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25  
26  package javax.sound.sampled;
27  
28  
29  /**
30   * A source data line is a data line to which data may be written.  It acts as
31   * a source to its mixer. An application writes audio bytes to a source data line,
32   * which handles the buffering of the bytes and delivers them to the mixer.
33   * The mixer may mix the samples with those from other sources and then deliver
34   * the mix to a target such as an output port (which may represent an audio output
35   * device on a sound card).
36   * <p>
37   * Note that the naming convention for this interface reflects the relationship
38   * between the line and its mixer.  From the perspective of an application,
39   * a source data line may act as a target for audio data.
40   * <p>
41   * A source data line can be obtained from a mixer by invoking the
42   * <code>{@link Mixer#getLine getLine}</code> method of <code>Mixer</code> with
43   * an appropriate <code>{@link DataLine.Info}</code> object.
44   * <p>
45   * The <code>SourceDataLine</code> interface provides a method for writing
46   * audio data to the data line's buffer. Applications that play or mix
47   * audio should write data to the source data line quickly enough to keep the
48   * buffer from underflowing (emptying), which could cause discontinuities in
49   * the audio that are perceived as clicks.  Applications can use the
50   * <code>{@link DataLine#available available}</code> method defined in the
51   * <code>DataLine</code> interface to determine the amount of data currently
52   * queued in the data line's buffer.  The amount of data which can be written
53   * to the buffer without blocking is the difference between the buffer size
54   * and the amount of queued data.  If the delivery of audio output
55   * stops due to underflow, a <code>{@link LineEvent.Type#STOP STOP}</code> event is
56   * generated.  A <code>{@link LineEvent.Type#START START}</code> event is generated
57   * when the audio output resumes.
58   *
59   * @author Kara Kytle
60   * @see Mixer
61   * @see DataLine
62   * @see TargetDataLine
63   * @since 1.3
64   */
65  public interface SourceDataLine extends DataLine {
66  
67  
68      /**
69       * Opens the line with the specified format and suggested buffer size,
70       * causing the line to acquire any required
71       * system resources and become operational.
72       * <p>
73       * The buffer size is specified in bytes, but must represent an integral
74       * number of sample frames.  Invoking this method with a requested buffer
75       * size that does not meet this requirement may result in an
76       * IllegalArgumentException.  The actual buffer size for the open line may
77       * differ from the requested buffer size.  The value actually set may be
78       * queried by subsequently calling <code>{@link DataLine#getBufferSize}</code>.
79       * <p>
80       * If this operation succeeds, the line is marked as open, and an
81       * <code>{@link LineEvent.Type#OPEN OPEN}</code> event is dispatched to the
82       * line's listeners.
83       * <p>
84       * Invoking this method on a line which is already open is illegal
85       * and may result in an <code>IllegalStateException</code>.
86       * <p>
87       * Note that some lines, once closed, cannot be reopened.  Attempts
88       * to reopen such a line will always result in a
89       * <code>LineUnavailableException</code>.
90       *
91       * @param format the desired audio format
92       * @param bufferSize the desired buffer size
93       * @throws LineUnavailableException if the line cannot be
94       * opened due to resource restrictions
95       * @throws IllegalArgumentException if the buffer size does not represent
96       * an integral number of sample frames,
97       * or if <code>format</code> is not fully specified or invalid
98       * @throws IllegalStateException if the line is already open
99       * @throws SecurityException if the line cannot be
100      * opened due to security restrictions
101      *
102      * @see #open(AudioFormat)
103      * @see Line#open
104      * @see Line#close
105      * @see Line#isOpen
106      * @see LineEvent
107      */
108     public void open(AudioFormat format, int bufferSize) throws LineUnavailableException;
109 
110 
111     /**
112      * Opens the line with the specified format, causing the line to acquire any
113      * required system resources and become operational.
114      *
115      * <p>
116      * The implementation chooses a buffer size, which is measured in bytes but
117      * which encompasses an integral number of sample frames.  The buffer size
118      * that the system has chosen may be queried by subsequently calling
119      * <code>{@link DataLine#getBufferSize}</code>.
120      * <p>
121      * If this operation succeeds, the line is marked as open, and an
122      * <code>{@link LineEvent.Type#OPEN OPEN}</code> event is dispatched to the
123      * line's listeners.
124      * <p>
125      * Invoking this method on a line which is already open is illegal
126      * and may result in an <code>IllegalStateException</code>.
127      * <p>
128      * Note that some lines, once closed, cannot be reopened.  Attempts
129      * to reopen such a line will always result in a
130      * <code>LineUnavailableException</code>.
131      *
132      * @param format the desired audio format
133      * @throws LineUnavailableException if the line cannot be
134      * opened due to resource restrictions
135      * @throws IllegalArgumentException if <code>format</code>
136      * is not fully specified or invalid
137      * @throws IllegalStateException if the line is already open
138      * @throws SecurityException if the line cannot be
139      * opened due to security restrictions
140      *
141      * @see #open(AudioFormat, int)
142      * @see Line#open
143      * @see Line#close
144      * @see Line#isOpen
145      * @see LineEvent
146      */
147     public void open(AudioFormat format) throws LineUnavailableException;
148 
149 
150     /**
151      * Writes audio data to the mixer via this source data line.  The requested
152      * number of bytes of data are read from the specified array,
153      * starting at the given offset into the array, and written to the data
154      * line's buffer.  If the caller attempts to write more data than can
155      * currently be written (see <code>{@link DataLine#available available}</code>),
156      * this method blocks until the requested amount of data has been written.
157      * This applies even if the requested amount of data to write is greater
158      * than the data line's buffer size.  However, if the data line is closed,
159      * stopped, or flushed before the requested amount has been written,
160      * the method no longer blocks, but returns the number of bytes
161      * written thus far.
162      * <p>
163      * The number of bytes that can be written without blocking can be ascertained
164      * using the <code>{@link DataLine#available available}</code> method of the
165      * <code>DataLine</code> interface.  (While it is guaranteed that
166      * this number of bytes can be written without blocking, there is no guarantee
167      * that attempts to write additional data will block.)
168      * <p>
169      * The number of bytes to write must represent an integral number of
170      * sample frames, such that:
171      * <br>
172      * <center><code>[ bytes written ] % [frame size in bytes ] == 0</code></center>
173      * <br>
174      * The return value will always meet this requirement.  A request to write a
175      * number of bytes representing a non-integral number of sample frames cannot
176      * be fulfilled and may result in an <code>IllegalArgumentException</code>.
177      *
178      * @param b a byte array containing data to be written to the data line
179      * @param len the length, in bytes, of the valid data in the array
180      * (in other words, the requested amount of data to write, in bytes)
181      * @param off the offset from the beginning of the array, in bytes
182      * @return the number of bytes actually written
183      * @throws IllegalArgumentException if the requested number of bytes does
184      * not represent an integral number of sample frames,
185      * or if <code>len</code> is negative
186      * @throws ArrayIndexOutOfBoundsException if <code>off</code> is negative,
187      * or <code>off+len</code> is greater than the length of the array
188      * <code>b</code>.
189      *
190      * @see TargetDataLine#read
191      * @see DataLine#available
192      */
193     public int write(byte[] b, int off, int len);
194 
195     /**
196      * Obtains the number of sample frames of audio data that can be written to
197      * the mixer, via this data line, without blocking.  Note that the return
198      * value measures sample frames, not bytes.
199      * @return the number of sample frames currently available for writing
200      * @see TargetDataLine#availableRead
201      */
202     //public int availableWrite();
203 }