Package org.jline.utils

Class InputStreamReader

java.lang.Object

java.io.Reader

org.jline.utils.InputStreamReader

All Implemented Interfaces:

Closeable, AutoCloseable, Readable

public class InputStreamReader
extends Reader

A specialized InputStreamReader that reads the minimal number of bytes needed.

This class is a custom implementation of InputStreamReader that reads only the minimal number of bytes needed from the input stream to decode characters. Unlike the standard JRE InputStreamReader, which often reads more bytes than necessary, this implementation is optimized for character-by-character reading, which is essential for terminal input handling.

The standard InputStreamReader's behavior of reading ahead is problematic for terminal applications because:

• It can consume bytes that belong to the next user input
• It makes it difficult to implement non-blocking character reading
• It interferes with the character-by-character model used in terminals

This implementation is based on the Apache Harmony code and has been adapted for JLine's needs. It provides the same functionality as the standard InputStreamReader but with more precise control over how many bytes are read from the underlying input stream.

This class turns a byte stream into a character stream. Data read from the source input stream is converted into characters by either a default or a provided character converter. The default encoding is taken from the "file.encoding" system property. It contains a buffer of bytes read from the source stream and converts these into characters as needed. The buffer size is 8K.

This class is used internally by JLine components that need to read characters from input streams, such as terminal input handling and non-blocking readers.

See Also:

• OutputStreamWriter

Field Summary

Fields inherited from class java.io.Reader

lock

Constructor Summary

Constructors

Constructor	Description
InputStreamReader(InputStream in)	Constructs a new InputStreamReader on the InputStream in.
InputStreamReader(InputStream in, String enc)	Constructs a new InputStreamReader on the InputStream in.
InputStreamReader(InputStream in, Charset charset)	Constructs a new InputStreamReader on the InputStream in and Charset charset.
InputStreamReader(InputStream in, CharsetDecoder dec)	Constructs a new InputStreamReader on the InputStream in and CharsetDecoder dec.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes this reader.
String	getEncoding()	Returns the name of the encoding used to convert bytes into characters.
int	read()	Reads a single character from this reader and returns it as an integer with the two higher-order bytes set to 0.
int	read(char[] buf, int offset, int length)	Reads at most length characters from this reader and stores them at position offset in the character array buf.
boolean	ready()	Indicates whether this reader is ready to be read without blocking.

Methods inherited from class java.io.Reader

mark, markSupported, nullReader, read, read, reset, skip, transferTo

Methods inherited from class java.lang.Object

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

Constructor Details

InputStreamReader

public InputStreamReader(InputStream in)

Constructs a new InputStreamReader on the InputStream in. This constructor sets the character converter to the encoding specified in the "file.encoding" property and falls back to ISO 8859_1 (ISO-Latin-1) if the property doesn't exist.

Parameters:

in - the input stream from which to read characters.

InputStreamReader

public InputStreamReader(InputStream in,
 String enc)
                  throws UnsupportedEncodingException

Constructs a new InputStreamReader on the InputStream in. The character converter that is used to decode bytes into characters is identified by name by enc. If the encoding cannot be found, an UnsupportedEncodingException error is thrown.

Parameters:

in - the InputStream from which to read characters.

enc - identifies the character converter to use.

Throws:

NullPointerException - if enc is null.

UnsupportedEncodingException - if the encoding specified by enc cannot be found.

InputStreamReader

public InputStreamReader(InputStream in,
 CharsetDecoder dec)

Constructs a new InputStreamReader on the InputStream in and CharsetDecoder dec.

Parameters:

in - the source InputStream from which to read characters.

dec - the CharsetDecoder used by the character conversion.

InputStreamReader

public InputStreamReader(InputStream in,
 Charset charset)

Constructs a new InputStreamReader on the InputStream in and Charset charset.

Parameters:

in - the source InputStream from which to read characters.

charset - the Charset that defines the character converter

Method Details

close

public void close()
           throws IOException

Closes this reader. This implementation closes the source InputStream and releases all local storage.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in class Reader

Throws:

IOException - if an error occurs attempting to close this reader.

getEncoding

public String getEncoding()

Returns the name of the encoding used to convert bytes into characters. The value null is returned if this reader has been closed.

Returns:

the name of the character converter or null if this reader is closed.

read

public int read()
         throws IOException

Reads a single character from this reader and returns it as an integer with the two higher-order bytes set to 0. Returns -1 if the end of the reader has been reached. The byte value is either obtained from converting bytes in this reader's buffer or by first filling the buffer from the source InputStream and then reading from the buffer.

Overrides:

read in class Reader

Returns:

the character read or -1 if the end of the reader has been reached.

Throws:

IOException - if this reader is closed or some other I/O error occurs.

read

public int read(char[] buf,
 int offset,
 int length)
         throws IOException

Reads at most length characters from this reader and stores them at position offset in the character array buf. Returns the number of characters actually read or -1 if the end of the reader has been reached. The bytes are either obtained from converting bytes in this reader's buffer or by first filling the buffer from the source InputStream and then reading from the buffer.

Specified by:

read in class Reader

Parameters:

buf - the array to store the characters read.

offset - the initial position in buf to store the characters read from this reader.

length - the maximum number of characters to read.

Returns:

the number of characters read or -1 if the end of the reader has been reached.

Throws:

IndexOutOfBoundsException - if offset < 0 or length < 0, or if offset + length is greater than the length of buf.

IOException - if this reader is closed or some other I/O error occurs.

ready

public boolean ready()
              throws IOException

Indicates whether this reader is ready to be read without blocking. If the result is true, the next read() will not block. If the result is false then this reader may or may not block when read() is called. This implementation returns true if there are bytes available in the buffer or the source stream has bytes available.

Overrides:

ready in class Reader

Returns:

true if the receiver will not block when read() is called, false if unknown or blocking will occur.

Throws:

IOException - if this reader is closed or some other I/O error occurs.