org.jruby.embed.io
Class ReaderInputStream

java.lang.Object
  extended by java.io.InputStream
      extended by org.jruby.embed.io.ReaderInputStream
All Implemented Interfaces:
java.io.Closeable

public class ReaderInputStream
extends java.io.InputStream

A ReaderInputStream converts java.io.Reader to java.io.InputStream. The ReaderInputStream reads data in a given Reader object into its internal buffer so that users of this class can access the file that Reader read by using methods defined in java.io.InputStream.

Author:
Yoko Harada

Constructor Summary
ReaderInputStream(java.io.Reader reader)
          Creates ReaderInputStream from a given Reader type object with a default encoding.
ReaderInputStream(java.io.Reader reader, java.lang.String encoding)
          Creates ReaderInputStream from a given Reader type object with a specifed encoding.
 
Method Summary
 int available()
          Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream.
 void close()
          Closes this input stream and releases any system resources associated with the stream.
 void mark(int readlimit)
          Marks the current position in this input stream.
 boolean markSupported()
          Tests if this input stream supports the mark and reset methods.
 int read()
          Reads the next byte of data from the input stream.
 int read(byte[] b)
          Reads some number of bytes from the input stream and stores them into the buffer array b.
 int read(byte[] b, int off, int len)
          Reads up to len bytes of data from the input stream into an array of bytes.
 void reset()
          Repositions this stream to the position at the time the mark method was last called on this input stream.
 long skip(long n)
          Skips over and discards n bytes of data from this input stream.
 
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)
Creates ReaderInputStream from a given Reader type object with a default encoding.

Parameters:
reader - java.io.Reader object to be read data from.

ReaderInputStream

public ReaderInputStream(java.io.Reader reader,
                         java.lang.String encoding)
Creates ReaderInputStream from a given Reader type object with a specifed encoding.

Parameters:
reader - java.io.Reader object to be read data from.
encoding - an encoding of the created stream.
Method Detail

available

public int available()
              throws java.io.IOException
Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.

Note that while some implementations of InputStream will return the total number of bytes in the stream, many will not. It is never correct to use the return value of this method to allocate a buffer intended to hold all data in this stream.

A subclass' implementation of this method may choose to throw an IOException if this input stream has been closed by invoking the close() method.

The available method for class InputStream always returns 0.

Overrides:
available in class java.io.InputStream
Returns:
an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking or 0 when it reaches the end of the input stream.
Throws:
java.io.IOException - if an I/O error occurs.

close

public void close()
           throws java.io.IOException
Closes this input stream and releases any system resources associated with the stream.

Specified by:
close in interface java.io.Closeable
Overrides:
close in class java.io.InputStream
Throws:
java.io.IOException - if an I/O error occurs.

mark

public void mark(int readlimit)
Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at the last marked position so that subsequent reads re-read the same bytes.

The readlimit arguments tells this input stream to allow that many bytes to be read before the mark position gets invalidated.

The general contract of mark is that, if the method markSupported returns true, the stream somehow remembers all the bytes read after the call to mark and stands ready to supply those same bytes again if and whenever the method reset is called. However, the stream is not required to remember any data at all if more than readlimit bytes are read from the stream before reset is called.

Marking a closed stream should not have any effect on the stream.

The mark method of InputStream does nothing.

Overrides:
mark in class java.io.InputStream
Parameters:
readlimit - the maximum limit of bytes that can be read before the mark position becomes invalid.
See Also:
InputStream.reset()

markSupported

public boolean markSupported()
Tests if this input stream supports the mark and reset methods. Whether or not mark and reset are supported is an invariant property of a particular input stream instance.

Overrides:
markSupported in class java.io.InputStream
Returns:
true if this stream instance supports the mark and reset methods; false otherwise.
See Also:
InputStream.mark(int), InputStream.reset()

read

public int read()
         throws java.io.IOException
Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

A subclass must provide an implementation of this method.

Specified by:
read in class java.io.InputStream
Returns:
the next byte of data, or -1 if the end of the stream is reached.
Throws:
java.io.IOException - if an I/O error occurs.

read

public int read(byte[] b)
         throws java.io.IOException
Reads some number of bytes from the input stream and stores them into the buffer array b. The number of bytes actually read is returned as an integer. This method blocks until input data is available, end of file is detected, or an exception is thrown.

If the length of b is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at the end of the file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[0], the next one into b[1], and so on. The number of bytes read is, at most, equal to the length of b. Let k be the number of bytes actually read; these bytes will be stored in elements b[0] through b[k-1], leaving elements b[k] through b[b.length-1] unaffected.

The read(b) method for class InputStream has the same effect as:

 read(b, 0, b.length) 

Overrides:
read in class java.io.InputStream
Parameters:
b - the buffer into which the data is read.
Returns:
the total number of bytes read into the buffer, or -1 is there is no more data because the end of the stream has been reached.
Throws:
java.io.IOException - If the first byte cannot be read for any reason other than the end of the file, if the input stream has been closed, or if some other I/O error occurs.
java.lang.NullPointerException - if b is null.
See Also:
InputStream.read(byte[], int, int)

read

public int read(byte[] b,
                int off,
                int len)
         throws java.io.IOException
Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read. The number of bytes actually read is returned as an integer.

This method blocks until input data is available, end of file is detected, or an exception is thrown.

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[off], the next one into b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k] through b[off+len-1] unaffected.

In every case, elements b[0] through b[off] and elements b[off+len] through b[b.length-1] are unaffected.

The read(b, off, len) method for class InputStream simply calls the method read() repeatedly. If the first such call results in an IOException, that exception is returned from the call to the read(b, off, len) method. If any subsequent call to read() results in a IOException, the exception is caught and treated as if it were end of file; the bytes read up to that point are stored into b and the number of bytes read before the exception occurred is returned. The default implementation of this method blocks until the requested amount of input data len has been read, end of file is detected, or an exception is thrown. Subclasses are encouraged to provide a more efficient implementation of this method.

Overrides:
read in class java.io.InputStream
Parameters:
b - the buffer into which the data is read.
off - the start offset in array b at which the data is written.
len - the maximum number of bytes to read.
Returns:
the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
Throws:
java.io.IOException - If the first byte cannot be read for any reason other than end of file, or if the input stream has been closed, or if some other I/O error occurs.
java.lang.NullPointerException - If b is null.
java.lang.IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off
See Also:
InputStream.read()

reset

public void reset()
           throws java.io.IOException
Repositions this stream to the position at the time the mark method was last called on this input stream.

The general contract of reset is:

Overrides:
reset in class java.io.InputStream
Throws:
java.io.IOException - if this stream has not been marked or if the mark has been invalidated.
See Also:
InputStream.mark(int), IOException

skip

public long skip(long n)
          throws java.io.IOException
Skips over and discards n bytes of data from this input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. This may result from any of a number of conditions; reaching end of file before n bytes have been skipped is only one possibility. The actual number of bytes skipped is returned. If n is negative, no bytes are skipped.

Overrides:
skip in class java.io.InputStream
Parameters:
n - the number of bytes to be skipped.
Returns:
the actual number of bytes skipped.
Throws:
java.io.IOException - if the stream does not support seek, or if some other I/O error occurs.


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