Html5 Filesystem

Front 1

How does a web application obtains access to the HTML5 Filesystem

Back 1

A web application obtains access to the HTML5 Filesystem by requesting a LocalFileSystem object using a global method, window.requestFileSystem():

Front 2

What is the syntax for window.requestFileSystem()

Back 2

window.requestFileSystem(type, size, successCallback, opt_errorCallback)

Front 3

Describe the type parameter of the window.requestFileSystem method.

Back 3

Whether the storage should be persistent. Possible values are TEMPORARY or PERSISTENT.

Data stored using TEMPORARY can be removed at the browser’s discretion (for example if more space is needed).

PERSISTENT storage cannot cleared unless explicitly authorized by the user or the application.

Front 4

Describe the size parameter of the window.requestFileSystem method.

Back 4

An indicator of how much storage space, in bytes, the application expects to need.

Front 5

Describe the successCallback parameter of the window.requestFileSystem method.

Back 5

A callback function that is called when the user agent successfully provides a filesystem. Its argument is a FileSystem object.

Front 6

Describe the opt_errorCallback parameter of the window.requestFileSystem method.

Back 6

An optional callback function which is called when an error occurs, or the request for a filesystem is denied. Its argument is a FileError object.

Front 7

What happens when you call window.requestFileSystem for the first time?

Back 7

Calling window.requestFileSystem() for the first time creates a new sandboxed storage space for the app and origin that requested it

Front 8

What is the restrictions on a filesystem

Back 8

A filesystem is restricted to a single application and cannot access another application’s stored data.

Front 9

What is the problem with using this method now.

Back 9

This method is currently vendor prefixed as window.webkitRequestFile System.

Front 10

Requesting a filesystem temporary storage

Back 10

var onError = function(fs) {
console.log('There was an error');
};
var onFS = function(fs) {
console.log('Opened filesystem: ' + fs.name);
};
//window.requestFileSystem(window.TEMPORARY, //5*1024*1024 /*5MB*/, onFs, onError);
*******use vendor prefixed********
window.requestFileSystem(window.TEMPORARY, 5*1024*1024 /*5MB*/, onFs, onError);

Front 11

If all goes well, the success callback (onFS) is called and passed a FileSystem object containing what two properties?

Back 11

1. name
A unique name for the filesystem, assigned by the browser
2. root
A read-only DirectoryEntry representing the root of the filesystem

Front 12

Howdo you get around the fact that applications are granted zero persistent quota by default

Back 12

You need to request some persistent quota before opening the filesystem. That might mean simply wrapping the call to window.requestFileSystem() in the requestQuota() callback.

Front 13

Show an example of requesting the file system with persistent storage

Back 13

const SIZE = 5*1024*1024; /*5MB*/
const TYPE = PERSISTENT;
window.webkitStorageInfo.requestQuota(TYPE, SIZE, function(grantedBytes) {
window.requestFileSystem(TYPE, grantedBytes, onFs, onError);
}, function(e) {
console.log('Error', e);
});

Front 14

How are files in a sandbox filesystem represented?

Back 14

Files in the sandboxed filesystem are represented by the FileEntry interface.

Front 15

What are the properties of the fileEntry interface?

Back 15

1. isFile
2. isDirectory
3. name
4. fullPath
5. filesystem

Front 16

Describe the isFile property of the FileEntry Interface.

Back 16

Boolean. True if the entry is a file.

Front 17

Describe the isDirectory property of the FileEntry Interface.

Back 17

Boolean. True if the entry is a directory.

Front 18

Describe the name property of the FileEntry Interface.

Back 18

DOMString. The name of the entry, excluding the path leading to it.

Front 19

Describe the fullPath property of the FileEntry Interface.

Back 19

DOMString. The full absolute path from the root to the entry.

Front 20

Describe the FileSystem property of the FileEntry Interface.

Back 20

The filesystem on which the entry resides.

Front 21

Describe the methods of the FileEntry Interface.

Back 21

1. getMetadata
2. moveTo
3. copyTo
4. toURL
5. remove
6. getParent
7. createWriter
8. file

Front 22

Describe getMetadata + syntax

Back 22

getMetadata (successCallback, opt_errorCallback)
Look up metadata about this entry.

Front 23

Describe moveTo + syntax

Back 23

moveTo (parentDirEntry, opt_newName, opt_successCallback, opt_errorCallback)

Move an entry to a different location on the filesystem.

Front 24

Describe copyTo + syntax

Back 24

copyTo (parentDirEntry, opt_newName, opt_successCallback, opt_errorCallback)
Copies an entry to a different parent on the filesystem. Directory copies are always
recursive. It is an error to copy a directory inside itself or to copy it into its parent
if a new name is not provided.

Front 25

Describe moveTo + syntax

Back 25

toURL ();
Returns a filesystem: URL that can be used to identify this file. See

Front 26

Describe toURL + syntax

Back 26

remove (successCallback, opt_errorCallback)
Deletes a file or directory. It is an error to attempt to delete the root directory of a
filesystem or a directory that is not empty.

Front 27

Describe getParent + syntax

Back 27

getParent (successCallback, opt_errorCallback)

Return the parent DirectoryEntry containing this entry. If this entry is the root directory, its parent is itself.

Front 28

Describe createWriter + syntax

Back 28

createWriter (successCallback, opt_errorCallback)

Creates a new FileWriter which can be used to write content to this FileEntry.

Front 29

Describe file + syntax

Back 29

file (successCallback, opt_errorCallback)

Returns a File representing the FileEntry to the success callback.

Front 30

How would you look up a file in a directory

Back 30

To look up or create a file in a directory, call its getFile(), passing the name of the file to create.

Front 31

Why would you want to only use asynchronus FileSystem IO

Back 31

In order to avoid blocking UI actions while waiting on filesystem IO

Front 32

What are the methods of the localFileSystem Object

Back 32

1. requestFileSystem
2. resolveLocalFileSystemURL

Front 33

Describe the method resolveLocalFileSystemURL of the localFileSystem Object.

Back 33

Allows the user to look up the Entry for a file or directory referred to by a local URL.

Front 34

What is the syntax for resolveLocalFileSystemURL

Back 34

It has three parameter
1. the URL :
A URL referring to a local file in a filesystem accessable via this API.
2. successCallback:
A callback that is called to report the Entry to which the supplied URL refers.
3. errorCallback(optional):
A callback that is called when errors happen, or when the request to obtain the Entry is denied.

Front 35

Describe the Directory Entry Interface

Back 35

This interface represents a directory on a file system.

Front 36

What are the methods of the DirectoryEntry interface

Back 36

1. createReader
2. getDirectory
3. getFile
4. removeRecursively

Front 37

Describe the createReader method of the DirectoryEntry interface.

Back 37

Creates a new DirectoryReader to read Entries from this Directory.

No parameters.
Return type: DirectoryReader

Front 38

Describe the getDirectory method of the DirectoryEntry interface.

Back 38

Creates or looks up a directory.
parameters:
1. path (DomString)
2. options(Flags Object)
3. succesCallBack(entry Callback)
4. errorCallback(errorCAllback)

Front 39

Describe the path parameter of the getDirectory method.

Back 39

path is a required DomString that is either an absolute path or a relative path from this DirectoryEntry to the directory to be looked up or created. It is an error to attempt to create a directory whose immediate parent does not yet exist.

Front 40

Describe the options parameter of the getDirectory method.

Back 40

Is an optional flag object that sets two flgs create and exclusive to define behaviors if they are true or false the behaciors are as follows
1. If create and exclusive are both true and the path already exists, getDirectory must fail.
2. If create is true, the path doesn't exist, and no other error occurs, getDirectory must create and return a corresponding DirectoryEntry.
3. If create is not true and the path doesn't exist, getDirectory must fail.
4. If create is not true and the path exists, but is a file, getDirectory must fail.
5. Otherwise, if no other error occurs, getDirectory must return a DirectoryEntry corresponding to path.

Front 41

Describe the getFile method of the DirectoryEntry interface.

Back 41

Creates or looks up a file. Same signiture as getDirectory
parameters:
1. path (DomString)
2. options(Flags Object)
3. succesCallBack(entry Callback)
4. errorCallback(errorCAllback)

Front 42

Describe the removeRecursively method of the DirectoryEntry interface.

Back 42

Deletes a directory and all of its contents, if any. In the event of an error [e.g. trying to delete a directory that contains a file that cannot be removed], some of the contents of the directory may be deleted. It is an error to attempt to delete the root directory of a filesystem.
parameters:
successCallback
errorCallback

Front 43

How do you use PERSISTENT storage with the FileSystem API

Back 43

To use PERSISTENT storage with the FileSystem API, Chrome exposes a new API under window.webkitStorageInfo to request storage

Front 44

How do you query an origins current quota usage and allocation?

Back 44

There is also an API to query an origin's current quota usage and allocation: window.webkitStorageInfo.queryUsageAndQuota()