qflib 0.98.0

de.qfs.lib.util
Class CountingInputStream

java.lang.Object
  |
  +--java.io.InputStream
        |
        +--de.qfs.lib.util.InputStreamAdapter
              |
              +--de.qfs.lib.util.CountingInputStream

public class CountingInputStream
extends InputStreamAdapter

This class adapts an InputStream to count the bytes read from it. It notifies its registered CountListeners whenever some bytes are successfully read from the stream.

The intention of this class is to provide the necessary data for a progress bar while parsing some input file, where the size of the file is known in advance. For this reason there is no similar CountingReader, since the number of (possibly multibyte) characters in a file cannot be determined in advance. In effect a CountingReader can be created with the help of new InputStreamReader(new CountingInputStream(...)).

Since:
0.96.0
Version:
$Revision: 1.3 $
Author:
Gregor Schmid

Field Summary
protected  long count
          The current byte count for the stream.
protected  java.util.Vector listeners
          The registered CountListeners.
protected  long mark
          The byte count for the mark position.
 
Fields inherited from class de.qfs.lib.util.InputStreamAdapter
stream
 
Constructor Summary
CountingInputStream(java.io.InputStream stream)
          Create a new CountingInputStream.
 
Method Summary
 void addCountListener(CountListener listener)
          Register a new CountListener.
protected  void fireCountChanged(long count)
          Notify all registered listeners of a change in the read count.
 void mark(int readlimit)
          Marks the current position in this input stream.
 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 removeCountListener(CountListener listener)
          Unregister a CountListener.
 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 de.qfs.lib.util.InputStreamAdapter
available, close, markSupported
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

count

protected long count
The current byte count for the stream.

mark

protected long mark
The byte count for the mark position.

listeners

protected java.util.Vector listeners
The registered CountListeners.
Constructor Detail

CountingInputStream

public CountingInputStream(java.io.InputStream stream)
Create a new CountingInputStream.
Parameters:
stream - The InputStream used for delegation.
Method Detail

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. Marks the current position in this input stream.

Overrides:
mark in class InputStreamAdapter
Parameters:
readlimit - The maximum limit of bytes that can be read before the mark position becomes invalid.

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.
Overrides:
read in class InputStreamAdapter
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 b is null, a NullPointerException 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 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[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.

If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

Overrides:
read in class InputStreamAdapter
Parameters:
b - The buffer into which the data is 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 an I/O error occurs.

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, possibly zero. 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 b is null, a NullPointerException is thrown.

If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException 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.

If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

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. Subclasses are encouraged to provide a more efficient implementation of this method.

Overrides:
read in class InputStreamAdapter
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 an I/O error occurs.

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.
Overrides:
reset in class InputStreamAdapter
Throws:
java.io.IOException - If an I/O error occurs.

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 InputStreamAdapter
Parameters:
n - The number of bytes to be skipped.
Returns:
The actual number of bytes skipped.
Throws:
java.io.IOException - If an I/O error occurs.

addCountListener

public void addCountListener(CountListener listener)
Register a new CountListener.
Parameters:
listener - The listener to register.

removeCountListener

public void removeCountListener(CountListener listener)
Unregister a CountListener.
Parameters:
listener - The listener to unregister.

fireCountChanged

protected void fireCountChanged(long count)
Notify all registered listeners of a change in the read count.

qflib 0.98.0