com.purplehillsbooks.streams

Class ReaderUTF8InputStream

java.lang.Object

java.io.InputStream

com.purplehillsbooks.streams.ReaderUTF8InputStream

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public class ReaderUTF8InputStream
extends java.io.InputStream

ReaderUTF8InputStream Imagine that you have a Reader object, and you want to call a method that requires an InputStream. You don't always have access to the underlying InputStream that the Reader is reading from. This class allows you to "down-convert" from a character oriented Reader back to a byte oriented InputStream with correct UTF-8 encoding characters into the bytes. This is a *proper* conversion from UTF-16 string to UTF-8 byte stream. A string with full Unicode characters can be streamed out as UTF-8 bytes. It performs the conversion on the fly, without needing any large byte buffer internally. Supports UTF-8, the ONLY encoding that guarantees that all characters in the UTF-16 can be expressed without loss of characters. In spite of that logic, some might still insist that this class is more general if it had a parameters to specify the encoding to use. This would greatly slow down the operation of the class, because knowledge of UTF-8 encoding is used to keep the amount of memory low, and to make the conversion very fast. Mark is not supported because you might try to mark in the middle of a multi-byte sequence, and the sequence would have to be stored away. Have not worked through all the implications of this, so for now not supported. Author: Keith Swenson Copyright: Keith Swenson, all rights reserved License: This code is made available under the GNU Lesser GPL license.

Constructor Summary

Constructors

Constructor and Description
ReaderUTF8InputStream(java.io.Reader source) Composes an InputStream stream from any other Reader you may have around.
ReaderUTF8InputStream(java.lang.String source) Composes a stream from a String.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the Stringreader.
void	mark(int limit) Marks the read limit of the StringReader.
boolean	markSupported()
int	read() Reads from the Stringreader.
void	reset() Resets to the beginning by resetting the wrapped Reader.

Methods inherited from class java.io.InputStream

available, read, read, skip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ReaderUTF8InputStream

public ReaderUTF8InputStream(java.io.Reader source)

Composes an InputStream stream from any other Reader you may have around.

Parameters:

source - The Reader object to read from. Must not be null.

ReaderUTF8InputStream

public ReaderUTF8InputStream(java.lang.String source)

Composes a stream from a String. This is a convenience constructor that constructs a StringReader, and then wraps that Reader.

Parameters:

source - The string to read from. Must not be null.

Method Detail

read

public int read()
         throws java.io.IOException

Reads from the Stringreader. If the value is less than 128 it is returned directly, because UTF-8 encoding is this way. If more than 127 the character is broken into a multibyte sequence which will be returned over 2 or more subsequent reads.

Specified by:

read in class java.io.InputStream

Returns:

the value of the next byte of the UTF-8 stream, or -1 if there is nothing left in the original string.

Throws:

java.io.IOException - if the original StringReader fails to be read

close

public void close()
           throws java.io.IOException

Closes the Stringreader.

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Overrides:

close in class java.io.InputStream

Throws:

java.io.IOException - if the original Reader fails to be closed

mark

public void mark(int limit)

Marks the read limit of the StringReader. throws an UnsupportedOperationException. This method is not supported in this class. It is difficult to figure how to translate the mark in bytes to a mark in characters, and to return to it correctly. So simply not supported in this version of the class.

Overrides:

mark in class java.io.InputStream

reset

public void reset()
           throws java.io.IOException

Resets to the beginning by resetting the wrapped Reader.

Overrides:

reset in class java.io.InputStream

Throws:

java.io.IOException - if the StringReader fails to be reset

markSupported

public boolean markSupported()

Overrides:

markSupported in class java.io.InputStream

See Also:

InputStream.markSupported()