SourceDataLine.java

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package javax.sound.sampled;


/**
 * A source data line is a data line to which data may be written.  It acts as
 * a source to its mixer. An application writes audio bytes to a source data line,
 * which handles the buffering of the bytes and delivers them to the mixer.
 * The mixer may mix the samples with those from other sources and then deliver
 * the mix to a target such as an output port (which may represent an audio output
 * device on a sound card).
 * <p>
 * Note that the naming convention for this interface reflects the relationship
 * between the line and its mixer.  From the perspective of an application,
 * a source data line may act as a target for audio data.
 * <p>
 * A source data line can be obtained from a mixer by invoking the
 * <code>{@link Mixer#getLine getLine}</code> method of <code>Mixer</code> with
 * an appropriate <code>{@link DataLine.Info}</code> object.
 * <p>
 * The <code>SourceDataLine</code> interface provides a method for writing
 * audio data to the data line's buffer. Applications that play or mix
 * audio should write data to the source data line quickly enough to keep the
 * buffer from underflowing (emptying), which could cause discontinuities in
 * the audio that are perceived as clicks.  Applications can use the
 * <code>{@link DataLine#available available}</code> method defined in the
 * <code>DataLine</code> interface to determine the amount of data currently
 * queued in the data line's buffer.  The amount of data which can be written
 * to the buffer without blocking is the difference between the buffer size
 * and the amount of queued data.  If the delivery of audio output
 * stops due to underflow, a <code>{@link LineEvent.Type#STOP STOP}</code> event is
 * generated.  A <code>{@link LineEvent.Type#START START}</code> event is generated
 * when the audio output resumes.
 *
 * @author Kara Kytle
 * @see Mixer
 * @see DataLine
 * @see TargetDataLine
 * @since 1.3
 */
public interface SourceDataLine extends DataLine {


    /**
     * Opens the line with the specified format and suggested buffer size,
     * causing the line to acquire any required
     * system resources and become operational.
     * <p>
     * The buffer size is specified in bytes, but must represent an integral
     * number of sample frames.  Invoking this method with a requested buffer
     * size that does not meet this requirement may result in an
     * IllegalArgumentException.  The actual buffer size for the open line may
     * differ from the requested buffer size.  The value actually set may be
     * queried by subsequently calling <code>{@link DataLine#getBufferSize}</code>.
     * <p>
     * If this operation succeeds, the line is marked as open, and an
     * <code>{@link LineEvent.Type#OPEN OPEN}</code> event is dispatched to the
     * line's listeners.
     * <p>
     * Invoking this method on a line which is already open is illegal
     * and may result in an <code>IllegalStateException</code>.
     * <p>
     * Note that some lines, once closed, cannot be reopened.  Attempts
     * to reopen such a line will always result in a
     * <code>LineUnavailableException</code>.
     *
     * @param format the desired audio format
     * @param bufferSize the desired buffer size
     * @throws LineUnavailableException if the line cannot be
     * opened due to resource restrictions
     * @throws IllegalArgumentException if the buffer size does not represent
     * an integral number of sample frames,
     * or if <code>format</code> is not fully specified or invalid
     * @throws IllegalStateException if the line is already open
     * @throws SecurityException if the line cannot be
     * opened due to security restrictions
     *
     * @see #open(AudioFormat)
     * @see Line#open
     * @see Line#close
     * @see Line#isOpen
     * @see LineEvent
     */
    public void open(AudioFormat format, int bufferSize) throws LineUnavailableException;


    /**
     * Opens the line with the specified format, causing the line to acquire any
     * required system resources and become operational.
     *
     * <p>
     * The implementation chooses a buffer size, which is measured in bytes but
     * which encompasses an integral number of sample frames.  The buffer size
     * that the system has chosen may be queried by subsequently calling
     * <code>{@link DataLine#getBufferSize}</code>.
     * <p>
     * If this operation succeeds, the line is marked as open, and an
     * <code>{@link LineEvent.Type#OPEN OPEN}</code> event is dispatched to the
     * line's listeners.
     * <p>
     * Invoking this method on a line which is already open is illegal
     * and may result in an <code>IllegalStateException</code>.
     * <p>
     * Note that some lines, once closed, cannot be reopened.  Attempts
     * to reopen such a line will always result in a
     * <code>LineUnavailableException</code>.
     *
     * @param format the desired audio format
     * @throws LineUnavailableException if the line cannot be
     * opened due to resource restrictions
     * @throws IllegalArgumentException if <code>format</code>
     * is not fully specified or invalid
     * @throws IllegalStateException if the line is already open
     * @throws SecurityException if the line cannot be
     * opened due to security restrictions
     *
     * @see #open(AudioFormat, int)
     * @see Line#open
     * @see Line#close
     * @see Line#isOpen
     * @see LineEvent
     */
    public void open(AudioFormat format) throws LineUnavailableException;


    /**
     * Writes audio data to the mixer via this source data line.  The requested
     * number of bytes of data are read from the specified array,
     * starting at the given offset into the array, and written to the data
     * line's buffer.  If the caller attempts to write more data than can
     * currently be written (see <code>{@link DataLine#available available}</code>),
     * this method blocks until the requested amount of data has been written.
     * This applies even if the requested amount of data to write is greater
     * than the data line's buffer size.  However, if the data line is closed,
     * stopped, or flushed before the requested amount has been written,
     * the method no longer blocks, but returns the number of bytes
     * written thus far.
     * <p>
     * The number of bytes that can be written without blocking can be ascertained
     * using the <code>{@link DataLine#available available}</code> method of the
     * <code>DataLine</code> interface.  (While it is guaranteed that
     * this number of bytes can be written without blocking, there is no guarantee
     * that attempts to write additional data will block.)
     * <p>
     * The number of bytes to write must represent an integral number of
     * sample frames, such that:
     * <br>
     * <center><code>[ bytes written ] % [frame size in bytes ] == 0</code></center>
     * <br>
     * The return value will always meet this requirement.  A request to write a
     * number of bytes representing a non-integral number of sample frames cannot
     * be fulfilled and may result in an <code>IllegalArgumentException</code>.
     *
     * @param b a byte array containing data to be written to the data line
     * @param len the length, in bytes, of the valid data in the array
     * (in other words, the requested amount of data to write, in bytes)
     * @param off the offset from the beginning of the array, in bytes
     * @return the number of bytes actually written
     * @throws IllegalArgumentException if the requested number of bytes does
     * not represent an integral number of sample frames,
     * or if <code>len</code> is negative
     * @throws ArrayIndexOutOfBoundsException if <code>off</code> is negative,
     * or <code>off+len</code> is greater than the length of the array
     * <code>b</code>.
     *
     * @see TargetDataLine#read
     * @see DataLine#available
     */
    public int write(byte[] b, int off, int len);

    /**
     * Obtains the number of sample frames of audio data that can be written to
     * the mixer, via this data line, without blocking.  Note that the return
     * value measures sample frames, not bytes.
     * @return the number of sample frames currently available for writing
     * @see TargetDataLine#availableRead
     */
    //public int availableWrite();
}