Package com.github.dmac100.jshellscriptengine.io

Class ReaderInputStream

java.lang.Object

java.io.InputStream

com.github.dmac100.jshellscriptengine.io.ReaderInputStream

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public class ReaderInputStream
extends java.io.InputStream

InputStream implementation that reads a character stream from a Reader and transforms it to a byte stream using a specified charset encoding. The stream is transformed using a CharsetEncoder object, guaranteeing that all charset encodings supported by the JRE are handled correctly. In particular for charsets such as UTF-16, the implementation ensures that one and only one byte order marker is produced.

Since in general it is not possible to predict the number of characters to be read from the Reader to satisfy a read request on the ReaderInputStream, all reads from the Reader are buffered. There is therefore no well defined correlation between the current position of the Reader and that of the ReaderInputStream. This also implies that in general there is no need to wrap the underlying Reader in a BufferedReader.

ReaderInputStream implements the inverse transformation of InputStreamReader; in the following example, reading from in2 would return the same byte sequence as reading from in (provided that the initial byte sequence is legal with respect to the charset encoding):

 InputStream in = ...
 Charset cs = ...
 InputStreamReader reader = new InputStreamReader(in, cs);
 ReaderInputStream in2 = new ReaderInputStream(reader, cs);

ReaderInputStream implements the same transformation as OutputStreamWriter, except that the control flow is reversed: both classes transform a character stream into a byte stream, but OutputStreamWriter pushes data to the underlying stream, while ReaderInputStream pulls it from the underlying stream.

Note that while there are use cases where there is no alternative to using this class, very often the need to use this class is an indication of a flaw in the design of the code. This class is typically used in situations where an existing API only accepts an InputStream, but where the most natural way to produce the data is as a character stream, i.e. by providing a Reader instance. An example of a situation where this problem may appear is when implementing the javax.activation.DataSource interface from the Java Activation Framework.

Given the fact that the Reader class doesn't provide any way to predict whether the next read operation will block or not, it is not possible to provide a meaningful implementation of the InputStream.available() method. A call to this method will always return 0. Also, this class doesn't support InputStream.mark(int).

Instances of ReaderInputStream are not thread safe.

Since:

2.0

See Also:

org.apache.commons.io.output.WriterOutputStream

Constructor Summary

Constructors

Constructor and Description
ReaderInputStream(java.io.Reader reader) Construct a new ReaderInputStream that uses the default character encoding with a default input buffer size of 1024 characters.
ReaderInputStream(java.io.Reader reader, java.nio.charset.Charset charset) Construct a new ReaderInputStream with a default input buffer size of 1024 characters.
ReaderInputStream(java.io.Reader reader, java.nio.charset.CharsetEncoder encoder) Construct a new ReaderInputStream.
ReaderInputStream(java.io.Reader reader, java.nio.charset.CharsetEncoder encoder, int bufferSize) Construct a new ReaderInputStream.
ReaderInputStream(java.io.Reader reader, java.nio.charset.Charset charset, int bufferSize) Construct a new ReaderInputStream.
ReaderInputStream(java.io.Reader reader, java.lang.String charsetName) Construct a new ReaderInputStream with a default input buffer size of 1024 characters.
ReaderInputStream(java.io.Reader reader, java.lang.String charsetName, int bufferSize) Construct a new ReaderInputStream.

Method Summary

Modifier and Type	Method and Description
void	close() Close the stream.
int	read() Read a single byte.
int	read(byte[] b) Read the specified number of bytes into an array.
int	read(byte[] b, int off, int len) Read the specified number of bytes into an array.

Methods inherited from class java.io.InputStream

available, mark, markSupported, readAllBytes, readNBytes, reset, skip, transferTo

Methods inherited from class java.lang.Object

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

Constructor Detail

ReaderInputStream

public ReaderInputStream(java.io.Reader reader,
                         java.nio.charset.CharsetEncoder encoder)

Construct a new ReaderInputStream.

Parameters:

reader - the target Reader

encoder - the charset encoder

Since:

2.1

ReaderInputStream

public ReaderInputStream(java.io.Reader reader,
                         java.nio.charset.CharsetEncoder encoder,
                         int bufferSize)

Construct a new ReaderInputStream.

Parameters:

reader - the target Reader

encoder - the charset encoder

bufferSize - the size of the input buffer in number of characters

Since:

2.1

ReaderInputStream

public ReaderInputStream(java.io.Reader reader,
                         java.nio.charset.Charset charset,
                         int bufferSize)

Construct a new ReaderInputStream.

Parameters:

reader - the target Reader

charset - the charset encoding

bufferSize - the size of the input buffer in number of characters

ReaderInputStream

public ReaderInputStream(java.io.Reader reader,
                         java.nio.charset.Charset charset)

Construct a new ReaderInputStream with a default input buffer size of 1024 characters.

Parameters:

reader - the target Reader

charset - the charset encoding

ReaderInputStream

public ReaderInputStream(java.io.Reader reader,
                         java.lang.String charsetName,
                         int bufferSize)

Construct a new ReaderInputStream.

Parameters:

reader - the target Reader

charsetName - the name of the charset encoding

bufferSize - the size of the input buffer in number of characters

ReaderInputStream

public ReaderInputStream(java.io.Reader reader,
                         java.lang.String charsetName)

Construct a new ReaderInputStream with a default input buffer size of 1024 characters.

Parameters:

reader - the target Reader

charsetName - the name of the charset encoding

ReaderInputStream

public ReaderInputStream(java.io.Reader reader)

Construct a new ReaderInputStream that uses the default character encoding with a default input buffer size of 1024 characters.

Parameters:

reader - the target Reader

Method Detail

read

public int read(byte[] b,
                int off,
                int len)
         throws java.io.IOException

Read the specified number of bytes into an array.

Overrides:

read in class java.io.InputStream

Parameters:

b - the byte array to read into

off - the offset to start reading bytes into

len - the number of bytes to read

Returns:

the number of bytes read or -1 if the end of the stream has been reached

Throws:

java.io.IOException - if an I/O error occurs

read

public int read(byte[] b)
         throws java.io.IOException

Read the specified number of bytes into an array.

Overrides:

read in class java.io.InputStream

Parameters:

b - the byte array to read into

Returns:

the number of bytes read or -1 if the end of the stream has been reached

Throws:

java.io.IOException - if an I/O error occurs

read

public int read()
         throws java.io.IOException

Read a single byte.

Specified by:

read in class java.io.InputStream

Returns:

either the byte read or -1 if the end of the stream has been reached

Throws:

java.io.IOException - if an I/O error occurs

close

public void close()
           throws java.io.IOException

Close the stream. This method will cause the underlying Reader to be closed.

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 an I/O error occurs