Class FileStream
Object | +--FileStream
- class FileStream
A FileStream allows reading or writing specific parts of a File.
The FileStream class exposes several ways of reading from and writing to Files.
Examples include reading and writing bytes, strings and lines.
When the FileStream is created a pointer is usually set at the beginning of the file.
As the read methods are called, the pointer moves through the file. Subsequent
calls to the read methods read from that point and onward. When the end of
the file is reached, the eof property is set to true.
This class supports Base64 data for use in cases like XMLHttpRequest. This
object does not support writing binary data, so the Base64 methods can be
used to write binary data encoded as strings.
By default, the FileStream object uses an UTF-8 encoding when writing. You
can change this by setting the encoding property of the FileStream or by
supplying a charset argument to the various methods that write characters.
Defined in file-io.js
| Field Summary | |
int |
bytesAvailable
Number of of bytes available from the current position to the end of the FileStream. |
String |
encoding
The encoding of this FileStream. |
boolean |
eof
Whether ot not the end of the FileStream has been reached. |
String |
newLine
Newline character used for this particular FileStream. |
int |
position
The current byte index position of this FileStream. |
String |
systemNewLine
The system default character for separating lines in a file. |
| Constructor Summary | |
FileStream
()
This class has no public constructor. |
|
| Method Summary | |
void
|
close( )
Close the FileStream for reading or writing.
|
String
|
read( <int> length, <String> charset )
Read a number of characters from the FileStream. |
String
|
readBase64( <int> length )
Read bytes from the FileStream and encode it as Base64
|
ByteArray
|
readBytes( <int> length )
Read a number of bytes from the FileStream
|
String
|
readLine( <String> charset )
Read a line of characters from the FileStream
|
void
|
write( <String> string, <String> charset )
Write a string of characters to the FileStream
|
void
|
writeBase64( <String> string )
Decode a Base64 encoded string and write the data to the FileStream.
|
void
|
writeBytes( <ByteArray> bytes, <int> length )
Write a set of bytes to the FileStream
|
void
|
writeFile( <File> file )
Write a File to the FileStream.
|
void
|
writeImage( <HTMLImageElement> image )
Write an image to the FileStream.
|
void
|
writeLine( <String> string, <String> charset )
Write a line of characters to the FileStream |
| Field Detail |
bytesAvailable
int bytesAvailable
FileStream.
The value of this property is effectively fileSize - position.
encoding
String encoding
FileStream.
This property defaults to UTF-8. Change it to override the default encoding
used when writing to the FileStream. This can be overriden on a case-by-case
basis by supplying the charset argument to the various methods
which write characters.
eof
boolean eof
FileStream has been reached.
If the FileStream is unreadable, this property is true.
newLine
String newLine
FileStream.
This is the same as systemNewLine when the FileStream is created.
This can be set to override the default character used for splitting lines when calling
readLine() or writeLine().
position
int position
FileStream.
You may set the position programmatically. If it is set to < 0, the position will be 0.
If it is set to > fileSize, the position will be fileSize.
systemNewLine
String systemNewLine
| Constructor Detail |
FileStream
FileStream()
| Method Detail |
close
void close( )
FileStream for reading or writing.read
String read( <int> length, <String> charset )
This function will read length number
of characters from the stream.
If there are less than length characters left
in the file, only the remaining characters in the file are
read, and the eof property is set to true.
If eof is true when this method is called,
null will be returned.
The resulting String is encoded with the charset in the
FileStream.encoding property unless the optional charset
argument is given.
length - Number of characters to read. charset - The character set to use when reading. readBase64
String readBase64( <int> length )
FileStream and encode it as Base64
This method will read length number of
bytes from the FileStream and return the data as a Base64
encoded String.
This is typically used to encode data from binary files
in order to transfer them for example over XMLHttpRequest.
As the method will read a number of bytes as specified
in the length argument, and then encode it, a call to
stream.readBase64(100) will not necessarily end
up as a String with a length of 100.
If there are less than length bytes left
in the file, only the remaining bytes in the file are
read, and the eof property is set to true.
If eof is true when this method is called,
null will be returned.
length - Number of bytes to read. FileStream as a Base64 encoded String, or null if there are no data to read. readBytes
ByteArray readBytes( <int> length )
FileStream
This function will read length number
of bytes from the FileStream.
If there are less than length bytes left
in the file, only the remaining bytes in the file are
read, and the eof property is set to true.
If eof is true when this method is called,
null will be returned.
length - The number of bytes to read. readLine
String readLine( <String> charset )
FileStream
This functions will read all characters up to and including the next
newline in the FileStream as defined by the newLine property.
If there are no newlines left in the stream, the resulting string will
not have a newline character and the eof property is set
to true.
If eof is true when this method is called,
null is returned.
The resulting String is encoded with the charset in the
FileStream.encoding property unless the optional charset
argument is given.
charset - The character set to use when reading. Optional. write
void write( <String> string, <String> charset )
FileStream
This method will write the given String of characters to the FileStream, using
the given charset or the charset in the FileStream.encoding property.
The charset argument is currently ignored.
string - The String of characters to write. charset - The charset to use when writing. Optional. writeBase64
void writeBase64( <String> string )
FileStream.
This method takes a String encoded as Base64, decodes it and writes
the resulting data to the FileStream. It is typically used for
binary data encoded as Base64 when its transferred for example
over XMLHttpRequest.string - Base64 encoded String to write. writeBytes
void writeBytes( <ByteArray> bytes, <int> length )
FileStream
This method will write the length first bytes
from the given ByteArray to the stream.bytes - The bytes to write. length - The number of bytes to write. writeFile
void writeFile( <File> file )
FileStream.
This will write the entire contents of the given File
to the FileStream.file - The File to write. writeImage
void writeImage( <HTMLImageElement> image )
FileStream.
This function will take either an HTMLImageElement or an HTMLCanvasElement
and write the binary data to the FileStream. In the case of HTMLCanvasElement,
the image is first encoded as a PNG image.image - The HTMLImageElement or HTMLCanvasElement to write. writeLine
void writeLine( <String> string, <String> charset )
This method will write the given String with an appended newline character taken from
the newLine property to the FileStream, using the given charset or the charset
in the FileStream.encoding property.
The charset argument is currently ignored.
string - The string of characters to write. charset - The charset to use when writing. Optional.