blobURLref = window.URL.createObjectURL(file);
1555: myimg.src = blobURLref;
1.98 arangana 1556:
1.109 arangana 1557: // blobURLref persists till explicitly revoked
1558: // using a URL.revokeObjectURL() call
1559: // Otherwise it will persist with the document
1560:
1561:
1.88 arangana 1562: }
1563:
1.110 arangana 1564: In the example below, there is no need to call URL.revokeObjectURL() since the oneTimeOnly boolean has been set to true.
1.98 arangana 1565:
1566: var file = document.getElementById('file').files[0];
1567: if(file){
1.106 arangana 1568: blobURLref = window.URL.createObjectURL(file, {oneTimeOnly: true});
1.98 arangana 1569: myimg.src = blobURLref;
1.106 arangana 1570:
1.109 arangana 1571: // The above automatically revokes blobURLref after first use
1.107 arangana 1572: // Subsequent refs to blobURLref return a 500 error response
1573:
1.98 arangana 1574: }
1575:
1.88 arangana 1576:
1577: - The
revokeObjectURL static method
1.88 arangana 1579: Revokes the Blob URI provided in the string url argument.
1580:
1581:
1582: - If the
url refers to a Blob that is both valid and in the
1.94 arangana 1583: same origin of the global object's URL property on which this static method was called,
1.123 arangana 1584: user agents must return a 500 response code when the url is dereferenced.
1.88 arangana 1585: - If the
url refers to a Blob that is NOT valid OR if the value provided for
1586: the url argument is not a Blob URI OR if the url argument
1587: refers to a Blob that is NOT in the same origin as the global object's URL property,
1.123 arangana 1588: this method call does nothing. User agents may display a message on the error console.
1.88 arangana 1589:
1590: The url argument to the revokeObjectURL method is a Blob URI string.
1591:
1592: In the example below, window1 and window2 are separate, but in the same origin; window2 could be an iframe
1593: [HTML] inside window1.
1594:
1595: myurl = window1.URL.createObjectURL(myblob);
1596: window2.URL.revokeObjectURL(myurl);
1597:
1598: Since window1 and window2 are in the same origin, the
1.92 arangana 1599: URL.revokeObjectURL call ensures that subsequent dereferencing of myurl results in a 500 Error Condition response.
1.88 arangana 1600:
1601:
1603:
1604:
1.107 arangana 1605:
1606: Examples of Blob URI Creation and Revocation
1.110 arangana 1607: Blob URIs are strings that dereference Blob objects, and can persist for as long as the document from which they were minted using URL.createObjectURL() - see Lifetime of Blob URIs. To revoke them before the unloading document cleanup steps, web developers must explicitly revoke them with URL.revokeObjectURL(), OR create them for one time only usage, using the oneTimeOnly key in the options dictionary.
1.107 arangana 1608:
1609: This section gives sample usage of creation and revocation of Blob URIs with explanations.
1610:
1.110 arangana 1611: In the example below, two img elements [HTML] refer to the same Blob URI, which was minted for one-time use only using the boolean key in the optional dictionary argument:
1.107 arangana 1612:
1613: var file = document.getElementById('filePicker').files[0];
1614:
1615: var blobURLref = URL.createObjectURL(file, {oneTimeOnly: true});
1616:
1617: img1 = new Image();
1618: img2 = new Image();
1619:
1620: // Only one of the assignments below will work
1621: // One will generate a 500 response when dereferenced
1622:
1623:
1624: img1.src = blobURLref;
1625: img2.src = blobURLref;
1626:
1627:
1628: In the example above, this is equivalent to calling revokeObjectURL() from the onload event handler for each of the images, but use of the boolean key oneTimeOnly reduces boilerplate code. Multiple references to a Blob URI explicitly marked for oneTimeOnly use should be strongly discouraged.
1.109 arangana 1629: In the usage above, if the user toggles images on and off, any assignment to a Blob URI with oneTimeOnly set to true would break that image. Additionally, the image element cannot be cloned, nor can the image's src attribute be read after assignment.
1.107 arangana 1630:
1.108 arangana 1631: In the example below, URL.revokeObjectURL() is explicitly called.
1.107 arangana 1632:
1633:
1634: var blobURLref = URL.createObjectURL(file);
1635: img1 = new Image();
1636: img2 = new Image();
1637:
1638: // Both assignments below work as expected
1639:
1640: img1.src = blobURLref;
1641: img2.src = blobURLref;
1642:
1643: // ... Following body load
1644: // Check if both images have loaded
1645:
1646:
1647: if(img1.complete && img2.complete)
1648: {
1649: // Ensure that subsequent refs return a 500
1650:
1651: URL.revokeObjectURL(blobURLref);
1652: }
1653: else {
1654:
1655: msg("Images cannot be previewed!");
1656:
1657: // revoke the string-based reference
1658:
1659: URL.revokeObjectURL(blobURLref);
1660:
1661: }
1662:
1.109 arangana 1663: The example above allows multiple references to a single Blob URI, but revokes the Blob URI string after both image objects have been loaded. While not restricting number of uses of the Blob URI offers more flexibility, it creates the potential for strings that linger after they are useful, especially in web applications where the document may persist for a while.
1.107 arangana 1664:
1665:
1.106 arangana 1666:
1.88 arangana 1667:
1668: Security Considerations
1669:
1670: This section is informative.
1671:
1672:
1673: This specification allows web content to read files from the underlying file system, as well as provides a means for files to be accessed by unique identifiers,
1674: and as such is subject to some security considerations. This specification also assumes that the
1675: primary user interaction is with the <input type="file"/> element of HTML forms [HTML], and that all files that are being read by
1676: FileReader objects have first been selected by the user. Important security considerations include preventing malicious file
1677: selection attacks (selection looping), preventing access to system-sensitive files, and guarding against modifications of files on disk after a selection has taken place.
1678:
1679: Preventing selection looping. During file selection, a user may be bombarded with the file picker associated with <input
1680: type="file"/> (in a "must choose" loop that forces selection before the file picker is dismissed) and a user agent may prevent file
1681: access to any selections by making the FileList object returned be of size 0.
System-sensitive files (e.g. files in /usr/bin, password files, and other native operating system executables) typically should not
1.123 arangana 1683: be exposed to web content, and should not be accessed via Blob URIs. User agents may throw a SecurityError exception for synchronous read methods, or return a SecurityError DOMError for asynchronous reads.
Cross-origin requests on Blob URIs occur when a Blob URI is accessed across origins. User agents should ensure that the
1685: 500 Error Condition response
1.93 arangana 1686: is used in cross-origin request contexts.
1.88 arangana 1687:
1689: This section is provisional; more security data may supplement this in subsequent drafts.
1690:
1691:
1692: Requirements and Use Cases
1693: This section covers what the requirements are for this API, as well as illustrates some use cases. This version of the API does not satisfy all use cases;
1694: subsequent versions may elect to address these.
1695:
1696: Once a user has given permission, user agents should provide the ability to read and parse data directly from a local file programmatically.
1697:
1698: - Example: A lyrics viewer. User wants to read song lyrics from songs in his plist file. User browses for plist file. File is opened,
1699: read, parsed, and presented to the user as a sortable, actionable list within a web application. User can select songs to fetch lyrics. User uses the
1700: "browse for file" dialog.
1701:
1702: Data should be able to be stored locally so that it is available for later use, which is useful for offline data access for web applications.
1704:
1705: - Example: A Calendar App. User's company has a calendar. User wants to sync local events to company calendar, marked
1706: as "busy" slots (without leaking personal info). User browses for file and selects it. The text/calendar file is parsed
1707: in the browser, allowing the user to merge the files to one calendar view.
1708: The user wants to then save the file back to his local calendar file. (using "Save As" ?). The user can also send the
1709: integrated calendar file back to the server calendar store asynchronously.
1710:
1711:
1712: User agents should provide the ability to save a local file programmatically given an amount of data and a file name.
1714:
1715: - Example: A Spreadsheet App. User interacts with a form, and generates some input. The form then generates a
1716: CSV (Comma Separated Variables) output for the user to import into a spreadsheet, and uses "Save...". The generated
1717: output can also be directly integrated into a web-based spreadsheet, and
1718: uploaded asynchronously.
1719:
1720: User agents should provide a streamlined programmatic ability to send data from a file to a remote server that works more
1722: efficiently than form-based uploads today
1723:
1724: - Example: A Video/Photo Upload App. User is able to select large files for upload, which can then be "chunk-transfered" to the server.
1725:
1726: User agents should provide an API exposed to script that exposes the features above. The user is notified by UI anytime interaction with the file
1728: system takes place, giving the user full ability to cancel or abort the transaction. The user is notified of any file selections, and can cancel these.
1729: No invocations to these APIs occur silently without user intervention.
1730:
1.88 arangana 1733:
1734:
1735: Appendix A
1736: This section is informative and not normative.
1737:
1738: An ABNF for UUID
1739: The following is an informative ABNF [ABNF] for UUID, which is a strongly encouraged choice for the
1740: opaqueString production of Blob URIs.
1741:
1742: UUID = time-low "-" time-mid "-"
1743: time-high-and-version "-"
1744: clock-seq-and-reserved
1745: clock-seq-low "-" node
1746: time-low = 4hexOctet
1747: time-mid = 2hexOctet
1748: time-high-and-version = 2hexOctet
1749: clock-seq-and-reserved = hexOctet
1750: clock-seq-low = hexOctet
1751: node = 6hexOctet
1752: hexOctet = hexDigit hexDigit
1753: hexDigit =
1754: "0" / "1" / "2" / "3" / "4" / "5" / "6" / "7" / "8" / "9" /
1755: "a" / "b" / "c" / "d" / "e" / "f" /
1756: "A" / "B" / "C" / "D" / "E" / "F"
1757:
1758:
1759:
1760:
1761:
1762: Acknowledgements
1763:
1764:
1765: This specification was originally developed by the SVG Working Group. Many thanks to Mark Baker and Anne van Kesteren for their feedback.
1766: Thanks to Robin Berjon for editing the original specification.
1767: Special thanks to Olli Pettay, Nikunj Mehta, Garrett Smith, Aaron Boodman, Michael Nordman, Jian Li, Dmitry Titov, Ian Hickson, Darin Fisher, Sam Weinig, Adrian Bateman and Julian Reschke.
1768: Thanks to the W3C WebApps WG, and to participants on the public-webapps@w3.org listserv
1769:
1770:
1771: References
1772:
1773: Normative references
1774:
1775: - RFC2119
1776: - http://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels, S. Bradner. IETF.
1777: - HTML
1778: - http://dev.w3.org/html5/spec/Overview.html">HTML5: A vocabulary and associated APIs for HTML and XHTML (work in progress), I. Hickson. W3C.
1779: - ProgressEvents
1780: - http://www.w3.org/TR/progress-events/">Progress Events, A. van Kesteren. W3C.
1781: - RFC2397
1782: - http://tools.ietf.org/html/rfc2397">The "data" URL Scheme, L. Masinter. IETF.
1783: - Web Workers
1784: - http://dev.w3.org/html5/workers/">Web Workers (work in progress), I. Hickson. W3C.
1.110 arangana 1785: - DOM4
1786: - http://www.w3.org/TR/domcore/">DOM4 (work in progress), A. Gregor, A. van Kesteren, Ms2ger. W3C.
1.88 arangana 1787: - Unicode
1788: - http://www.unicode.org/versions/Unicode5.2.0/">The Unicode Standard, Version 5.2.0., J. D. Allen, D. Anderson, et al. Unicode Consortium.
1789: - RFC2616
1790: - http://tools.ietf.org/html/rfc2616">Hypertext Transfer Protocol -- HTTP/1.1, R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee. IETF.
1791: - RFC2046
1792: - http://tools.ietf.org/html/rfc2046">Multipurpose Internet Mail Extensions (MIME) Part Two: Media Extensions, N. Freed, N. Borenstein. IETF.
1793: - IANA Charsets
1794: - http://www.iana.org/assignments/character-sets">Official Names for Character Sets on the Internet, K. Simonsen, W.Choi, et al. IANA.
1795: - Typed Arrays
1796: - https://cvs.khronos.org/svn/repos/registry/trunk/public/webgl/doc/spec/TypedArray-spec.html">Typed Arrays (work in progress), V. Vukicevic, K. Russell. Khronos Group.
1797: - RFC5234
1798: - http://tools.ietf.org/html/rfc5234">Augmented BNF for Syntax Specifications: ABNF, D. Crocker, P. Overell. IETF.
1.110 arangana 1799: - URL API Specification
1800: - http://dvcs.w3.org/hg/url/raw-file/tip/Overview.html">URL API (work in progress), A. Barth. W3C.
1.88 arangana 1801: - WebIDL Specification
1802: - http://www.w3.org/TR/WebIDL/">WebIDL (work in progress), C. McCormack.
1803: - ECMAScript
1804: - http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMAScript 5th Edition, A. Wirfs-Brock, P. Lakshman et al.
1805: - MIME Sniffing
1806: - http://mimesniff.spec.whatwg.org/">MIME Sniffing (work in progress), A. Barth and I. Hickson.
1807:
1808:
1809:
1810: Informative References
1811:
1812: - XMLHttpRequest
1813: - http://www.w3.org/TR/XMLHttpRequest2/">XMLHttpRequest Level 2 (work in progress), A. van Kesteren. W3C.
1814: - Google Gears Blob API
1815: - http://code.google.com/apis/gears/api_blob.html">Google Gears Blob API (deprecated)
1816: - RFC4122
1817: - http://tools.ietf.org/html/rfc4122">A Universally Unique IDentifier (UUID) URN Namespace, P. Leach, M. Mealling, R. Salz. IETF.
1818: - RFC3986
1819: - http://tools.ietf.org/html/rfc3986">Uniform Resource Identifier (URI): Generic Syntax, T. Berners-Lee, R. Fielding, L. Masinter. IETF.
1820: - RFC1630
1821: - http://tools.ietf.org/html/rfc1630">Universal Resource Identifiers in WWW, T. Berners-Lee. IETF.
1822: - RFC1738
1823: - http://tools.ietf.org/html/rfc1738">Uniform Resource Locators (URL), T. Berners-Lee, L. Masinter, M. McCahill. IETF.
1824: - Stream API
1.110 arangana 1825: - http://dev.w3.org/2011/webrtc/editor/webrtc.html#stream-api">The Stream API, A. Bergkvist, D. Burnett, C. Jennings, A. Narayanan. W3C.
1.88 arangana 1826:
1827:
1828:
1.79 arangana 1829:
1.88 arangana 1830:
1831:
1.1 arangana 1832: