projects / OpenSPARC-T2-SAM / blame
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| 55 | <H2><A NAME="SECTION009550000000000000000"></A><A NAME="event-objects"></A> | |
| 56 | <BR> | |
| 57 | 7.5.5 Event Objects | |
| 58 | </H2> | |
| 59 | ||
| 60 | <P> | |
| 61 | This is one of the simplest mechanisms for communication between | |
| 62 | threads: one thread signals an event and other threads wait for it. | |
| 63 | ||
| 64 | <P> | |
| 65 | An event object manages an internal flag that can be set to true with | |
| 66 | the <tt class="method">set()</tt> method and reset to false with the <tt class="method">clear()</tt> | |
| 67 | method. The <tt class="method">wait()</tt> method blocks until the flag is true. | |
| 68 | ||
| 69 | <P> | |
| 70 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 71 | <td><nobr><b><span class="typelabel">class</span> <tt id='l2h-2733' xml:id='l2h-2733' class="class">Event</tt></b>(</nobr></td> | |
| 72 | <td><var></var>)</td></tr></table></dt> | |
| 73 | <dd> | |
| 74 | The internal flag is initially false. | |
| 75 | </dl> | |
| 76 | ||
| 77 | <P> | |
| 78 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 79 | <td><nobr><b><tt id='l2h-2734' xml:id='l2h-2734' class="method">isSet</tt></b>(</nobr></td> | |
| 80 | <td><var></var>)</td></tr></table></dt> | |
| 81 | <dd> | |
| 82 | Return true if and only if the internal flag is true. | |
| 83 | </dl> | |
| 84 | ||
| 85 | <P> | |
| 86 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 87 | <td><nobr><b><tt id='l2h-2735' xml:id='l2h-2735' class="method">set</tt></b>(</nobr></td> | |
| 88 | <td><var></var>)</td></tr></table></dt> | |
| 89 | <dd> | |
| 90 | Set the internal flag to true. | |
| 91 | All threads waiting for it to become true are awakened. | |
| 92 | Threads that call <tt class="method">wait()</tt> once the flag is true will not block | |
| 93 | at all. | |
| 94 | </dl> | |
| 95 | ||
| 96 | <P> | |
| 97 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 98 | <td><nobr><b><tt id='l2h-2736' xml:id='l2h-2736' class="method">clear</tt></b>(</nobr></td> | |
| 99 | <td><var></var>)</td></tr></table></dt> | |
| 100 | <dd> | |
| 101 | Reset the internal flag to false. | |
| 102 | Subsequently, threads calling <tt class="method">wait()</tt> will block until | |
| 103 | <tt class="method">set()</tt> is called to set the internal flag to true again. | |
| 104 | </dl> | |
| 105 | ||
| 106 | <P> | |
| 107 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 108 | <td><nobr><b><tt id='l2h-2737' xml:id='l2h-2737' class="method">wait</tt></b>(</nobr></td> | |
| 109 | <td><var></var><big>[</big><var>timeout</var><big>]</big><var></var>)</td></tr></table></dt> | |
| 110 | <dd> | |
| 111 | Block until the internal flag is true. | |
| 112 | If the internal flag is true on entry, return immediately. Otherwise, | |
| 113 | block until another thread calls <tt class="method">set()</tt> to set the flag to | |
| 114 | true, or until the optional timeout occurs. | |
| 115 | ||
| 116 | <P> | |
| 117 | When the timeout argument is present and not <code>None</code>, it should be a | |
| 118 | floating point number specifying a timeout for the operation in | |
| 119 | seconds (or fractions thereof). | |
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| 158 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
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