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The FileReaderSync
interface allows to read File
or Blob
objects in a synchronous way.
This interface is only available in workers as it enables synchronous I/O that could potentially block.
Method overview
ArrayBuffer readAsArrayBuffer(Blob blob); |
DOMString readAsBinaryString(Blob blob); |
DOMString readAsText (Blob blob, optional DOMString encoding); |
DOMString readAsDataURL(Blob blob); |
Properties
There aren't any property for this interface.
Methods
readAsArrayBuffer()
This method reads the contents of the specified Blob
or File
. When the read operation is finished, it returns an ArrayBuffer
representing the file's data. If an error happened during the read, the adequate exception is sent.
ArrayBuffer readAsArrayBuffer( in Blob blob );
Parameters
blob
- The DOM
Blob
orFile
to read into theArrayBuffer
.
Return value
An ArrayBuffer
representing the file's data.
Exceptions
The following exceptions can be raised by this method:
NotFoundError
- is raised when the resource represented by the DOM
Blob
orFile
cannot be found, e. g. because it has been erased. SecurityError
- is raised when one of the following problematic situation is detected:
- the resource has been modified by a third party;
- too many read are performed simultaneously;
- the file pointed by the resource is unsafe for a use from the Web (like it is a system file).
NotReadableError
- is raised when the resource cannot be read due to a permission problem, like a concurrent lock.
EncodingError
- is raised when the resource is a data URL and exceed the limit length defined by each browser.
readAsBinaryString()
This method reads the contents of the specified Blob
, which may be a File
. When the read operation is finished, it returns a DOMString
containing the raw binary data from the file. If an error happened during the read, the adequate exception is sent.
readAsArrayBuffer()
should be used instead.String readAsBinaryString( in Blob blob );
Parameters
Return value
A
DOMString
containing the raw binary data from the resource
Exceptions
The following exceptions can be raised by this method:
NotFoundError
- is raised when the resource represented by the DOM
Blob
orFile
cannot be found, e. g. because it has been erased. SecurityError
- is raised when one of the following problematic situation is detected:
- the resource has been modified by a third party;
- two many read are performed simultaneously;
- the file pointed by the resource is unsafe for a use from the Web (like it is a system file).
NotReadableError
- is raised when the resource cannot be read due to a permission problem, like a concurrent lock.
EncodingError
- is raised when the resource is a data URL and exceed the limit length defined by each browser.
readAsText()
This methods reads the specified blob's contents. When the read operation is finished, it returns a DOMString
containing the file represented as a text string. The optional encoding
parameter indicates the encoding to be used. If not present, the method will apply a detection algorithm for it. If an error happened during the read, the adequate exception is sent.
String readAsText(
in Blob blob,
in DOMString encoding Optional
);
Parameters
blob
- The DOM
Blob
orFile
to read into theDOMString
. encoding
- Optional. A string representing the encoding to be used, like iso-8859-1 or UTF-8.
Return value
A DOMString
containing the raw binary data from the resource
Exceptions
The following exceptions can be raised by this method:
NotFoundError
- is raised when the resource represented by the DOM
Blob
orFile
cannot be found, e. g. because it has been erased. SecurityError
- is raised when one of the following problematic situation is detected:
- the resource has been modified by a third party;
- two many read are performed simultaneously;
- the file pointed by the resource is unsafe for a use from the Web (like it is a system file).
NotReadableError
- is raised when the resource cannot be read due to a permission problem, like a concurrent lock.
readAsDataURL()
This method reads the contents of the specified Blob
or File
. When the read operation is finished, it returns a data URL representing the file's data. If an error happened during the read, the adequate exception is sent.
String readAsDataURL( in Blob file );
Return value
An DOMString
representing the file's data as a data URL.
Exceptions
The following exceptions can be raised by this method:
NotFoundError
- is raised when the resource represented by the DOM
Blob
orFile
cannot be found, e. g. because it has been erased. SecurityError
- is raised when one of the following problematic situation is detected:
- the resource has been modified by a third party;
- too many read are performed simultaneously;
- the file pointed by the resource is unsafe for a use from the Web (like it is a system file).
NotReadableError
- is raised when the resource cannot be read due to a permission problem, like a concurrent lock.
EncodingError
- is raised when the resource is a data URL and exceed the limit length defined by each browser.
See also
- File API Specification: FileReaderSyncWD
- Related interfaces:
FileReader
,BlobBuilder
,File
,Blob